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Low band gap

Minas M Stylianakis, Temur Maksudov, Apostolos Panagiotopoulos, George Kakavelakis, Konstantinos Petridis
Inorganic and organic-inorganic (hybrid) perovskite semiconductor materials have attracted worldwide scientific attention and research effort as the new wonder semiconductor material in optoelectronics. Their excellent physical and electronic properties have been exploited to boost the solar cells efficiency beyond 23% and captivate their potential as competitors to the dominant silicon solar cells technology. However, the fundamental principles in Physics, dictate that an excellent direct band gap material for photovoltaic applications must be also an excellent light emitter candidate...
March 14, 2019: Materials
Swagato Sarkar, Vaibhav Gupta, Mohit Kumar, Jonas Schubert, Patrick Probst, Joby Joseph, Tobias A F Koenig
For many photonic applications, it is important to confine light of specific wavelength at a certain volume of interest at low losses. So far, it is only possible to use the polarized light perpendicular to the solid grid lines to excite waveguide plasmon polaritons in a waveguide supported hybrid structure. In our work, we use a plasmonic grating fabricated by colloidal self-assembly and an ultrathin injection layer to guide the resonant modes selectively. We use gold nanoparticles self-assembled in a linear template on a titanium dioxide (TiO2) layer to study the dispersion relation with conventional UV-vis-NIR spectroscopic methods...
March 15, 2019: ACS Applied Materials & Interfaces
Munirah A Almessiere, Yassibe Slimani, Murat Sertkol, Muhammed Nawaz, Ali Sadaqat, Abdulhadi Baykal, Ismail Ercan, Bekir Ozçelik
Co0.5 Ni0.5 Nbx Fe2-x O₄ (0.00 ≤ x ≤ 0.10) nanoparticles (NPs) were prepared using the hydrothermal approach. The X-ray powder diffraction (XRD) pattern confirmed the formation of single-phase spinel ferrite. The crystallite size was found to range from 18 to 26 nm. The lattice parameters were found to increase with greater Niobium ion (Nb3+ ) concentration, caused by the variance in the ionic radii between the Nb3+ and Fe3+ . Fourier transform infrared analysis also proved the existence of the spinal ferrite phase...
March 13, 2019: Nanomaterials
Darius Dobrovolskas, Shingo Arakawa, Shinichiro Mouri, Tsutomu Araki, Yasushi Nanishi, Jūras Mickevičius, Gintautas Tamulaitis
Indium nitride (InN) luminescence is substantially enhanced by the introduction of a multilayer graphene interlayer, mitigating the lattice mismatch between the InN epilayer and the Gallium nitride (GaN) template on a sapphire substrate via weak van der Waals interaction between graphene and nitride layers. The InN epilayers are deposited by radio-frequency plasma-assisted molecular beam epitaxy (MBE), and are characterized by spatially-resolved photoluminescence spectroscopy using confocal microscopy. A small blue shift of the emission band from the band gap evidences a low density of equilibrium carriers, and a high quality of InN on multilayer graphene...
March 12, 2019: Nanomaterials
Xiaohong Liu, Guilin Feng, Enhui Wang, Hui Chen, Zhen-Guo Wu, Wei Xiang, Yan-Jun Zhong, Yanxiao Chen, Xiao-Dong Guo, Benhe Zhong
The peak-loading shift function of sodium ion batteries in large-grid energy storage station confront great challenge owing to the poor rate performance of cathodes. NASICON type Na3V2(PO4)3 with stable three-dimensional structure and fast ion diffusion channels has been regarded as one of the potential candidates and was widely studied. Nevertheless, a multilevel integrated strategy to boost the performance of Na3V2(PO4)3 from crystal structure modulation, coated carbon graphitization regulation and particle morphology design is rarely reported and deserves much attention...
March 14, 2019: ACS Applied Materials & Interfaces
Prithviraj Deshmukh, Jia Li, Surya Nalamati, Manish Sharma, Shanthi Iyer
We report on the bandgap engineering of the GaAsSb/GaAsSbN heterostructured nanowires (NWs) in the core-shell architecture using the unique properties of dilute nitride material system for near-infrared (NIR) photodetection. A high density of vertical GaAsSb/GaAsSb(N)/GaAlAs core-multishell configured nanowires with well faceted, smooth surface morphology has been grown on Si (111) substrates using Ga-assisted molecular beam epitaxy. A low Sb content GaAsSb core has been shown to enable the coherently strained growth of dilute nitride shell with higher Sb content in GaAsSbN shell NWs...
March 13, 2019: Nanotechnology
Hannah L Stern, Ruizhi Wang, Ye Fan, Ryo Mizuta, James C Stewart, Lisa-Maria Needham, Trevor D Roberts, Rebecca Wai, Naomi S Ginsberg, David Klenerman, Stephan Hofmann, Steven F Lee
Hexagonal boron nitride (h-BN) is a 2D, wide band-gap semiconductor that has recently been shown to display bright room-temperature emission in the visible region, sparking immense interest in the material for use in quantum applications. In this work, we study highly crystalline, single atomic layers of chemical vapour deposition (CVD)-grown h-BN and find predominantly one type of emissive state. Using a multidimensional super-resolution fluorescence microscopy technique we simultaneously measure spatial position, intensity and spectral properties of the emitters, as they are exposed to continuous wave illumination over minutes...
March 13, 2019: ACS Nano
Jin-Hyoung Kim, So-Yoen Kim, Dae Won Cho, Ho-Jin Son, Sang Ook Kang
A new series of homoleptic cyclometalated iridium(iii) complexes based on a phenylpyridine (ppy) ligand containing bulky substituents have been synthesized and characterized. The phosphorescence behavior of the Ir complexes is investigated by steady-state and time-resolved emission spectroscopic techniques. Comparison of the results with those of the reference Ir(ppy)3 reveals that the emission color and photophysical properties of other Ir complexes are influenced by the electron-donating groups (-CH3 and phenyl derivatives) attached to the ppy ligand...
March 13, 2019: Physical Chemistry Chemical Physics: PCCP
Raja Sen, Priya Johari
Ever since the discovery of two-dimensional (2D) material graphene, humongous interest has been generated in exploring low dimensional materials that can be exfoliated from their three-dimensional counterpart and show enriched properties due to quantum confinement. Two members of Sn-S family, \mathbf{\mathit{Pnma}}-SnS and P\overline{3}m1-SnS_{2} that possess layered structure with 2D nanosheets stacked via. weak van der Waals (vdW) interactions, have widely been studied in this regard. While, the other member \mathbf{\mathit{Pnma}}-Sn_{2}S_{3} comprising 1D nanochains bound via...
March 12, 2019: ACS Applied Materials & Interfaces
Kheibar Dashtian, Mehrorang Ghaedi, Shaaker Hajati
An ultrasensitive Visible light-triggered photoelectrochemical (PEC) sensor was designed based on ideal photoactive lead sulfoiodide (Pb5 S2 I6 ) as low band gap crystal, which hydrothermally synthesized rapidly at low temperature (160 °C) in hydrochloride acid media followed by its incorporation into polydopamine as reactive photo-biointerface, through a facile in situ electropolymerization method, coated on nanoporous TiO2 grown by anodization on Ti foil. The structure of as-prepared samples and their photoelectrochemical properties were fully characterized...
February 22, 2019: Biosensors & Bioelectronics
Y I Seo, W J Choi, Shin-Ichi Kimura, Yong Seung Kwon
For high-Tc superconductors, clarifying the role and origin of the pseudogap is essential for understanding the pairing mechanism. Among the various models describing the pseudogap, the preformed Cooper pair model is a potential candidate. Therefore, we present experimental evidence for the preformed Cooper pair model by studying the pseudogap spectrum observed in the optical conductivity of a Ca10 (Pt4 As8 )(Fe2 As2 )5 (Tc  = 34.6 K) single crystal. We observed a clear pseudogap structure in the optical conductivity and observed its temperature dependence...
March 8, 2019: Scientific Reports
Kakarla Raghava Reddy, Ch Venkata Reddy, Mallikarjuna N Nadagouda, Nagaraj P Shetti, Shim Jaesool, Tejraj M Aminabhavi
In recent years, various facile and low-cost methods have been developed for the synthesis of advanced nanostructured photocatalytic materials. These catalysts are required to mitigate the energy crisis, environmental deterioration, including water and air pollution. Among the various semiconductors explored, recently novel classes of polymeric graphitic carbon nitride (g-C3 N4 )-based heterogeneous photocatalysts have established much greater importance because of their unique physiochemical properties, large surface area, low price, and long service life, ease of synthesis, product scalability, controllable band gap properties, low toxicity, and high photocatalytic activity...
March 4, 2019: Journal of Environmental Management
Michael P Esch, Yinan Shu, Benjamin G Levine
The utility of optoelectronic materials can be greatly reduced by the presence of efficient pathways for nonradiative recombination (NRR). Lead halide perovskites have garnered much attention in recent years as materials for solar energy conversion because they readily absorb visible light, are easy to synthesize, and have a low propensity for NRR. Here we report a theoretical study of the pathways for NRR in an archetypal lead halide perovskite: CsPbBr3 . Specifically, we have identified a set of conical intersection (CIs) in both a molecule-sized cluster model (Cs4 PbBr6 ) and nanoparticle model (Cs12 Pb4 Br20 ) of the CsPbBr3 surface...
March 7, 2019: Journal of Physical Chemistry. A
Ping Li, R Z Zeng, Y B Liao, Q W Zhang, J H Zhou
The state-of-art Si Matel-Oxide-Semiconductor Field-Effect-Transistor (MOS-FET) meets the problem of the Power Consumption (PC ) can not be effecively deceased guided by the Moore's Law as before. The GFET has the problem of the device can not be effectively turned off, since the band-gap of the graphene is zero. To solve these problems, noticing the amount of the carriers in the 2 dementional semiconductor material is limited, we propose a Matel-Semi-Insulator-Semiconductor Field-Effect-Transistor (MSIS-FET) to replace the traditional MOS-FET...
March 6, 2019: Scientific Reports
Nannan Zhang, Xiao Liu, Zhongchao Wei, Haiying Liu, Jie Peng, Liya Zhou, Hongmei Li, Haihua Fan
In recent years, two-photon excited semiconductor quantum dots (QDs) have been the subject of intense investigation due to their long excitation wavelength which helps to achieve deeper penetration and higher image resolution in optical bioimaging. In this paper, water-soluble CdS QDs were synthesized using a hydrothermal method and applied to human liver hepatocellular carcinoma (HepG2) cells. The first-principles calculation suggested that the S-rich defected structure contributes to a narrower band gap compared to the pristine structure...
March 5, 2019: Nanomaterials
T Edvinsson
Low-dimensional nanomaterials have been explored extensively in the last decades, partly fuelled by the new possibilities for tuning and controlling their electronic properties. In a broader perspective within catalysis, two-, one- and zero-dimensional (2D, 1D and 0D) inorganic nanomaterials represent a bridge between the selectivity of molecular catalysts and the high performance and stability of inorganic catalysts. As a consequence of the low dimensions, higher surface areas are obtained but also introduce new physics and increased tuneability of the electronic states in the nanostructured system...
September 2018: Royal Society Open Science
Krishnamoorthy Arumugam, Devon Renock, Udo Becker
Pyrite, one of the most important minerals to catalyze redox reactions in nature and a bulk low-spin Fe mineral, needs to provide high-spin Fe on surfaces to moderate spin-forbidden transitions. Here, the spin state of pyrite is investigated using density functional theory (DFT) calculations on cluster and periodic models. The energies of clusters FexS2x (where x = 4, 8, 16, and 32) were calculated as a function of total spin and different up/down spin configurations. The undercoordinated Fe on surfaces, edges, and corners were found to provide intermediate and high-spin Fe necessary for catalysis...
March 6, 2019: Physical Chemistry Chemical Physics: PCCP
Songyu Li, Xiaoqing Chen, Fa-Min Liu, Yongfeng Chen, Beiyun Liu, Wenjie Deng, Boxing An, Feihong Chu, Guoqing Zhang, Shanlin Li, Xuhong Li, Yongzhe Zhang
Transition metal dichalcogenides (TMDs) are a category of promising 2D materials for the optoelectronic devices, while the unique characteristics include tunable band-gap, non-dangling bonds as well as compatibility to large-scale fabrication, for instance, chemical vapor deposition (CVD). MoS2 is one of the first TMDs which is well-studied in the photodetection area widely. However, low photoresponse restricts its applications in photodetectors, unless the device is applied with ultrahigh source-drain voltage (VDS ) and gate voltage (VGS )...
March 6, 2019: ACS Applied Materials & Interfaces
Xuanmeng He, Fen Wang, Hui Liu, Xinzhen Wang, Jiaojiao Gao
The highly dispersed SiO2/BiVO4 hybrid pigments with spherical structure and high NIR reflectance were successfully fabricated by a facile sol-gel method followed by calcinations treatment. The particles morphology and size of the hybrid pigments were controlled by the SiO2 microspheres supporter, and its colors were adjusted by the band gap energy which was changed with the incorporation of SiO2 microspheres. The SiO2/BiVO4-3 hybrid pigments presented higher yellow hues (b*=91.42) and more dispersed spherical particle than other as-prepared hybrid pigments and commercially available BiVO4-based yellow pigment...
March 5, 2019: Nanotechnology
Nejc Rozman, David M Tobaldi, Uroš Cvelbar, Harinarayanan Puliyalil, João A Labrincha, Andraž Legat, Andrijana Sever Škapin
In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO₂ with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO₄ as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd...
February 28, 2019: Materials
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