Quantum size confinement in gallium selenide nanosheets: band gap tunability versus stability limitation

ABSTRACTOptical band-gap and cathode luminescence (CL) properties of anatase TiO2 nanopowders mixed with γ- Al2O3 powders by planetary ball mill were evaluated as a function of a powder mass ratio (x=Al2O3/TiO2) of 0 to 0.5 and their correlation with XRD spectra was also investigated. The optical band-gap of TiO2 increased from 3.36 eV to 3.41eV with increasing milling time (tm) up to 600 min, which was in good agreement with the blue shifts observed in the CL spectra with increasing tm and it was interpreted as a quantum size effect. In addition, the optical band-gap of TiO2 powders mixed with Al2O3 with tm=60min greatly increased from 3.36 eV to 3.48 eV with increasing x up to x=0.5. On the other hand, the optical band-gap of all the powders was decreased by annealing at temperatures above 600°C, which was evidenced by the XRD spectra to be due to the growth of grain size.

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Visible Electro- and Photoluminescence from Porous Silicon and its Related Optoelectronic Properties

MRS Proceedings ◽

10.1557/proc-256-219 ◽

1991 ◽

Vol 256 ◽

Cited By ~ 19

Author(s):

Nobuyoshi Koshida ◽

Hideki Koyama

Keyword(s):

Porous Silicon ◽

Optical Absorption ◽

Size Effect ◽

Band Gap ◽

Visible Region ◽

Optoelectronic Properties ◽

Porous Si ◽

Quantum Size ◽

Effect Model ◽

Injection Type

ABSTRACTThe optoelectronic properties of porous Si (PS) are presented in terms of electroluminescence (EL), photoluminescence (PL), photoconduction (PC), and optical absorption. Observations of injection-type EL, efficient PL, band-gap widening, and photosensitivities In the visible region are consistent with the quantum size effect model in PS.

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Tuning band gap and optical properties of SnX2 nanosheets: Hybrid functional studies

Modern Physics Letters B ◽

10.1142/s0217984916501207 ◽

2016 ◽

Vol 30 (10) ◽

pp. 1650120 ◽

Cited By ~ 2

Author(s):

P. Guo ◽

Y. W. Luo ◽

Y. Jia

Keyword(s):

Optical Properties ◽

Optical Absorption ◽

Band Gap ◽

Electronic Structures ◽

Threshold Values ◽

Hybrid Functional ◽

Functional Studies ◽

Quantum Size ◽

Light Activity ◽

Optical Applications

Based on hybrid functional calculations, the electronic structures and optical properties are investigated in the monolayer and bilayer tin dichalcogenides SnX2 (X = S and Se) nanosheets. Numerical results show that quantum size effects are obvious on the electronic structures and optical absorption in the SnS2 and SnSe2 nanosheets. The band gap values increase when the nanosheets layer numbers decrease. Moreover, for SnSe2 nanosheet, the optical absorption coefficients are high and its threshold values lie in the visible light activity range. These results are interesting and indicate that SnS2 and SnSe2 nanosheets may serve as the promising candidates for visible optical applications.

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The band-gap excitons in gallium selenide

Il Nuovo Cimento B ◽

10.1007/bf02832647 ◽

1973 ◽

Vol 18 (1) ◽

pp. 164-208 ◽

Cited By ~ 197

Author(s):

E. Mooser ◽

M. Schlüter

Keyword(s):

Band Gap ◽

Gallium Selenide

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Quantum size effects on the optical band gap of microcrystalline Si:H

Physical Review B ◽

10.1103/physrevb.38.5726 ◽

1988 ◽

Vol 38 (8) ◽

pp. 5726-5729 ◽

Cited By ~ 362

Author(s):

Shoji Furukawa ◽

Tatsuro Miyasato

Keyword(s):

Band Gap ◽

Size Effects ◽

Optical Band Gap ◽

Quantum Size Effects ◽

Quantum Size

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Effect of Nickel Doping on Optical Properties of CdS Nanoparticles Synthesized via. Co-precipitation Technique

Material Science Research India ◽

10.13005/msri/140102 ◽

2017 ◽

Vol 14 (1) ◽

pp. 05-08 ◽

Cited By ~ 3

Author(s):

Suresh Kumar ◽

J. K Sharma

Keyword(s):

Band Gap ◽

Cadmium Sulphide ◽

Cds Nanoparticles ◽

Nickel Doping ◽

Quantum Size ◽

Precipitation Technique ◽

Uv Visible ◽

Co Precipitation ◽

Optical Behavior ◽

Comprehensive Study

This work presents a comprehensive study on the optical behavior of cadmium sulphide (CdS) nanoparticles under the effect of nickel (Ni2+ ions) doping. The pristine and Ni-doped CdS nanoparticles (CdS:Ni) have been synthesized via. conventional co-precipitation technique and analyzed using UV-visible spectrophotometer. Ni2+ ions with different concentrations (2% and 4%) incorporate in CdS structure, modify it and hence, exhibit a red shift of absorption edge. The increase in Ni2+ ions concentration from 0% to 4% leads to tailor the optical band gap of CdS from 2.70 eV to 2.47 eV. These band gap values are higher than that of bulk CdS which confirm a quantum size effect in the synthesized nanoparticles.

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Facile one-step sonochemical synthesis of AgCl quantum dots with enhanced photocatalytic activity and its size effects

Functional Materials Letters ◽

10.1142/s1793604720510364 ◽

2020 ◽

Vol 13 (06) ◽

pp. 2051036

Author(s):

Junjie Zhang ◽

Hujiabudula Maimaitizi ◽

Tao Zhang ◽

Yalkunjan Tursun ◽

Dilinuer Talifu ◽

...

Keyword(s):

Quantum Dots ◽

Photocatalytic Activity ◽

Band Gap ◽

Size Effects ◽

Ultrasonic Method ◽

Energy Levels ◽

Average Diameter ◽

Light Illumination ◽

Quantum Size ◽

One Step

In this work, a facile ultrasonic method for the fabrication of AgCl quantum dots (AgCl QDs) with an average diameter of about 2.5[Formula: see text]nm was reported for the first time. The material was analyzed by various techniques. In addition, effects of material’s size on its photocatalytic activities were studied. Results suggested that the AgCl QDs exhibited excellent photocatalytic activity to degrade Rhodamine B (RhB) and tetracycline (TC) under visible light illumination, and the degradation rate of RhB (TC) had reached up to 96.6% (72.2%) in 20 min, which was higher than that of AgCl nanoparticles (23[Formula: see text]nm) and AgCl nanospheres (114[Formula: see text]nm), respectively. Besides, the band gap of the material was increased when the size of material decreased from 23[Formula: see text]nm to 2.5[Formula: see text]nm. The significantly improved photocatalytic performance and increased band gap of AgCl QDs were mainly related to the quantum size effects of AgCl, which results in the more electron fluctuation in quantized energy levels and the lower recombination of electrons and holes.

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First-Principles Calculations on the Electronic Structure of ZnO Nanowires

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.198-199.23 ◽

2012 ◽

Vol 198-199 ◽

pp. 23-27

Author(s):

Nan Zhang ◽

Hong Sheng Zhao ◽

Dong Yang ◽

Wen Jie Yan

Keyword(s):

Electronic Structure ◽

Band Gap ◽

Valence Band ◽

Conduction Band ◽

First Principles ◽

Density Functional ◽

Valence Band Maximum ◽

Zno Nanowires ◽

Cross Sectional ◽

Quantum Size

Based upon the density functional theory (DFT) in this paper, the first-principles approach is used to study the electronic structure of different cross-sectional diameters of ZnO [0001] nanowires of wurtzite structure. The results show that ZnO [0001] nanowires have a wide direct band gap. Located in the G-point of the Brillouin zone the conduction band minimum and valence band maximum are relatively smooth. The conduction band is mainly composed of Zn 4s and Zn 4p states, and the valence band is composed of Zn 3d and O 2p states. The effective mass of conduction band electrons and valence band holes are large while their mobility is very low which show that conductive ability of pure defect-free [0001] ZnO nanowires is weak. Along with the increase of the cross-sectional diameters, the band gap gradually decreases that indicates quantum size effects are obvious in the nano size range.

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