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Suman Chowdhury, Debnarayan Jana
Inspired by the success of graphene, various two dimensional (2D) structures in free standing (FS) (hypothetical) form and on different substrates have been proposed recently. Silicene, a silicon counterpart of graphene, is predicted to possess massless Dirac fermions and to exhibit an experimentally accessible quantum spin Hall effect. Since the effective spin-orbit interaction is quite significant compared to graphene, buckling in silicene opens a gap of 1.55 meV at the Dirac point. This band gap can be further tailored by applying in plane stress, an external electric field, chemical functionalization and defects...
October 18, 2016: Reports on Progress in Physics
Youngho Kang, Ho-Hyun Nahm, Seungwu Han
The persistent photoconductivity (PPC) in ZnO has been a critical problem in opto-electrical devices employing ZnO such as ultraviolet sensors and thin film transistors for the transparent display. While the metastable state of oxygen vacancy (VO) is widely accepted as the microscopic origin of PPC, recent experiments on the influence of temperature and oxygen environments are at variance with the VO model. In this study, using the density-functional theory calculations, we propose a novel mechanism of PPC that involves the hydrogen-zinc vacancy defect complex (2H-VZn)...
October 17, 2016: Scientific Reports
Eva Bladt, Relinde J A van Dijk-Moes, Joep Peters, Federico Montanarella, Celso de Mello Donegá, Daniël Vanmaekelbergh, Sara Bals
Hetero-nanocrystals consisting of a CdSe core and a giant CdS shell have shown remarkable optical properties which are promising for applications in opto-electrical devices. Since these properties sensitively depend on the size and shape, a morphological characterization is of high interest. Here, we present a High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) study of CdSe (core) / CdS (giant shell) hetero-nanocrystals. Electron tomography reveals that the nanocrystals have a bullet shape, either ending in a tip or a small dip, and that the CdSe core is positioned closer to the tip (or dip) than to the hexagonal base...
October 14, 2016: Journal of the American Chemical Society
Jihyeon Kim, Ju Won Lim, Filipe Marques Mota, Ji-Eun Lee, Ramireddy Boppella, Keun Yong Lim, Kyungkon Kim, Won Kook Choi, Dong Ha Kim
Transparent conductive electrodes (TCEs) are widely used in a wide range of optical-electronic devices. Recently, metal nanowires (NWs), e.g. Ag and Cu, have drawn attention as promising flexible materials for TCEs. Although the study of core-shell metal NWs, and the encapsulation/overcoating of the surface of single-metal NWs have separately been an object of focus in the literature, herein for the first time we simultaneously applied both strategies in the fabrication of highly stable Ag-Cu NW-based TCEs by the utilization of Ag nanoparticles covered with reduced graphene oxide (rGO)...
October 14, 2016: Nanoscale
Joon-Suh Park, Ji-Hoon Kyhm, Honghee Kim, Shin-Young Jeong, JoonHyun Kang, Song-Ee Lee, Kyu-Tae Lee, Kisun Park, Nilesh Barange, JiYeong Han, Jin Dong Song, Won-Kook Choi, Il Ki Han
Although various colloidal quantum dot (QD) coating and patterning techniques have been developed to meet the demands in opto-electronic applications over the past years, each of the previously demonstrated methods has one or more limitations and trade-offs in forming multi-color, high-resolution, or large-area patterns of QDs. In this study, we present an alternative QD patterning technique using conventional photolithography combined with charge-assisted layer-by-layer (LbL) assembly to solve the trade-offs of the traditional patterning processes...
October 13, 2016: Nano Letters
Shanming Ke, Chang Chen, Nian-Qing Fu, Hua Zhou, Mao Ye, Peng Lin, Wen-Xiang Yuan, Xierong Zeng, Lang Chen, Haitao Huang
Sn-doped In2O3 (ITO) electrodes were deposited on transparent and flexible muscovite mica. The use of mica substrate makes a high-temperature annealing process (up to 500 °C) possible. ITO/mica retains its low electric resistivity even after continuous bending of 1000 times on account of the unique layered structure of mica. When used as a transparent flexible heater, ITO/mica shows an extremely fast ramping (< 15 s) up to a high temperature of over 438 °C. When used as a transparent electrode, ITO/mica permits a high temperature annealing (450 °C) approach to fabricate flexible perovskite solar cells (PSCs) with high efficiency...
October 11, 2016: ACS Applied Materials & Interfaces
Khaled M Yassien, Mostafa Agour
A method for studying the effect of temperature on the optical properties of basalt fiber is presented. It is based on recording a set of phase-shifted digital holograms for the sample under the test. The holograms are obtained utilizing a system based on Mach-Zehnder interferometer, where the fiber sample inserted in an immersion liquid is placed within a temperature controlled chamber. From the recorded digital holograms the optical path differences which are used to calculate the refractive indices are determined...
October 11, 2016: Microscopy Research and Technique
Oksana Ostroverkhova
Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials...
October 10, 2016: Chemical Reviews
Nils Lenngren, Mohamed A Abdellah, Kaibo Zheng, Mohammed J Al-Marri, Donatas Zigmantas, Karel Žídek, Tõnu Pullerits
Colloidal quantum dots (QDs) have attracted interest as materials for opto-electronic applications, wherein their efficient energy use requires the understanding of carrier relaxation. In QDs capped by bifunctional thiols, used to attach the QDs to a surface, the relaxation is complicated by carrier traps. Using 2D spectroscopy at 77 K, we follow excitations in thiol-capped CdSe QDs with state specificity and high time resolution. We unambiguously identify the lowest state as an optically allowed hole trap, and identify an electron trap with excited-state absorption...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Guillaume H V Bertrand, Anatolii Polovitsyn, Sotirios Christodoulou, Ali Hossain Khan, Iwan Moreels
The lateral dimensions of CdSe nanoplatelets have a strong and unique influence on their opto-electronic properties, with sizes that can be tuned from the weak to the strong exciton confinement regime. There are state-of-the-art reports on several nanoplatelet syntheses; however, at present only the thickness is well-controlled. We demonstrate here that we can achieve a control over the aspect ratio and overall nanoplate area by carefully adjusting the reagents that induce the in-plane growth. A variation of the fraction of hydrated Cd(OAc)2 in a Cd(OAc)2/Cd(OAc)2·2H2O mixture tailors the nanoplatelet aspect ratio...
September 29, 2016: Chemical Communications: Chem Comm
Woo-Yong Jang, Zahyun Ku, Jiyeon Jeon, Jun Oh Kim, Sang Jun Lee, James Park, Michael J Noyola, Augustine Urbas
In our previous theoretical study, we performed target detection using a plasmonic sensor array incorporating the data-processing technique termed "algorithmic spectrometry". We achieved the reconstruction of a target spectrum by extracting intensity at multiple wavelengths with high resolution from the image data obtained from the plasmonic array. The ultimate goal is to develop a full-scale focal plane array with a plasmonic opto-coupler in order to move towards the next generation of versatile infrared cameras...
October 10, 2016: Scientific Reports
Jalal Sadeghi, Amir Hossein Baradaran Ghasemi, Hamid Latifi
The ability to accurately measure the flow rate, concentration, and temperature in real-time in micro total analysis systems (μTAS) is crucial when improving their practical sensing capabilities within extremely small volumes. Our label-free infrared (1500-1600 nm) opto-fluidic method, presented in this study, utilizes a cantilever-based flow meter integrated with two parallel optical fiber Fabry-Perot interferometers (FPIs). The first FPI serves as an ultra-sensitive flow meter and includes a Fiber Bragg Grating (FBG) tip for localized temperature sensing...
October 5, 2016: Lab on a Chip
Alborz Feizi, Yibo Zhang, Alon Greenbaum, Alex Guziak, Michelle Luong, Raymond Yan Lok Chan, Brandon Berg, Haydar Ozkan, Wei Luo, Michael Wu, Yichen Wu, Aydogan Ozcan
Monitoring yeast cell viability and concentration is important in brewing, baking and biofuel production. However, existing methods of measuring viability and concentration are relatively bulky, tedious and expensive. Here we demonstrate a compact and cost-effective automatic yeast analysis platform (AYAP), which can rapidly measure cell concentration and viability. AYAP is based on digital in-line holography and on-chip microscopy and rapidly images a large field-of-view of 22.5 mm(2). This lens-free microscope weighs 70 g and utilizes a partially-coherent illumination source and an opto-electronic image sensor chip...
September 30, 2016: Lab on a Chip
Meilin Tian, Shixin Ye
Allostery is essential to neuronal receptor function, but its transient nature poses a challenge for characterization. The N-terminal domains (NTDs) distinct from ligand binding domains are a major locus for allosteric regulation of NMDA receptors (NMDARs), where different modulatory binding sites have been observed. The inhibitor ifenprodil, and related phenylethanoamine compounds specifically targeting GluN1/GluN2B NMDARs have neuroprotective activity. However, whether they use differential structural pathways than the endogenous inhibitor Zn(2+) for regulation is unknown...
October 7, 2016: Scientific Reports
Rico Gutzler
Conjugated polymers find widespread application in (opto)electronic devices, sensing, and as catalysts. Their common one-dimensional structure can be extended into the second dimension to create conjugated planar sheets of covalently linked molecules. Extending π-conjugation into the second dimension unlocks a new class of semiconductive polymers which as a consequence of their unique electronic properties can find usability in numerous applications. In this article the theoretical band structures of a set of conjugated 2D polymers are compared and information on the important characteristics band gap and valence/conduction band dispersion is extracted...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Jin Young Kim, Changho Lee, Kyungjin Park, Sangyeob Han, Chulhong Kim
Optical-resolution photoacoustic microscopy (OR-PAM), a promising microscopic imaging technique with high ultrasound resolution and superior optical sensitivity, can provide anatomical, functional, and molecular information at scales ranging from the microvasculature to single red blood cells. In particular, real-time OR-PAM imaging with a high signal-to-noise ratio (SNR) is a prerequisite for widespread use in preclinical and clinical applications. Although several technical approaches have been pursued to simultaneously improve the imaging speed and SNR of OR-PAM, they are bulky, complex, not sensitive, and/or not actually real-time...
October 6, 2016: Scientific Reports
Xiao Wang, Ranran Wang, Haitao Zhai, Xi Shen, Tao Wang, Liangjing Shi, Richeng Yu, Jing Sun
Cu nanowires (Copper nanowires) have attracted lots of attention recently due to their potential applications in transparent electrodes, SERS sensors and solar cells. However, as the surface composition and morphology of Cu nanowires severely influence the performance of the devices based on them, facial surface modification methods need to be developed. Herein, we propose a room-temperature, time-saving aqueous solution method, which can simultaneously clean the surface of copper nanowires and decorate them with Ag nanoparticles at room temperature without any atmospheric control...
October 5, 2016: ACS Applied Materials & Interfaces
Maria Antonietta Ferrara, Edoardo De Tommasi, Giuseppe Coppola, Luca De Stefano, Ilaria Rea, Principia Dardano
The frustule of diatoms, unicellular microalgae, shows very interesting photonic features, generally related to its complicated and quasi-periodic micro- and nano-structure. In order to simulate light propagation inside and through this natural structure, it is important to develop three-dimensional (3D) models for synthetic replica with high spatial resolution. In this paper, we present a new method that generates images of microscopic diatoms with high definition, by merging scanning electron microscopy and digital holography microscopy or atomic force microscopy data...
2016: International Journal of Molecular Sciences
Drew Dickson, Aniruddha Agarwal, Mohammad Ali Sadiq, Muhammad Hassan, Robin High, Quan Dong Nguyen, Yasir J Sepah
BACKGROUND: Conventional fundus imaging has been used to assess vitreous haze (VH) in patients with uveitis. Ultra-wide field (UWF) retinal imaging that uses scanning laser technology has not been evaluated for the detection of VH. This pilot study evaluates the ability of UWF imaging in detecting VH. Patients with intermediate, posterior, or panuveitis were examined to assess the level of VH using slit-lamp biomicroscopy. Colored fundus images were acquired using a Carl Zeiss FF450 camera...
December 2016: Journal of Ophthalmic Inflammation and Infection
N Mehta, A Cocking, C Zhang, D Ma, Y Xu, Z Liu
We present the fabrication and characterization of an opto-electronic fiber device which can allow for both electromechanical functionality and optical waveguiding capability. The air holes of a photonic crystal fiber are selectively sealed and then pumped with molten metal under pressure. The metal filled holes act as electrodes to which individual carbon nanotubes (CNT) are attached precisely by a laser-welding technique or a focused ion beam assisted pick-and-bond technique. The optical modal profile and the group velocity dispersion of the fabricated device are studied both numerically and experimentally...
September 29, 2016: Nanotechnology
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