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Nano Letters

Amber McCreary, Jeffrey R Simpson, Yuanxi Wang, Daniel Rhodes, Kazunori Fujisawa, Luis Balicas, Madan Dubey, Vincent H Crespi, Mauricio Terrones, Angela R Hight Walker
The strong in-plane anisotropy of rhenium disulfide (ReS2) offers an additional physical parameter that can be tuned for advanced applications such as logic circuits, thin-film polarizers, and polarization-sensitive photodetectors. ReS2 also presents advantages for optoelectronics, as it is both a direct-gap semiconductor for few-layer thicknesses (unlike MoS2 or WS2) and stable in air (unlike black phosphorus). Raman spectroscopy is one of the most powerful characterization techniques to non-destructively and sensitively probe the fundamental photo-physics of a 2D material...
August 18, 2017: Nano Letters
Damien Canneson, Elena V Shornikova, Dmitri R Yakovlev, Tobias Rogge, Anatolie A Mitioglu, Mariana V Ballottin, Peter C M Christianen, Emmanuel Lhuillier, Manfred Bayer, Louis Biadala
The optical properties of colloidal cesium lead halide perovskite (CsPbBr3) nanocrystals are examined by time-resolved and polarization-resolved spectroscopy in high magnetic fields up to 30 T. We unambiguously show that at cryogenic temperatures the emission is dominated by recombination of negatively charged excitons with radiative decay time of 300 ps. The additional long-lived emission with a decay time of 10-30 ns, which decay time shortens and relative amplitude increases in high magnetic fields, evidence the presence of a dark exciton...
August 18, 2017: Nano Letters
Martin Mittendorff, Ryan J Suess, Edward Leong, Thomas E Murphy
Photoconductive antennas are widely used for time-resolved detection of THz pulses. In contrast to photothermoelectric or bolometric THz detection, the coherent detection allows direct measurement of the electric field transient of a THz pulse, which contains both, spectral and phase information. In this letter we demonstrate for the first time photoconductive detection of free-space propagating THz radiation with thin flakes of a van der Waals material. Mechanically exfoliated flakes of black phosphorus are combined with an antenna that concentrates the THz fields to the small flake (~10 μm)...
August 18, 2017: Nano Letters
Matthew R Jones, Kevin L Kohlstedt, Matthew N O'Brien, Jinsong Wu, George C Schatz, Chad A Mirkin
The physical properties of matter rely fundamentally on the symmetry of constituent building blocks. This is particularly true for structures that interact with light via the collective motion of their conduction electrons (i.e., plasmonic materials), where the observation of exotic optical effects, such as negative refraction and electromagnetically induced transparency, require the coupling of modes that are only present in systems with nontrivial broken symmetries. Lithography has been the predominant fabrication technique for constructing plasmonic metamaterials, as it can be used to form patterns of arbitrary complexity, including those with broken symmetry...
August 18, 2017: Nano Letters
Cordula Reuther, Matthäus Mittasch, Sundar Naganathan, Stephan Grill, Stefan Diez
Molecular motors, highly-efficient biological nano-machines, hold the potential to be employed for a wide range of nanotechnological applications. Towards this end, kinesin, dynein or myosin motor proteins are commonly surface-immobilized within engineered environments in order to transport cargo attached to cytoskeletal filaments. Being able to flexibly control the direction of filament motion - in particular on planar, non-topographical surfaces - has, however, remained challenging. Here, we demonstrate the applicability of a UV-laser-based ablation technique to programmably generate highly-localized patterns of functional kinesin-1 motors with different shapes and sizes on PLL-g-PEG-coated polystyrene surfaces...
August 18, 2017: Nano Letters
Amir Nasajpour, Serena Mandla, Sindu Shree, Ebrahim Mostafavi, Roholah Sharifi, Akbar Khalilpour, Saghi Saghazadeh, Shabir Hassan, Michael J Mitchell, Jeroen Leijten, Xu Hou, Alireza Moshaverinia, Nasim Annabi, Rainer Adelung, Yogendra Kumar Mishra, SuRyon Shin, Ali Tamayol, Ali Khademhosseini
Nanoparticles have been used for engineering composite materials to improve the intrinsic properties and/or add functionalities to pristine polymers. The majority of the studies have focused on the incorporation of spherical nanoparticles within the composite fibers. Herein, we incorporate anisotropic branched-shaped zinc oxide (ZnO) nanoparticles into fibrous scaffolds fabricated by electrospinning. The addition of the branched particles resulted in their protrusion from fibers, mimicking the architecture of a rose-stem...
August 18, 2017: Nano Letters
Peida Zhao, Matin Amani, Der-Hsien Lien, Geun Ho Ahn, Daisuke Kiriya, James P Mastandrea, Joel W Ager, Eli Yablonovitch, Daryl C Chrzan, Ali Javey
Understanding edge effects and quantifying their impact on the carrier properties of two-dimensional (2D) semiconductors is an essential step toward utilizing this material for high performance electronic and optoelectronic devices. WS2 monolayers patterned into disks of varying diameters are used to experimentally explore the influence of edges on the material's optical properties. Carrier lifetime measurements show a decrease in the effective lifetime, τeffective, as a function of decreasing diameter, suggesting that the edges are active sites for carrier recombination...
August 18, 2017: Nano Letters
Zhuangqiang Gao, Haihang Ye, Dianyong Tang, Jing Tao, Sanaz Habibi, Adrienne Minerick, Dianping Tang, Xiaohu Xia
Au nanoparticles (AuNPs) as signal reporters have been utilized in colorimetric in vitro diagnostics (IVDs) for decades. Nevertheless, it remains a grand challenge to substantially enhance the detection sensitivity of AuNP-based IVDs as confined by the inherent plasmonics of AuNPs. In this work, we circumvent this confinement by developing a unique dual-functional AuNPs that were engineered by coating conventional AuNPs with ultrathin Pt skins of sub-10 atomic layers (i.e., Au@Pt NPs). The Au@Pt NPs retain the plasmonic activity of initial AuNPs, while possess ultrahigh catalytic activity enabled by Pt skins...
August 18, 2017: Nano Letters
F Hu, Y Luan, Z Fei, I Z Palubski, M D Goldflam, S Dai, J-S Wu, K W Post, G C A M Janssen, M M Fogler, D N Basov
We report a nanoinfrared (IR) imaging study of the localized plasmon resonance modes of graphene nanoribbons (GNRs) using a scattering-type scanning near-field optical microscope (s-SNOM). By comparing the imaging data of GNRs that are aligned parallel and perpendicular to the in-plane component of the excitation laser field, we observed symmetric and asymmetric plasmonic interference fringes, respectively. Theoretical analysis indicates that the asymmetric fringes are formed due to the interplay between the localized surface plasmon resonance (SPR) mode excited by the GNRs and the propagative surface plasmon polariton (SPP) mode launched by the s-SNOM tip...
August 18, 2017: Nano Letters
Philipp Tonndorf, Osvaldo Del Pozo-Zamudio, Nico Gruhler, Johannes Kern, Robert Schmidt, Alexander I Dmitriev, Anatoly P Bakhtinov, Alexander I Tartakovskii, Wolfram Pernice, Steffen Michaelis de Vasconcellos, Rudolf Bratschitsch
Fully integrated quantum technology based on photons is in the focus of current research, because of its immense potential concerning performance and scalability. Ideally, the single-photon sources, the processing units, and the photon detectors are all combined on a single chip. Impressive progress has been made for on-chip quantum circuits and on-chip single-photon detection. In contrast, nonclassical light is commonly coupled onto the photonic chip from the outside, because presently only few integrated single-photon sources exist...
August 18, 2017: Nano Letters
Liming Zhang, Litianqi Sun, Zixuan Guan, Sang Chul Lee, Yingzhou Li, Haitao Dean Deng, Yiyang Li, Nadia Ahlborg, Madhur Boloor, Nicholas A Melosh, William C Chueh
Minority carrier diffusion length (LD) is a crucial property that determines the performance of light absorbers in photoelectrochemical (PEC) cells. Many transition-metal oxides are stable photoanodes for solar water splitting but exhibit a small to moderate LD, ranging from a few nanometers (such as α-Fe2O3 and TiO2) to a few tens of nanometers (such as BiVO4). Under operating conditions, temperature of PEC cells can deviate substantially from ambient, yet the temperature-dependence of LD has not been quantified...
August 17, 2017: Nano Letters
Yifan Dong, Bingliang Wang, Kangning Zhao, Yanhao Yu, Xudong Wang, Liqiang Mai, Song Jin
The development of inexpensive electrode materials with high volumetric capacity and long cycle-life is a central issue for large-scale lithium-ion batteries. Here, we report a nanostructured porous Fe2N anode fully encapsulated in carbon microboxes (Fe2N@C) prepared through a facile confined anion conversion method. The resulting carbon microboxes could not only protect the air-sensitive Fe2N from oxidation, but also retain thin and stable SEI layer. The appropriate internal voids in the Fe2N cubes help to release the volume expansion during lithiation/delithiation processes and Fe2N is kept inside the carbon microboxes without breaking the shell, resulting in a very low electrode volume expansion (the electrode thickness variation upon lithiation is ~9%)...
August 17, 2017: Nano Letters
Ofer Kedem, Bryan Lau, Emily A Weiss
Biological systems utilize a combination of asymmetry, noise, and chemical energy to produce motion in the highly damped environment of the cell with molecular motors, many of which are "ratchets", non-equilibrium devices for producing directed transport using non-directional perturbations, without a net bias. The underlying ratchet principle has been implemented in man-made micro- and nano-devices, to transport charged particles by oscillating an electric potential with repeating asymmetric features. In this experimental study, the ratcheting of electrons in an organic semiconductor is optimized by tuning the temporal modulation of the oscillating potential, applied using nanostructured electrodes...
August 17, 2017: Nano Letters
Yang Zhao, Lyudmila V Goncharova, Qian Zhang, Payam Kaghazchi, Qian Sun, Andrew Lushington, Biqiong Wang, Ruying Li, Xueliang Sun
Metallic Na anode is considered as the promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to the high specific capacity, low potential. However, the unstable solid electrolyte interphase (SEI) layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we firstly demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as protective layer for metallic Na anode...
August 17, 2017: Nano Letters
Deyang Chen, Christopher T Nelson, Xiaohong Zhu, Claudy R Serrao, James D Clarkson, Zhe Wang, Ya Gao, Shang-Lin Hsu, Liv R Dedon, Zuhuang Chen, Di Yi, Heng-Jui Liu, Dechang Zeng, Ying-Hao Chu, Jian Liu, Darrell G Schlom, Ramamoorthy Ramesh
A strain-driven orthorhombic (O) to rhombohedral (R) phase transition is reported in La-doped BiFeO3 thin films on silicon substrates. Biaxial compressive epitaxial strain is found to stabilize the rhombohedral phase at La concentrations beyond the morphotropic phase boundary (MPB). By tailoring the residual strain with film thickness, we demonstrate a mixed O/R phase structure consisting of O phase domains measuring tens of nanometers wide within a predominant R phase matrix. A combination of piezoresponse force microscopy (PFM), transmission electron microscopy (TEM), polarization-electric field hysteresis loop (P-E loop), and polarization maps reveal that the O-R structural change is an antiferroelectric to ferroelectric (AFE-FE) phase transition...
August 17, 2017: Nano Letters
Julian Gargiulo, Thomas Brick, Ianina L Violi, Facundo C Herrera, Toshihiko Shibanuma, Pablo Albella, Félix G Requejo, Emiliano Cortés, Stefan A Maier, Fernando D Stefani
Optical printing holds great potential to enable the use of the vast variety of colloidal nanoparticles (NPs) in nano- and microdevices and circuits. By means of optical forces, it enables the direct assembly of NPs, one by one, onto specific positions of solid surfaces with great flexibility of pattern design and no need of previous surface patterning. However, for unclear causes it was not possible to print identical NPs closer to each other than 300 nm. Here, we show that the repulsion restricting the optical printing of close by NPs arises from light absorption by the printed NPs and subsequent local heating...
August 17, 2017: Nano Letters
Clevin Handschin, Péter Makk, Peter Rickhaus, Romain Maurand, Kenji Watanabe, Takashi Taniguchi, Klaus Richter, Ming-Hao Liu, Christian Schönenberger
At high magnetic fields the conductance of graphene is governed by the half-integer quantum Hall effect. By local electrostatic gating a p-n junction perpendicular to the graphene edges can be formed, along which quantum Hall channels copropagate. It has been predicted by Tworzidło and co-workers that if only the lowest Landau level is filled on both sides of the junction, the conductance is determined by the valley (isospin) polarization at the edges and by the width of the flake. This effect remained hidden so far due to scattering between the channels copropagating along the p-n interface (equilibration)...
August 17, 2017: Nano Letters
Siyuan Dai, Qiong Ma, Yafang Yang, Jeremy Rosenfeld, Michael D Goldflam, Alex McLeod, Zhiyuan Sun, Trond I Andersen, Zhe Fei, Mengkun Liu, Yinming Shao, Kenji Watanabe, Takashi Taniguchi, Mark Thiemens, Fritz Keilmann, Pablo Jarillo-Herrero, Michael M Fogler, D N Basov
We investigated phonon-polaritons in hexagonal boron nitride-a naturally hyperbolic van der Waals material-by means of the scattering-type scanning near-field optical microscopy. Real-space nanoimages we have obtained detail how the polaritons are launched when the light incident on a thin hexagonal boron nitride slab is scattered by various intrinsic and extrinsic inhomogeneities, including sample edges, metallic nanodisks deposited on its top surface, random defects, and surface impurities. The scanned tip of the near-field microscope is itself a polariton launcher whose efficiency proves to be superior to all the other types of polariton launchers we studied...
August 17, 2017: Nano Letters
Seungtaeg Oh, Hakhyeon Song, Jihun Oh
Photoelectrochemical (PEC) cells have attracted much attention as a viable route for storing solar energy and producing value-added chemicals and fuels. However, the competition between light absorption and electrocatalysis at a restrained cocatalyst area on conventional planar-type photoelectrodes could limit their conversion efficiency. Here, we demonstrate a new monolithic photoelectrode architecture that eliminate the optical-electrochemical coupling by forming locally nanostructured cocatalysts on a photoelectrode...
August 17, 2017: Nano Letters
Sergey S Kharintsev, Anton Kharitonov, Semion Saikin, Alexander M Alekseev, Sergei G Kazarian
We consider a nonlinear mechanism of localized light inelastic scattering within nano-patterned plasmonic and Raman-active titanium nitride (TiN) thin films exposed to continuous-wave (cw) modest-power laser light. Owing to the strong third-order nonlinear interaction between optically excited broadband surface plasmons and localized Stokes and anti-Stokes waves, both stimulated and inverse Raman effects can be observed. We provide experimental evidences for coherent amplification of the localized Raman signals using a planar square shaped refractory antenna...
August 16, 2017: Nano Letters
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