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Nano Letters

Kumari Gaurav Rana, Fasil Dejene, Neeraj Kumar, Catherine Rajamathi, Kornelia Sklarek, Claudia Felser, Stuart S P Parkin
WTe2 is one of a series of recently discovered high mobility semimetals, some of whose properties are characteristic of topological Dirac or Weyl metals. One of its most interesting properties is the unsaturated giant magnetoresistance that it exhibits at low temperatures. An important question is the degree to which this property can be ascribed to a conventional semi-metallic model in which a highly compensated, high mobility metal exhibits large magnetoresistance. Here we show that the longitudinal thermopower (Seebeck effect) of semi-metallic WTe2 exfoliated flakes exhibits periodic sign changes about zero with increasing magnetic field that indicates distinct electron and hole Landau levels and nearly fully compensated electron and hole carrier densities...
September 21, 2018: Nano Letters
Christoph Bäumer, Carsten Funck, Andrea Locatelli, Tevfik Onur Menteş, Francesca Genuzio, Thomas Heisig, Felix Hensling, Nicolas Raab, Claus M Schneider, Stephan Menzel, Rainer Waser, Regina Dittmann
Point defects such as oxygen vacancies cause emergent phenomena like resistive switching in transition metal oxides, but their influence on the electronic transport properties is far from being understood. Here, we employ direct mapping of the electronic structure of a memristive device by spectromicroscopy. We find that oxygen vacancies result in in-gap states which we use as input for single band transport simulations. Since the in-gap states are situated below the Fermi level, they do not contribute to the current directly, but impact the shape of the conduction band...
September 21, 2018: Nano Letters
Tingbin Zhang, Yuanyu Huang, Xiaowei Ma, Ningqiang Gong, Xiaoli Liu, Lu Liu, Xiaoxia Ye, Bo Hu, Chunhui Li, Jianhua Tian, Andrea Magrini, Jinchao Zhang, Weisheng Guo, Jinfeng Xing, Massimo Bottini, Xing-Jie Liang
Efficient small interfering RNA (siRNA) delivery in presence of serum is of crucial importance for effective gene therapy. Fluorinated vectors are considered to be attractive candidates for siRNA-mediated gene therapy because of their delivery efficacy in serum-containing media. However, the mechanisms driving the superior gene transfection behavior of fluorinated vectors are still not well understood and comprehensive investigations are warranted. Herein, we fabricated a library of perfluorooctanoyl fluoride (PFF)-fluorinated oligoethylenimines (fxOEIs, x is the PFF:OEI feeding ratio), which can readily form nano-assemblies (fxOEI NAs) capable of efficient siRNA delivery in cells cultured in medium both devoid of and supplemented with fetal bovine serum (FBS)...
September 21, 2018: Nano Letters
Ben Shi, Qinglong Yan, Jie Tang, Kai Xin, Jichao Zhang, Ying Zhu, Ge Xu, Rongchen Wang, Jian Chen, Wei Gao, Tianli Zhu, Jiye Shi, Chunhai Fan, Chunchang Zhao, He Tian
Near-infrared (NIR)-II fluorescence agents hold great promise for deep-tissue photothermal therapy (PTT) of cancers, which nevertheless remains restricted by the inherent non-specificity and toxicity of PTT. In response to this challenge, we herein develop a hydrogen sulfide (H2S)-activatable nanostructured photothermal agent (Nano-PT) for site-specific NIR-II fluorescence-guided PTT of colorectal cancer (CRC). Our in-vivo studies reveal that this theranostic Nano-PT probe is specifically activated in H2S-rich CRC tissues whereas non-functional in normal tissues...
September 21, 2018: Nano Letters
Cen-Feng Fu, Jiuyu Sun, Qiquan Luo, Xingxing Li, Wei Hu, Jinlong Yang
Two-dimensional (2D) materials with the vertical intrinsic electric fields show great promise in inhibiting the recombination of photo-generated carriers and widening light absorption region for the photocatalytic applications. For the first time, we investigated the potential feasibility of experimentally attainable 2D M2 X3 (M = Al, Ga, In; X = S, Se, Te) family featuring out-of-plane ferroelectricity used in photocatalytic water splitting. By using first-principles calculations, all the nine members of 2D M2 X3 are verified to be available photocatalysts for overall water splitting...
September 21, 2018: Nano Letters
Zhi Zhang, Nishuang Liu, Luying Li, Jun Su, Ping-Ping Chen, Wei Lu, Yihua Gao, Jin Zou
In situ transmission electron microscopy investigation of structural transformation in III-V nanowires is essential for providing direct insight into the structural stability of III-V nanowires under elevated temperature. In this study, through in situ heating investigation in a transmission electron microscope, the detailed structural transformation of InAs nanowires from wurtzite structure to zinc-blende structure at the catalyst/nanowire interface is witnessed on the atomic level. Through detailed structural and dynamic analysis, it was found that the nucleation site of each new layer of InAs and catalyst surface energy play a decisive role in the growth of the zinc-blende structure...
September 21, 2018: Nano Letters
Folkert K de Vries, Jie Shen, Rafal J Skolasinski, Michal P Nowak, Daniel Varjas, Lin Wang, Michael Wimmer, Joost Ridderbos, Floris A Zwanenburg, Ang Li, Sebastian Koelling, Marcel A Verheijen, Erik P A M Bakkers, Leo P Kouwenhoven
Low dimensional semiconducting structures with strong spin-orbit interaction (SOI) and induced superconductivity attracted great interest in the search for topological superconductors. Both the strong SOI and hard superconducting gap are directly related to the topological protection of the predicted Majorana bound states. Here we explore the one-dimensional hole gas in germanium silicon (Ge-Si) core-shell nanowires (NWs) as a new material candidate for creating a topological superconductor. Fitting multiple Andreev reflection measurements shows that the NW has two transport channels only, underlining its one-dimensionality...
September 21, 2018: Nano Letters
Chieh-Wen Liu, Feng Wei, Kasun Premasiri, Shuhao Liu, Song Ma, Zhidong Zhang, Xuan P A Gao
The Drude model is one of the most fundamental models used to understand the electronic carrier transport in materials, including recently discovered topological materials. Here, we present a magneto-transport study revealing the non-Drude transport behavior in a heterostructure of topological crystalline insulator (TCI) SnTe and band insulator PbTe which exhibits a nonsaturating linear magneto-resistance (MR) effect, a novel phenomenon widely observed in topological materials with gapless dispersion. It is shown that in the van der Pauw geometry in which the longitudinal and transverse magneto-resistances are measured to extract the magneto-conductivity, the two-band Drude model is not sufficient to self-consistently describe both the longitudinal and transverse magneto-conductivities...
September 21, 2018: Nano Letters
Robert Walder, William J Van Patten, Dustin B Ritchie, Rebecca K Montange, Ty W Miller, Michael T Woodside, Thomas T Perkins
The folding of RNA into a wide range of structures is essential to its diverse biological functions, from enzymatic catalysis to ligand binding and gene regulation. The unfolding and refolding of individual RNA molecules can be probed by single-molecule force spectroscopy (SMFS), enabling detailed characterization of the conformational dynamics of the molecule as well as the free-energy landscape underlying folding. Historically, high-precision SMFS studies of RNA have been limited to custom-built optical traps...
September 20, 2018: Nano Letters
Emma Desvignes, Anais Bouissou, Adrian Laborde, Thomas Mangeat, Amsha Proag, Christophe Vieu, Christophe Thibault, Isabelle Maridonneau-Parini, Renaud Poincloux
In vivo, immune cells migrate through a wide variety of tissues, including confined and constricting environments. Deciphering how cells apply forces when infiltrating narrow areas is a critical issue that requires novel experimental procedures. To reveal the distribution and dynamics of the forces of cells migrating in confined environments, we designed a device combining microchannels of controlled dimensions with integrated deformable micropillars serving as sensors of nanoscale subcellular forces. First, a specific process composed of two steps of photolithography and dry etching was tuned to obtain micrometric pillars of controlled stiffness and dimensions inside microchannels...
September 20, 2018: Nano Letters
Heedae Kim, Seongho Park, Rin Okuyama, Kwangseuk Kyhm, Mikio Eto, Robert A Taylor, Gilles Nogues, Le Si Dang, Marek Potemski, Koochul Je, Jongsu Kim, Jihoon Kyhm, Jindong Song
We found that optical Aharonov-Bohm oscillations in a single GaAs/GaAlAs quantum ring can be controlled by excitation intensity. With a weak excitation intensity of 1.2 kW cm-2 , the optical Aharonov-Bohm oscillation period of biexcitons was observed to be half that of excitons in accordance with the period expected for a two-exciton Wigner molecule. When the excitation intensity is increased by an order of magnitude (12 kW cm-2 ), a gradual deviation of the Wigner molecule condition occurs with decreased oscillation periods and diamagnetic coefficients for both excitons and biexcitons along with a spectral shift...
September 20, 2018: Nano Letters
Cory D Sago, Melissa P Lokugamage, Gwyneth N Lando, Naima Djeddar, Nirav N Shah, Chris Syed, Anton V Bryksin, James E Dahlman
Nanoparticles are often targeted to receptors expressed on specific cells, but few receptors are (i) highly expressed on one cell type and (ii) involved in endocytosis. One unexplored alternative is manipulating an endocytic gene expressed on multiple cell types; an ideal gene would inhibit delivery to cell type A more than cell type B, promoting delivery to cell type B. This would require a commonly expressed endocytic gene to alter nanoparticle delivery in a cell type-dependent manner in vivo; whether this can occur is unknown...
September 20, 2018: Nano Letters
Che Chen, Daniel A Mohr, Han-Kyu Choi, Daehan Yoo, Mo Li, Sang-Hyun Oh
The integration of nanoplasmonic devices with a silicon photonic platform affords a new approach for efficient light delivery by combining the high field enhancement of plasmonics and the ultralow propagation loss of dielectric waveguides. Such a hybrid integration obviates the need for a bulky free-space optics setup and can lead to fully integrated, on-chip optical sensing systems. Here, we demonstrate ultracompact plasmonic resonators directly patterned atop a silicon waveguide for mid-infrared spectroscopic chemical sensing...
September 20, 2018: Nano Letters
Srinivas Vanka, Elisabetta Arca, Shaobo Cheng, Kai Sun, Gianluigi A Botton, Glenn Teeter, Zetian Mi
Photoelectrochemical water splitting is a clean and environmentally friendly method for solar hydrogen generation. Its practical application, however, has been limited by the poor stability of semiconductor photoelectrodes. In this work, we demonstrate the use of GaN nanostructures as a multifunctional protection layer for an otherwise unstable, low-performance photocathode. The direct integration of GaN nanostructures on n+ -p Si wafer not only protects Si surface from corrosion but also significantly reduces the charge carrier transfer resistance at the semiconductor/liquid junction, leading to long-term stability (>100 h) at a large current density (>35 mA/cm2 ) under 1 sun illumination...
September 20, 2018: Nano Letters
James C Kaczmarek, Kevin J Kauffman, Owen S Fenton, Kaitlyn Sadtler, Asha K Patel, Michael W Heartlein, Frank DeRosa, Daniel G Anderson
mRNA therapeutics hold great potential for treating a variety of diseases through protein-replacement, immunomodulation, and gene editing. However, much like siRNA therapy the majority of progress in mRNA delivery has been confined to the liver. Previously, we demonstrated that poly(β-amino esters), a class of degradable polymers, are capable of systemic mRNA delivery to the lungs in mice when formulated into nanoparticles with poly(ethylene glycol)-lipid conjugates. Using experimental design, a statistical approach to optimization that reduces experimental burden, we demonstrate herein that these degradable polymer-lipid nanoparticles can be optimized in terms of polymer synthesis and nanoparticle formulation to achieve a multiple order-of-magnitude increase in potency...
September 20, 2018: Nano Letters
Rucha Deshpande, Vladimir A Zenin, Fei Ding, N Asger Mortensen, Sergey I Bozhevolnyi
Metasurfaces based on gap surface-plasmon resonators allow one to arbitrarily control the phase, amplitude, and polarization of reflected light with high efficiency. However, the performance of densely packed metasurfaces is reduced, often quite significantly, in comparison with simple analytical predictions. We argue that this reduction is mainly because of the near-field coupling between metasurface elements, which results in response from each element being different from the one anticipated by design simulations, which are commonly conducted for each individual element being placed in an artificial periodic arrangement...
September 19, 2018: Nano Letters
Jose García-Guirado, Mikael Svedendahl, Joaquim Puigdollers, Romain Quidant
Building blocks of life show well-defined chiral symmetry which has a direct influence on their properties and role in Nature. Chiral molecules are typically characterized by optical techniques such as circular dichroism (CD) where they exhibit signatures in the ultraviolet frequency region. Plasmonic nanostructures have the potential to enhance the sensitivity of chiral detection and translate the molecular chirality to the visible spectral range. Despite recent progress, to date, it remains unclear which properties plasmonic sensors should exhibit to maximize this effect and apply it to reliable enantiomer discrimination...
September 19, 2018: Nano Letters
Adrian Solyom, Zackary Flansberry, Märta A Tschudin, Nathaniel Leitao, Michel Pioro-Ladrière, Jack C Sankey, Lilian I Childress
The point-like nature and exquisite magnetic field sensitivity of the nitrogen vacancy (NV) center in diamond can provide information about the inner workings of magnetic nanocircuits in complement with traditional transport techniques. Here, we use a single NV in bulk diamond to probe the stray field of a ferromagnetic nanowire controlled by spin transfer (ST) torques. We first report an unambiguous measurement of ST tuned, parametrically driven, large-amplitude magnetic oscillations. At the same time, we demonstrate that such magnetic oscillations alone can directly drive NV spin transitions, providing a potential new means of control...
September 19, 2018: Nano Letters
Xiaoqing He, Chayanin Kiratipaiboon, Dale W Porter, Liying W Rojanasakul, Cerasela Zoica Dinu, Kai Wang, Yong Yang, Yon Rojanasakul
Fibroblast stem cells or stemlike cells (FSCs) are proposed to play a pivotal role in extracellular matrix (ECM) regeneration by serving as a key source of ECM-producing fibroblasts. We developed a mechanism-based in vitro model for fibrogenicity testing of nanomaterials based on their ability to induce FSCs. Using a FSC-enriched fibroblast focus model to mimic in vivo fibrogenic response, we demonstrated a dose-dependent increase in fibroblast focus formation and collagen production by primary lung fibroblasts treated with multiwalled carbon nanotubes (MWCNTs)...
September 19, 2018: Nano Letters
Xifan Wang, Charlotte I Evans, Douglas Natelson
A thin coating of gold oxide, metastable at room temperature, can be formed by placing gold in a strongly oxidizing environment such as an oxygen plasma. We report scanning photovoltage measurements of lithographically defined gold nanowires subsequent to oxygen plasma exposure. Photovoltages are detected during the first optical scan of the devices that are several times larger than those mapped on subsequent scans. The first-scan enhanced photovoltage correlates with a reduction of the electrical resistance of the nanostructure back to pre-oxygen-exposure levels...
September 18, 2018: Nano Letters
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