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Band gap semiconductor

Yayao Lan, Zhifeng Liu, Zhengang Guo, Xifei Li, Lei Zhao, Li Zhan, Min Zhang
It is known that heterojunction photoelectrodes can improve light absorption and accelerate the separation of photogenerated carriers in the field of photoelectrochemical (PEC) water splitting. However, the key to efficient photoelectrochemical performance is to build heterojunctions with a narrow band gap semiconductor loaded on a wide band gap semiconductor uniformly and densely. Herein, a ZnO/ZnFe2O4 uniform core-shell heterojunction photoelectrode is prepared by a simple ion etching method. Moreover, the chemical reaction process and mechanism are discussed in detail...
August 14, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Mohammed Moaied, Jiyoul Lee, Jisang Hong
Using first principles calculations, we explored the physical properties of two-dimensional (2D) Cr-trihalide X3-Cr2-X3 or CrX3 (X = Cl, Br, I) and its Janus monolayers X3-Cr2-Y3 (X and Y = Cl, Br, I) where X ≠ Y. We found that Janus monolayer X3-Cr2-Y3 materials are dynamically stable and that it is feasible to synthesize X3-M2-Y3 2D-crystals. Both pristine and Janus layers have intrinsic two-dimensional ferromagnetic semiconducting band structures; the largest band gap of 2.3 eV was found in Cl3-Cr2-Cl3, while the band gaps decreased in heavier halide systems...
August 14, 2018: Physical Chemistry Chemical Physics: PCCP
Siyong Gu, Chien-Te Hsieh, Tzu-Wei Lin, Chun-Yao Yuan, Yasser Ashraf Gandomi, Jeng-Kuei Chang, Jianlin Li
Graphene sheets that can exhibit electrical conducting and semiconducting properties are highly desirable and have potential applications in fiber communications, photodetectors, solar cells, semiconductors, and broadband modulators. However, there is currently no efficient method that is able to tune the band gap of graphene sheets. This work adopts an efficient atomic layer oxidation (ALO) technique to cyclically increase the oxidation level of graphene sheets, thus, tuning their electrical conductance, band-gap structure, and photoluminescence (PL) response...
August 13, 2018: Nanoscale
Rui Xu, Nan Gao, Hongdong Li, Dongchao Qiu, Qiliang Wang, Shaoheng Cheng
Two-dimensional rhombic silicene (named r-silicene) bonded on the diamond (111) surface with a (1 × 1) configuration is predicted by density functional theory. The planar structure of r-silicene has P6/mmm symmetry, and it is dynamically and thermodynamically stable on the diamond surface. r-Silicene has a metallic character, which is different to both bulk cubic Si and hexagonal silicene. The hybrid structure of r-silicene/diamond consists of a metallic surface and a wide band gap semiconductor diamond substrate, providing a novel low-dimensional composite based on silicon-diamond to realize high performance nanodevices...
August 13, 2018: Physical Chemistry Chemical Physics: PCCP
Bekir Çakıroğlu, Mahmut Özacar
In this study, a photoelectrochemical (PEC) biosensor was constructed by depositing supercapacitor carbon nanotubes (CNT) and Co3 O4 onto the anatase TiO2 coated ITO electrodes. Herein, supercapacitor Co3 O4 was employed as a semiconductor with a band gap of ~2.07 eV, and the supercapacitor behavior of the PEC system was improved by introducing CNT into the electrode material. Furthermore, a self-empowering glucose biosensor operating at 0 V was constructed for the first time. Also, upon the formation of p-n junction, Co3 O4 was rendered electron accepting material, unlike its usual use in photocatalytic systems...
July 27, 2018: Biosensors & Bioelectronics
Kibret A Messalea, Benjamin J Carey, Azmira Jannat, Nitu Syed, Md Mohiuddin, Bao Yue Zhang, Ali Zavabeti, Taimur Ahmed, Nasir Mahmood, Enrico Della Gaspera, Khashayar Khoshmanesh, Kourosh Kalantar-Zadeh, Torben Daeneke
Atomically thin, semiconducting transition and post transition metal oxides are emerging as a promising category of materials for high-performance oxide optoelectronic applications. However, the wafer-scale synthesis of crystalline atomically thin samples has been a challenge, particularly for oxides that do not present layered crystal structures. Herein we use a facile, scalable method to synthesise ultrathin bismuth oxide nanosheets using a liquid metal facilitated synthesis approach. Monolayers of α-Bi2O3 featuring sub-nanometre thickness, high crystallinity and large lateral dimensions could be isolated from the liquid bismuth surface...
August 9, 2018: Nanoscale
Juliana Srour, Michael Badawi, Fouad El Haj Hassan, Andrei Postnikov
Equilibrium crystal structures, electron band dispersions, and bandgap values of layered GaSe and InSe semiconductors, each being represented by four polytypes, are studied via first-principles calculations within the density functional theory. A number of practical algorithms to take into account dispersion interactions are tested, from empirical Grimme corrections to many-body dispersion schemes. Due to the utmost technical accuracy achieved in the calculations, nearly degenerate energy-volume curves of different polytypes are resolved, and the conclusions concerning the relative stability of competing polytypes drawn...
August 7, 2018: Journal of Chemical Physics
Achyut J Raghavendra, Wren E Gregory, Tyler J Slonecki, Yongchang Dong, Indushekhar Persaud, Jared M Brown, Terri F Bruce, Ramakrishna Podila
Background: Although optical spectroscopy promises improved lateral resolution for cancer imaging, its clinical use is seriously impeded by background fluorescence and photon attenuation even in the so-called two-photon absorption (2PA) imaging modality. An efficient strategy to meet the clinical cancer imaging needs, beyond what two-photon absorption (2PA) offers, is to use longer excitation wavelengths through three-photon absorption (3PA). A variety of fluorescent dyes and nanoparticles (NPs) have been used in 3PA imaging...
2018: International Journal of Nanomedicine
Jiangwei Li, Qin Yu, Yihui He, Constantinos C Stoumpos, Guangda Niu, Giancarlo Trimarchi, Hang Guo, Guifang Dong, Dong Wang, Liduo Wang, Mercouri G Kanatzidis
The two-dimensional Ruddlesden-Popper (RP) phases are an important class of halide perovskites with versatile optoelec-tronic properties. So far, only organic-inorganic hybrid RP phases involving long organic spacers were reported in this class. Here, we report an all-inorganic RP phase lead halide perovskite, Cs2PbI2Cl2 (1, I4/mmm space group; a = 5.6385(8) Å, c = 18.879(4) Å), synthesized by a solid state method. The compound exhibits a band gap of Eg~3.04 eV and photocon-ductivity. We find an anomalous band gap evolution in Cs2Pb1-xSnxI2Cl2 solid solutions...
August 7, 2018: Journal of the American Chemical Society
Hao Li, Zhien Zhang, Yulu Liu, Wanglai Cen, Xubiao Luo
Graphitic carbon nitride (g-C₃N₄) is a promising semiconductor material which has been widely studied in nanoscience. However, the effect of modifying the performance of g-C₃N₄ is still under debate. In this communication, we show the size and functional group effects on the g-C₃N₄ using density functional theory (DFT) calculations. It was found that a molecule with six repeated g-C₃N₄ units (g-C₃N₄-6) could be the smallest unit that converges to the limit of its HOMO⁻LUMO gap. Calculations of g-C₃N₄-6 with varying numbers of substituted C≡N, C=O, and O-H functional groups show that C≡N and C=O could narrow down the HOMO⁻LUMO gap, while O-H could slightly raise the gap...
August 3, 2018: Nanomaterials
Mahdi Zarrabi, Mohammad Haghighi, Reza Alizadeh
In this paper, ZnO/Graphene Oxide (ZnO/GO) is synthesized via ultrasound assisted precipitation method and the effect of power and ultrasound time irradiation is studied on photocatalyst properties. The synthesized samples are used for methylene blue (MB) degradation as an organic water pollutant. Physicochemical properties of the samples are investigated by XRD, FESEM, EDX, BET-BJH, FTIR and DRS techniques. Moreover, pHpzc of the sample with the best performance is calculated to study the effect of acidity on the photocatalyst efficiency in photocatalytic process...
November 2018: Ultrasonics Sonochemistry
Teerayut Uwanno, Takashi Taniguchi, Kenji Watanabe, Kosuke Nagashio
Bilayer graphene field-effect transistors (BLG-FETs), unlike conventional semiconductors, are greatly sensitive to potential fluctuations due to the charged impurities in high- k gate stacks since the potential difference between two layers induced by the external perpendicular electrical filed is the physical origin behind the band gap opening. The assembly of BLG with layered h-BN insulators into van der Waals heterostructure has been widely recognized to achieve the superior electrical transport properties...
August 6, 2018: ACS Applied Materials & Interfaces
Yan-Dong Guo, Hong-Bo Zhang, Hong-Li Zeng, Hai-Xia Da, Xiao-Hong Yan, Wen-Yue Liu, Xin-Yi Mou
Breaking the symmetry in the out-of-plane direction in two-dimensional materials to trigger distinctive electronic properties has long been predicted. Inspired by the recent progress in the experimental synthesis of a sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit [Zhang et al., ACS Nano, 2017, 11, 8192-8198], we investigate the transport and electronic structure of two-faced XMoY monolayers (X, Y = O, S, Se and Te) through first-principles calculations. It is found that all the monolayers are semiconductors except OMoTe, which is metallic...
August 6, 2018: Physical Chemistry Chemical Physics: PCCP
Yangguang Zhong, Qi Wei, Zhen Liu, Qiuyu Shang, Liyun Zhao, Ruiwen Shao, Zhepeng Zhang, Jie Chen, Wenna Du, Chao Shen, Jun Zhang, Yanfeng Zhang, Peng Gao, Guichuan Xing, Xinfeng Liu, Qing Zhang
Lead Iodide (PbI2 ) is a layered semiconductor with direct band gap holding great promises in green light emission and detection devices. Recently, PbI2 planar lasers are demonstrated using hexagonal whispering-gallery-mode microcavities, but the lasing threshold is quite high. In this work, lasing from vapor phase deposition derived PbI2 trapezoidal nanoplatelets (NPs) with threshold that is at least an order of magnitude lower than the previous value is reported. The growth mechanism of the trapezoidal NPs is explored and attributed to the synergistic effects of van der Waals interactions and lattice mismatching...
July 31, 2018: Small
Menglei Hu, Ziao Wang, Yanheng Xu, Jiechun Liang, Jiagen Li, Xi Zhu
A structurally stable silicon allotrope is predicted by means of first principles calculations. This new structure is composed of a six-membered ring, a five-membered ring and a three-membered ring with the space group PA3[combining macron] and fvs topology, which is named fvs-Si48. The calculations of geometrical, vibrational, and electronic and optical properties reveal that fvs-Si48 has good mechanical stability with a mass density of 1.86 g cm-3. More importantly, it is a semiconductor with a direct band gap of 2...
July 31, 2018: Physical Chemistry Chemical Physics: PCCP
Ying Lv, Zhanglian Xu, Koji Nakane, Hisayoshi Kobayashi
In this work, a simple binary oxygen-deficient Bi2 O4-x oxide was prepared, and its crystal structure, optical property, band structure and electronic structure were systematically investigated. Plane-wave-based density functional theory (DFT) calculations were also carried out to determine that Bi2 O4-x is a typical indirect-gap semiconductor with the bandgap of 1.1 eV. Bi2 O4-x adsorbed ca. 99% of rhodamine B and methyl orange, ca. 95% of methylene blue and ca. 80% of phenol in the dark within initial 30 min...
July 24, 2018: Journal of Colloid and Interface Science
Xiang Wu, Ziao Tian, Hui Cong, Yang Wang, Riyanto Edy, Gaoshan Huang, Zengfeng Di, Chunlai Xue, Yongfeng Mei
Germanium-Tin (GeSn) alloys have attracted great amounts of attention as these group IV semiconductors present direct band-gap behavior with high Sn content and are compatible with current complementary metal oxide semiconductor technology. In this work, three dimensional tubular GeSn/Ge micro-resonators with a diameter of around 7.3 μm were demonstrated by rolling up GeSn nanomembranes (NM) grown on a Ge-on-insulator wafer via molecular beam epitaxy. The microstructural properties of the resonators were carefully investigated and the strain distributions of the rolled-up GeSn/Ge microcavities along the radial direction were studied by utilizing micro-Raman spectroscopy with different excitation laser wavelengths...
July 27, 2018: Nanotechnology
Lunjie Zeng, Christoph Gammer, Burak Ozdol, Thomas Nordqvist, Jesper Nygård, Peter Krogstrup, Andrew M Minor, Wolfgang Jäger, Eva Olsson
Free-standing semiconductor nanowires constitute an ideal material system for the direct manipulation of electrical and optical properties by strain engineering. In this study, we present a direct quantitative correlation between electrical conductivity and nanoscale lattice strain of individual InAs nanowires passivated with a thin epitaxial In0.6 Ga0.4 As shell. With an in situ electron microscopy electromechanical testing technique, we show that the piezoresistive response of the nanowires is greatly enhanced compared to bulk InAs, and that uniaxial elastic strain leads to increased conductivity, which can be explained by a strain-induced reduction in the band gap...
August 8, 2018: Nano Letters
Hong An Tang, Miao Miao Zhang, Yun Gong, Jian Hua Lin
Using 4-[5-(1H-pyrazol-4-yl)-4H-[1,2,4]triazol-3-yl]-pyridine (L1) and 2-(3-carboxypyridin-2-yl) nicotinic acid (H2L2), two coordination polymers (CPs) formulated as [Cu(HL1)2(Mo8O26)]·5H2O (1) and [{Cu4(L2)4(H2O)6}(H3PMo12O40)]·7H2O (2) were hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The two CPs exhibit a 2D architecture, but strong interlayer π-π stacking interactions are only observed in the structure of CP 1. Diffuse reflectance spectroscopy (DRS) and DFT calculations reveal that CP 1 is a semiconductor with a narrow band gap of 1...
August 14, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Weifeng Zheng, Yue Chen, Xihong Peng, Kehua Zhong, Yingbin Lin, Zhigao Huang
P-type binary copper oxide semiconductor films for various O₂ flow rates and total pressures ( P t ) were prepared using the reactive magnetron sputtering method. Their morphologies and structures were detected by X-ray diffraction, Raman spectrometry, and SEM. A phase diagram with Cu₂O, Cu₄O₃, CuO, and their mixture was established. Moreover, based on Kelvin Probe Force Microscopy (KPFM) and conductive AFM (C-AFM), by measuring the contact potential difference ( V CPD ) and the field emission property, the work function and the carrier concentration were obtained, which can be used to distinguish the different types of copper oxide states...
July 20, 2018: Materials
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