MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Nano Letters' source. Wed, 17 Mar 2010 17:09:23 +0100 http://www.medworm.com/index.php?rid=3362932&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20222669%26dopt%3DAbstract Authors: Martin PN, Aksamija Z, Pop E, Ravaioli U We model and compare the thermal conductivity of rough semiconductor nanowires (NWs) of Si, Ge, and GaAs for thermoelectric devices. On the basis of full phonon dispersion relations, the effect of NW surface roughness on thermal conductivity is derived from perturbation theory and appears as an efficient way to scatter phonons in Si, Ge, and GaAs NWs with diameter D < 200 nm. For small diameters and large root-mean-square roughness Delta, thermal conductivity is limited by surface asperities and varies quadratically as (D/Delta)(2). At room temperature, our model previously agreed with experimental observations of thermal conductivity down to 2 W m(-1) K(-1) in rough 56 nm Si NWs with Delta = 3 nm. In comparison to Si, we predict her... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362932 Thu, 11 Mar 2010 00:00:00 +0100 3362932 http://www.medworm.com/index.php?rid=3362931&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20222740%26dopt%3DAbstract Authors: Kang T, Yoo SM, Yoon I, Lee SY, Kim B A Au particle-on-wire system that can be used as a specific, sensitive, and multiplex DNA sensor is developed. A pattern formed by multiple Au nanowire sensors provides positional address and identification for each sensor. By using this system, multiplex sensing of target DNAs was possible in a quantitative manner with a detection limit of 10 pM. Target DNAs from reference bacteria and clinical isolates were successfully identified by this sensor system, enabling diagnostics for infectious diseases. PMID: 20222740 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362931 Thu, 11 Mar 2010 00:00:00 +0100 3362931 http://www.medworm.com/index.php?rid=3362930&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20222744%26dopt%3DAbstract We present a new way to tune the electron-phonon coupling (EPC) in graphene by changing the deformation potential with electron/hole doping. We show the EPC for highest optical branch at the high symmetry point K acquires a strong dependency on the doping level due to electron-electron correlation not accounted in mean-field approaches. Such a dependency influences the dispersion (with respect to the laser energy) of the Raman D and 2D lines and the splitting of the 2D peak in multilayer graphene. Finally this doping dependence opens the possibility to construct tunable electronic devices through external control of the EPC. PMID: 20222744 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362930 Thu, 11 Mar 2010 00:00:00 +0100 3362930 http://www.medworm.com/index.php?rid=3362938&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218630%26dopt%3DAbstract We present a nanomechanical device, operating as a reprogrammable logic gate, and performing fundamental logic functions such as AND/OR and NAND/NOR. The logic function can be programmed (e.g., from AND to OR) dynamically, by adjusting the resonator's operating parameters. The device can access one of two stable steady states, according to a specific logic function; this operation is mediated by the noise floor which can be directly adjusted, or dynamically "tuned" via an adjustment of the underlying nonlinearity of the resonator, i.e., it is not necessary to have direct control over the noise floor. The demonstration of this reprogrammable nanomechanical logic gate affords a path to the practical realization of a new generation of mechanical computers. PMID: 20218630 [PubMed - as supp... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362938 Wed, 10 Mar 2010 00:00:00 +0100 3362938 http://www.medworm.com/index.php?rid=3362937&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218633%26dopt%3DAbstract Authors: Lafkioti M, Krauss B, Lohmann T, Zschieschang U, Klauk H, Klitzing KV, Smet JH The intrinsic doping level of graphene prepared by mechanical exfoliation and standard lithography procedures on thermally oxidized silicon varies significantly and seems to depend strongly on processing details and the substrate morphology. Moreover, transport properties of such graphene devices suffer from hysteretic behavior under ambient conditions. The hysteresis presumably originates from dipolar adsorbates on the substrate or graphene surface. Here, we demonstrate that it is possible to reliably obtain low intrinsic doping levels and to strongly suppress hysteretic behavior even in ambient air by depositing graphene on top of a thin, hydrophobic self-assembled layer of hexamethyldisilazane (H... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362937 Wed, 10 Mar 2010 00:00:00 +0100 3362937 http://www.medworm.com/index.php?rid=3362936&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218653%26dopt%3DAbstract Authors: Walther A, Bjurhager I, Malho JM, Pere J, Ruokolainen J, Berglund LA, Ikkala O Although remarkable success has been achieved to mimic the mechanically excellent structure of nacre in laboratory-scale models, it remains difficult to foresee mainstream applications due to time-consuming sequential depositions or energy-intensive processes. Here, we introduce a surprisingly simple and rapid methodology for large-area, lightweight, and thick nacre-mimetic films and laminates with superior material properties. Nanoclay sheets with soft polymer coatings are used as ideal building blocks with intrinsic hard/soft character. They are forced to rapidly self-assemble into aligned nacre-mimetic films via paper-making, doctor-blading or simple painting, giving rise to strong and thick film... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362936 Wed, 10 Mar 2010 00:00:00 +0100 3362936 http://www.medworm.com/index.php?rid=3362935&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218662%26dopt%3DAbstract Authors: Kurepa J, Paunesku T, Vogt S, Arora H, Rabatic BM, Lu J, Wanzer MB, Woloschak GE, Smalle JA While few publications have documented the uptake of nanoparticles in plants, this is the first study describing uptake and distribution of the ultrasmall anatase TiO(2) in the plant model system Arabidopsis. We modified the nanoparticle surface with Alizarin red S and sucrose and demonstrated that nanoconjugates traversed cell walls, entered into plant cells, and accumulated in specific subcellular locations. Optical and X-ray fluorescence microscopy coregistered the nanoconjugates in cell vacuoles and nuclei. PMID: 20218662 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362935 Wed, 10 Mar 2010 00:00:00 +0100 3362935 http://www.medworm.com/index.php?rid=3362934&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218663%26dopt%3DAbstract Authors: Yang Y, Liu G, Liu H, Li D, Fan C, Liu D In this Letter, we have realized the electrical actuation of a DNA molecular device in a rapid and reliable manner with a microfabricated chip. The three-electrode chip containing Ir, IrO(2), and Ag electrodes deposited in designed shapes and positions on the SiO(2) surface was made by photolithography and magnetron reaction sputter deposition technology. In this design, the negative feedback property enabled the system to rapidly change and maintain the solution pH at arbitrary value by water electrolysis. As a proof-of-concept, we can drive a DNA switch based on the opening and close of an i-motif structure by switching the potential between the working and reference electrodes between -304 and -149 mV. We have demonstrated that DNA c... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362934 Wed, 10 Mar 2010 00:00:00 +0100 3362934 http://www.medworm.com/index.php?rid=3362933&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20218702%26dopt%3DAbstract We present a novel fluorescence lifetime imaging microscopy technique to measure absolute positions of fluorescent molecules within 100 nm above a metalized surface based on distance-dependent fluorescence lifetime modulations. We apply this technique to fluorescently labeled microtubules as optical probes with various unlabeled proteins attached. By measuring the fluorescence lifetimes, we obtain the position of the microtubules and therefore determine the geometrical size of the attached proteins with nanometer precision. PMID: 20218702 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3362933 Wed, 10 Mar 2010 00:00:00 +0100 3362933 http://www.medworm.com/index.php?rid=3347443&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20210348%26dopt%3DAbstract Authors: Huang L, Hartland GV, Chu LQ, Luxmi , Feenstra RM, Lian C, Tahy K, Xing H Transient absorption microscopy was employed to image charge carrier dynamics in epitaxial multilayer graphene. The carrier cooling exhibited a biexponential decay that showed a significant dependence on carrier density. The fast and slow relaxation times were assigned to coupling between electrons and optical phonon modes and the hot phonon effect, respectively. The limiting value of the slow relaxation time at high pump intensity reflects the lifetime of the optical phonons. Significant spatial heterogeneity in the dynamics was observed due to differences in coupling between graphene layers and the substrate. PMID: 20210348 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347443 Mon, 08 Mar 2010 00:00:00 +0100 3347443 http://www.medworm.com/index.php?rid=3347442&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20210349%26dopt%3DAbstract Authors: Wang J, Xiong SJ, Wu XL, Li TH, Chu PK We have produced glycerol-bonded 3C-SiC nanocrystal (NC) films, which when excited by photons of different wavelengths, produce strong and tunable violet to blue-green (360-540 nm) emission as a result of the quantum confinement effects rendered by the 3C-SiC NCs. The emission is so intense that the emission spots are visible to the naked eyes. The light emission is very stable and even after storing in air for more than six months, no intensity degradation can be observed. X-ray photoelectron spectroscopy and absorption fine structure measurements indicate that the Si-terminated NC surfaces are completely bonded to glycerol molecules. Calculations of geometry optimization and electron structures based on the density functional theory for... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347442 Mon, 08 Mar 2010 00:00:00 +0100 3347442 http://www.medworm.com/index.php?rid=3347441&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20210362%26dopt%3DAbstract We report generation of ballistic electric currents in unbiased epitaxial graphene at 300 K via quantum interference between phase-controlled cross-polarized fundamental and second harmonic 220 fs pulses. The transient currents are detected via the emitted terahertz radiation. Because of graphene's special structure symmetry, the injected current direction can be well controlled by the polarization of the pump beam in epitaxial graphene. This all optical injection of current provides not only a noncontact way of injecting directional current in graphene but also new insight into optical and transport process in epitaxial graphene. PMID: 20210362 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347441 Mon, 08 Mar 2010 00:00:00 +0100 3347441 http://www.medworm.com/index.php?rid=3347447&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20205414%26dopt%3DAbstract Authors: Wheeler PJ, Russom JN, Evans K, King NS, Natelson D Shot noise encodes additional information not directly inferable from simple electronic transport measurements. Previous measurements in atomic-scale metal junctions at cryogenic temperatures have shown suppression of the shot noise at particular conductance values. This suppression demonstrates that transport in these structures proceeds via discrete quantum channels. Using a high-frequency technique, we simultaneously acquire noise data and conductance histograms in Au junctions at room temperature and ambient conditions. We observe noise suppression at up to three conductance quanta, with possible indications of current-induced local heating and 1/f noise in the contact region at high biases. These measurements demonstrate... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347447 Fri, 05 Mar 2010 00:00:00 +0100 3347447 http://www.medworm.com/index.php?rid=3347446&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20205446%26dopt%3DAbstract Authors: Akopian N, Patriarche G, Liu L, Harmand JC, Zwiller V In semiconducting nanowires, both zinc blende and wurtzite(1) crystal structures can coexist.(2-4) The band structure difference between the two structures can lead to charge confinement.(5) Here we fabricate and study single quantum dot devices(6) defined solely by crystal phase in a chemically homogeneous nanowire and observe single photon generation. More generally, our results show that this type of carrier confinement represents a novel degree of freedom in device design at the nanoscale. PMID: 20205446 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347446 Fri, 05 Mar 2010 00:00:00 +0100 3347446 http://www.medworm.com/index.php?rid=3347445&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20205454%26dopt%3DAbstract We present a cell-free artificial photosynthesis platform that couples the requisite enzymes of the Calvin cycle with a nanoscale photophosphorylation system engineered into a foam architecture using the Tungara frog surfactant protein Ranaspumin-2. This unique protein surfactant allowed lipid vesicles and coupled enzyme activity to be concentrated to the microscale Plateau channels of the foam, directing photoderived chemical energy to the singular purpose of carbon fixation and sugar synthesis, with chemical conversion efficiencies approaching 96%. PMID: 20205454 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347445 Fri, 05 Mar 2010 00:00:00 +0100 3347445 http://www.medworm.com/index.php?rid=3347444&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20205455%26dopt%3DAbstract Authors: Teweldebrhan D, Goyal V, Balandin AA Bismuth telluride (Bi(2)Te(3)) and its alloys are the best bulk thermoelectric materials known today. In addition, stacked quasi-two-dimensional (2D) layers of Bi(2)Te(3) were recently identified as promising topological insulators. In this Letter we describe a method for "graphene-inspired" exfoliation of crystalline bismuth telluride films with a thickness of a few atoms. The atomically thin films were suspended across trenches in Si/SiO(2) substrates, and subjected to detail material characterization, which included atomic force microscopy and micro-Raman spectroscopy. The presence of the van der Waals gaps allowed us to disassemble Bi(2)Te(3) crystal into its quintuple building blocks-five monatomic sheets-consisting of Te((1))-Bi-Te((2... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3347444 Fri, 05 Mar 2010 00:00:00 +0100 3347444 http://www.medworm.com/index.php?rid=3338470&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20201533%26dopt%3DAbstract Authors: Ryu W, Bai SJ, Park JS, Huang Z, Moseley J, Fabian T, Fasching RJ, Grossman AR, Prinz FB There are numerous sources of bioenergy that are generated by photosynthetic processes, for example, lipids, alcohols, hydrogen, and polysaccharides. However, generally only a small fraction of solar energy absorbed by photosynthetic organisms is converted to a form of energy that can be readily exploited. To more efficiently use the solar energy harvested by photosynthetic organisms, we evaluated the feasibility of generating bioelectricity by directly extracting electrons from the photosynthetic electron transport chain before they are used to fix CO(2) into sugars and polysaccharides. From a living algal cell, Chlamydomonas reinhardtii, photosynthetic electrons (1.2 pA at 6000 mA/m(2)) ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338470 Thu, 04 Mar 2010 00:00:00 +0100 3338470 http://www.medworm.com/index.php?rid=3338475&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20199031%26dopt%3DAbstract We report direct observation of controlled and reversible switching of magnetic domains using static (dc) electric fields applied in situ during Lorentz microscopy. The switching is realized through electromechanical coupling in thin film Fe(0.7)Ga(0.3)/BaTiO(3) bilayer structures mechanically released from the growth substrate. The domain wall motion is observed dynamically, allowing the direct association of local magnetic ordering throughout a range of applied electric fields. During application of approximately 7-11 MV/m electric fields to the piezoelectric BaTiO(3) film, local magnetic domains rearrange in the ferromagnetic Fe(0.7)Ga(0.3) layer due to the transfer of strain from the BaTiO(3) film. A simulation based on micromagnetic modeling shows a magnetostrictive anisotropy of 25 k... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338475 Wed, 03 Mar 2010 00:00:00 +0100 3338475 http://www.medworm.com/index.php?rid=3338474&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20199032%26dopt%3DAbstract Authors: Pevzner A, Engel Y, Elnathan R, Ducobni T, Ben-Ishai M, Reddy K, Shpaisman N, Tsukernik A, Oksman M, Patolsky F The large-scale assembly of nanowire elements with controlled and uniform orientation and density at spatially well-defined locations on solid substrates presents one of the most significant challenges facing their integration in real-world electronic applications. Here, we present the universal "knocking-down" approach, based on the controlled in-place planarization of nanowire elements, for the formation of large-scale ordered nanowire arrays. The controlled planarization of the nanowires is achieved by the use of an appropriate elastomer-covered rigid-roller device. After being knocked down, each nanowire in the array can be easily addressed electrically, by a sim... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338474 Wed, 03 Mar 2010 00:00:00 +0100 3338474 http://www.medworm.com/index.php?rid=3338473&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20199056%26dopt%3DAbstract Authors: Kim Y, Han H, Lee W, Baik S, Hesse D, Alexe M Switching dynamics of nanoscale ferroelectric capacitors with a radius of 35 nm were investigated using piezoresponse force microscopy. Polarization switching starts with only one nucleation event occurring only at the predetermined places. The switching dynamics of nanoscale capacitors did not follow the classical Kolmogorov-Avrami-Ishibashi model. On the basis of the consideration of two separate (nucleation and growth) steps within a nonstatistical finite system, we have proposed a model which is in good agreement with the experimental results. PMID: 20199056 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338473 Wed, 03 Mar 2010 00:00:00 +0100 3338473 http://www.medworm.com/index.php?rid=3338472&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20199057%26dopt%3DAbstract Authors: Gómez-Navarro C, Meyer JC, Sundaram RS, Chuvilin A, Kurasch S, Burghard M, Kern K, Kaiser U Using high resolution transmission electron microscopy, we identify the specific atomic scale features in chemically derived graphene monolayers that originate from the oxidation-reduction treatment of graphene. The layers are found to comprise defect-free graphene areas with sizes of a few nanometers interspersed with defect areas dominated by clustered pentagons and heptagons. Interestingly, all carbon atoms in these defective areas are bonded to three neighbors maintaining a planar sp(2)-configuration, which makes them undetectable by spectroscopic techniques. Furthermore, we observe that they introduce significant in-plane distortions and strain in the surrounding lattice. ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338472 Wed, 03 Mar 2010 00:00:00 +0100 3338472 http://www.medworm.com/index.php?rid=3338471&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20199061%26dopt%3DAbstract Authors: He X, Gao F, Tu G, Hasko D, Hüttner S, Steiner U, Greenham NC, Friend RH, Huck WT In this paper, we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14)/mm(2)) of interpenetrating nanoscale columnar features in the active polymer blend layer. The smallest feature sizes are as small as 25 nm on a 50 nm pitch, which results in a spacing of heterojunctions at or below the exciton diffusion length. Photovoltaic devices based on double-imprinted poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (F8TBT)/ poly(3-hexylthioph... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3338471 Wed, 03 Mar 2010 00:00:00 +0100 3338471 http://www.medworm.com/index.php?rid=3331696&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20196539%26dopt%3DAbstract Authors: Podila R, Queen W, Nath A, Arantes JT, Schoenhalz AL, Fazzio A, Dalpian GM, He J, Hwu SJ, Skove MJ, Rao AM An unexpected presence of ferromagnetic (FM) ordering in nanostructured nonmagnetic metal oxides has been reported previously. Though this property was attributed to the presence of defects, systematic experimental and theoretical studies to pinpoint its origin and mechanism are lacking. While it is widely believed that oxygen vacancies are responsible for FM ordering, surprisingly we find that annealing as-prepared samples at low temperature (high temperature) in flowing oxygen actually enhances (diminishes) the FM ordering. For these reasons, we have prepared, annealed in different environments, and measured the ensuing magnetization in micrometer and nanoscale ZnO with... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331696 Tue, 02 Mar 2010 00:00:00 +0100 3331696 http://www.medworm.com/index.php?rid=3331695&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20196550%26dopt%3DAbstract Authors: Koren E, Berkovitch N, Rosenwaks Y We have measured the radial distribution and diffusion of active dopant atoms in individual silicon nanowires grown by the vapor-liquid-solid (VLS) method. Our method is based on successive surface etching of a portion of a contacted nanowire, followed by measurement of the potential difference between the etched and unetched areas using Kelvin probe force microscopy (KPFM). The radial dopant distribution is obtained by fitting the measured potentials with a three-dimensional solution of Poisson equation. We find that the radial active dopant distribution decreases by almost 2 orders of magnitude from the wire surface to its core even when there is no indication for tapering. In addition, the dopant profile is consistent with a very large dif... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331695 Tue, 02 Mar 2010 00:00:00 +0100 3331695 http://www.medworm.com/index.php?rid=3331694&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20196552%26dopt%3DAbstract Authors: Tcherniak A, Ha JW, Dominguez-Medina S, Slaughter LS, Link S In 1908, Gustav Mie solved Maxwell's equations to account for the absorption and scattering of spherical plasmonic particles. Since then much attention has been devoted to the size dependent optical properties of metallic nanoparticles. However, ensemble measurements of colloidal solutions generally only yield the total extinction cross sections of the nanoparticles. Here, we show how Mie's prediction on the size dependence of the surface absorption and scattering can be probed separately for the same gold nanoparticle by using two single particle spectroscopy techniques, (1) dark-field scattering and (2) photothermal imaging, which selectively only measure scattering and absorption, respectively. Combining the optic... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331694 Tue, 02 Mar 2010 00:00:00 +0100 3331694 http://www.medworm.com/index.php?rid=3331702&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192229%26dopt%3DAbstract Authors: Kim M, Safron NS, Han E, Arnold MS, Gopalan P We demonstrate the fabrication of nanoperforated graphene materials with sub-20-nm features using cylinder-forming diblock copolymer templates across >1 mm(2) areas. Hexagonal arrays of holes are etched into graphene membranes, and the remaining constrictions between holes interconnect forming a honeycomb structure. Quantum confinement, disorder, and localization effects modulate the electronic structure, opening an effective energy gap of 100 meV in the nanopatterned material. The field-effect conductivity can be modulated by 40x (200x) at room temperature (T = 105 K) as a result. A room temperature hole mobility of 1 cm(2) V(-1) s(-1) was measured in the fabricated nanoperforated graphene field effect transistors. This scalabl... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331702 Mon, 01 Mar 2010 00:00:00 +0100 3331702 http://www.medworm.com/index.php?rid=3331701&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192230%26dopt%3DAbstract Authors: Jo SH, Chang T, Ebong I, Bhadviya BB, Mazumder P, Lu W A memristor is a two-terminal electronic device whose conductance can be precisely modulated by charge or flux through it. Here we experimentally demonstrate a nanoscale silicon-based memristor device and show that a hybrid system composed of complementary metal-oxide semiconductor neurons and memristor synapses can support important synaptic functions such as spike timing dependent plasticity. Using memristors as synapses in neuromorphic circuits can potentially offer both high connectivity and high density required for efficient computing. PMID: 20192230 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331701 Mon, 01 Mar 2010 00:00:00 +0100 3331701 http://www.medworm.com/index.php?rid=3331700&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192231%26dopt%3DAbstract We present a noninvasive optical method to determine the local strain in individual semiconductor nanowires. InP nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy. Sections of the nanowires with a high curvature showed significantly broadened phonon lines. These observations together with deformation potential theory show that compressive and tensile strain inside the nanowires is the physical origin of the observed phonon energy variations. PMID: 20192231 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331700 Mon, 01 Mar 2010 00:00:00 +0100 3331700 http://www.medworm.com/index.php?rid=3331699&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192232%26dopt%3DAbstract We report on a theoretical discovery of a generic piezoelectric field in strained core-shell compound semiconductor nanowires. We show, using both an analytical model and numerical simulations based on fully electroelastically coupled continuum elasticity theory, that lattice-mismatch-induced strain in an epitaxial core-shell nanowire gives rise to an internal electric field along the axis of the nanowire. This piezoelectric field results predominantly from atomic layer displacements along the nanowire axis within both the core and shell materials and can appear in both zinc blende and wurtzite crystalline core-shell nanowires. The effect can be employed to separate photon-generated electron-hole pairs in the core-shell nanowires and thus offers a new device concept for solar energy conver... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331699 Mon, 01 Mar 2010 00:00:00 +0100 3331699 http://www.medworm.com/index.php?rid=3331698&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192234%26dopt%3DAbstract Authors: Lee SJ, Piorek BD, Meinhart CD, Moskovits M Surface-immobilized, densely packed gold nanoparticles in contact with aqueous silver ions and exposed to red light rapidly photoreduce silver ions in solution producing radially symmetric metal deposits with diameters many times larger than the diameter of the illuminating laser beam. The average particle sizes in the deposit increase with radial distance from the center of the deposit. This reduction-at-a-distance effect arises from surface-plasmon-mediated photoemission, with the photoemitted electrons conducting along percolating silver pathways, reducing silver ions along these conducting channels and especially at their periphery, thereby propagating the effect of the illuminating laser outward. PMID: 20192234 [PubMed - as ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331698 Mon, 01 Mar 2010 00:00:00 +0100 3331698 http://www.medworm.com/index.php?rid=3331697&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20192246%26dopt%3DAbstract In this report, we combined the electrical biasing with the application of mechanical stress, which impacts the charge carriers' concentration, to achieve an electrically controlled giant piezoresistance in nanowires. This phenomenon was used to create a stress-gated field-effect transistor, exhibiting a maximum gauge factor of 5000, 2 orders of magnitude increase over bulk value. Giant piezoresistance can be tailored to create highly sensitive mechanical sensors operating in a discrete mode such as nanoelectromechanical switches. PMID: 20192246 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3331697 Mon, 01 Mar 2010 00:00:00 +0100 3331697 http://www.medworm.com/index.php?rid=3316440&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20184292%26dopt%3DAbstract Authors: Liao X, Braunschweig AB, Mirkin CA Polymer pen lithography is a recently developed molecular printing technique which can produce features with diameters ranging from 80 nm to >10 mum in a single writing step using massively parallel (>10(7) pens) arrays of pyramidal, elastomeric pens. Leveling these pen arrays with respect to the surface to produce uniform features over large areas remains a considerable challenge. Here, we describe a new method for leveling the pen arrays that utilizes the force between the pen arrays and the surface to achieve leveling with a tilt of less than 0.004 degrees , thereby producing features that vary by only 50 nm over 1 cm. PMID: 20184292 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3316440 Thu, 25 Feb 2010 00:00:00 +0100 3316440 http://www.medworm.com/index.php?rid=3316439&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20184381%26dopt%3DAbstract Authors: Govorov AO, Fan Z, Hernandez P, Slocik JM, Naik RR Our calculations show that a nonchiral nanocrystal is able to dramatically change the circular dichroism (CD) of a chiral molecule when the nanocrystal and molecule form a complex and couple via dipole and multipole Coulomb interactions. Plasmon resonances of metal nanocrystals in the nanocrystal-molecule complex result in both the resonant enhancement of CD signals of molecules and the appearance of new spectral structures. Two mechanisms, in which a nanocrystal can influence the CD effect, have been identified. The first mechanism is the plasmon-induced change in the electromagnetic field inside the chiral molecule. The second is the optical absorption of the nanocrystal-molecule complex due to the chiral currents inside the... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3316439 Thu, 25 Feb 2010 00:00:00 +0100 3316439 http://www.medworm.com/index.php?rid=3316438&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20184382%26dopt%3DAbstract Authors: Yang Y, McDowell MT, Jackson A, Cha JJ, Hong SS, Cui Y Rechargeable lithium ion batteries are important energy storage devices; however, the specific energy of existing lithium ion batteries is still insufficient for many applications due to the limited specific charge capacity of the electrode materials. The recent development of sulfur/mesoporous carbon nanocomposite cathodes represents a particularly exciting advance, but in full battery cells, sulfur-based cathodes have to be paired with metallic lithium anodes as the lithium source, which can result in serious safety issues. Here we report a novel lithium metal-free battery consisting of a Li(2)S/mesoporous carbon composite cathode and a silicon nanowire anode. This new battery yields a theoretical specific energy of 1550... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3316438 Thu, 25 Feb 2010 00:00:00 +0100 3316438 http://www.medworm.com/index.php?rid=3312337&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20180525%26dopt%3DAbstract Authors: Checco A, Hofmann T, Dimasi E, Black CT, Ocko BM The details of air nanobubble trapping at the interface between water and a nanostructured hydrophobic silicon surface are investigated using X-ray scattering and contact angle measurements. Large-area silicon surfaces containing hexagonally packed, 20 nm wide hydrophobic cavities provide ideal model surfaces for studying the morphology of air nanobubbles trapped inside cavities and its dependence on the cavity depth. Transmission small-angle X-ray scattering measurements show stable trapping of air inside the cavities with a partial water penetration of 5-10 nm into the pores, independent of their large depth variation. This behavior is explained by consideration of capillary effects and the cavity geometry. For parabolic cavit... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312337 Wed, 24 Feb 2010 00:00:00 +0100 3312337 http://www.medworm.com/index.php?rid=3312336&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20180594%26dopt%3DAbstract Authors: Weinstein D, Bhave SA This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312336 Wed, 24 Feb 2010 00:00:00 +0100 3312336 http://www.medworm.com/index.php?rid=3312341&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20178355%26dopt%3DAbstract Authors: Kim DR, Lee CH, Zheng X Bottom-up nanowires are useful building blocks for functional devices because of their controllable physical and chemical properties. However, assembling nanowires into large-scale integrated systems remains a critical challenge that becomes even more daunting when different nanowires need to be simultaneously assembled in close proximity to one another. Herein, we report a new method to directly grow nanowire devices consisting of different nanowires. The method is based on the epitaxial growth of nanowires from the sidewalls of electrodes and on the matching of electrode design with synthesis conditions to electrically connect different nanowires during growth. Specifically, the method was used to grow silicon nanowire-based AND and OR diode logic gat... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312341 Tue, 23 Feb 2010 00:00:00 +0100 3312341 http://www.medworm.com/index.php?rid=3312340&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20178356%26dopt%3DAbstract Authors: Maclean K, Mentzel TS, Kastner MA We measure charge transport in a hydrogenated amorphous silicon (a-Si:H) thin film using a nanometer scale silicon MOSFET as a charge sensor. This charge detection technique makes possible the measurement of extremely large resistances even in the presence of blocking contacts. At high temperatures, where the resistance of the a-Si:H is not too large, the charge detection measurement agrees with a direct measurement of current. The device geometry allows us to probe both the field effect and dispersive transport in the a-Si:H using charge sensing and to extract the density of states near the Fermi energy. PMID: 20178356 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312340 Tue, 23 Feb 2010 00:00:00 +0100 3312340 http://www.medworm.com/index.php?rid=3312339&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20178369%26dopt%3DAbstract Authors: Williams SS, Retterer S, Lopez R, Ruiz R, Samulski ET, Desimone JM Several perfluoropolyether (PFPE)-based elastomers for high-resolution replica molding applications are explored. The modulus of the elastomeric materials was increased through synthetic and additive approaches while maintaining relatively low surface tension values (<25 mN/m). Using large area (>4 in.(2)) master templates, we experimentally show the relationship between mold resolution and material properties such as modulus and surface tension for materials used in this study. A composite mold approach was used to form flexible molds out of stiff, high modulus materials that allow for replication of sub-20 nm post structures. Sub-100 nm line grating master templates, formed using e-beam lithography, wer... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312339 Tue, 23 Feb 2010 00:00:00 +0100 3312339 http://www.medworm.com/index.php?rid=3312338&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20178372%26dopt%3DAbstract Authors: Jiang N, Zhang YY, Liu Q, Cheng ZH, Deng ZT, Du SX, Gao HJ, Beck MJ, Pantelides ST The development of methods for controlling the motion and arrangement of molecules adsorbed on a metal surface would provide a powerful tool for the design of molecular electronic devices. Recently, metal phthalocyanines (MPc) have been extensively considered for use in such devices. Here we show that applied electric fields can be used to turn off the diffusivity of iron phthalocyanine (FePc) on Au(111) at fixed temperature, demonstrating a practical and direct method for controlling and potentially patterning FePc layers. Using scanning tunneling microscopy, we show that the diffusivity of FePc on Au(111) is a strong function of temperature and that applied electric fields can be used to retar... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3312338 Tue, 23 Feb 2010 00:00:00 +0100 3312338 http://www.medworm.com/index.php?rid=3295112&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20170193%26dopt%3DAbstract Authors: Hu R, Cola BA, Haram N, Barisci JN, Lee S, Stoughton S, Wallace G, Too C, Thomas M, Gestos A, Cruz ME, Ferraris JP, Zakhidov AA, Baughman RH Low efficiencies and costly electrode materials have limited harvesting of thermal energy as electrical energy using thermo-electrochemical cells (or "thermocells"). We demonstrate thermocells, in practical configurations (from coin cells to cells that can be wrapped around exhaust pipes), that harvest low-grade thermal energy using relatively inexpensive carbon multiwalled nanotube (MWNT) electrodes. These electrodes provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency. Thermocell efficiency is further ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3295112 Fri, 19 Feb 2010 00:00:00 +0100 3295112 http://www.medworm.com/index.php?rid=3291658&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20166745%26dopt%3DAbstract We present a method for making polymer chips with a narrow-band near-infrared absorber layer that enables light-induced local heating of liquids inside fluidic micro- and nanochannels fabricated by thermal imprint in polymethyl methacrylate. We have characterized the resulting liquid temperature profiles in microchannels using the temperature dependent fluorescence of the complex [Ru(bpy)(3)](2+). We demonstrate thermophoretic manipulation of individual YOYO-1 stained T4 DNA molecules inside micro- and nanochannels. PMID: 20166745 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3291658 Thu, 18 Feb 2010 00:00:00 +0100 3291658 http://www.medworm.com/index.php?rid=3288002&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20163124%26dopt%3DAbstract Authors: Donadio D, Galli G We compute the lattice thermal conductivity (kappa) of silicon nanowires as a function of temperature by molecular dynamics simulations. In wires with amorphous surfaces kappa may reach values close to that of amorphous silicon and is nearly constant between 200 and 600 K; this behavior is determined by the presence of a majority of nonpropagating vibrational modes. We develop a parameter-free model that accounts for the temperature dependence observed in our simulations and provides a qualitative explanation of recent experiments. PMID: 20163124 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3288002 Wed, 17 Feb 2010 00:00:00 +0100 3288002 http://www.medworm.com/index.php?rid=3288001&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20163125%26dopt%3DAbstract Authors: Wallentin J, Persson JM, Wagner JB, Samuelson L, Deppert K, Borgström MT We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications. PMID: 20163125 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3288001 Wed, 17 Feb 2010 00:00:00 +0100 3288001 http://www.medworm.com/index.php?rid=3287999&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20163134%26dopt%3DAbstract We report on the nanometer scale spectral imaging of surface plasmons within individual silver triangular nanoprisms by electron energy loss spectroscopy and on related discrete dipole approximation simulations. A dependence of the energy and intensity of the three detected modes as function of the edge length is clearly identified both experimentally and with simulations. We show that for experimentally available prisms (edge lengths ca. 70 to 300 nm) the energies and intensities of the different modes show a monotonic dependence as function of the aspect ratio of the prisms. For shorter or longer prisms, deviations to this behavior are identified thanks to simulations. These modes have symmetric charge distribution and result from the strong coupling of the upper and lower triangular sur... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3287999 Wed, 17 Feb 2010 00:00:00 +0100 3287999 http://www.medworm.com/index.php?rid=3287996&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20163184%26dopt%3DAbstract Authors: Brunel FM, Lewis JD, Destito G, Steinmetz NF, Manchester M, Stuhlmann H, Dawson PE Multivalent nanoparticle platforms are attractive for biomedical applications because of their improved target specificity, sensitivity, and solubility. However, their controlled assembly remains a considerable challenge. An efficient hydrazone ligation chemistry was applied to the assembly of Cowpea mosaic virus (CPMV) nanoparticles with individually tunable levels of a VEGFR-1 ligand and a fluorescent PEGylated peptide. The nanoparticles recognized VEGFR-1 on endothelial cell lines and VEGFR1-expressing tumor xenografts in mice, validating targeted CPMV as a nanoparticle platform in vivo. PMID: 20163184 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3287996 Wed, 17 Feb 2010 00:00:00 +0100 3287996 http://www.medworm.com/index.php?rid=3288008&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20158248%26dopt%3DAbstract Authors: Rohr C, Balbás Gambra M, Gruber K, Constable EC, Frey E, Franosch T, Hermann BA Scanning tunneling microscopy (STM) images of self-organized monolayers of Frechet dendrons display a variety of two-dimensional ordering motifs, which are influenced by engineering the molecular interactions. An interaction-site model condenses the essential molecular properties determined by molecular mechanics modeling, which in a Monte Carlo approach successfully predicts the various ordering motifs. This confirms that geometry as well as a few salient weak interaction sites encode these structural motifs. PMID: 20158248 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3288008 Tue, 16 Feb 2010 00:00:00 +0100 3288008 http://www.medworm.com/index.php?rid=3288007&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20158249%26dopt%3DAbstract Authors: Anderson JP, Reynolds BL, Baum K, Williams JG Highly labeled DNA nanoballs functionalized with phosphate-linked nucleotide triphosphates (dNTPs) were developed as a source of dNTPs for DNA polymerase. The particles were prepared by strand-displacement polymerization from a self-complementary circular template. Imaged by atomic force microscopy, these functionalized particles appear as condensed fuzzy balls with diameters between 50 and 150 nm. They emit a bright fluorescent signal, detected in 2 ms exposures with a signal-to-noise ratio of 25 when imaged using a TIR fluorescence microscope. PMID: 20158249 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3288007 Tue, 16 Feb 2010 00:00:00 +0100 3288007 http://www.medworm.com/index.php?rid=3288006&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20158260%26dopt%3DAbstract Authors: Kobayashi M, Seki M, Tabata H, Watanabe Y, Yamashita I We used genetically modified tube-shaped tobamoviruses to produce 3 nm aligned magnetic nanoparticles. Amino acid residues facing the central channel of the virus were modified to increase the number of nucleation sites. Energy dispersive X-ray spectroscopy and superconducting quantum interference device analysis suggest that the particles consisted of Co-Pt alloy. The use of tobamovirus mutants is a promising approach to making a variety of components that can be applied to fabricate nanometer-scaled electronic devices. PMID: 20158260 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3288006 Tue, 16 Feb 2010 00:00:00 +0100 3288006 http://www.medworm.com/index.php?rid=3280397&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155914%26dopt%3DAbstract Authors: Cohen-Tanugi D, Akey A, Yao N Functional nanowires, made from materials such as zinc oxide, offer the promise of energy scavenging and precise sensing due to their vibrational properties, but their high intrinsic resonance frequencies (in the kilohertz to megahertz range) have limited the applications in nanotechnology. In this paper, we describe a method for introducing a new type of resonance at ultralow frequencies in ZnO nanowires. By using in situ ion implantation, nanodevice assembly, electronic signal generation, mechanical measurement, and electron beam characterization, we have achieved resonance at frequencies two orders of magnitude lower than the natural resonance frequency. Through both experimental investigation and theoretical simulation, we show that electric c... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280397 Mon, 15 Feb 2010 00:00:00 +0100 3280397 http://www.medworm.com/index.php?rid=3280396&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155964%26dopt%3DAbstract Authors: Khalap VR, Sheps T, Kane AA, Collins PG Individual single-walled carbon nanotubes (SWCNTs) become sensitive to H(2) gas when their surfaces are decorated with Pd metal, and previous reports measure typical chemoresistive increases to be approximately 2-fold. Here, thousand-fold increases in resistance are demonstrated in the specific case where a Pd cluster decorates a SWCNT sidewall defect site. Measurements on single SWCNTs, performed both before and after defect incorporation, prove that defects have extraordinary consequences on the chemoresistive response, especially in the case of SWCNTs with metallic band structure. Undecorated defects do not contribute to H(2) chemosensitivity, indicating that this amplification is due to a specific but complex interdependence between ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280396 Mon, 15 Feb 2010 00:00:00 +0100 3280396 http://www.medworm.com/index.php?rid=3280395&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155965%26dopt%3DAbstract We present measurements of the ac response of a single-electron box (SEB). We apply a radio frequency signal with a frequency larger than the tunneling rate and drive the system out of equilibrium. We observe much more dissipation in the SEB then one would expect from a simple circuit model. We can explain this in terms of a mechanism that we call the Sisyphus resistance. The Sisyphus resistance has a strong gate dependence which can be used for electrometery applications. PMID: 20155965 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280395 Mon, 15 Feb 2010 00:00:00 +0100 3280395 http://www.medworm.com/index.php?rid=3280394&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155966%26dopt%3DAbstract Authors: Gao Y, Shao N, Pei Y, Zeng XC Structural and catalytic properties of the gold alloy nanocluster Au(43)Cu(12) are investigated using a density-functional method. In contrast to the pure Au(55) nanocluster, which exhibits a low-symmetry C(1) structure, the 55-atom "crown gold" nanocluster exhibits a multishell structure, denoted by Au@Cu(12)@Au(42), with the highest icosahedral group-symmetry. In addition, density functional calculations suggest that this geometric magic-number nanocluster possesses comparable catalytic capability as a small-sized Au(10) cluster for the CO oxidation, due in part to their low-coordinated Au atoms on vertexes. The gold alloy nanocluster also shows higher selectivity for styrene oxidation than the bare Au(111) surface. PMID: 20155966 [PubMed - ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280394 Mon, 15 Feb 2010 00:00:00 +0100 3280394 http://www.medworm.com/index.php?rid=3280393&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20155969%26dopt%3DAbstract Authors: Kauffman DR, Sorescu DC, Schofield DP, Allen BL, Jordan KD, Star A We have explored the room temperature response of metal nanoparticle decorated single-walled carbon nanotubes (NP-SWNTs) using a combination of electrical transport, optical spectroscopy, and electronic structure calculations. We have found that upon the electrochemical growth of Au NPs on SWNTs, there is a transfer of electron density from the SWNT to the NP species, and that adsorption of CO molecules on the NP surface is accompanied by transfer of electronic density back into the SWNT. Moreover, the electronic structure calculations indicate dramatic variations in the charge density at the NP-SWNT interface, which supports our previous observation that interfacial potential barriers dominate the electrical b... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280393 Mon, 15 Feb 2010 00:00:00 +0100 3280393 http://www.medworm.com/index.php?rid=3280401&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20151696%26dopt%3DAbstract Authors: Stein D, Deurvorst Z, van der Heyden FH, Koopmans WJ, Gabel A, Dekker C DNA molecules can be concentrated in a narrow region of a nanochannel when driven electrokinetically in submillimolar salt solutions. Transport experiments and theoretical modeling reveal the interplay of electrophoresis, electro-osmosis, and the unique statistical properties of confined polymers that lead to DNA aggregation. A finite conductance through the bulk of the device also plays a crucial role by influencing the electric fields in the nanochannel. We build on this understanding by demonstrating how a nanofluidic device with integrated electrodes can preconcentrate DNA at selected locations and at physiological salt concentrations that are relevant to lab-on-a-chip applications. PMID: 20151696 ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280401 Fri, 12 Feb 2010 00:00:00 +0100 3280401 http://www.medworm.com/index.php?rid=3280400&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20151697%26dopt%3DAbstract Authors: Yang H, Mayne AJ, Boucherit M, Comtet G, Dujardin G, Kuk Y Electron scattering at graphene edges is expected to make a crucial contribution to the electron transport in graphene nanodevices by producing quantum interferences. Atomic-scale scanning tunneling microscopy (STM) topographies of different edge structures of monolayer graphene show that the localization of the electronic density of states along the C-C bonds, a property unique to monolayer graphene, results in quantum interference patterns along the graphene carbon bond network, whose shapes depend only on the edge structure and not on the electron energy. PMID: 20151697 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280400 Fri, 12 Feb 2010 00:00:00 +0100 3280400 http://www.medworm.com/index.php?rid=3280399&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20151698%26dopt%3DAbstract Authors: Zhang W, Huang L, Santschi C, Martin OJ The optical trapping of Au nanoparticles with dimensions as small as 10 nm in the gap of plasmonic dipole antennas is demonstrated. Single nanoparticle trapping events are recorded in real time by monitoring the Rayleigh scattering spectra of individual plasmonic antennas. Numerical simulations are also performed to interpret the experimental results, indicating the possibility to trap nanoparticles only a few nanometers in size. This work unveils the potential associated with the integration of plasmonic trapping with localized surface plasmon resonance based sensing techniques, in order to deliver analyte to specific, highly sensitive regions ("hot spots"). PMID: 20151698 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280399 Fri, 12 Feb 2010 00:00:00 +0100 3280399 http://www.medworm.com/index.php?rid=3280398&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20151700%26dopt%3DAbstract Authors: Mpourmpakis G, Andriotis AN, Vlachos DG The design and performance optimization of future nanocatalysts will depend on our understanding of adsorbate-metal interactions. Using first principle calculations, we identify suitable descriptors, namely, the coordination number and curvature angle of the surface Au atoms, capable of predicting the CO binding strength on every site of Au nanoparticles. Our results unravel how the size, shape, and symmetry of nanoparticles affect their electronic properties and, consequently, their interaction with CO. Importantly, these descriptors can be successfully applied to other metals using structural inputs from experiments and/or molecular modeling. PMID: 20151700 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3280398 Fri, 12 Feb 2010 00:00:00 +0100 3280398 http://www.medworm.com/index.php?rid=3270118&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20148567%26dopt%3DAbstract We report the design and characterization of a novel double-sided CdS and CdSe quantum dot cosensitized ZnO nanowire arrayed photoanode for photoelectrochemical (PEC) hydrogen generation. The double-sided design represents a simple analogue of tandem cell structure, in which the dense ZnO nanowire arrays were grown on an indium-tin oxide substrate followed by respective sensitization of CdS and CdSe quantum dots on each side. As-fabricated photoanode exhibited strong absorption in nearly the entire visible spectrum up to 650 nm, with a high incident-photon-to-current-conversion efficiency (IPCE) of approximately 45% at 0 V vs Ag/AgCl. On the basis on a single white light illumination of 100 mW/cm(2), the photoanode yielded a significant photocurrent density of approximately 12 mA/cm(2) at ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3270118 Thu, 11 Feb 2010 00:00:00 +0100 3270118 http://www.medworm.com/index.php?rid=3270117&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20148568%26dopt%3DAbstract Authors: Zhou S, Liu X, Wang D We synthesized a unique heteronanostructure consisting of two-dimensional TiSi(2) nanonets and particulate Si coating. The high conductivity and the structural integrity of the TiSi(2) nanonet core were proven as great merits to permit reproducible Li(+) insertion and extraction into and from the Si coating. This heteronanostructure was tested as the anode material for Li(+) storage. At a charge/discharge rate of 8400 mA/g, we measured specific capacities >1000 mAh/g. Only an average of 0.1% capacity fade per cycle was observed between the 20th and the 100th cycles. The combined high capacity, long capacity life, and fast charge/discharge rate represent one of the best anode materials that have been reported. The remarkable performance was enabled by t... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3270117 Thu, 11 Feb 2010 00:00:00 +0100 3270117 http://www.medworm.com/index.php?rid=3270121&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20146428%26dopt%3DAbstract Authors: de Jonge N, Bigelow WC, Veith GM Scanning transmission electron microscope (STEM) images of gold nanoparticles at atmospheric pressure have been recorded through a 0.36 mm thick mixture of CO, O(2), and He. This was accomplished using a reaction cell consisting of two electron-transparent silicon nitride membranes. Gold nanoparticles of a full width at half-maximum diameter of 1.0 nm were visible above the background noise, and the achieved edge resolution was 0.4 nm in accordance with calculations of the beam broadening. PMID: 20146428 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3270121 Wed, 10 Feb 2010 00:00:00 +0100 3270121 http://www.medworm.com/index.php?rid=3270120&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20146429%26dopt%3DAbstract Authors: Jung YS, Chang JB, Verploegen E, Berggren KK, Ross CA The templated self-assembly of block copolymer (BCP) thin films can generate regular arrays of 10-50 nm scale features with good positional and orientational accuracy, but the ordering, registration and pattern transfer of sub-10-nm feature sizes is not well established. Here, we report solvent-annealing and templating methods that enable the formation of highly ordered grating patterns with a line width of 8 nm and period 17 nm from a self-assembled poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymer. The BCP patterns can be registered hierarchically on a larger-period BCP pattern, which can potentially diversify the available pattern geometries and enables precise pattern registration at small feature sizes. Sub-... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3270120 Wed, 10 Feb 2010 00:00:00 +0100 3270120 http://www.medworm.com/index.php?rid=3270119&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20146505%26dopt%3DAbstract We describe a simple method for scale fabrication of highly oriented Ta(3)N(5) nanotube array films, by anodization of tantalum foil to achieve vertically oriented tantalum oxide nanotube arrays followed by a 700 degrees C ammonia anneal for sample crystallization and nitridation. The thin walled amorphous nanotube array structure enables transformation from tantalum oxide to Ta(3)N(5) to occur at relatively low temperatures, while high-temperature annealing related structural aggregation that commonly occurs in particle films is avoided. In 1 M KOH solution, under AM 1.5 illumination with 0.5 V dc bias typical sample (nanotube length approximately 240 nm, wall thickness approximately 7 nm) visible light incident photon conversion efficiencies (IPCE) as high as 5.3% were obtained. The enha... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3270119 Wed, 10 Feb 2010 00:00:00 +0100 3270119 http://www.medworm.com/index.php?rid=3263379&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143874%26dopt%3DAbstract Authors: Lançon F, Ye J, Caliste D, Radetic T, Minor AM, Dahmen U The intriguing possibility of frictionless gliding of one solid surface on another has been predicted for certain incommensurate interfaces in crystals, based on Aubry's solution to the Frenkel-Kontorova model of a harmonic chain in a periodic potential field. Here we test this prediction for grain boundaries by comparing atomistic simulations with direct experimental observations on the structure and load-deformation behavior of gold nanopillars containing a root-two incommensurate grain boundary. The simulations show supergliding at this boundary limited by finite-size effects which cause edges to act as defects of the incommensurate structure. Structural relaxation at the edges generates stacking faults, dislocat... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263379 Wed, 10 Feb 2010 00:00:00 +0100 3263379 http://www.medworm.com/index.php?rid=3263382&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143792%26dopt%3DAbstract Authors: Lim SI, Ojea-Jiménez I, Varon M, Casals E, Arbiol J, Puntes V The introduction of metallic traces into the synthesis of platinum nanocrystals (Pt NCs) has been investigated as a surfactant-independent means of controlling shape. Various nanocrystal morphologies have been produced without modification of the reaction conditions, composition, and concentration other than the presence of cobalt traces (<5%). In the presence of metallic cobalt (a strong reducer for Pt cations) cubic Pt NCs are obtained, while cobalt ions or gold NCs have no effect on the synthesis, and as a result, polypods are obtained. Intermediate shapes such as cemented cubes or cuboctahedron NCs are also obtained under similar conditions. Thus, various NC shapes can be obtained with subtle changes, ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263382 Tue, 09 Feb 2010 00:00:00 +0100 3263382 http://www.medworm.com/index.php?rid=3263381&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143865%26dopt%3DAbstract We present results from composite plasmonic nanostructures designed to achieve the cascaded enhancement of electromagnetic fields at optical frequencies. Our structures comprise a small metallic nanodisc suspended above a larger disk. We probe the optical properties of these structures by coating them with a layer of a visible-light fluorophore and observing fluorescence signals with the help of scanning confocal microscopy. A 43 +/- 5-fold increase in the far-field fluorescence signal has been observed for two-tier composite nanostructures, when compared to the signal obtained from individual nanodiscs. Our results offer the prospect of using such nanostructures for field concentration, optical manipulation of nanoobjects, chemical and biological sensing. PMID: 20143865 [PubMed - as s... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263381 Tue, 09 Feb 2010 00:00:00 +0100 3263381 http://www.medworm.com/index.php?rid=3263380&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20143866%26dopt%3DAbstract Authors: Groves C, Blakesley JC, Greenham NC In this letter, we examine the effect of charge trapping on geminate recombination and organic photovoltaic performance using a Monte Carlo model. We alter the degree of charge trapping by considering energetic disorder to be spatially uncorrelated or correlated. On correlating energetic disorder, and so reducing the degree of trapping, it is found that power conversion efficiency of blend and bilayer devices improves by factors of 3.1 and 2.6, respectively. These results are related to the experimental data and quantum chemical calculations for poly[9,9-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine] (PFB)/poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as well as poly(3-hexylthiophene) (P3HT)/(6,6)-ph... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263380 Tue, 09 Feb 2010 00:00:00 +0100 3263380 http://www.medworm.com/index.php?rid=3263387&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20141118%26dopt%3DAbstract We report experimental observation of a normal incidence phononic band gap in one-dimensional periodic (SiO(2)/poly(methyl methacrylate)) multilayer film at gigahertz frequencies using Brillouin spectroscopy. The band gap to midgap ratio of 0.30 occurs for elastic wave propagation along the periodicity direction, whereas for inplane propagation the system displays an effective medium behavior. The phononic properties are well captured by numerical simulations. The porosity in the silica layers presents a structural scaffold for the introduction of secondary active media for potential coupling between phonons and other excitations, such as photons and electrons. PMID: 20141118 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263387 Mon, 08 Feb 2010 00:00:00 +0100 3263387 http://www.medworm.com/index.php?rid=3263386&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20141155%26dopt%3DAbstract Authors: Aristov VY, Urbanik G, Kummer K, Vyalikh DV, Molodtsova OV, Preobrajenski AB, Zakharov AA, Hess C, Hänke T, Büchner B, Vobornik I, Fujii J, Panaccione G, Ossipyan YA, Knupfer M The outstanding properties of graphene, a single graphite layer, render it a top candidate for substituting silicon in future electronic devices. The so far exploited synthesis approaches, however, require conditions typically achieved in specialized laboratories and result in graphene sheets whose electronic properties are often altered by interactions with substrate materials. The development of graphene-based technologies requires an economical fabrication method compatible with mass production. Here we demonstrate for the fist time the feasibility of graphene synthesis on commercially ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263386 Mon, 08 Feb 2010 00:00:00 +0100 3263386 http://www.medworm.com/index.php?rid=3263385&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20141156%26dopt%3DAbstract Authors: Han SE, Chen G We investigate silicon nanohole arrays as light absorbing structures for solar photovoltaics via simulation. To obtain the same ultimate efficiency as a standard 300 mum crystalline silicon wafer, we find that nanohole arrays require twelve times less silicon by mass. Moreover, our calculations show that nanohole arrays have an efficiency superior to nanorod arrays for practical thicknesses. With well-established fabrication techniques, nanohole arrays have great potential for efficient solar photovoltaics. PMID: 20141156 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263385 Mon, 08 Feb 2010 00:00:00 +0100 3263385 http://www.medworm.com/index.php?rid=3263384&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20141157%26dopt%3DAbstract Authors: Barth M, Schietinger S, Fischer S, Becker J, Nüsse N, Aichele T, Löchel B, Sönnichsen C, Benson O We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q approximately 900) opens new routes for the control of light-matter interaction at the nanoscale. PMID: 20141157 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263384 Mon, 08 Feb 2010 00:00:00 +0100 3263384 http://www.medworm.com/index.php?rid=3263383&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20141183%26dopt%3DAbstract Authors: Chang S, Huang S, He J, Liang F, Zhang P, Li S, Chen X, Sankey O, Lindsay S Nucleosides diffusing through a 2 nm electron-tunneling junction generate current spikes of sub-millisecond duration with a broad distribution of peak currents. This distribution narrows 10-fold when one of the electrodes is functionalized with a reagent that traps nucleosides in a specific orientation with hydrogen bonds. Functionalizing the second electrode reduces contact resistance to the nucleosides, allowing them to be identified via their peak currents according to deoxyadenosine > deoxycytidine > deoxyguanosine > thymidine, in agreement with the order predicted by a density functional calculation. PMID: 20141183 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3263383 Mon, 08 Feb 2010 00:00:00 +0100 3263383 http://www.medworm.com/index.php?rid=3255504&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20136098%26dopt%3DAbstract Authors: Cohen-Karni T, Qing Q, Li Q, Fang Y, Lieber CM Nanowire field-effect transistors (NW-FETs) have been shown to be powerful building blocks for nanoscale bioelectronic interfaces with cells and tissue due to their excellent sensitivity and their capability to form strongly coupled interfaces with cell membranes. Graphene has also been shown to be an attractive building block for nanoscale electronic devices, although little is known about its interfaces with cells and tissue. Here we report the first studies of graphene field effect transistors (Gra-FETs) as well as combined Gra- and NW-FETs interfaced to electrogenic cells. Gra-FET conductance signals recorded from spontaneously beating embryonic chicken cardiomyocytes yield well-defined extracellular signals with signal-to-noi... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3255504 Fri, 05 Feb 2010 00:00:00 +0100 3255504 http://www.medworm.com/index.php?rid=3245890&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131918%26dopt%3DAbstract Authors: Cha JJ, Williams JR, Kong D, Meister S, Peng H, Bestwick AJ, Gallagher P, Goldhaber-Gordon D, Cui Y A simple surface band structure and a large bulk band gap have allowed Bi(2)Se(3) to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi(2)Se(3) in nanostructures is advantageous because of the high surface-to-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245890 Fri, 05 Feb 2010 00:00:00 +0100 3245890 http://www.medworm.com/index.php?rid=3245889&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131919%26dopt%3DAbstract Authors: Unterreithmeier QP, Faust T, Manus S, Kotthaus JP An integrable on-chip displacement transduction of nanomechenical motion is developed that senses the modulation of the optical near-field of an illuminated vibrating string with a nearby Schottky photodiode. This scheme poses no restrictions on resonator material and avoids additional damping. The achieved sensitivity of 1 pm/Hz(1/2) enables the detection of Brownian motion of our mechanical resonators at room temperature. Implementing a feedback scheme of the detected signal into the electrical actuation, we demonstrate self-oscillation. PMID: 20131919 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245889 Fri, 05 Feb 2010 00:00:00 +0100 3245889 http://www.medworm.com/index.php?rid=3245895&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131810%26dopt%3DAbstract Authors: Finkler A, Segev Y, Myasoedov Y, Rappaport ML, Ne'eman L, Vasyukov D, Zeldov E, Huber ME, Martin J, Yacoby A A nanometer-sized superconducting quantum interference device (nanoSQUID) is fabricated on the apex of a sharp quartz tip and integrated into a scanning SQUID microscope. A simple self-aligned fabrication method results in nanoSQUIDs with diameters down to 100 nm with no lithographic processing. An aluminum nanoSQUID with an effective area of 0.034 mum(2) displays flux sensitivity of 1.8 x 10(-6) Phi(0)/Hz(1/2) and operates in fields as high as 0.6 T. With projected spin sensitivity of 65 mu(B)/Hz(1/2) and high bandwidth, the SQUID on a tip is a highly promising probe for nanoscale magnetic imaging and spectroscopy. PMID: 20131810 [PubMed - as supplied by publisher]... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245895 Thu, 04 Feb 2010 00:00:00 +0100 3245895 http://www.medworm.com/index.php?rid=3245894&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131812%26dopt%3DAbstract We present S-parameter measurements performed on a matrix consisting of 70 InAs nanowire MOSFETs, which have a gate length of about 100 nm. The highest unity current gain cutoff frequency, f(t), extracted from these measurements is 7.4 GHz and the maximum frequency of oscillation, f(max), is higher than 20 GHz. This demonstrates that this is a viable technique for fabricating high-frequency integrated circuits consisting of vertical nanowires. PMID: 20131812 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245894 Thu, 04 Feb 2010 00:00:00 +0100 3245894 http://www.medworm.com/index.php?rid=3245893&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131813%26dopt%3DAbstract Authors: Song YJ, Lee K, Kim SH, Choi BY, Yu J, Kuk Y We mapped spatially varying intramolecular electronic structures on a pentacene-gold interface using scanning tunneling spectroscopy. Along with ab initio calculations based on density functional theory, we found that the directional nature of the d orbitals of Au atoms plays an important role in the interaction at the pentacene-gold contact. The gold-induced interface states are broadened and shifted by various pentacene-gold distances determined by the various registries of a pentacene molecule on a gold substrate. PMID: 20131813 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245893 Thu, 04 Feb 2010 00:00:00 +0100 3245893 http://www.medworm.com/index.php?rid=3245892&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131863%26dopt%3DAbstract Authors: Montazeri M, Fickenscher M, Smith LM, Jackson HE, Yarrison-Rice J, Kang JH, Gao Q, Tan HH, Jagadish C, Guo Y, Zou J, Pistol ME, Pryor CE Highly strained GaAs/GaP nanowires of excellent optical quality were grown with 50 nm diameter GaAs cores and 25 nm GaP shells. Photoluminescence from these nanowires is observed at energies dramatically shifted from the unstrained GaAs free exciton emission energy by 260 meV. Using Raman scattering, we show that it is possible to separately measure the degree of compressive and shear strain of the GaAs core and show that the Raman response of the GaP shell is consistent with tensile strain. The Raman and photoluminescence measurement are both on good agreement with 8 band k.p calculations. This result opens up new possibilities for engineeri... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245892 Thu, 04 Feb 2010 00:00:00 +0100 3245892 http://www.medworm.com/index.php?rid=3245891&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20131909%26dopt%3DAbstract We present a comprehensive nucleation model to explain the formation of these markedly different crystal phases under these growth conditions. Critical to achieving phase purity are changes in surface energy of the nanowire side facets, which in turn are controlled by the basic growth parameters of temperature and V/III ratio. This ability to tune crystal structure between twin-free zinc blende and stacking-fault-free wurtzite not only will enhance the performance of nanowire devices but also opens new possibilities for engineering nanowire devices, without restrictions on nanowire diameters or doping. PMID: 20131909 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245891 Thu, 04 Feb 2010 00:00:00 +0100 3245891 http://www.medworm.com/index.php?rid=3245896&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20128610%26dopt%3DAbstract Authors: Chen KP, Drachev VP, Borneman JD, Kildishev AV, Shalaev VM The effect of grain boundaries on the electron relaxation rate is significant even for large area noble metal films and more so for plasmonic nanostructures. Optical spectroscopy and X-ray diffraction show a substantial improvement in plasmon resonance quality for square-particle nanoantennas after annealing due to an enlarged grain size from 22 to 40 nm and improved grain boundaries described by the electron reflection coefficient. The electron relaxation rate due to the grains is shown to decrease by a factor of 3.2. PMID: 20128610 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3245896 Wed, 03 Feb 2010 00:00:00 +0100 3245896 http://www.medworm.com/index.php?rid=3239917&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121193%26dopt%3DAbstract Authors: Liao J, Agustsson JS, Wu S, Schönenberger C, Calame M, Leroux Y, Mayor M, Jeannin O, Ran YF, Liu SX, Decurtins S Redox-active dithiolated tetrathiafulvalene derivatives (TTFdT) were inserted in two-dimensional nanoparticle arrays to build interlinked networks of molecular junctions. Upon oxidation of the TTFdT to the dication state, we observed a conductance increase of the networks by up to 1 order of magnitude. Successive oxidation and reduction cycles demonstrated a clear switching behavior of the molecular junction conductance. These results show the potential of interlinked nanoparticle arrays as chemical sensors. PMID: 20121193 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239917 Tue, 02 Feb 2010 00:00:00 +0100 3239917 http://www.medworm.com/index.php?rid=3239916&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121212%26dopt%3DAbstract Authors: Marsh RA, Hodgkiss JM, Albert-Seifried S, Friend RH We employ sub-picosecond TA spectroscopy on operating P3HT:PCBM devices to probe the effect of annealing on charge transfer dynamics and nanoscale morphology. Our measurement configuration allows us to remove the effect of high excitation densities that would otherwise dominate. Charge transfer in pristine P3HT:PCBM devices proceeds on a sub-picosecond time scale, implying molecular level intermixing and explaining the more localized character of excitons and charges. In annealed devices, annealing results in diffusion-limited charge generation with a half-life time of approximately 3 ps, complete only after 30 ps. This is the result of exclusion of PCBM molecules and ordering of P3HT domains and is correlated with improved p... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239916 Tue, 02 Feb 2010 00:00:00 +0100 3239916 http://www.medworm.com/index.php?rid=3239915&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121238%26dopt%3DAbstract Authors: Xu Z, Yang X, Yang Z Here we report a larger-scale atomic-level molecular dynamics (MD) simulation for the self-assembly of sodium dodecyl sulfate (SDS) surfactant on single-walled carbon nanotube (SWNT) surfaces and the interaction between supramolecular SDS/SWNT aggregates. We make an effort to address several important problems in regard to carbon nanotube dispersion/separation. At first, the simulation provides comprehensive direct evidence for SDS self-assembly structures on carbon nanotube surfaces, which can help to clarify the relevant debate over the exact adsorption structure. We also, for the first time, simulated the potential of mean force (PMF) between two SWNTs embedded in SDS surfactant micelles. A novel unified PMF approach has been applied to reveal various c... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239915 Tue, 02 Feb 2010 00:00:00 +0100 3239915 http://www.medworm.com/index.php?rid=3239914&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121259%26dopt%3DAbstract Authors: Chan TL, Chelikowsky JR The ability to control the diffusion of dopants or impurities is a controlling factor in the functionalization of materials used in devices both at the macro- and nanoscales. At the nanoscale, manipulating diffusion of dopants is complicated by a number of factors such as the role of quantum confinement and the large surface to volume ratio. Here we examine Li in Si nanostructures, as atoms with low atomic mass such as Li can be used as a carrier for energy storage with high specific energy capacity. Specifically, Li-ion batteries with specific energy capacity as high as 4200 mA h g(-1) using Si nanowires as anodes have been achieved. Using ab initio calculations, we determine how the factors of size and dimensionality can be used to achieve an optimal ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239914 Tue, 02 Feb 2010 00:00:00 +0100 3239914 http://www.medworm.com/index.php?rid=3239922&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121062%26dopt%3DAbstract Authors: Jiang Z, Lin XM, Sprung M, Narayanan S, Wang J Critical photonic, electronic, and magnetic applications of two-dimensional nanocrystal superlattices often require nanostructures in perfect single-crystal phases with long-range order and limited defects. Here we discovered a crystalline phase with quasi-long-range positional order for two-dimensional nanocrystal superlattice domains self-assembled at the liquid-air interface during droplet evaporation, using in situ time-resolved X-ray scattering along with rigorous theories on two dimensional crystal structures. Surprisingly, it was observed that drying these superlattice domains preserved only an orientational order but not a long-range positional order, also supported by quantitative analysis of transmission electron microsc... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239922 Mon, 01 Feb 2010 00:00:00 +0100 3239922 http://www.medworm.com/index.php?rid=3239921&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121064%26dopt%3DAbstract We report a comprehensive study of the gate-induced electromodulated transmittance of infrared light by single-walled carbon nanotube (SWNT) thin films. The observed electromodulation is significantly enhanced by utilizing large diameter SWNTs, increasing the ratio of semiconducting to metal SWNTs, and by decreasing the SWNT film thickness. The amplitude of the effect reported herein ( approximately 7%) is more than an order of magnitude larger than in previous SWNT thin film solid state devices. PMID: 20121064 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239921 Mon, 01 Feb 2010 00:00:00 +0100 3239921 http://www.medworm.com/index.php?rid=3239920&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121107%26dopt%3DAbstract Authors: Wickersham CE, Cash KJ, Pfeil SH, Bruck I, Kaplan DL, Plaxco KW, Lipman EA Optical encoders are commonly used in macroscopic machines to make precise measurements of distance and velocity by translating motion into a periodic signal. Here we show how Forster resonance energy transfer can be used to implement this technique at the single-molecule scale. We incorporate a series of acceptor dye molecules into self-assembling DNA, and the periodic signal resulting from unhindered motion of a donor-labeled molecular motor provides nanometer-scale resolution in milliseconds. PMID: 20121107 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239920 Mon, 01 Feb 2010 00:00:00 +0100 3239920 http://www.medworm.com/index.php?rid=3239919&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121163%26dopt%3DAbstract Authors: Trambly de Laissardière G, Mayou D, Magaud L For Dirac electrons the Klein paradox implies that the confinement is difficult to achieve with an electrostatic potential although it can be of great importance for graphene-based devices. Here, ab initio and tight-binding approaches are combined and show that the wave function of Dirac electrons can be localized in rotated graphene bilayers due to the Moire pattern. This localization of wave function is maximum in the limit of the small rotation angle between the two layers. PMID: 20121163 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239919 Mon, 01 Feb 2010 00:00:00 +0100 3239919 http://www.medworm.com/index.php?rid=3239918&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20121164%26dopt%3DAbstract Authors: Murphy-Armando F, Fagas G, Greer JC The role of reduced dimensionality and of the surface on electron-phonon (e-ph) coupling in silicon nanowires is determined from first principles. Surface termination and chemistry is found to have a relatively small influence, whereas reduced dimensionality fundamentally alters the behavior of deformation potentials. As a consequence, electron coupling to "breathing modes" emerges that cannot be described by conventional treatments of e-ph coupling. The consequences for physical properties such as scattering lengths and mobilities are significant: the mobilities for [110] grown wires are 6 times larger than those for [100] wires, an effect that cannot be predicted without the form we find for Si nanowire deformation potentials. PMID: 20... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3239918 Mon, 01 Feb 2010 00:00:00 +0100 3239918 http://www.medworm.com/index.php?rid=3232023&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20112921%26dopt%3DAbstract Authors: Hwang E, Smolyaninov II, Davis CC We experimentally demonstrate the enhancement of fluorescence from quantum dots excited by interaction with surface plasmon polaritons on nanostructured metal surfaces. The relationship between observed enhancement and geometrical factors of the surface structure has been used to explore the behavior of quantum dots on different substrates. Imaging using standard fluorescence optical microscopy clearly demonstrates a strong dependence of fluorescence enhancement on fundamental parameters for periodic surface structures. PMID: 20112921 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3232023 Fri, 29 Jan 2010 00:00:00 +0100 3232023 http://www.medworm.com/index.php?rid=3232022&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20112928%26dopt%3DAbstract Authors: Luo Z, Somers LA, Dan Y, Ly T, Kybert NJ, Mele EJ, Johnson AT We observe that gold atoms deposited by physical vapor deposition onto few-layer graphenes condense upon annealing to form nanoparticles with an average diameter that is determined by the graphene film thickness. The data are well described by a theoretical model in which the electrostatic interactions arising from charge transfer between the graphene and the gold particle limit the size of the growing nanoparticles. The model predicts a nanoparticle size distribution characterized by a mean diameter D that follows a D proportional, variant m(1/3) scaling law where m is the number of carbon layers in the few-layer graphene film. PMID: 20112928 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3232022 Fri, 29 Jan 2010 00:00:00 +0100 3232022 http://www.medworm.com/index.php?rid=3225131&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20108926%26dopt%3DAbstract We report a one-step direct transfer technique for the fabrication of functional nanoelectronic devices using pristine single-walled carbon nanotubes (SWNTs). Suspended SWNTs grown by the chemical vapor deposition (CVD) method are aligned and directly transferred onto prepatterned device electrodes at ambient temperature. Using this technique, we successfully fabricated SWNT electromechanical resonators with gate-tunable resonance frequencies. A fully suspended SWNT p-n diode has also been demonstrated with the diode ideality factor equal to 1. Our method eliminates the organic residues on SWNTs resulting from conventional lithography and solution processing. The results open up opportunities for the fundamental study of electron transport physics in ultraclean SWNTs and for room temperatu... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3225131 Thu, 28 Jan 2010 00:00:00 +0100 3225131 http://www.medworm.com/index.php?rid=3225130&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20108927%26dopt%3DAbstract Authors: Lee TI, Choi WJ, Moon KJ, Choi JH, Kar JP, Das SN, Kim YS, Baik HK, Myoung JM In order for recently developed advanced nanowire (NW) devices(1-5) to be produced on a large scale, high integration of the separately fabricated nanoscale devices into intentionally organized systems is indispensible. We suggest a unique fabrication route for semiconductor NW electronics. This route provides a high yield and a large degree of freedom positioning the device on the substrate. Hence, we can achieve not only a uniform performance of Si NW devices with high fabrication yields, suppressing device-to-device variation, but also programmable integration of the NWs. Here, keeping pace with recent progress of direct-writing circuitry,(6-8) we show the flexibility of our approach through the i... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3225130 Thu, 28 Jan 2010 00:00:00 +0100 3225130 http://www.medworm.com/index.php?rid=3225129&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20108946%26dopt%3DAbstract Authors: Schwind M, Zhdanov VP, Zorić I, Kasemo B Using the localized surface plasmon resonance as a probe in solid and liquid Sn nanoparticles of 107 nm diameter and 52 nm height, we have studied their kinetics of melting and freezing at temperature ramps and, for the first time, at fixed temperatures. During temperature ramps, the kinetics exhibit distinct hysteresis. The melting occurs near the bulk melting point while the freezing is observed at much lower temperatures so that the undercooling interval is approximately 130 K. The time scale of the freezing kinetics measured at different fixed temperatures rapidly decreases as the latter are lowered. All these findings have been quantitatively described by assuming the nucleation to occur on the edges of nanoparticles and emp... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3225129 Thu, 28 Jan 2010 00:00:00 +0100 3225129 http://www.medworm.com/index.php?rid=3225128&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20108969%26dopt%3DAbstract Authors: Garnett E, Yang P Thin-film structures can reduce the cost of solar power by using inexpensive substrates and a lower quantity and quality of semiconductor material. However, the resulting short optical path length and minority carrier diffusion length necessitates either a high absorption coefficient or excellent light trapping. Semiconducting nanowire arrays have already been shown to have low reflective losses compared to planar semiconductors, but their light-trapping properties have not been measured. Using optical transmission and photocurrent measurements on thin silicon films, we demonstrate that ordered arrays of silicon nanowires increase the path length of incident solar radiation by up to a factor of 73. This extraordinary light-trapping path length enhancement fac... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3225128 Thu, 28 Jan 2010 00:00:00 +0100 3225128 http://www.medworm.com/index.php?rid=3221130&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20104855%26dopt%3DAbstract We report a first-principles study of hydrogen storage media consisting of calcium atoms and graphene-based nanostructures. We find that Ca atoms prefer to be individually adsorbed on the zigzag edge of graphene with a Ca-Ca distance of 10 A without clustering of the Ca atoms, and up to six H(2) molecules can bind to a Ca atom with a binding energy of approximately 0.2 eV/H(2). A Ca-decorated zigzag graphene nanoribbon (ZGNR) can reach the gravimetric capacity of approximately 5 wt % hydrogen. We also consider various edge geometries of the graphene for Ca dispersion. PMID: 20104855 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221130 Wed, 27 Jan 2010 00:00:00 +0100 3221130 http://www.medworm.com/index.php?rid=3221129&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20104856%26dopt%3DAbstract Authors: Chen H, Wang H, Zhang XH, Lee CS, Lee ST Silicon nanowires (SiNWs) having curved structures may have unique advantages in device fabrication. However, no methods are available to prepare curved SiNWs controllably. In this work, we report the preparation of three types of single-crystal SiNWs with various turning angles via metal-assisted chemical etching using (111)-oriented silicon wafers near room temperature. The zigzag SiNWs are single crystals and can be p- or n-doped using corresponding Si wafer as substrate. The controlled growth direction is attributed to the preferred movement of Ag nanoparticles along 001 and other directions in Si wafer. Our results demonstrate that metal-assisted chemical etching may be a viable approach to fabricate SiNWs with desired turning angl... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221129 Wed, 27 Jan 2010 00:00:00 +0100 3221129 http://www.medworm.com/index.php?rid=3221128&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20104878%26dopt%3DAbstract Authors: Baranov D, Fiore A, van Huis M, Giannini C, Falqui A, Lafont U, Zandbergen H, Zanella M, Cingolani R, Manna L Arranging anisotropic nanoparticles into ordered assemblies remains a challenging quest requiring innovative and ingenuous approaches. The variety of interactions present in colloidal solutions of nonspherical inorganic nanocrystals can be exploited for this purpose. By tuning depletion attraction forces between hydrophobic colloidal nanorods of semiconductors, dispersed in an organic solvent, these could be assembled into 2D monolayers of close-packed hexagonally ordered arrays directly in solution. Once formed, these layers could be fished onto a substrate, and sheets of vertically standing rods were fabricated, with no additional external bias applied. Alternatively... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221128 Wed, 27 Jan 2010 00:00:00 +0100 3221128 http://www.medworm.com/index.php?rid=3221134&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20102185%26dopt%3DAbstract Authors: Hällström W, Lexholm M, Suyatin DB, Hammarin G, Hessman D, Samuelson L, Montelius L, Kanje M, Prinz CN We used epitaxially grown monodisperse nanowire arrays to measure cellular forces with a spatial resolution of 1 mum. Nerve cells were cultured on the array and cellular forces were calculated from the displacement of the nanowire tips. The measurements were done in situ on live cells using confocal microscopy. Forces down to 15 pN were measured on neural growth cones, showing that this method can be used to study the fine details of growth-cone dynamics. PMID: 20102185 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221134 Tue, 26 Jan 2010 00:00:00 +0100 3221134 http://www.medworm.com/index.php?rid=3221133&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20102189%26dopt%3DAbstract Authors: Qi Y, Jafferis NT, Lyons K, Lee CM, Ahmad H, McAlpine MC The development of a method for integrating highly efficient energy conversion materials onto stretchable, biocompatible rubbers could yield breakthroughs in implantable or wearable energy harvesting systems. Being electromechanically coupled, piezoelectric crystals represent a particularly interesting subset of smart materials that function as sensors/actuators, bioMEMS devices, and energy converters. Yet, the crystallization of these materials generally requires high temperatures for maximally efficient performance, rendering them incompatible with temperature-sensitive plastics and rubbers. Here, we overcome these limitations by presenting a scalable and parallel process for transferring crystalline piezoelectric nano... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221133 Tue, 26 Jan 2010 00:00:00 +0100 3221133 http://www.medworm.com/index.php?rid=3221132&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20102190%26dopt%3DAbstract We report the synthesis and photoelectrochemical (PEC) studies of TiO(2) nanoparticles and nanowires simultaneously doped with nitrogen and sensitized with CdSe quantum dots (QDs). These novel nanocomposite structures have been applied successfully as photoanodes for PEC hydrogen generation using Na(2)S and Na(2)SO(3) as sacrificial reagents. We observe significant enhanced photoresponse in these nanocomposites compared to N-doped TiO(2) or CdSe QD sensitized TiO(2). The enhancement is attributed to the synergistic effect of CdSe sensitization and N-doping that facilitate hole transfer/transport from CdSe to TiO(2) through oxygen vacancy states (V(o)) mediated by N-doping. The results demonstrate the importance of designing and manipulating the energy band alignment in composite nanomateri... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221132 Tue, 26 Jan 2010 00:00:00 +0100 3221132 http://www.medworm.com/index.php?rid=3221131&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20102212%26dopt%3DAbstract We report laterally and vertically phase-separated thin film structures in conjugated polymer blends created by polymer molecular weight variation. We find that micrometer-scale lateral phase separation is critical in achieving high initial device efficiency of light-emitting diodes, whereas improved balance of charge carrier mobilities and film thickness uniformity are important in maintaining high efficiency at high voltages. The optoelectronic properties of these blend thin films and devices are strongly influenced by the polymer chain order/disorder and the interface state formed at polymer/polymer heterojunctions. PMID: 20102212 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3221131 Tue, 26 Jan 2010 00:00:00 +0100 3221131 http://www.medworm.com/index.php?rid=3213291&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20099876%26dopt%3DAbstract Authors: Chang C, Tran VH, Wang J, Fuh YK, Lin L Nanogenerators capable of converting energy from mechanical sources to electricity with high effective efficiency using low-cost, nonsemiconducting, organic nanomaterials are attractive for many applications, including energy harvesters. In this work, near-field electrospinning is used to direct-write poly(vinylidene fluoride) (PVDF) nanofibers with in situ mechanical stretch and electrical poling characteristics to produce piezoelectric properties. Under mechanical stretching, nanogenerators have shown repeatable and consistent electrical outputs with energy conversion efficiency an order of magnitude higher than those made of PVDF thin films. The early onset of the nonlinear domain wall motions behavior has been identified as one mecha... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3213291 Mon, 25 Jan 2010 00:00:00 +0100 3213291 http://www.medworm.com/index.php?rid=3213292&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20095628%26dopt%3DAbstract Authors: Doll JD, Pilania G, Ramprasad R, Papadimitrakopoulos F The role of oxygen in directing the low temperature (125 degrees C), redox-assisted, unidimensional and unidirectional growth of CdSe nanocrystals (NCs) was investigated. In the presence of oxygen, CdSe quantum dots grow selectively along their c axis with little to no change in their width. Reduction of oxygen in the growth medium results in three-dimensional growth. Moreover the one-dimensional growth was found to occur only from one of the two inequivalent polar (0001) facets, as supported by the seeded growth of Cd(x)Hg(1-x)Se onto CdSe seeds. This is in agreement with density functional theory simulations, which indicate that due to selective oxygen passivation growth can occur only along the [0001] direction. The abi... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3213292 Fri, 22 Jan 2010 00:00:00 +0100 3213292 http://www.medworm.com/index.php?rid=3201261&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20092328%26dopt%3DAbstract Authors: Kim H, Park J, Cho SW, Lee SY, Kang M, Lee B The generation of surface plasmon vortices with arbitrary higher order vortex topological charges with novel plasmonic vortex lens is experimentally demonstrated. It is shown that the polarization sensitivity of the plasmonic vortex lens can be utilized for the dynamic switching of the surface plasmon vortices with different topological charges. A simple algebraic rule related to the vortex topological charge change in the dynamic switching is formulated, and its proof is provided with theory and experiment. The synthesis and dynamic switching of higher order surface plasmon vortices have profound potential in optical trapping, optical data storage, and other related fields. PMID: 20092328 [PubMed - as supplied by publisher] (So... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3201261 Thu, 21 Jan 2010 00:00:00 +0100 3201261 http://www.medworm.com/index.php?rid=3201260&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20092332%26dopt%3DAbstract Authors: Xia F, Farmer DB, Lin YM, Avouris P Graphene is considered to be a promising candidate for future nanoelectronics due to its exceptional electronic properties. Unfortunately, the graphene field-effect transistors (FETs) cannot be turned off effectively due to the absence of a band gap, leading to an on/off current ratio typically around 5 in top-gated graphene FETs. On the other hand, theoretical investigations and optical measurements suggest that a band gap up to a few hundred millielectronvolts can be created by the perpendicular E-field in bilayer graphenes. Although previous carrier transport measurements in bilayer graphene transistors did indicate a gate-induced insulating state at temperatures below 1 K, the electrical (or transport) band gap was estimated to be a few ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3201260 Thu, 21 Jan 2010 00:00:00 +0100 3201260 http://www.medworm.com/index.php?rid=3197634&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20088589%26dopt%3DAbstract We present "Print-and-Peel", a high-throughput method to generate multicomponent biomolecular arrays with sub-100 nm nanoscale feature width. An inkjet printer is first aligned to a parylene template containing nanoscale openings. After printing, the parylene is peeled off to reveal uniformly patterned nanoscale features, despite the imperfect morphologies of the original inkjet spots. We further patterned combinatorial nanoarrays by performing a second print-run superimposed over the first, thereby extending the multiplexing capability of the technique. PMID: 20088589 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197634 Wed, 20 Jan 2010 00:00:00 +0100 3197634 http://www.medworm.com/index.php?rid=3197633&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20088590%26dopt%3DAbstract Authors: Singer A, Wanunu M, Morrison W, Kuhn H, Frank-Kamenetskii M, Meller A We demonstrate a purely electrical method for the single-molecule detection of specific DNA sequences, achieved by hybridizing double-stranded DNA (dsDNA) with peptide nucleic acid (PNA) probes and electrophoretically threading the DNA through sub-5 nm silicon nitride pores. Bis-PNAs were used as the tagging probes in order to achieve high affinity and sequence specificity. Sequence detection is performed by reading the ion current traces of individual translocating DNA molecules, which display a characteristic secondary blockade level, absent in untagged molecules. The potential for barcoding DNA is demonstrated through nanopore analysis of once-tagged and twice-tagged DNA at different locations on the same... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197633 Wed, 20 Jan 2010 00:00:00 +0100 3197633 http://www.medworm.com/index.php?rid=3197641&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085271%26dopt%3DAbstract Authors: Delaney P, Greer JC, Larsson JA The nitrogen-vacancy (NV) center in diamond has shown great promise for quantum information due to the ease of initializing the qubit and of reading out its state. Here we show the leading mechanism for these effects gives results opposite from experiment; instead both must rely on new physics. Furthermore, NV centers fabricated in nanometer-sized diamond clusters are stable, motivating a bottom-up qubit approach, with the possibility of quite different optical properties to bulk. PMID: 20085271 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197641 Tue, 19 Jan 2010 00:00:00 +0100 3197641 http://www.medworm.com/index.php?rid=3197638&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085284%26dopt%3DAbstract Authors: Vitali L, Ohmann R, Kern K, Garcia-Lekue A, Frederiksen T, Sanchez-Portal D, Arnau A Molecular junctions have been characterized to determine the influence of the metal contact formation in the electron transport process through a single molecule. With inelastic electron tunneling spectroscopy and first-principles calculations, the vibration modes of a carbon monoxide molecule have been surveyed as a function of the distance from a copper electrode with unprecedented accuracy. We observe a continuous but nonlinear blue shift of the frustrated rotation mode in tunneling with decreasing distance followed by an abrupt softening upon contact formation. This indicates that the presence of the metal electrode sensibly alters the structural and conductive properties of the junction e... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197638 Tue, 19 Jan 2010 00:00:00 +0100 3197638 http://www.medworm.com/index.php?rid=3197637&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085344%26dopt%3DAbstract Authors: Chan-Thaw CE, Villa A, Katekomol P, Su D, Thomas A, Prati L An important goal in the preparation of highly active supported metal particles is the enhancement of the metal support interaction, providing a more stable catalyst, especially for liquid phase reactions as the leaching and reconstruction of the active phase causes deactivation. In this work, a covalent triazine framework (CTF) as support for Pd nanoparticles is compared to activated carbon (AC), the typical support used in liquid phase reactions. The results indicate that the presence of the N-heterocyclic moieties on the surface of the frameworks is beneficial for improving the stability of Pd nanoparticles during the liquid phase glycerol oxidation. Pd/CTF showed better activity and in particular better stability ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197637 Tue, 19 Jan 2010 00:00:00 +0100 3197637 http://www.medworm.com/index.php?rid=3197636&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085345%26dopt%3DAbstract Authors: Dresselhaus MS, Jorio A, Hofmann M, Dresselhaus G, Saito R Raman spectroscopy is here shown to provide a powerful tool to differentiate between two different sp(2) carbon nanostructures (carbon nanotubes and graphene) which have many properties in common and others that differ. Emphasis is given to the richness of both carbon nanostructures as prototype examples of nanostructured materials. A glimpse toward future developments in this field is presented. PMID: 20085345 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197636 Tue, 19 Jan 2010 00:00:00 +0100 3197636 http://www.medworm.com/index.php?rid=3197635&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20085369%26dopt%3DAbstract We report on a mass-spectrometry (time-of-flight secondary ion mass spectrometry, TOF-SIMS) based method for multiplexed DNA detection utilizing a random array, where the lipid composition of small unilamellar liposomes act as chemical barcodes to identify unique DNA target sequences down to the single molecule level. In a sandwich format, suspended target-DNA to be detected mediates the binding of capture-DNA modified liposomes to surface-immobilized probe-DNA. With the lipid composition of each liposome encoding a unique target-DNA sequence, TOF-SIMS analysis was used to determine the chemical fingerprint of the bound liposomes. Using high-resolution TOF-SIMS imaging, providing sub-200 nm spatial resolution, single DNA targets could be detected and identified via the chemical fingerprint... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3197635 Tue, 19 Jan 2010 00:00:00 +0100 3197635 http://www.medworm.com/index.php?rid=3189597&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20078065%26dopt%3DAbstract Authors: Cao L, Fan P, Vasudev AP, White JS, Yu Z, Cai W, Schuller JA, Fan S, Brongersma ML Photovoltaic (PV) cells can serve as a virtually unlimited clean source of energy by converting sunlight into electrical power. Their importance is reflected in the tireless efforts that have been devoted to improving the electrical and structural properties of PV materials. More recently, photon management (PM) has emerged as a powerful additional means to boost energy conversion efficiencies. Here, we demonstrate an entirely new PM strategy that capitalizes on strong broad band optical antenna effects in one-dimensional semiconductor nanostructures to dramatically enhance absorption of sunlight. We show that the absorption of sunlight in Si nanowires (Si NWs) can be significantly enhanced over... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3189597 Fri, 15 Jan 2010 00:00:00 +0100 3189597 http://www.medworm.com/index.php?rid=3189596&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20078068%26dopt%3DAbstract We report a new wet-chemical approach of preparing monodisperse Pt(3)Ni nanoctahedra and nanocubes terminated with {111} and {100} facets, respectively. We further show that the ORR activity on the Pt(3)Ni nanoctahedra is approximately 5-fold higher than that of nanocubes with a similar size. Comparison of ORR activity between carbon-supported Pt(3)Ni nanoctahedra and commercial Pt/C reveals that the Pt(3)Ni nanoctahedra are highly active electrocatalysts. This synthetic strategy may be extended to the preparation of other shape-controlled fuel cell electrocatalysts. PMID: 20078068 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3189596 Fri, 15 Jan 2010 00:00:00 +0100 3189596 http://www.medworm.com/index.php?rid=3189595&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20078108%26dopt%3DAbstract Authors: Park CH, Louie SG Recent measurements have shown that a continuously tunable bandgap of up to 250 meV can be generated in biased bilayer graphene [ Zhang , Y. ; et al. Nature 2009, 459 , 820 ], opening up pathway for possible graphene-based nanoelectronic and nanophotonic devices operating at room temperature. Here, we show that the optical response of this system is dominated by bound excitons. The main feature of the optical absorbance spectrum is determined by a single symmetric peak arising from excitons, a profile that is markedly different from that of an interband transition picture. Under laboratory conditions, the binding energy of the excitons may be tuned with the external bias going from zero to several tens of millielectronvolts. These novel strong excitonic behav... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3189595 Fri, 15 Jan 2010 00:00:00 +0100 3189595 http://www.medworm.com/index.php?rid=3172793&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20067277%26dopt%3DAbstract Authors: Park JU, Lee S, Unarunotai S, Sun Y, Dunham S, Song T, Ferreira PM, Alleyene AG, Paik U, Rogers JA Nearly all research in micro- and nanofabrication focuses on the formation of solid structures of materials that perform some mechanical, electrical, optical, or related function. Fabricating patterns of charges, by contrast, is a much less well explored area that is of separate and growing interesting because the associated electric fields can be exploited to control the behavior of nanoscale electronic and mechanical devices, guide the assembly of nanomaterials, or modulate the properties of biological systems. This paper describes a versatile technique that uses fine, electrified liquid jets formed by electrohydrodynamics at micro- and nanoscale nozzles to print complex patter... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172793 Tue, 12 Jan 2010 00:00:00 +0100 3172793 http://www.medworm.com/index.php?rid=3172792&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20067286%26dopt%3DAbstract Authors: Nonnenmann SS, Leaffer OD, Gallo EM, Coster MT, Spanier JE We demonstrate that ferroelectric (FE) polarizations oriented along the finite thickness direction in ultrathin films are enhanced by the introduction of extreme curvature, thereby suppressing the finite-size-driven evolution of the FE phase transition temperature T(C). The measured responses within individual nanoshells possess magnitudes nearly three times that for their planar counterparts while exhibiting finite curvature-dependent offsets in FE switching hystereses. In stark contrast to the expected scaling of a depression of T(C) with inverse thickness, results based on modified Landau-Ginzburg model calculations indicate geometric curvature-driven polarization gradients in ultrathin films result in significant i... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172792 Tue, 12 Jan 2010 00:00:00 +0100 3172792 http://www.medworm.com/index.php?rid=3172791&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20067296%26dopt%3DAbstract Authors: Neacsu CC, Berweger S, Olmon RL, Saraf LV, Ropers C, Raschke MB Focusing light to subwavelength dimensions has been a long-standing desire in optics but has remained challenging, even with new strategies based on near-field effects, polaritons, and metamaterials. The adiabatic propagation of surface plasmon polaritons (SPP) on a conical taper as proposed theoretically has recently emerged as particularly promising to obtain a nanoconfined light source at the tip. Employing grating-coupling of SPPs onto gold tips, we demonstrate plasmonic nanofocusing into a localized excitation of approximately 20 nm in size and investigate its near- and far-field behavior. For cone angles of approximately 10-20 degrees , the breakdown of the adiabatic propagation conditions is found to be loc... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172791 Tue, 12 Jan 2010 00:00:00 +0100 3172791 http://www.medworm.com/index.php?rid=3172797&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20063862%26dopt%3DAbstract Authors: Gutbrod R, Khoptyar D, Steiner M, Chizhik AM, Chizhik AI, Bär S, Meixner AJ A tightly focused radially polarized laser beam forms an unusual bimodal field distribution in an optical lambda/2-microresonator. We use a single-molecule dipole to probe the vector properties of this field distribution by tuning the resonator length with nanometer precision. Comparing calculated and experimental excitation patterns provides the three-dimensional orientation of the single-molecule dipole in the microresonator. PMID: 20063862 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172797 Mon, 11 Jan 2010 00:00:00 +0100 3172797 http://www.medworm.com/index.php?rid=3172796&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20063863%26dopt%3DAbstract We report white light-emitting diodes fabricated with ultrasmall CdSe nanocrystals, which demonstrate electroluminescence from a size of nanocrystals (<2 nm) previously thought to be unattainable. These LEDs have excellent color characteristics, defined by their pure white CIE color coordinates (0.333, 0.333), correlated color temperatures of 5461-6007 K, and color rendering indexes as high as 96.6. The effect of high voltage on the trap states responsible for the white emission is also described. PMID: 20063863 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172796 Mon, 11 Jan 2010 00:00:00 +0100 3172796 http://www.medworm.com/index.php?rid=3172795&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20063864%26dopt%3DAbstract Authors: McConnell MD, Kraeutler MJ, Yang S, Composto RJ Multiregion and patchy optically active Janus particles were synthesized via a hierarchical self-assembly process. Gold nanoparticles were assembled on the top surfaces of nano- and submicrometer silica particles, which were selectively protected on their bottom surfaces by covalent attachment to a copolymer film. The morphologies of the gold particle layer, and the resulting optical properties of the Janus particles, were tuned by changing the surface energy between the silica and gold particles, followed by annealing. PMID: 20063864 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172795 Mon, 11 Jan 2010 00:00:00 +0100 3172795 http://www.medworm.com/index.php?rid=3172794&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20063896%26dopt%3DAbstract Authors: Varghese OK, Paulose M, Latempa TJ, Grimes CA PMID: 20063896 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3172794 Mon, 11 Jan 2010 00:00:00 +0100 3172794 http://www.medworm.com/index.php?rid=3164693&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058872%26dopt%3DAbstract Authors: Zhu L, Wang J, Zhang T, Ma L, Lim CW, Ding F, Zeng XC Inspired by strong mechanical stability of "Y"-shaped beams for building construction, we design a new class of quasi-one-dimensional graphene nanostructures, namely, tri-wing graphene (TWG) nanoribbons. TWG possesses significantly augmented mechanical stability against torsional and compression forces, and also each wing of the TWG can retain independent electronic properties of the constituent graphene nanoribbons. As such, by tailoring the wing structures, the TWGs can provide broader property tunability for nanoelectronic application. In addition, zigzag-edged TWG is a metallic ferromagnet with a large magnetic moment. When its edges are decorated with suitable chemical functional groups, a TWG can be converted to a hal... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164693 Fri, 08 Jan 2010 00:00:00 +0100 3164693 http://www.medworm.com/index.php?rid=3164692&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058873%26dopt%3DAbstract Authors: Mashoff T, Pratzer M, Geringer V, Echtermeyer TJ, Lemme MC, Liebmann M, Morgenstern M The truly two-dimensional material graphene is an ideal candidate for nanoelectromechanics due to its large strength and mobility. Here we show that graphene flakes provide natural nanomembranes of diameter down to 3 nm within its intrinsic rippling. The membranes can be lifted either reversibly or hysteretically by the tip of a scanning tunneling microscope. The clamped-membrane model including van-der-Waals and dielectric forces explains the results quantitatively. AC-fields oscillate the membranes, which might lead to a completely novel approach to controlled quantized oscillations or single atom mass detection. PMID: 20058873 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164692 Fri, 08 Jan 2010 00:00:00 +0100 3164692 http://www.medworm.com/index.php?rid=3164691&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058874%26dopt%3DAbstract Authors: Kim C, Kim HS, Qin H, Blick RH We observe Coulomb blockade in the field-emission current of a metallic island between two electrodes freely suspended by thin tunneling barriers. A third electrode serves as a gating contact to trace the Coulomb staircase of the device. Coulomb blockade is revealed at 77 K in conjunction with field emission. The measurements are in very good agreement with a theoretical model, taking into account orthodox Coulomb blockade and field emission. PMID: 20058874 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164691 Fri, 08 Jan 2010 00:00:00 +0100 3164691 http://www.medworm.com/index.php?rid=3164690&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058897%26dopt%3DAbstract Authors: Brus L To celebrate the tenth anniversary of Nano Letters, this short commentary discusses a scientific issue of current interest, increased electron-electron interactions in nanostructures. The two major factors of reduced dimensionality and low screening are analyzed. Carbon nanotubes and graphene are molecular in many of their properties and show strong electron-electron interactions. In specific circumstances, excited-state decay by exciton generation rather than phonon generation can be efficient in carbon nanotubes. PMID: 20058897 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164690 Fri, 08 Jan 2010 00:00:00 +0100 3164690 http://www.medworm.com/index.php?rid=3164689&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058898%26dopt%3DAbstract Authors: Yang SC, Kobori H, He CL, Lin MH, Chen HY, Li C, Kanehara M, Teranishi T, Gwo S We apply a nanomanipulation technique to assemble pairs of monodispersed octahedral gold nanocrystals (side length, 150 nm) along their major axes with a varying tip-to-tip separation (25-125 nm). These pairs are immobilized onto indium tin oxide coated silica substrates and studied as plasmonic dimers by polarization-selective total internal reflection (TIR) microscopy and spectroscopy. We confirm that the plasmon coupling modes with the scattering polarization along the incident light direction result from the transverse-magnetic-polarized incident light, which induces two near-field-coupled dipole moments oriented normal to the air-substrate interface. In such cases, both in-phase (antibonding) ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164689 Fri, 08 Jan 2010 00:00:00 +0100 3164689 http://www.medworm.com/index.php?rid=3164688&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20058908%26dopt%3DAbstract Authors: Vogelsang J, Cordes T, Forthmann C, Steinhauer C, Tinnefeld P In recent years different implementations of superresolution microscopy based on targeted switching (STED, GSD, and SSIM) have been demonstrated. The key elements to break the diffraction barrier are two distinct molecular states that generate a saturable nonlinear fluorescence response with respect to the excitation intensity. In this paper, we demonstrate that a nonlinearity can even be encoded in fluorescent probes, which then increase the resolution of a standard confocal microscope. This nonlinearity is achieved by an intensity dependent blocking of the resonance energy transfer between a donor and one or more acceptor fluorophores, utilizing radical anion states of the acceptor. In proof-of-principle experimen... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3164688 Fri, 08 Jan 2010 00:00:00 +0100 3164688 http://www.medworm.com/index.php?rid=3156603&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055430%26dopt%3DAbstract Authors: Sharma R, Baik JH, Perera CJ, Strano MS The reactivity of graphene and its various multilayers toward electron transfer chemistries with 4-nitrobenzene diazonium tetrafluoroborate is probed by Raman spectroscopy after reaction on-chip. Single graphene sheets are found to be almost 10 times more reactive than bi- or multilayers of graphene according to the relative disorder (D) peak in the Raman spectrum examined before and after chemical reaction in water. A model whereby electron puddles that shift the Dirac point locally to values below the Fermi level is consistent with the reactivity difference. Because the chemistry at the graphene edge is important for controlling its electronic properties, particularly in ribbon form, we have developed a spectroscopic test to examine th... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156603 Thu, 07 Jan 2010 00:00:00 +0100 3156603 http://www.medworm.com/index.php?rid=3156602&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055431%26dopt%3DAbstract Authors: Chen Q, Huang L, Lai YC, Grebogi C, Dietz D We carry out detailed a bifurcation analysis for a common class of electrostatically driven nanowires in a multiphysics model. A finding is that the nanoscale system can exhibit distinct chaotic states: chaos with symmetry breaking and extensive chaos possessing the full symmetry of the system. Potential applications such as nanoscale random number generator and controlling extensive chaos to achieve desirable performance are articulated. PMID: 20055431 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156602 Thu, 07 Jan 2010 00:00:00 +0100 3156602 http://www.medworm.com/index.php?rid=3156601&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055432%26dopt%3DAbstract Authors: Katira P, Hess H Nanoscale sensors enable the detection of analytes with improved signal-to-noise ratio but suffer from mass transport limitations. Molecular shuttles, assembled from, e.g., antibody-functionalized microtubules and kinesin motor proteins, can selectively capture analytes from solution and deliver the analytes to a sensor patch. This two-stage process can accelerate mass transport to nanoscale biosensors and facilitate the rapid detection of analytes. Here, the possible increase of the signal-to-noise ratio is calculated, and the optimal layout of a system which integrates active transport is determined. PMID: 20055432 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156601 Thu, 07 Jan 2010 00:00:00 +0100 3156601 http://www.medworm.com/index.php?rid=3156600&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055433%26dopt%3DAbstract Authors: Lightcap IV, Kosel TH, Kamat PV Using reduced graphene oxide (RGO) as a two-dimensional support, we have succeeded in selective anchoring of semiconductor and metal nanoparticles at separate sites. Photogenerated electrons from UV-irradiated TiO(2) are transported across RGO to reduce silver ions into silver nanoparticles at a location distinct from the TiO(2) anchored site. The ability of RGO to store and shuttle electrons, as visualized via a stepwise electron transfer process, demonstrates its capability to serve as a catalyst nanomat and transfer electrons on demand to adsorbed species. These findings pave the way for the development of next generation catalyst systems and can spur advancements in graphene-based composites for chemical and biological sensors. PMID: 200... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156600 Thu, 07 Jan 2010 00:00:00 +0100 3156600 http://www.medworm.com/index.php?rid=3156599&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055479%26dopt%3DAbstract Authors: Gentle AR, Smith GB Nanoparticles that have narrow absorption bands that lie entirely within the atmosphere's transparent window from 7.9 to 13 mum can be used to radiatively cool to temperatures that are well below ambient. Heating from incoming atmospheric radiation in the remainder of the Planck radiation spectrum, where the atmosphere is nearly "black", is reduced if the particles are dopants in infrared transmitting polymers, or in transmitting coatings on low emittance substrates. Crystalline SiC nanoparticles stand out with a surface phonon resonance from 10.5 to 13 mum clear of the atmospheric ozone band. Resonant SiO(2) nanoparticles are complementary, absorbing from 8 to 10 mum, which includes atmospheric ozone emissions. Their spectral location has made SiC nanopart... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156599 Thu, 07 Jan 2010 00:00:00 +0100 3156599 http://www.medworm.com/index.php?rid=3156581&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20055480%26dopt%3DAbstract Authors: Deutsch B, Hillenbrand R, Novotny L The control of optical fields on the nanometer scale is a central theme of plasmonics and nanophotonics. Methods for characterizing localized optical field distributions are necessary to validate theoretical predictions, to test nanofabrication procedures, and to provide feedback for design improvements. Typical methods of probing near fields (e.g., single molecule fluorescence and near-field microscopy) cannot probe both the complex-valued and vectorial nature of the field distributions. We demonstrate that a nanoparticle probe with isotropic polarizability in combination with polarization control of excitation and detection beams provides access to this information through the interaction tensor. For a sample consisting of a single nanopar... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3156581 Thu, 07 Jan 2010 00:00:00 +0100 3156581 http://www.medworm.com/index.php?rid=3149504&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050673%26dopt%3DAbstract We report on optical modes in rolled-up microtube resonators that are excited by PbS nanocrystals filled into the microtube core. Long ranging evanescent fields into the very thin walled microtubes cause strong emission of the nanocrystals into the resonator modes and a mode shift after a self-removal of the solvent. We present a method to precisely control the number, the energy and the localization of the modes along the microtube axis. PMID: 20050673 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149504 Tue, 05 Jan 2010 00:00:00 +0100 3149504 http://www.medworm.com/index.php?rid=3149503&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050674%26dopt%3DAbstract Authors: Chueh YL, Boswell CN, Yuan CW, Shin SJ, Takei K, Ho JC, Ko H, Fan Z, Haller EE, Chrzan DC, Javey A A tunable structural engineering of nanowires based on template-assisted alloying and phase segregation processes is demonstrated. The Au-Ge system, which has a low eutectic temperature and negligible solid solubility (<10(-3) atom %) of Au in Ge at low temperatures, is utilized. Depending on the Au concentration of the initial nanowires, final structures ranging from nearly periodic nanodisk patterns to core/shell and fully alloyed nanowires are produced. The formation mechanisms are discussed in detail and characterized by in situ transmission electron microscopy and energy-dispersive spectrometry analyses. Electrical measurements illustrate the metallic and semiconducting c... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149503 Tue, 05 Jan 2010 00:00:00 +0100 3149503 http://www.medworm.com/index.php?rid=3149502&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050675%26dopt%3DAbstract Authors: Ho X, Ye L, Rotkin SV, Cao Q, Unarunotai S, Salamat S, Alam MA, Rogers JA Recent studies and device demonstrations indicate that horizontally aligned arrays of linearly configured single-walled carbon nanotubes (SWNTs) can serve as an effective thin film semiconductor material, suitable for scalable use in high-performance transistors. This paper presents the results of systematic investigations of the dependence of device properties on channel length, to reveal the role of channel and contact resistance in the operation. The results indicate that, for the range of channel lengths and SWNT diameters studied here, source and drain contacts of Pd yield transistors with effectively Ohmic contacts that exhibit negligible dependence of their resistances on gate voltage. For devices... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149502 Tue, 05 Jan 2010 00:00:00 +0100 3149502 http://www.medworm.com/index.php?rid=3149501&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050676%26dopt%3DAbstract Authors: van den Hout M, Vilfan ID, Hage S, Dekker NH Solid-state nanopores can be employed to detect and study local structure along single molecules by voltage driven translocation through the nanopore. Their sensitivity and versatility can be augmented by combining them with a direct force probe, for example, optical tweezers. Such a tool could potentially be used to directly probe RNA secondary structure through the sequential unfolding of duplex regions. Here, we demonstrate the first application of such a system to the study of RNA by directly measuring the net force on individual double-stranded RNA (dsRNA) molecules. We have probed the force on dsRNA over a large range of nanopore sizes from 35 nm down to 3.5 nm and find that it decreases as the pore size is increased, in accor... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149501 Tue, 05 Jan 2010 00:00:00 +0100 3149501 http://www.medworm.com/index.php?rid=3149500&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050689%26dopt%3DAbstract Authors: Ozturk S, Hassan YA, Ugaz VM A recent report describing dramatic anomalous enhancement in mass transport properties of nanofluids (>1000% increase in tracer dye diffusivity) has excited intense interest, but the findings have yet to be conclusively confirmed or explained. Here we investigate these phenomena using a microfluidic approach to directly probe tracer diffusion so that interactions between the suspension's principle components (nanoparticles, surfactant, and dye) can be clearly identified. Under conditions matching previously reported studies, we unexpectedly observe spontaneous formation of highly focused and intensely fluorescent plumes at the interface between fluid streams, suggesting strong complexation interactions between the dye and nanoparticles. These ph... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149500 Tue, 05 Jan 2010 00:00:00 +0100 3149500 http://www.medworm.com/index.php?rid=3149499&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050691%26dopt%3DAbstract Authors: Hu L, Pasta M, Mantia FL, Cui L, Jeong S, Deshazer HD, Choi JW, Han SM, Cui Y Recently there is strong interest in lightweight, flexible, and wearable electronics to meet the technological demands of modern society. Integrated energy storage devices of this type are a key area that is still significantly underdeveloped. Here, we describe wearable power devices using everyday textiles as the platform. With an extremely simple "dipping and drying" process using single-walled carbon nanotube (SWNT) ink, we produced highly conductive textiles with conductivity of 125 S cm(-1) and sheet resistance less than 1 Omega/sq. Such conductive textiles show outstanding flexibility and stretchability and demonstrate strong adhesion between the SWNTs and the textiles of interest. Supercapacit... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149499 Tue, 05 Jan 2010 00:00:00 +0100 3149499 http://www.medworm.com/index.php?rid=3149498&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050692%26dopt%3DAbstract Authors: Yoo Y, Seo K, Han S, Varadwaj KS, Kim HY, Ryu JH, Lee HM, Ahn JP, Ihee H, Kim B We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO(3) substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations. PMID: 20050692 [PubMed - as suppl... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149498 Tue, 05 Jan 2010 00:00:00 +0100 3149498 http://www.medworm.com/index.php?rid=3149497&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20050693%26dopt%3DAbstract Authors: Klontzas E, Tylianakis E, Froudakis GE Hydrogen storage properties have been studied on newly designed three-dimensional covalent-organic framework (3D-COF). The design of these materials was based on the ctn network of the ultralow density COF-102. The structures were optimized by multiscale techniques and the optimized structures were checked for their storage capacities by grand canonical Monte Carlo simulations. Our simulations demonstrate that the gravimetric uptake of one of these new COFs can overpass the value of 25 wt % in 77 K and reach the Department of Energy's target of 6 wt % in room temperature, classifying them between the top hydrogen storage materials. PMID: 20050693 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3149497 Tue, 05 Jan 2010 00:00:00 +0100 3149497 http://www.medworm.com/index.php?rid=3143111&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20044838%26dopt%3DAbstract Authors: Ford AC, Chuang S, Ho JC, Chueh YL, Fan Z, Javey A Gas phase p-doping of InAs nanowires with Zn atoms is demonstrated as an effective route for enabling postgrowth dopant profiling of nanostructures. The versatility of the approach is demonstrated by the fabrication of high-performance gated diodes and p-MOSFETs. High Zn concentrations with electrically active content of approximately 1 x 10(19) cm(-3) are achieved which is essential for compensating the electron-rich surface layers of InAs to enable heavily p-doped structures. This work could have important practical implications for the fabrication of planar and nonplanar devices based on InAs and other III-V nanostructures which are not compatible with conventional ion implantation processes that often cause severe lattice ... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3143111 Mon, 04 Jan 2010 00:00:00 +0100 3143111 http://www.medworm.com/index.php?rid=3143110&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20044840%26dopt%3DAbstract Authors: Malmström J, Christensen B, Jakobsen HP, Lovmand J, Foldbjerg R, Sørensen ES, Sutherland DS Focal adhesion development in cells adherent to surface bound fibronectin presented as 200, 500, or 1000 nm diameter circular patches or as homogeneous controls is studied by fluorescence and scanning electron microscopy. Fundamental cellular processes such as adhesion, spreading, focal adhesion and stress fiber formation are shown to be dependent on the spatial distribution of ligands at this scale. Large area samples enable the study of whole cell populations and opens for new potential applications. PMID: 20044840 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3143110 Mon, 04 Jan 2010 00:00:00 +0100 3143110 http://www.medworm.com/index.php?rid=3143109&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20044841%26dopt%3DAbstract Authors: Lee Y, Bae S, Jang H, Jang S, Zhu SE, Sim SH, Song YI, Hong BH, Ahn JH We developed means to produce wafer scale, high-quality graphene films as large as 3 in. wafer size on Ni and Cu films under ambient pressure and transfer them onto arbitrary substrates through instantaneous etching of metal layers. We also demonstrated the applications of the large-area graphene films for the batch fabrication of field-effect transistor (FET) arrays and stretchable strain gauges showing extraordinary performances. Transistors showed the hole and electron mobilities of the device of 1100 +/- 70 and 550 +/- 50 cm(2)/(V s) at drain bias of -0.75 V, respectively. The piezo-resistance gauge factor of strain sensor was approximately 6.1. These methods represent a significant step toward the real... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3143109 Mon, 04 Jan 2010 00:00:00 +0100 3143109 http://www.medworm.com/index.php?rid=3143108&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20044842%26dopt%3DAbstract Authors: Postma HW I propose a technique for reading the base sequence of a single DNA molecule using a graphene nanogap to read the DNA's transverse conductance. Because graphene is a single atom thick, single-base resolution of the conductance is readily obtained. The nonlinear current-voltage characteristic is used to determine the base type independent of nanogap-width variations that cause the current to change by 5 orders of magnitude. The expected sequencing error rate is 0% up to a nanogap width of 1.6 nm. PMID: 20044842 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3143108 Mon, 04 Jan 2010 00:00:00 +0100 3143108 http://www.medworm.com/index.php?rid=3137810&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20043661%26dopt%3DAbstract Authors: Lin H, Camacho R, Tian Y, Kaiser TE, Würthner F, Scheblykin IG Fluorescence blinking corresponding to collective quenching of up to 100 dye monomers is reported for individual J-aggregates of a perylene bisimide (PBI) dye. This implies an exciton diffusion length up to 70 nm in these one-dimensional assemblies. The number of quenched monomers was directly measured by comparing the fluorescence brightness of the J-aggregates with that of noncoupled PBI molecules. This brightness analysis technique is useful for unraveling photophysical parameters of any individual fluorescent nanosystem. PMID: 20043661 [PubMed - as supplied by publisher] (Source: Nano Letters) Nano Letters journals http://www.medworm.com/rss/comments.php?id=3137810 Thu, 31 Dec 2009 00:00:00 +0100 3137810 http://www.medworm.com/index.php?rid=3136007&cid=s_36731_174_f&fid=36731&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20041665%26dopt%3DAbstract Authors: Chae DH, Krauss B, von Klitzing K, Smet JH Phonon-carrier interactions can have significant impact on device performance. They can be probed by measuring the phonon lifetime, which reflects the interaction strength of a phonon with other quasi-particles, in particular charge carriers as well as its companion phonons. The carrier phonon and phonon-phonon contributions to the phonon lifetime can be disentangled from temperature-dependent studies. Here, we address the importance of phonon-carrier interactions in Joule-heated graphene constrictions in order to contribute to the understanding of energy dissipation in graphene-based electronic devices. We demonstrate that gapless graphene grants electron-phonon interactions uncommon significance in particular at low carrier density.... Nano Letters journals http://www.medworm.com/rss/comments.php?id=3136007 Wed, 30 Dec 2009 00:00:00 +0100 3136007