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Nano Letters

Frank Ceballos, Ming-Gang Ju, Samuel D Lane, Xiao Cheng Zeng, Hui Zhao
Two dimensional materials, such as graphene and monolayer transition metal dichalcogenides, allow the fabrication of multilayer structures without lattice matching restriction. A central issue in developing such artificial materials is to understand and control the interlayer electron transfer process, which plays a key role in harvesting their emergent properties. Recent photoluminescence and transient absorption measurements revealed that the electron transfer in hetero-bilayers occurs on ultrafast time scales...
February 17, 2017: Nano Letters
Barbara Fresch, Juanita Bocquel, Sven Rogge, Raphael D Levine, Francoise Remacle
Exploiting the potential of nanoscale devices for logic processing requires the implementation of computing functionalities departing from the conventional switching paradigm. We report on the design and the experimental realisation of a probabilistic finite state machine in a single phosphorus donor atom placed in a silicon matrix electrically addressed and probed by Scanning Tunnelling Spectroscopy (STS). The single atom logic unit simulates the flow of visitors in a maze whose topology is determined by the dynamics of the electronic transport through the states of the dopant...
February 17, 2017: Nano Letters
Alexander Georgi, Peter Nemes-Incze, Ramon Carrillo-Bastos, Daiara Faria, Silvia Viola Kusminskiy, Dawei Zhai, Martin Schneider, Dinesh Subramaniam, Torge Mashoff, Nils Michael Freitag, Marcus Liebmann, Marco Pratzer, Ludger Wirtz, Colin R Woods, Roman Vladislavovich Gorbachev, Yang Cao, Kostya S Novoselov, Nancy Sandler, Markus Morgenstern
One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudo-magnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudo-magnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudo-magnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene's pseudospin due to a strain induced pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic field...
February 17, 2017: Nano Letters
Johannes Binder, Freddie Withers, Maciej R Molas, Clement Faugeras, Karol Nogajewski, Kenji Watanabe, Takashi Taniguchi, Aleksey Kozikov, Andre K Geim, Kostya S Novoselov, Marek Potemski
We report on experimental investigations of an electrically driven WSe2 based light-emitting van der Waals heterostructure. We observe a threshold voltage for electroluminescence significantly lower than the corresponding single particle band gap of monolayer WSe2. This observation can be interpreted by considering the Coulomb interaction and a tunneling process involving excitons, well beyond the picture of independent charge carriers. An applied magnetic field reveals pronounced magneto-oscillations in the electroluminescence of the free exciton emission intensity with a 1/B-periodicity...
February 17, 2017: Nano Letters
Y Liu, P P Lopes, W Cha, R Harder, J Maser, E Maxey, M J Highland, N M Markovic, S O Hruszkewycz, G B Stephenson, H You, A Ulvestad
Dissolution is critical to nanomaterial stability, especially for partially dealloyed nanoparticle catalysts. Unfortunately, highly active catalysts are often not stable in their reactive environments, preventing widespread application. Thus, focusing on the structure-stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. Recent advances in imaging capability have come from electron, X-ray, and other techniques but tend to be limited to specific sample environments and/or two-dimensional images...
February 17, 2017: Nano Letters
Muhammad Arslan Shehzad, Sajjad Hussain, Junsu Lee, Jongwan Jung, Naesung Lee, Gunn Kim, Yongho Seo
Direct observation of grains and boundaries is a vital factor in altering the electrical and optoelectronic properties of transition metal dichalcogenides (TMDs) i.e. MoSe2 and WSe2. Here, we report visualization of grains and boundaries of chemical vapor deposition grown MoSe2 and WSe2 on silicon, using optical birefringence of 2D layer covered with nematic liquid crystal (LC). An in-depth study was performed to determine the alignment orientation of LC molecules and their correlation with other grains. Interestingly, we found that alignment of liquid crystal has discrete preferential orientations...
February 16, 2017: Nano Letters
Elaine Y Yu, Mindy Bishop, Bo Zheng, R Matthew Ferguson, Amit P Khandhar, Scott J Kemp, Kannan M Krishnan, Patrick W Goodwill, Steven M Conolly
Cancer remains one of the leading causes of death worldwide. Biomedical imaging plays a crucial role in all phases of cancer management. Physicians often need to choose the ideal diagnostic imaging modality for each clinical presentation based on complex trade-offs between spatial resolution, sensitivity, contrast, access, cost, and safety. Magnetic particle imaging (MPI) is an emerging tracer imaging modality that detects superparamagnetic iron oxide (SPIO) nanoparticle tracer with high image contrast (zero tissue background signal), high sensitivity (200 nM Fe) with linear quantitation and zero signal depth attenuation...
February 16, 2017: Nano Letters
Hong Chang, Jia Lv, Xin Gao, Xing Wang, Hui Wang, Hui Chen, Xu He, Lei Li, Yiyun Cheng
The efficient delivery of biopharmaceutical drugs such as proteins and peptides into the cytosol of target cells poses substantial challenges owing to their large size and susceptibility to degradation. Current protein delivery vehicles have limitations such as the need for protein modification, insufficient delivery of large-size proteins or small peptides, and loss of protein function after the delivery. Here, we adopted a rational approach to design a polymer with robust efficacy for intracellular protein and peptide delivery...
February 16, 2017: Nano Letters
Mingda Li, Zhiwei Ding, Qingping Meng, Jiawei Zhou, Yimei Zhu, Hong Liu, M S Dresselhaus, Gang Chen
Despite the long history of dislocation-phonon interaction studies, there are many problems that have not been fully resolved during this development. These include an incompatibility between a perturbative approach and the long-range nature of a dislocation, the relation between static and dynamic scattering, and their capability of dealing with thermal transport phenomena for bulk material only. Here by utilizing a fully quantized dislocation field, which we called a "dislon", a phonon interacting with a dislocation is renormalized as a quasi-phonon, with shifted quasi-phonon energy, and accompanied by a finite quasi-phonon lifetime, which are reducible to classical results...
February 16, 2017: Nano Letters
Renwei Liu, Suna Fan, Dongdong Xiao, Jin Zhang, Mengzhou Liao, Shansheng Yu, Fanling Meng, Baoli Liu, Lin Gu, Sheng Meng, Guangyu Zhang, Weitao Zheng, Shuxin Hu, Ming Li
Organic two-dimensional (2D) crystals are fundamentally important for development of future devices. Despite that more than a half of man-made products contain polymers, 2D crystals consisting of long linear chains have yet to be explored. Here we report on the fabrication of 2D polyaniline (PANI) crystals via rational electrochemical polymerization followed by liquid-phase exfoliation. The 2D PANI is molecularly thin (~0.8 nm) and composed of PANI chains with a number-average molecular weight of ~31000. The chains are parallel to each other with the benzene rings standing almost vertically to the surface, implying a face-to-face arrangement of the neighboring chains held together by abundant pi-pi interactions augmented with hydrogen bonds...
February 15, 2017: Nano Letters
Henrique Pereira Coutada Miranda, Sven Reichardt, Guillaume Froehlicher, Alejandro Molina-Sánchez, Stéphane Berciaud, Ludger Wirtz
We present a combined experimental and theoretical study of resonant Raman spectroscopy in single- and triple-layer MoTe2. Raman intensities are computed entirely from first principles by calculating finite differences of the dielectric susceptibility. In our analysis, we investigate the role of quantum interference effects and the electron-phonon coupling. With this method, we explain the experimentally observed intensity inversion of the A'1 vibrational modes in triple-layer MoTe2 with increasing laser photon energy...
February 15, 2017: Nano Letters
Maider Ormaza, Nicolas Bachellier, Marisa N Faraggi, Benjamin Verlhac, Paula Abufager, Philippe Ohresser, Loïc Joly, Michelangelo Romeo, Fabrice Scheurer, Marie-Laure Bocquet, Nicolas Lorente, Laurent Limot
Inelastic electron tunneling spectroscopy (IETS) within the junction of a scanning tunneling microscope (STM) uses current-driven spin-flip excitations for an all-electrical characterization of the spin state of a single object. Usually decoupling layers between the single object, atom or molecule, and the supporting surface are needed in order to observe these excitations. Here we study the surface magnetism of a sandwich nickelocene molecule (Nc) adsorbed directly on Cu(100) by means of X-ray magnetic circular dichroism (XMCD) and density functional theory calculations (DFT), and show with IETS that it exhibits an exceptionally efficient spin-flip excitation...
February 15, 2017: Nano Letters
Dongping Lu, Jinhui Tao, Pengfei Yan, Wesley A Henderson, Qiuyan Li, Yuyan Shao, Monte L Helm, Oleg Borodin, Gordon L Graff, Bryant Polzin, Chong-Min Wang, Mark Engelhard, Ji-Guang Zhang, James J De Yoreo, Jun Liu, Jie Xiao
Li-ion batteries (LIB) have been successfully commercialized after the identification of ethylene-carbonate (EC)-containing electrolyte that can form a stable solid electrolyte interphase (SEI) on carbon anode surface to passivate further side reactions but still enable the transportation of the Li(+) cation. These electrolytes are still utilized, with only minor changes, after three decades. However, the long-term cycling of LIB leads to continuous consumption of electrolyte and growth of SEI layer on the electrode surface, which limits the battery's life and performance...
February 15, 2017: Nano Letters
Quinten A Akkerman, Eros Radicchi, Sungwook Park, Francesca Nunzi, Edoardo Mosconi, Filippo De Angelis, Rosaria Brescia, Prachi Rastogi, Mirko Prato, Liberato Manna
We have developed a colloidal synthesis of nearly monodisperse nanocrystals of pure Cs4PbX6 (X = Cl, Br, I) and their mixed halide compositions, with sizes ranging from 9 nm to 37 nm. The optical absorption spectra of these nanocrystals display a sharp, high energy peak due to transitions between states localized in individual PbX64- octahedra. These spectral features are insensitive to the size of the particles and in agreement with the features of the corresponding bulk materials. Samples with mixed halide composition exhibit absorption bands that are intermediate in spectral position between those of the pure halide compounds...
February 14, 2017: Nano Letters
José-Eduardo Barrios-Vargas, Bohayra Mortazavi, Aron W Cummings, Rafael Martinez-Gordillo, Miguel Pruneda, Luciano Colombo, Timon Rabczuk, Stephan Roche
We present a theoretical study of electronic and thermal transport in polycrystalline heterostructures combining graphene (G) and hexagonal boron nitride (hBN) grains of varying size and distribution. By increasing the hBN grain density from a few percent to 100%, the system evolves from a good conductor to an insulator, with the mobility dropping by orders of magnitude and the sheet resistance reaching the MΩ regime. The Seebeck coefficient is suppressed above 40% mixing, while the thermal conductivity of polycrystalline hBN is found to be on the order of 30-120 Wm(-1)K(-1)...
February 14, 2017: Nano Letters
Yanpeng Liu, Zhizhan Qiu, Alexandra Carvalho, Yang Bao, Hai Xu, Sherman Jun Rong Tan, Wei Liu, Antonio H Castro Neto, Kian Ping Loh, Jiong Lu
Two-dimensional black phosphorus (BP) has sparked enormous research interest due to its high carrier mobility, layer-dependent direct bandgap and outstanding in-plane anisotropic properties. BP is one of the few two-dimensional materials where it is possible to tune the bandgap over a wide energy range from the visible up to the infrared. In this article, we report the observation of a giant Stark effect in electrostatically-gated few-layer BP. Using low temperature scanning tunnelling microscopy, we observed that in few-layer BP, when electrons are injected, a monotonic reduction of the bandgap occurs...
February 14, 2017: Nano Letters
Shan Wang, Rémi Cazelles, Wei-Ching Liao, Margarita Vázquez-González, Amani Zoabi, Raed Abu-Reziq, Itamar Willner
Cu(2+)-ion-modified graphene oxide nanoparticles, Cu(2+)-GO NPs, act as a heterogeneous catalyst mimicking functions of horseradish peroxidase, HRP, and of NADH peroxidase. The Cu(2+)-GO NPs catalyze the oxidation of dopamine to aminochrome by H2O2 and catalyze the generation of chemiluminescence in the presence of luminol and H2O2. The Cu(2+)-GO NPs provide an active material for the chemiluminescence detection of H2O2 and allow the probing of the activity of H2O2-generating oxidases and the detection of their substrates...
February 14, 2017: Nano Letters
Gowoon Cheon, Karel-Alexander N Duerloo, Austin D Sendek, Chase Porter, Yuan Chen, Evan J Reed
Layered materials held together by weak interactions including van der Waals forces, such as graphite, have attracted interest for both technological applications and fundamental physics in their layered form and as an isolated single-layer. Only a few dozen single-layer van der Waals solids have been subject to considerable research focus, although there are likely to be many more and which could have superior properties. To identify a broad spectrum of layered materials, we present a novel data mining algorithm that determines the dimensionality of weakly bonded subcomponents based on the atomic positions of bulk, 3D crystal structures...
February 13, 2017: Nano Letters
Vishwas Srivastava, Wenyong Liu, Eric M Janke, Vladislav Kamysbayev, Alexander S Filatov, Chengjun Sun, Byeongdu Lee, Tijana Rajh, Richard D Schaller, Dmitri V Talapin
GaAs is one of the most important semiconductors. However, colloidal GaAs nanocrystals remain largely unexplored because of the difficulties with their synthesis. Traditional synthetic routes either fail to produce pure GaAs phase or result in materials whose optical properties are very different from the behavior expected for quantum dots of direct-gap semiconductors. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS, transient absorption, and EPR spectroscopies, we conclude that unusual optical properties of colloidal GaAs NCs can be related to the presence of Ga vacancies and lattice disorder...
February 13, 2017: Nano Letters
Yan Yu, Jun Liu, Litao Yu, Chao Wu, Yuren Wen, Kuibo Yin, Fu-Kuo Chiang, Renzong Hu, Jiangwen Liu, Litao Sun, Lin Gu, Joachim Maier, Min Zhu
In the current research project, we have designed and fabricated a biomimetic yolk-shell structure Sb@C anode for both Li- and Na-ion batteries via a nanoconfined galvanic replacement route. The yolk-shell microstructure consists of Sb hollow yolk completely protected by a self-supporting carbon thin shell. The substantial void space in the hollow yolk and the gap between the shell and inner yolk allows for the full expansion of inner Sb nanoparticles while preserving the structural integrity of the Sb@C anode and stable SEI film on the outside carbon surface...
February 13, 2017: Nano Letters
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