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Haobin Chen, Jian Zhang, Kaiwen Chang, Xiaoju Men, Xiaofeng Fang, Libo Zhou, Dongliang Li, Duyang Gao, Shengyan Yin, Xuanjun Zhang, Zhen Yuan, Changfeng Wu
Semiconducting polymers with specific absorption are useful in various applications, including organic optoelectronics, optical imaging, and nanomedicine. However, the optical absorption of a semiconducting polymer with a determined structure is hardly tunable when compared with that of inorganic semiconductors. In this work, we show that the optical absorption of polymer nanoparticles from one conjugated backbone can be effectively tuned through judicious design of the particle morphology and the persistence length of polymers...
August 12, 2017: Biomaterials
Makoto Naruse, Yuta Terashima, Atsushi Uchida, Song-Ju Kim
Reinforcement learning involves decision making in dynamic and uncertain environments and constitutes an important element of artificial intelligence (AI). In this work, we experimentally demonstrate that the ultrafast chaotic oscillatory dynamics of lasers efficiently solve the multi-armed bandit problem (MAB), which requires decision making concerning a class of difficult trade-offs called the exploration-exploitation dilemma. To solve the MAB, a certain degree of randomness is required for exploration purposes...
August 18, 2017: Scientific Reports
Frank Bello, A Freddie Page, Andreas Pusch, Joachim M Hamm, John F Donegan, Ortwin Hess
We investigate media which exhibits epsilon-near-zero (ENZ) behavior while simultaneously sustaining stopped light energy bands which contain multiple points of zero group velocity (ZGV). This allows the merging of state-of-the-art phenomena that was hitherto attainable in media that demonstrated these traits separately. Specifically, we demonstrate the existence of Ferrell-Berreman (FB) modes within frequency bands bounded by points of ZGV with the goal to improve the coupling efficiency and localization of light in the media...
August 18, 2017: Scientific Reports
Jamie C Wang, Kyle Violette, Omotola O Ogunsolu, Seda Cekli, Eric Lambers, Hadi M Fares, Kenneth Hanson
Self-assembled bilayer on nanocrystalline metal oxide films is an increasingly popular strategy for modulating electron and energy transfer at the dye-semiconductor interfaces. A majority of the work to date has relied on ZrII and ZnIV linking ions to assemble the films. In this report we demonstrate that several different cations (CdII, CuII, FeII, LaIII, MnII, and SnIV) are not only effective in generating the bilayer assemblies but also have a profound influence on the stability and photophysical properties of the films...
August 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Emilson Ribeiro Viana, Geraldo Mathias Ribeiro, Alfredo G de Oliveira, Juan Carlos Gonzalez Perez
An individual tin oxide (SnO<sub>2</sub>) nanobelt was connected in a back-gate field-effect transistor (FET) configuration and the conductivity of the nanobelt were measured at different temperatures from 400K to 4K, in darkness and under UV illumination. In darkness, the SnO<sub>2</sub> nanobelts show semiconductor behaviour for the whole temperature range measured. But when subject to UV illumination the photoinduced carriers was high enough that leads to a Metal-to-Insulator transition, near room temperature, at T<sub>MIT</sub> = 240 K...
August 18, 2017: Nanotechnology
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
Dazhen Huang, Huiying Yao, Yutao Cui, Ye Zou, Fengjiao Zhang, Chao Wang, Hongguang Shen, Wenlong Jin, Jia Zhu, Ying Diao, Wei Xu, Chong-An Di, Daoben Zhu
Conjugated backbones play a fundamental role in determining the electronic properties of organic semiconductors. Based on two solution-processable dropyrrolo[3,4-c]pyrrole-1,4-diylidene)bis(thieno[3,2-b]thiophene derivatives with aromatic and quinoid structures, we have carried out a systematic study of the relationship between the conjugated-backbone structure and the thermoelectric properties. In particular, a combination of UV-vis-NIR spectra, photoemission spectroscopy and doping optimization are utilized to probe the interplay between energy levels, chemical doping, and thermoelectric performance...
August 18, 2017: Journal of the American Chemical Society
Yan Fang, Spandhana Gonuguntla, Siowling Soh
Static charge generated by contact electrification on surfaces can lead to many undesirable consequences, such as a reduction in the efficiency of manufacturing processes, damage to equipment, and explosions. However, it is extremely challenging to avoid contact electrification because it is ubiquitous - almost all types of materials charge on contact. Here, we coated materials with naturally-occurring polydopamine (PDA) and tannic acid (TA) for preparing non-charging surfaces. Importantly, these coatings are very versatile and can be coated on a wide range of materials, including metals, inorganic materials, semiconductors, and polymers...
August 18, 2017: ACS Applied Materials & Interfaces
Yandong Ma, Agnieszka Kuc, Thomas Heine
First metal-shrouded two-dimensional semicon-ductor, single-layer Tl2O, is discussed from first-principles. It is thermally and dynamically stable, has a low cleavage energy call-ing for exfoliation from layered Tl2O bulk, and a very small inter-face mismatch compared to (001) Tl metal. Single-layer Tl2O ex-hibits a direct band gap of 1.56 eV and a very high charge carrier mobility of 4.3×103 cm2 V-1 s-1. The metal-shrouded 2D semicon-ductor promises interesting applications in 2D electronics. An in-triguing layer-thickness dependent direct-to-indirect bandgap tran-sition is observed, and contrary to early literature, the bulk is also a semiconductor...
August 18, 2017: Journal of the American Chemical Society
Mohamed Abdellah, Felipe Poulsen, Qiushi Zhu, Nan Zhu, Karel Žídek, Pavel Chábera, Annamaria Corti, Thorsten Hansen, Qijin Chi, Sophie E Canton, Kaibo Zheng, Tõnu Pullerits
Ultrafast fluorescence spectroscopy was used to investigate the hole injection in CdxSeyZn1-xS1-y gradient core-shell quantum dot (CSQD) sensitized p-type NiO photocathodes. A series of CSQDs with a wide range of shell thicknesses was studied. Complementary photoelectrochemical cell measurements were carried out to confirm that the hole injection from the active core through the gradient shell to NiO takes place. The hole injection from the valence band of the QDs to NiO depends much less on the shell thickness when compared to the corresponding electron injection to n-type semiconductor (ZnO)...
August 18, 2017: Nanoscale
Yousuke Ooyama, Toshiaki Enoki, Satoshi Aoyama, Joji Ohshita
We designed and developed a fused-bibenzo[c]thiophene, namely, 2,9-bis(tert-butyldimethylsilyl)phenanthro[9,8-bc:10,1-b'c']dithiophene (PHDT-Si), as a new π-building block in the emitters, photosensitizers and semiconductors for organic optoelectronic devices. Based on photophysical (photoabsorption, fluorescence and time-resolved fluorescence spectroscopy) and electrochemical measurements (cyclic voltammetry), and density functional theory (DFT) calculations, this work reveals that the fused-bibenzo[c]thiophene PHDT-Si, which is prepared by an efficient synthesis method, has a rigid, high planar and expanded π-conjugation structure, and possesses intense photoabsorption and fluorescence properties (λ = 598 nm (εmax = 41 000 M(-1) cm(-1)) and λ = 613 nm (Φf = 0...
August 18, 2017: Organic & Biomolecular Chemistry
Michal J Mleczko, Chaofan Zhang, Hye Ryoung Lee, Hsueh-Hui Kuo, Blanka Magyari-Köpe, Robert G Moore, Zhi-Xun Shen, Ian R Fisher, Yoshio Nishi, Eric Pop
The success of silicon as a dominant semiconductor technology has been enabled by its moderate band gap (1.1 eV), permitting low-voltage operation at reduced leakage current, and the existence of SiO2 as a high-quality "native" insulator. In contrast, other mainstream semiconductors lack stable oxides and must rely on deposited insulators, presenting numerous compatibility challenges. We demonstrate that layered two-dimensional (2D) semiconductors HfSe2 and ZrSe2 have band gaps of 0.9 to 1.2 eV (bulk to monolayer) and technologically desirable "high-κ" native dielectrics HfO2 and ZrO2, respectively...
August 2017: Science Advances
Kwangwook Park, Kirstin Alberi
Integrating different semiconductor materials into an epitaxial device structure offers additional degrees of freedom to select for optimal material properties in each layer. However, interfaces between materials with different valences (i.e. III-V, II-VI and IV semiconductors) can be difficult to form with high quality. Using ZnSe/GaAs as a model system, we explore the use of ultraviolet (UV) illumination during heterovalent interface growth by molecular beam epitaxy as a way to modify the interface properties...
August 17, 2017: Scientific Reports
Hongcen Yang, Shouwei Zhang, Ruya Cao, Xiaolong Deng, Zhipeng Li, Xijin Xu
Ultrafine particles, more heterojunction interfaces and amorphous materials can effectively enhance the photocatalytic activity of photocatalysts. In this work, a facile in-situ precipitation method was developed to prepare ultrafine amorphous iron oxyhydroxide/ultrathin g-C3N4 nanosheets heterojunction composites. The amorphous iron oxyhydroxide possessed an ultrafine particle size and a wide range of visible light absorption. In this process, the ultrafine particles not only shortened the diffusion distance of photogenerated carriers, but also facilitated the formation of more heterojunctions with ultrathin g-C3N4 nanosheets...
August 17, 2017: Scientific Reports
Enquan Jin, Mizue Asada, Qing Xu, Sasanka Dalapati, Matthew A Addicoat, Michael A Brady, Hong Xu, Toshikazu Nakamura, Thomas Heine, Qiuhong Chen, Donglin Jiang
We synthesized a two-dimensional (2D) crystalline covalent organic framework (sp(2)c-COF) that was designed to be fully π-conjugated and constructed from all sp(2) carbons by C=C condensation reactions of tetrakis(4-formylphenyl)pyrene and 1,4-phenylenediacetonitrile. The C=C linkages topologically connect pyrene knots at regular intervals into a 2D lattice with π conjugations extended along both x and y directions and develop an eclipsed layer framework rather than the more conventionally obtained disordered structures...
August 18, 2017: Science
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", nonequilibrium devices for producing directed transport using nondirectional perturbations without a net bias. The underlying ratchet principle has been implemented in man-made micro- and nanodevices 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 21, 2017: Nano Letters
Monika Gupta, Santosh Prasad Gupta, Santanu Kumar Pal
A straightforward synthesis of triphenylene-based oligomeric systems that self-organize into room temperature columnar structures is presented. The compounds with longer spacer length (m = 10 and 12) exhibit columnar rectangular (Colr) mesophase whereas the compound with m = 8 exists in glassy Colr state. Interestingly, the Colr self-assembly of these compounds switches to columnar hexagonal (Colh) on doping the compounds with 2, 4, 7-trinitrofluorenone (TNF). For the dopant concentration of 1:1 with respect to native compound, an intermediate transition state between Colr and Colh phase was observed which completely transformed into the hexagonal phase on increasing the concentration to 1:2 (compound: TNF) and afterwards...
August 17, 2017: Journal of Physical Chemistry. B
Fabio Scholl, Paulo Morais, Rayla Gabriel, Michael J Schöning, Jose Roberto Siqueira, Luciano Caseli
In this paper, carbon nanotubes (CNTs) were incorporated in penicillinase-phospholipid Langmuir and Langmuir-Blodgett (LB) films to enhance the enzyme catalytic properties. Adsorption of the penicillinase and CNTs at dimyristoylphosphatidic acid (DMPA) monolayers at the air-water interface was investigated by surface pressure-area isotherms, vibrational spectroscopy and Brewster angle microscopy. The floating monolayers were transferred to solid supports through the LB technique, forming mixed DMPA-CNTs-PEN films, which were investigated by quartz crystal microbalance, vibrational spectroscopy, and atomic force microscopy...
August 17, 2017: ACS Applied Materials & Interfaces
Andreas Schwaighofer, Markus Brandstetter, Bernhard Lendl
Quantum cascade lasers (QCL) are the first room temperature semiconductor laser source for the mid-IR spectral region, triggering substantial development for the advancement of mid-IR spectroscopy. Mid-IR spectroscopy in general provides rapid, label-free and objective analysis, particularly important in the field of biomedical analysis. Due to their unique properties, QCLs offer new possibilities for development of analytical methods to enable quantification of clinically relevant concentration levels and to support medical diagnostics...
August 17, 2017: Chemical Society Reviews
Xing Huang, Travis Jones, Hua Fan, Marc-Georg Willinger
Void formation in semiconductors is generally considered to be deteriorating. However, for some systems, void formation and evolution are beneficial and can be used for the fabrication of novel nanostructures. In either scenario, the understanding of void formation and evolution is of both scientific and technical high importance. Herein, using ZnS ribbons as an example, we report real-time observations of void formation and the kinetics of growth at the nano- and atomic scales upon heating. Direct imaging reveals that voids, created by a focused electron beam in wurtzite (WZ) ribbons, have a rectangular shape elongated along the <0001> direction...
August 17, 2017: Nanoscale
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