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Nano Letters

Junwei Liu, Hua Wang, Chen Fang, Liang Fu, Xiaofeng Qian
Novel materials with nontrivial electronic and photonic band topology are crucial for realizing novel devices with low power consumption and heat dissipation and quantum computing free of decoherence. Here, we theoretically predict a novel class of ternary transition metal chalcogenides that exhibit dual topological characteristics, quantum spin Hall insulators (QSHIs) in their two-dimensional (2D) monolayers and topological Weyl semimetals in their 3D noncentrosymmetric crystals upon van der Waals (vdW) stacking...
December 9, 2016: Nano Letters
Mi-Jin Jin, Seon Young Moon, Jungmin Park, Vijayakumar Modepalli, Junhyeon Jo, Shin-Ik Kim, Hyun Cheol Koo, Byoung-Chul Min, Hyun-Woo Lee, Seung-Hyub Baek, Jung-Woo Yoo
A two-dimensional electron gas emerged at a LaAlO3/SrTiO3 interface is an ideal system for "spin-orbitronics" as the structure itself strongly couple the spin and orbital degree of freedom through the Rashba spin-orbit interaction. One of core experiments toward this direction is the nonlocal spin transport measurement, which has remained elusive due to the low spin injection efficiency to this system. Here we bypass the problem by generating a spin current not through the spin injection from outside but instead through the inherent spin Hall effect and demonstrate the nonlocal spin transport...
December 9, 2016: Nano Letters
Deyang Chen, Zuhuang Chen, Qian He, James D Clarkson, Claudy R Serrao, Ajay K Yadav, Mark E Nowakowski, Zhen Fan, Long You, Xingsen Gao, Dechang Zeng, Lang Chen, Albina Y Borisevich, Sayeef Salahuddin, Jun-Ming Liu, Jeffrey Bokor
A wealth of fascinating phenomena have been discovered at the BiFeO3 domain walls, examples such as domain wall conductivity, photovoltaic effects, and magnetoelectric coupling. Thus, the ability to precisely control the domain structures and accurately study their switching behaviors is critical to realize the next generation of novel devices based on domain wall functionalities. In this work, the introduction of a dielectric layer leads to the tunability of the depolarization field both in the multilayers and superlattices, which provides a novel approach to control the domain patterns of BiFeO3 films...
December 9, 2016: Nano Letters
Zhigang Chen, Lianhui Li, Shan Cong, Jinnan Xuan, Dengsong Zhang, Fengxia Geng, Ting Zhang, Zhigang Zhao
A key challenge in current superhard materials research is the design of novel superhard nanocrystals (NCs) whereby new and unexpected properties may be predicted. Cubic boron nitride (c-BN) is a superhard material which ranks next to diamond; however, downsizing c-BN material below the 10 nm scale is rather challenging, and the interesting new properties of c-BN NCs remain unexplored and wide open. Herein we report an electrochemical shock method to prepare uniform c-BN NCs with a lateral size of only 3.4 ± 0...
December 9, 2016: Nano Letters
Yabin Chen, Feng Ke, Penghong Ci, Changhyun Ko, Taegyun Park, Sahar Saremi, Huili Liu, Yeonbae Lee, Joonki Suh, Lane W Martin, Joel W Ager, Bin Chen, Junqiao Wu
Hydrostatic pressure applied using diamond anvil cells (DAC) has been widely explored to modulate physical properties of materials by tuning their lattice degree of freedom. Independently, electrical field is able to tune the electronic degree of freedom of functional materials via, for example, the field-effect transistor (FET) configuration. Combining these two orthogonal approaches would allow discovery of new physical properties and phases going beyond the known phase space. Such experiments are, however, technically challenging and have not been demonstrated...
December 9, 2016: Nano Letters
Pin Chieh Wu, Wei-Yi Tsai, Wei Ting Chen, Yao-Wei Huang, Ting-Yu Chen, Jia-Wern Chen, Chun Yen Liao, Cheng Hung Chu, Greg Sun, Din Ping Tsai
All forms of light manipulation rely on light-matter interaction, the primary mechanism of which is the modulation of its electromagnetic fields by the localized electromagnetic fields of atoms. One of the important factors that influence the strength of interaction is the polarization of the electromagnetic field. The generation and manipulation of light polarization have been traditionally accomplished with bulky optical components such as waveplates, polarizers, and polarization beam splitters that are optically thick...
December 8, 2016: Nano Letters
Balila Nagamani Jaya, Jeffrey Martin Wheeler, Juri Wehrs, James P Best, Rafael Soler, Johann Michler, Christoph Kirchlechner, Gerhard Dehm
The micro-mechanical fracture behavior of single crystalline silicon was investigated as a function of temperature in situ in the scanning electron microscope equipped with a nanoindenter. A gradual but continuous increase in KC was observed with increasing temperature above 300 °C, in contrast to the sharp transitions observed in earlier works. No sharp brittle to ductile transition temperature (BDTT) could be identified, but a clear change in cracking mechanism occurs at ~300 °C with multiple load drops accompanying the deformation...
November 2, 2016: Nano Letters
Fanming Qu, Jasper van Veen, Folkert K de Vries, Arjan J A Beukman, Michael Thomas Wimmer, Wei Yi, Andrey A Kiselev, Binh-Minh Nguyen, Marko Sokolich, Michael J Manfra, Fabrizio Nichele, Charles M Marcus, Leo P Kouwenhoven
Due to a strong spin-orbit interaction and a large Landé g-factor, InSb plays an important role in research on Majorana fermions. To further explore novel properties of Majorana fermions, hybrid devices based on quantum wells are conceived as an alternative approach to nanowires. In this work, we report a pronounced conductance quantization of quantum point contact devices in InSb/InAlSb quantum wells. Using a rotating magnetic field, we observe a large in-plane ( │g1│= 26 ) and out-of-plane ( │g1│= 52 ) g-factor anisotropy...
November 2, 2016: Nano Letters
Haiqing Zhou, Fang Yu, Jingying Sun, Hangtian Zhu, Ishwar Kumar Mishra, Shuo Chen, Zhifeng Ren
The large consumption of natural fossil fuels and accompanying environmental problems are driving the exploration of cost-effective and robust catalysts for hydrogen evolution reaction (HER) in water splitting. Tungsten dichalcogenides (WS2, WSe2, etc.) are promising candidates for such purpose, but their HER performances are inherently limited by the sparse catalytic edge sites and poor electrical conductivity. Here we demonstrate a highly active and stable HER catalyst by integrating ternary tungsten sulfoselenide WS2(1-x)Se2x particles with a 3D porous metallic NiSe2 foam, in which good electrical conductivity, good contact, high surface area, and high-density active edge sites are simultaneously obtained, thus contributing to good catalytic performance: large cathode current density (- 10 mA/cm2 at - 88 mV), low Tafel slope (46...
November 2, 2016: Nano Letters
Siyuan Zhao, Xiaojun Liu, Zheng Xu, Huaying Ren, Bing Deng, Miao Tang, Linlin Lu, Xuefeng Fu, Hailin Peng, Zhongfan Liu, Xiaojie Duan
Magnetic resonance imaging (MRI) compatible neural electrodes are important for combining high-resolution electrophysiological measurements with more global MRI mapping of brain activity, which is critical for fundamental neuroscience studies, as well as clinical evaluation and monitoring. Copper is a favorable material to use in MRI because it has magnetic susceptibility close to water and tissues. However, the cytotoxicity of copper precludes its direct implantation for neural recording. Here, we overcome this limitation by developing a graphene encapsulated copper (G-Cu) microelectrode...
November 1, 2016: Nano Letters
Andrew C Meng, Colleen Shang Fenrich, Michael R Braun, James P McVittie, Ann F Marshall, James S Harris, Paul C McIntyre
Germanium-tin alloy nanowires hold promise as silicon-compatible optoelectronic elements with the potential for achieving a direct band gap transition required for efficient light emission. In contrast to Ge1-xSnx epitaxial thin films, free-standing nanowires deposited on misfitting germanium or silicon substrates can avoid compressive elastic strains that inhibit formation of a direct gap. We demonstrate strong room temperature photoluminescence, consistent with band edge emission from both the Ge core nanowires, elastically strained in tension, and the almost unstrained Ge1-xSnx shells grown around them...
November 1, 2016: Nano Letters
Liang Gao, Kai Zeng, Jingshu Guo, Cong Ge, Jing Du, Yang Zhao, Chao Chen, Hui Deng, Yisu He, Haisheng Song, Guangda Niu, Jiang Tang
Photodetectors convert light signals into current or voltage outputs and are widely used for imaging, sensing and spectroscopy. Recently, perovskite-based photodetectors have shown high sensitivity and fast response due to the unprecedented low recombination loss in this solution processed semiconductor. Among various types of CH3NH3PbI3 morphology (film, single crystal, nanowire), single-crystalline CH3NH3PbI3 nanowires are of particularly interesting for photodetection because of their no grain boundary, morphological anisotropy and excellent mechanical flexibility...
November 1, 2016: Nano Letters
Thomas Tigges, Thomas Heuser, Rahul Tiwari, Andreas Walther
The rational design of anisotropic interaction patterns is a key step for programming colloid and nanoparticle self-assembly and emergent functions. Herein, we demonstrate a concept for harnessing the capabilities of 3D DNA origami for extensive supracolloidal self-assembly, and showcase its use for making truly monodisperse, patchy, divalent nanocuboids that can self-assemble into supracolloidal fibrils via programmable DNA hybridization. A change in the number of connector duplexes at the patches reveals that multivalency and cooperativity play crucial roles to enhance superstructure formation...
November 1, 2016: Nano Letters
Kyongjun Yoo, Byung-Gu Jeon, Sae Hwan Chun, Deepak Rajaram Patil, Yong-Jun Lim, Seung-Hyun Noh, Jihyo Gil, Jinwoo Cheon, Kee Hoon Kim
Bulk magnetite (Fe3O4), the loadstone used in magnetic compasses, has been known to exhibit magnetoelectric (ME) properties below ∼10 K; however, corresponding ME effects in Fe3O4 nanoparticles have been enigmatic. We investigate quantitatively the ME coupling of spherical Fe3O4 nanoparticles with uniform diameters (d) from 3 to 15 nm embedded in an insulating host, using a sensitive ME susceptometer. The intrinsic ME susceptibility (MES) of the Fe3O4 nanoparticles is measured, exhibiting a maximum value of ∼0...
November 1, 2016: Nano Letters
Kun Luo, Matthew R Roberts, Rong Hao, Niccoló Guerrini, Emanuela Liberti, Christopher S Allen, Angus I Kirkland, Peter G Bruce
Lithium-rich transition metal oxides, Li1+xTM1-xO2 (TM, transition metal), have attracted much attention as potential candidate cathode materials for next generation lithium ion batteries because their high theoretical capacity. Here we present the synthesis of Li[Li0.2Ni0.2Mn0.6]O2 using a facile one-pot resorcinol-formaldehyde method. Structural characterization indicates that the material adopts a hierarchical porous morphology consisting of uniformly distributed small pores and disordered large pore structures...
November 1, 2016: Nano Letters
Matthew C Wingert, Soonshin Kwon, Shengqiang Cai, Renkun Chen
Silica glass, with a glass transition temperature in excess of 1000 oC, is not expected to flow at room temperature. In this work, we showed that amorphous silica and Si nanotubes can actually flow at room temperature under Giga-Pascal stress when going to nanometer scale. This creep behavior is unique for the amorphous nanotubes, as it is absent in crystalline Si nanotubes of similar dimensions. The creep is also strongly size-dependent in the amorphous nanotubes with shell thickness down to ~8 nm, which can be attributed to the presence of a thin viscoelastic 'fluid-like' surface layer...
October 31, 2016: Nano Letters
Zhilin Yu, Faifan Tantakitti, Liam C Palmer, Samuel I Stupp
Asymmetry in chemical structure or shape at molecular, nanoscale, or microscopic levels is essential to a vast number of functionalities in both natural and artificial systems. Bottom-up approaches to create asymmetric supramolecular nanostructures are considered promising but this strategy suffers from the potentially dynamic nature of noncovalent interactions. We report here on supramolecular self-assembly of asymmetric peptide amphiphiles consisting of two different molecularly linked domains. We found that strong noncovalent interactions and a high degree of internal order among the asymmetric amphiphiles lead to nanoribbons with asymmetric faces due to the preferential self-association of the two domains...
October 31, 2016: Nano Letters
David Parobek, Benjamin J Roman, Yitong Dong, Ho Jin, Elbert Lee, Matthew Sheldon, Dong Hee Son
We report the one-pot synthesis of colloidal Mn-doped cesium lead halide (CsPbX3) perovskite nanocrystals and efficient intraparticle energy transfer between the exciton and dopant ions resulting in intense sensitized Mn luminescence. Mn-doped CsPbCl3 and CsPb(Cl/Br)3 nanocrystals maintained the same lattice structure and crystallinity as their undoped counterparts, with nearly identical lattice parameters at ~0.2% doping concentrations and no signature of phase separation. The strong sensitized luminescence from d-d transition of Mn(2+) ions upon band-edge excitation of the CsPbX3 host is indicative of sufficiently strong exchange coupling between the charge carriers of the host and dopant d electrons mediating the energy transfer, essential for obtaining unique properties of magnetically doped quantum dots...
October 31, 2016: Nano Letters
Naihao Chiang, Xing Chen, Guillaume Goubert, Dhabih V Chulhai, Xu Chen, Eric A Pozzi, Nan Jiang, Mark C Hersam, Tamar Seideman, Lasse Jensen, Richard P Van Duyne
Tip-enhanced Raman spectroscopy (TERS) combines the ability of scanning probe microscopy (SPM) to resolve atomic-scale surface features with the single molecule chemical sensitivity of surface-enhanced Raman spectroscopy (SERS). Here, we report additional insights into the nature of the conformational dynamics of a free-base porphyrin at room temperature adsorbed on a metal surface. We have interrogated the conformational switch between two meta-stable surface-mediated isomers of meso-tetrakis-(3,5-di-tertiarybutylphenyl)-porphyrin (H2TBPP) on a Cu(111) surface...
October 31, 2016: Nano Letters
Neil A Krueger, Aaron L Holsteen, Seung-Kyun Kang, Christian R Ocier, Weijun Zhou, Glennys A Mensing, John A Rogers, Mark L Brongersma, Paul V Braun
The emergence and growth of transformation optics over the last decade has revitalized interest in how a gradient refractive index (GRIN) can be used to control light propagation. Two-dimensional demonstrations with lithographically-defined silicon (Si) have displayed the power of GRIN optics and also represent a promising opportunity for integrating compact optical elements within Si photonic integrated circuits. Here, we demonstrate the fabrication of three-dimensional Si-based GRIN micro-optics through the shape-defined formation of porous Si (PSi)...
October 31, 2016: Nano Letters
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