Exploring Burstein–Moss type effects in nickel doped hematite dendrite nanostructures for enhanced photo-electrochemical water splitting

2019 ◽  
Vol 21 (36) ◽  
pp. 20463-20477 ◽  
Author(s):  
Soniya Gahlawat ◽  
Jaspreet Singh ◽  
Ashok Kumar Yadav ◽  
Pravin P. Ingole
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Water Splitting ◽  
Conduction Band ◽  
Optical Band Gap ◽  
Doped Semiconductors ◽  
Electrochemical Water Splitting

The Burstein–Moss suggests which that the optical band gap of degenerately doped semiconductors increases when all states close to the conduction band get populated is important to obtain different optical properties for the same material.

scholarly journals Optical Properties of Ferrite Powders of NixCo1-xFe2O4 System

2015 ◽  
Vol 16 (3) ◽  
pp. 506-510
Author(s):  
V.S. Bushkova
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Valence Band ◽  
Absorption Spectra ◽  
Conduction Band ◽  
Optical Band Gap ◽  
Sol Gel ◽  
Direct Transition ◽  
Nickel Cobalt ◽  
Auto Combustion

The aim of this work was to create and study of ferrite nickel-cobalt powders, using sol-gel technology with participation of auto-combustion. It is studied the optical properties of the powders depending on the degree of substitution of cobalt cations on nickel cations. As a result of analysis of the absorption spectra is revealed that for all investigated powders inherent allowed direct transition of electrons from the valence band to the conduction band.  It was shown that the optical band gap increases with increasing concentration of nickel cations in the composition of ferrites.

The Role of Reduced Graphene Oxide Concentration as Ablated Material on Optical Properties of Graphene Quantum Dots

2019 ◽  
Vol 948 ◽  
pp. 267-273 ◽  
Author(s):  
Fiqhri Heda Murdaka ◽  
Ahmad Kusumaatmaja ◽  
Isnaeni ◽  
Iman Santoso
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Graphene Oxide ◽  
Band Gap ◽  
Reduced Graphene Oxide ◽  
Optical Band Gap ◽  
Graphene Quantum Dots ◽  
Absorption Peak ◽  
Oxygen Defect ◽  
Reduced Graphene

We report the synthesize of Graphene Quantum Dots (GQDs) using ablation method with reduced Graphene Oxide (rGO) solution as a starting material. We have varied the concentration of rGO as following: 0.5, 2, 5 mg/ml and then have ablated them using 800 nm Ti-Sapphire femtosecond laser to obtain GQDs. From the UV-Vis data, we observed that the more concentration of rGO is being ablated, the more secondary absorption peak at 255.1 nm appeared. This secondary absorption peak is a characteristic of n-π* bonding due to the presence of oxygen defect which occurs as a result of the interaction between the laser and the water in rGO solution. We conclude that the population of oxigen defect in GQDs is increasing, following the increase of rGO concentration and could alter the optical properties of GQD. On the other hand, using Tauc’s plot, we confirm that the increase of rGO concentration as the ablated material does not alter GQDs optical band gap. However, it will slightly reduce both, direct and indirect Oxygen defect related optical band gap.

Optical Properties of Silica Borotellurite Glass Doped with Manganese Oxide

2017 ◽  
Vol 268 ◽  
pp. 18-22 ◽  
Author(s):  
I. Zaitizila ◽  
Mohamed Kamari Halimah ◽  
Farah Diana Mohammad ◽  
Mohd Shah Nurisya
Keyword(s):  
Optical Properties ◽  
Manganese Oxide ◽  
Band Gap ◽  
Diffraction Pattern ◽  
Optical Band Gap ◽  
Urbach Energy ◽  
Molar Fraction ◽  
Chemical Formula ◽  
Melt Quenching ◽  
Amorphous Nature

Silica borotellurite glasses doped with manganese oxide with chemical formula {[(TeO2)0.7(B2O3)0.3­]0.8[SiO2]0.2}1-x{MnO2}x (where x = 0.0, 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction) were fabricated. Silica were extracted from the burning process of rice husk. Glass samples were prepared by using the melt-quenching technique. The FTIR spectra showed that the addition of MnO₂ contributed to the transformation of TeO4 to TeO3. The diffraction pattern of XRD showed a broad hump which indicates the amorphous nature of the samples. The result for both optical band gap and Urbach energy showed decreasing trend as the concentration of manganese increased.

scholarly journals Optical properties of nanocrystal films: blue shifted transitions as signature of strong coupling

2020 ◽  
Vol 2 (1) ◽  
pp. 384-393
Author(s):  
Erik S. Skibinsky-Gitlin ◽  
Salvador Rodríguez-Bolívar ◽  
Marco Califano ◽  
Francisco M. Gómez-Campos
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Strong Coupling ◽  
Conduction Band ◽  
Red Shift ◽  
Nanocrystal Films ◽  
Interdot Coupling

Large blue shifts in the intra-conduction-band transitions and the red shift of the band gap absorption are both the manifestation of strong interdot coupling in the film.

The WS2 dependence on the elasticity and optical band gap energies of swollen PAAm composites

2020 ◽  
Vol 55 (1) ◽  
pp. 71-76
Author(s):  
Gülşen Akın Evingür ◽  
Nafia Alara Sağlam ◽  
Büşra Çimen ◽  
Bengü Özuğur Uysal ◽  
Önder Pekcan
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Polymer Composites ◽  
Optical Band Gap ◽  
Electronic Devices ◽  
Band Gap Energy ◽  
Tungsten Disulfide ◽  
High Electron ◽  
New Generation ◽  
Doped Polymer

New generation nano-filler polymer composites have many applications including biomedical, electronic and maritime related applications because of their mechanical, electronic and optical properties. The properties of composites were investigated as a function of nano-filler content. Among these, tungsten disulfide (WS2) has the potential to be used as a component in electronic devices owing to its high electron mobility and easily tunable optical band gap energy. Tungsten disulfide (WS2)- Polyacrylamide (PAAm) composite was prepared using free radical co-polymerization and wet laboratory methods with WS2 content. Composites were characterized for mechanical and optical properties using an Elasticity Instrument and UV-vis Spectrophotometer, respectively. Elastic modulus was modeled by a statistical thermodynamics model. Tauc’s and Urbach’s Tail model for direct transition were used to model for the optical band gap. In this study, the swelling and WS2 effect on the optical band gap and elasticity of WS2 - PAAm composites were investigated. It was observed that the elasticity presented a reversed behavior of optical band gap energies with respect to WS2 content. For the applications of nano-filler doped polymer composites in flexible electronic devices, WS2 content strongly influences the mechanical and optical properties.

Effects of Nitrogen Doping on Optical Properties of Tungsten Oxide Thin Films

2012 ◽  
Vol 616-618 ◽  
pp. 1773-1777
Author(s):  
Xi Lian Sun ◽  
Hong Tao Cao
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Tungsten Oxide ◽  
Nitrogen Doping ◽  
Optical Band Gap ◽  
Band Gap Energy ◽  
Gap Energy ◽  
Tungsten Oxide Thin Films

In depositing nitrogen doped tungsten oxide thin films by using reactive dc pulsed magnetron sputtering process, nitrous oxide gas (N2O) was employed instead of nitrogen (N2) as the nitrogen dopant source. The nitrogen doping effect on the structural and optical properties of WO3 thin films was investigated by X-ray diffraction, transmission electron microscopy and UV-Vis spectroscopy. The thickness, refractive index and optical band gap energy of these films have been determined by analyzing the SE spectra using parameterized dispersion model. Morphological images reveal that the films are characterized by a hybrid structure comprising nanoparticles embeded in amorphous matrix and open channels between the agglomerated nanoparticles. Increasing nitrogen doping concentration is found to decrease the optical band gap energy and the refractive index. The reduced band gaps are associated with the N 2p orbital in the N-doped tungsten oxide films.

scholarly journals Effect of gamma irradiation on structural, morphological and optical properties of p-quaterphenyl thin films

2018 ◽  
Vol 14 (2) ◽  
pp. 5624-5637
Author(s):  
A.A. Attia ◽  
M.M. Saadeldin ◽  
K. Sawaby
Keyword(s):  
Thin Films ◽  
Refractive Index ◽  
Optical Properties ◽  
Surface Morphology ◽  
Absorption Coefficient ◽  
Gamma Irradiation ◽  
Band Gap ◽  
Optical Band Gap ◽  
Thermal Evaporation Method ◽  
Single Oscillator Model

Para-quaterphenyl thin films were deposited onto glass and quartz substrates by thermal evaporation method. p-quaterphenyl thin films wereexposed to gamma radiation of Cobat-60 radioactive source at room temperature with a dose of 50 kGy to study the effect of ?-irradiation onthe structure and the surface morphology as well as the optical properties of the prepared films. The crystalline structure and the surface morphology of the as-deposited and ?-irradiated films were examined using the X-ray diffraction and the field emission scanning electron microscope. The optical constants (n & k) of the as-deposited and ?-irradiated films were obtained using the transmittance and reflectance measurements, in the wavelength range starting from 250 up to 2500 nm. The analysis of the absorption coefficient data revealed an allowed direct transition with optical band gap of 2.2 eV for the as-deposited films, which decreased to 2.06 eV after exposing film to gamma irradiation. It was observed that the Urbach energy values change inversely with the values of the optical band gap. The dispersion of the refractive index was interpreted using the single oscillator model. The nonlinear absorption coefficient spectra for the as-deposited and ?-irradiated p-quaterphenyl thin films were obtained using the linear refractive index.

scholarly journals First Principle Calculation of Electronic, Optical Properties and Photocatalytic Potential of CuO Surfaces

2016 ◽  
Vol 1 ◽  
Author(s):  
Faozan Ahmad
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Band Gap ◽  
Water Splitting ◽  
Co2 Reduction ◽  
Band Edge ◽  
Semiconductor Surface ◽  
First Principle Calculation ◽  
Stable Surface ◽  
Input Parameters

<p class="TTPKeywords">We have performed DFT calculations of electronic structure, optical properties and photocatalytic potential of the low-index surfaces of CuO. Photocatalytic reaction on the surface of semiconductor requires the appropriate band edge of the semiconductor surface to drive redox reactions. The calculation begins with the electronic structure of bulk system; it aims to determine realistic input parameters and band gap prediction. CuO is an antiferromagnetic material with strong electronic correlations, so that we have applied DFT + U calculation with spin polarized approach, beside it, we also have used GW approximation to get band gap correction. Based on the input parameters obtained, then we calculate surface energy, work function and band edge of the surfaces based on a framework developed by Bendavid et al (J. Phys. Chem. B, 117, 15750-15760) and then they are aligned with redox potential needed for water splitting and CO<sub>2</sub> reduction. Based on the calculations result can be concluded that not all of low-index CuO have appropriate band edge to push reaction of water splitting and CO2 reduction, only the surface CuO(111) and CuO(011) which meets the required band edge. Fortunately, based on the formation energy, CuO(111) and CuO(011) is the most stable surface. The last we calculate electronic structure and optical properties (dielectric function) of low-index surface of CuO, in order to determine the surface state of the most stable surface of CuO.</p>

scholarly journals Optical properties of zinc titanate perovskite prepared by reactive RF sputtering

2017 ◽  
Vol 68 (7) ◽  
pp. 10-16 ◽  
Author(s):  
Jarmila Müllerová ◽  
Pavol Šutta ◽  
Rostislav Medlín ◽  
Marie Netrvalová ◽  
Petr Novák
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Optical Band Gap ◽  
Rf Sputtering ◽  
Blue Shift ◽  
Optical Transmittance ◽  
Titanium Content ◽  
Zinc Titanate ◽  
Band Gap Engineering ◽  
Photocatalytic Applications

AbstractIn this paper we report results from optical transmittance spectroscopy complemented with data on structure from XRD measurements to determine optical properties of a series of ZnTiO3perovskite thin films deposited on glass by reactive magnetron co-sputtering. The members of the series differ by the titanium content that was revealed as an origin of the changes not only in structure but also in dispersive optical properties. Low porosity has been discovered and calculated using the Bruggeman effective medium approximation. An apparent blue-shift of the optical band gap energies with increasing titanium content was observed. The observed band gap engineering is a good prospective foregoptoelectronic and photocatalytic applications of ZnTiO3.

scholarly journals Conductivity and Density of States of New Polyphenylquinoline

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 934 ◽  
Author(s):  
Shamil R. Saitov ◽  
Dmitriy V. Amasev ◽  
Alexey R. Tameev ◽  
Vladimir V. Malov ◽  
Marine G. Tedoradze ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Absorption Coefficient ◽  
Band Gap ◽  
Density Of States ◽  
Optical Band Gap ◽  
Dark Conductivity ◽  
Localized States ◽  
Energy Distance ◽  
Temperature Dependences

Electrical, photoelectrical, and optical properties of thin films of a new heat-resistant polyphenylquinoline synthesized using facile methods were investigated. An analysis of the obtained temperature dependences of the dark conductivity and photoconductivity indicates the hopping mechanism of conductivity over localized states arranging at the energy distance of 0.8 eV from the Fermi level located inside the band gap of the investigated material. The optical band gap of the studied material was estimated from an analysis of the spectral dependences of the photoconductivity and absorption coefficient before (1.8–1.9 eV) and after (2.0–2.2 eV) annealing at temperatures exceeding 100 °C. The Gaussian character of the distribution of the localized states of density inside the band gap near the edges of the bands was established. A mechanism of changes in the optical band gap of the investigating polymer under its annealing is proposed.

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