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Nano Letters

Kwang Jin Kim, James Wortman, Sung-Yup Kim, Yue Qi
Quantifying the irreversible chemical and structural changes of Si during cycling remains challenging. In this study, a continuous reactive molecular dynamics delithiation algorithm, with well-controlled potential gradient and delithiation rate, was developed and used to investigate the "natural" delithiation responses of an aluminum-oxide coated silicon thin-film. Fast delithiation led to the formation of dense Si network near the surface and nanoporosity inside the a-LixSi, resulting in 141 % volume dilation and significant amount of Li trapped inside (a-Li1...
June 20, 2017: Nano Letters
M Carmen Martínez-Velarte, Bernhard Kretz, María Moro-Lagares, Myriam H Aguirre, Trevor M Riedemann, Thomas A Lograsso, Luis Morellón, M Ricardo Ibarra, Arán Garcia-Lekue, David Serrate
We show that the chemical inhomogeneity in ternary three-dimensional topological insulators preserves the topological spin texture of their surface states against a net surface magnetization. The spin texture is that of a Dirac cone with helical spin structure in the reciprocal space, which gives rise to spin-polarized and dissipation-less charge currents. Thanks to the nontrivial topology of the bulk electronic structure, this spin texture is robust against most types of surface defects. However, magnetic perturbations break the time-reversal symmetry, enabling magnetic scattering and loss of spin coherence of the charge carriers...
June 20, 2017: Nano Letters
Lizhi Zhang, Feng Zhai, Kyung-Hwan Jin, Bin Cui, Bing Huang, Zhiming Wang, JunQiang Lu, Feng Liu
Tunable spin transport in nano devices is highly desirable to spintronics. Here, we predict existence of quantum spin Hall effects and tunable spin transport in As-graphane, based on first-principle density functional theory and tight binding calculations. Monolayer As-graphane is constituted by using As adsorbing on graphane with honeycomb H vacancies. Owing to the surface strain, monolayer As-graphane nanoribbons will self-bend toward the graphane side. The naturally curved As-graphane nanoribbons then exhibit unique spin transport properties, distinctively different from the flat ones, which is a two-dimensional topological insulator...
June 19, 2017: Nano Letters
Nabeel Ahmad, Guillaume Wang, Jaysen Nelayah, Christian Ricolleau, Damien Alloyeau
The shape-dependent properties of gold nanostars (NSs) have motivated massive research efforts in the field of colloidal chemistry to gain a better control over the morphology of these promising nanostructures. Nevertheless, this challenge requires a better understanding of the atomic-scale processes leading to the formation of stellated nanoparticles. We hereby report an unprecedented in situ study focused on the seed-mediated synthesis of symmetric gold nanostars (NSs) performed by radiolysis in methanol...
June 19, 2017: Nano Letters
Feipeng Zhao, Sida Shen, Liang Cheng, Lu Ma, Junhua Zhou, Hualin Ye, Na Han, Tianpin Wu, Yanguang Li, Jun Lu
Sodium-ion batteries are potential low-cost alternatives to current lithium-ion technology, yet their performance still fall short of expectation due to the lack of suitable electrode materials with large capacity, long-term cycling stability and high-rate performance. In this work, we demonstrated that ultrasmall (~5 nm) iron selenide (FeSe2) nanoparticles exhibited a remarkable performance for sodium-ion storage. They were prepared from a high-temperature solution method with a narrow size distribution and high yield, and could be readily redispersed in non-polar organic solvents...
June 19, 2017: Nano Letters
Rui Yang, Jaesung Lee, Souvik Ghosh, Hao Tang, R Mohan Sankaran, Christian A Zorman, Philip X-L Feng
Emerging atomic layer semiconducting crystals such as molybdenum disulfide (MoS2) are promising candidates for flexible electronics and strain-tunable devices due to their ultrahigh strain limits (up to ~20-30%) and strain-tunable bandgaps. However, high strain levels, controllable isotropic and anisotropic biaxial strains in single- and few-layer MoS2 on device-oriented flexible substrates permitting convenient and fast strain tuning, remain unexplored. Here, we demonstrate a blown-bubble bulge technique for efficiently applying large biaxial strains to atomic layer MoS2 devices on flexible substrate...
June 19, 2017: Nano Letters
Cheng Han, Zehua Hu, Lidia C Gomes, Yang Bao, Alexandra Carvalho, Sherman Jun Rong Tan, Bo Lei, Du Xiang, Jing Wu, Dianyu Qi, Li Wang, Fengwei Huo, Wei Huang, Kian Ping Loh, Wei Chen
Two-dimensional black phosphorus configured field-effect transistor devices generally show a hole-dominated ambipolar transport characteristic, thereby limiting its applications in complementary electronics. Herein, we demonstrate an effective surface functionalization scheme on few-layer black phosphorus, through in situ surface modification with potassium, with a view towards high performance complementary device applications. Potassium induces a giant electron doping effect on black phosphorus along with a clear bandgap reduction, which is further corroborated by in situ photoelectron spectroscopy characterizations...
June 19, 2017: Nano Letters
Aaron Mascaro, Zi Wang, Pierre Hovington, Yoichi Miyahara, Andrea Paolella, Vincent Gariepy, Zimin Feng, Tyler Enright, Connor Aiken, Karim Zaghib, Kirk H Bevan, Peter Grutter
One of the main challenges in improving fast charging lithium-ion batteries is the development of suitable active materials for cathodes and anodes. Many materials suffer from unacceptable structural changes under high currents and/or low intrinsic conductivities. Experimental measurements are required to optimize these properties, but few techniques are able to spatially resolve ionic transport properties at small length scales. Here we demonstrate an atomic force microscope (AFM)-based technique to measure local ionic transport on LiFePO4 to correlate with the structural and compositional analysis of the same region...
June 19, 2017: Nano Letters
Tetiana Serdiuk, Stefania Anna Mari, Daniel J Müller
How complex cytoplasmic membrane proteins insert and fold into cellular membranes is not fully understood.  One problem is the lack of suitable approaches that allow investigating the process by which polypeptides insert and fold into membranes.  Here, we introduce a method to mechanically unfold and extract a single polytopic -helical membrane protein, the lactose permease (LacY), from a phospholipid membrane, transport the fully unfolded polypeptide to another membrane and insert and refold the polypeptide into the native structure...
June 19, 2017: Nano Letters
Alexander E Minovich, Manuel Peter, Felix Bleckmann, Manuel Becker, Stefan Linden, Anatoly V Zayats
The normal mapping technique is widely used in computer graphics to visualize three-dimensional (3D) objects displayed on a flat screen. Taking advantage of optical properties of metasurfaces, which provide a highly efficient approach for manipulation of incident light wavefront, we have designed a metasurface to implement diffuse reflection and used the concept of normal mapping to control its scattering properties. As a proof of principle, we have fabricated and characterized a flat diffuse metasurface imitating lighting and shading effects of a 3D cube...
June 19, 2017: Nano Letters
E J Sie, A Steinhoff, C Gies, C H Lui, Q Ma, M Rösner, G Schönhoff, F Jahnke, T O Wehling, Y-H Lee, J Kong, P Jarillo-Herrero, N Gedik
We report a rare atom-like interaction between excitons in monolayer WS2, measured using ultrafast absorption spectroscopy. At increasing excitation density, the exciton resonance energy exhibits a pronounced redshift followed by an anomalous blueshift. Using both material-realistic computation and phenomenological modeling, we attribute this observation to plasma effects and an attraction-repulsion crossover of the exciton-exciton interaction that mimics the Lennard-Jones potential between atoms. Our experiment demonstrates a strong analogy between excitons and atoms with respect to interparticle interaction, which holds promise to pursue the predicted liquid and crystalline phases of excitons in two-dimensional materials...
June 16, 2017: Nano Letters
Tuncay Ozel, Benjamin Zhang, Ruixuan Gao, Robert W Day, Charles M Lieber, Daniel G Nocera
Development of new synthetic methods for the modification of nanostructures has accelerated materials design advances to furnish complex architectures. Structures based on one-dimensional (1D) silicon (Si) structures using top-down and bottom-up methods are especially prominent for diverse applications in chemistry, physics, and medicine. Yet further elaboration of these structures with distinct metal-based and polymeric materials, which could open up new opportunities, has been difficult. We present a general electrochemical method for the deposition of conformal layers of various materials onto high aspect ratio Si micro- and nanowire arrays...
June 16, 2017: Nano Letters
Ozlem Yavas, Mikael Svedendahl, Paulina Dobosz, Vanesa Sanz, Romain Quidant
Nanophotonics has become a key enabling technology in biomedicine with great promises in early diagnosis and less invasive therapies. In this context, the unique capability of plasmonic noble metal nanoparticles to concentrate light on the nanometer scale has widely contributed to biosensing and enhanced spectroscopy. Recently, high-refractive index dielectric nanostructures featuring low loss resonances have been proposed as a promising alternative to nanoplasmonics, potentially offering better sensing performances along with full compatibility with the microelectronics industry...
June 16, 2017: Nano Letters
Maria Spies, Martien I den Hertog, Pascal Hille, Jörg Schörmann, Jakub Polaczyński, Bruno Gayral, Martin Eickhoff, Eva Monroy, Jonas Lähnemann
We present a study of GaN single-nanowire ultraviolet photodetectors with an embedded GaN/AlN superlattice. The heterostructure dimensions and doping profile were designed in such a way that the application of positive or negative bias leads to an enhancement of the collection of photogenerated carriers from the GaN/AlN superlattice or from the GaN base, respectively, as confirmed by electron beam-induced current measurements. The devices display enhanced response in the ultraviolet A (≈ 330-360 nm)/B (≈ 280-330 nm) spectral windows under positive/negative bias...
June 16, 2017: Nano Letters
Virginia Di Carlo, Paola Prete, Vladimir G Dubrovskii, Yury Berdnikov, Nico Lovergine
We report on the first Au-catalyzed growth of CdTe nanowires by metalorganic vapor phase epitaxy. The nanowires were obtained by a separate precursors flow process in which (i) di-isopropyl-telluride ((i)Pr2Te) was first flowed through the reactor to ensure the formation of liquid Au-Te alloy droplets, and (ii) after purging with pure H2 to remove unreacted (i)Pr2Te molecules from the vapor and the growth surface, (iii) dimethylcadmium (Me2Cd) was supplied to the vapor so that Cd atoms could enter the catalyst droplets, leading to nanowire self-assembly...
June 16, 2017: Nano Letters
Rong He, Jian Hua, Anqi Zhang, Chuanhao Wang, Jiayu Peng, Weijia Chen, Jie Zeng
Engineering electronic properties is a promising way to design nonprecious-metal or earth-abundant catalysts toward hydrogen evolution reaction (HER). Herein, we deposited catalytically active MoS2 flakes onto black phosphorus (BP) nanosheets to construct the MoS2-BP interfaces. In this case, electrons flew from BP to MoS2 in MoS2-BP nanosheets because of the higher Fermi level of BP than that of MoS2. MoS2-BP nanosheets exhibited remarkable HER performance with an overpotential of 85 mV at 10 mA cm(-2). Due to the electron donation from BP to MoS2, the exchange current density of MoS2-BP reached 0...
June 16, 2017: Nano Letters
Ji-Yin Wang, Shaoyun Huang, Guang-Yao Huang, Dong Pan, Jianhua Zhao, H Q Xu
A highly tunable linear triple quantum dot (TQD) device is realized in a single-crystalline pure-phase InAs nanowire using a local finger gate technique. The electrical measurements show that the charge stability diagram of the TQD can be represented by three kinds of current lines of different slopes and a simulation performed based on a capacitance matrix model confirms the experiment. We show that each current line observable in the charge stability diagram is associated with a case where a QD is on resonance with the Fermi level of the source and drain reservoirs...
June 16, 2017: Nano Letters
Steven Limpert, Adam Burke, I-Ju Chen, Nicklas Anttu, Sebastian Lehmann, Sofia Fahlvik, Stephen Bremner, Gavin Conibeer, Claes Thelander, Mats-Erik Pistol, Heiner Linke
The photothermoelectric (PTE) effect uses nonuniform absorption of light to produce a voltage via the Seebeck effect and is of interest for optical sensing and solar-to-electric energy conversion. However, the utility of PTE devices reported to date has been limited by the need to use a tightly focused laser spot to achieve the required, nonuniform illumination and by their dependence upon the Seebeck coefficients of the constituent materials, which exhibit limited tunability and, generally, low values. Here, we use InAs/InP heterostructure nanowires to overcome these limitations: first, we use naturally occurring absorption "hot spots" at wave mode maxima within the nanowire to achieve sharp boundaries between heated and unheated subwavelength regions of high and low absorption, allowing us to use global illumination; second, we employ carrier energy-filtering heterostructures to achieve a high Seebeck coefficient that is tunable by heterostructure design...
June 16, 2017: Nano Letters
Amol Ashok Pawar, Shira Halivni, Nir Waiskopf, Yuval Ben-Shahar, Michal Soreni-Harari, Sarah Bergbreiter, Uri Banin, Shlomo Magdassi
Additive manufacturing processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymerization, which is the most versatile technology enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process...
June 15, 2017: Nano Letters
Manuel Peter, Andre Hildebrandt, Christian Schlickriede, Kimia Gharib, Thomas Zentgraf, Jens Förstner, Stefan Linden
An important source of innovation in nanophotonics is the idea to scale down known radio wave technologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localized emitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like at optical frequencies. Thus, plasmonic nanoantennas are inherently lossy. Moreover, their resonant nature requires precise control of the antenna geometry...
June 21, 2017: Nano Letters
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