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Andre Neumann, Jessica Lindlau, Léo Colombier, Manuel Nutz, Sina Najmaei, Jun Lou, Aditya D Mohite, Hisato Yamaguchi, Alexander Högele
Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional optoelectronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides...
January 16, 2017: Nature Nanotechnology
Yunxia Jin, Kaiqing Wang, Yuanrong Cheng, Qibing Pei, Yuxi Xu, Fei Xiao
In this work, a composite silver nanowire (AgNW) transparent electrode that is large-area ultra-smooth without conductivity or transmittance scarifice, removable but with good resistance to both water and organic solvent is reported. Via a simple low-temperature solution process without complicated transfer steps or additional pressure pressing, a new kind of AgNWs composite with biocompatible and patternable chitosan polymer complex demonstrates a quite low RMS (root mean square) roughness ~7 nm at a largest reported scan size of 50 μm*50 μm, which is among the best flat surface...
January 16, 2017: ACS Applied Materials & Interfaces
Amitha Domalpally, Traci E Clemons, Ronald P Danis, SriniVas R Sadda, Catherine A Cukras, Cynthia A Toth, Thomas R Friberg, Emily Y Chew
PURPOSE: To compare rates of peripheral retinal changes in Age-Related Eye Disease Study 2 (AREDS2) participants with at least intermediate age-related macular degeneration (AMD) with control subjects without intermediate age-related changes (large drusen). DESIGN: Cross-sectional evaluation of clinic-based patients enrolled in AREDS2 and a prospective study. PARTICIPANTS: Participants from prospective studies. METHODS: The 200° pseudocolor and fundus autofluorescence (FAF) images were captured on the Optos 200 Tx Ultrawide-field device (Optos, Dunfermline, Scotland) by centering on the fovea and then steering superiorly and inferiorly...
January 12, 2017: Ophthalmology
Claudia Backes, Damien Hanlon, Beata M Szydlowska, Andrew Harvey, Ronan J Smith, Thomas M Higgins, Jonathan N Coleman
We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications...
December 20, 2016: Journal of Visualized Experiments: JoVE
Daniel Bellinger, Jens Pflaum, Christoph Brüning, Volker Engel, Bernd Engels
Perylene-based compounds are promising materials for opto-electronic thin film devices but despite intense investigations, important details of their electronic structure are still under debate. For perylene-3,4,9,10-tetracarboxylic dianhydrid (PTCDA), the theoretical models predict a different relative energetic order of Frenkel and Charge Transfer (CT) states. Additionally, while one model indicates strong differences between PTCDA on one hand and other perylene-based compounds on the other, recent ab initio computations indicate electronic properties of all perylene-based compounds to resemble each other...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Meng-Yang Ye, Zhi-Hao Zhao, Zhuo-Feng Hu, Le-Quan Liu, Hui-Ming Ji, Zhu-Rui Shen, Tian-Yi Ma
0D/2D heterojunctions, especially quantum dots (QDs)/nanosheets (NSs) have attracted significant attention for use of photoexcited electrons/holes due to their high charge mobility. Herein, unprecedent heterojunctions of vanadate (AgVO3 , BiVO4 , InVO4 and CuV2 O6 ) QDs/graphitic carbon nitride (g-C3 N4 ) NSs exhibiting multiple unique advances beyond traditional 0D/2D composites have been developed. The photoactive contribution, up-conversion absorption, and nitrogen coordinating sites of g-C3 N4 NSs, highly dispersed vanadate nanocrystals, as well as the strong coupling and band alignment between them lead to superior visible-light-driven photoelectrochemical (PEC) and photocatalytic performance, competing with the best reported photocatalysts...
January 4, 2017: Angewandte Chemie
Alessandro Fortunelli, Luca Sementa, Viraj Dhanushka Thanthirige, Tanya C Jones, Mauro Stener, Kevin J Gagnon, Amala Dass, Guda Ramakrishna
We introduce a class of gold nanomolecules exhibiting anisotropy as a major feature by reporting steady-state and time-resolved photoluminescence and anisotropy measurements and in-depth theoretical analysis of energetics and optical response of a recently synthesized Au21S(SAdm)15 nanomolecule (SAdm = adamantanethiol). Starting from single-crystal X-ray data showing that Au21S(SAdm)15 exhibits a symmetry-broken structure, we unambiguously demonstrate how this translates into a striking anisotropy of its properties, for example, of its (chiro)optical absorption spectrum of great promise for sensing, optoelectronic, and electrochemical applications, and argue about the abundance and general significance of this class of compounds...
January 19, 2017: Journal of Physical Chemistry Letters
Haiqing Liu, Jinkyu Han, Coray McBean, Crystal S Lewis, Prahlad Kumar Routh, Mircea Cotlet, Stanislaus S Wong
Understanding the key parameters necessary for generating uniform Er,Yb co-activated NaYF4 possessing various selected phases (i.e. cubic or hexagonal) represents an important chemical strategy towards tailoring optical behavior in these systems. Herein, we report on a straightforward hydrothermal synthesis in which the separate effects of reaction temperature, reaction time, and precursor stoichiometry in the absence of any surfactant were independently investigated. Interestingly, the presence and the concentration of NH4OH appear to be the most critical determinants of the phase and morphology...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
Adekunle T Bademosi, Elsa Lauwers, Pranesh Padmanabhan, Lorenzo Odierna, Ye Jin Chai, Andreas Papadopulos, Geoffrey J Goodhill, Patrik Verstreken, Bruno van Swinderen, Frédéric A Meunier
Syntaxin1A is organized in nanoclusters that are critical for the docking and priming of secretory vesicles from neurosecretory cells. Whether and how these nanoclusters are affected by neurotransmitter release in nerve terminals from a living organism is unknown. Here we imaged photoconvertible syntaxin1A-mEos2 in the motor nerve terminal of Drosophila larvae by single-particle tracking photoactivation localization microscopy. Opto- and thermo-genetic neuronal stimulation increased syntaxin1A-mEos2 mobility, and reduced the size and molecular density of nanoclusters, suggesting an activity-dependent release of syntaxin1A from the confinement of nanoclusters...
January 3, 2017: Nature Communications
Jiangjian Shi, Dongmei Li, Yanhong Luo, Huijue Wu, Qingbo Meng
An opto-electro-modulated transient photovoltage/photocurrent system has been developed to probe microscopic charge processes of a solar cell in its adjustable operating conditions. The reliability of this system is carefully determined by electric circuit simulations and experimental measurements. Using this system, the charge transport, recombination and storage properties of a conventional multicrystalline silicon solar cell under different steady-state bias voltages, and light illumination intensities are investigated...
December 2016: Review of Scientific Instruments
Viktor Tsvirkun, Siddharth Sivankutty, Géraud Bouwmans, Ori Katz, Esben Ravn Andresen, Hervé Rigneault
We demonstrate pixelation-free real-time widefield endoscopic imaging through an aperiodic multicore fiber (MCF) without any distal opto-mechanical elements or proximal scanners. Exploiting the memory effect in MCFs, the images in our system are directly obtained without any post-processing using a static wavefront correction obtained from a single calibration procedure. Our approach allows for video-rate 3D widefield imaging of incoherently illuminated objects with imaging speed not limited by the wavefront-shaping device refresh rate...
October 15, 2016: Optics Letters
Yingda Jiang, Sha Yang, Shuang Li, Wei Liu
Understanding the binding mechanism for aromatic molecules on transition-metal surfaces in atomic scale is a major challenge in designing functional interfaces for to (opto)electronic devices. Here, we employ the state-of-the-art many-body dispersion (MBD) approach, coupled with density functional theory methods, to study the interactions of benzene with low-index coinage metal surfaces. The many-body effects contribute mostly to the (111) surface, and leastly to the (110) surface. This corresponds to the same sequence of planar atomic density of face-centered-cubic lattices, i...
December 22, 2016: Scientific Reports
Elisabeth Gruber, Richard A Wilhelm, Rémi Pétuya, Valerie Smejkal, Roland Kozubek, Anke Hierzenberger, Bernhard C Bayer, Iñigo Aldazabal, Andrey K Kazansky, Florian Libisch, Arkady V Krasheninnikov, Marika Schleberger, Stefan Facsko, Andrei G Borisov, Andrés Arnau, Friedrich Aumayr
The way conduction electrons respond to ultrafast external perturbations in low dimensional materials is at the core of the design of future devices for (opto)electronics, photodetection and spintronics. Highly charged ions provide a tool for probing the electronic response of solids to extremely strong electric fields localized down to nanometre-sized areas. With ion transmission times in the order of femtoseconds, we can directly probe the local electronic dynamics of an ultrathin foil on this timescale. Here we report on the ability of freestanding single layer graphene to provide tens of electrons for charge neutralization of a slow highly charged ion within a few femtoseconds...
December 21, 2016: Nature Communications
Mahshid Ahmadi, Stevin S Pramana, Chris Boothroyd, Yeng Ming Lam
The performance of solar cells fabricated using Cu(In,Ga)(S,Se)2 nanocrystal (NC) inks synthesized using the hot injection method has yielded efficiencies up to 12% recently. The efficiency of these devices is highly dependent on the chemical composition and crystallographic quality of the NCs. The former has been extensively discussed as it can be easily correlated to the optical properties of the film, but detailed crystallographic structure of these NCs has scarcely been discussed and it can influence both the optical and electrical properties...
January 27, 2017: Nanotechnology
E Vannacci, S Granchi, L Belsito, A Roncaglia, E Biagi
An ultrasonic probe consisting of two optical fiber-based miniaturized transducers for wideband ultrasound emission and detection is employed for the characterization of in vitro biological tissues. In the probe, ultrasound generation is obtained by thermoelastic emission from patterned carbon films in Micro-Opto-Mechanical-System (MOMS) devices mounted on the tip of an optical fiber, whereas acousto-optical detection is performed in a similar way by a miniaturized polymeric interferometer. The microprobe presents a wide, flat bandwidth that is a very attractive feature for ultrasonic investigation, especially for tissue characterization...
March 2017: Ultrasonics
Aixue Shang, Xiaofeng Li
An opto-electro-thermal simulation of solar cells (SCs) is presented by addressing optoelectronic and thermodynamic responses simultaneously. The photocurrent losses due to carrier recombinations and the intrinsic heat generation (thermalization/Joule/Peltier/recombination heat) and dissipation (convective/radiative cooling) processes in the SCs are investigated quantitatively.
December 19, 2016: Advanced Materials
R Maiti, S Haldar, D Majumdar, A Singha, S K Ray
The novel opto-chemical doping effect in Ag nanoparticle-decorated monolayer graphene grown by chemical vapor deposition has been investigated using Raman spectroscopy for the first time. We used both noble metal nanoparticles and optical excitation, in a hybrid opto-chemical route, to tune the doping level in graphene. Metal nanoparticle-induced chemical effects and laser power-induced substrate effects alter the doping nature of graphene from p- to n-type. Compared with earlier studies, the proposed method significantly lowers the laser intensity required for optical power-dependent doping, resulting in prevention of damage to the sample due to local heating...
December 15, 2016: Nanotechnology
Mahmoud A Farghaly, Muhammad Nadeem Akram, Einar Halvorsen
WWe report a modeling framework for evaluating the performance of piezoelectrically actuated MEMS tunable lenses. It models the static opto-electromechanical coupling for symmetric configurations of piezoelectric actuators based on the laminated-plate theory, linear piezoelectricity, and ray tracing. With these assumptions, it helps to find geometrical parameters for actuators on clamped square or circular diaphragms that give a diffraction-limited tunable lens with minimum F-number. The tunable lens' optical performance and its focusing capability, alone and in combination with a paraxial fixed lens, were calculated in terms of object distance and actuation voltage...
December 12, 2016: Optics Express
Zhengxin Li, Jesus Nieto-Pescador, Alexander J Carson, Jolie C Blake, Lars Gundlach
A two-step chemical vapor deposition procedure is here employed to prepare tree-like hierarchical ZnO/CdSSe hetero-nanostructures. The structures are composed of CdSSe branches grown on ZnO nanowires that are vertically aligned on a transparent sapphire substrate. The morphology was measured via scanning electron microscopy. The crystal structure was determined by X-ray powder diffraction analysis. Both the ZnO stem and CdSSe branches have a predominantly wurtzite crystal structure. The mole ratio of S and Se in the CdSSe branches was measured by energy dispersive X-ray spectroscopy...
November 29, 2016: Journal of Visualized Experiments: JoVE
Carlos Balsalobre-Fernández, Hovannes Agopyan, Jean-Benoit Morin
The purpose of this investigation was to analyze the validity of an iPhone application (Runmatic) for measuring running mechanics. To do this, 96 steps from 12 different runs at speeds ranging from 2.77-5.55 m·s-1 were recorded simultaneously with Runmatic as well as with an opto-electronic device installed on a motorized treadmill to measure the contact and aerial time of each step. Additionally, several running mechanics variables were calculated using the contact and aerial times measured and previously validated equations...
December 5, 2016: Journal of Applied Biomechanics
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