scispace - formally typeset
Search or ask a question
Author

Parvez Ahmad Alvi

Bio: Parvez Ahmad Alvi is an academic researcher from Banasthali Vidyapith. The author has contributed to research in topics: Materials science & Heterojunction. The author has an hindex of 17, co-authored 83 publications receiving 715 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, the correlation between the concentration of dopant ions and oxygen vacancy defect of Sm-doped CeO2 nano-particles (NPs) were investigated systematically by X-ray diffraction (XRD), Ultraviolet-visible-near infrared spectroscopy (UV-Vis-NIR) and Surface-enhanced Raman spectrograph (SERS).

83 citations

Journal ArticleDOI
01 May 2019
TL;DR: Enhanced visible light photocatalytic activity of Gd‐doped CeO2 nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping, and a mechanism of water splitting is proposed on the basis of analyses.
Abstract: Enhanced visible light photocatalytic activity of Gd-doped CeO2 nanoparticles (NPs) is experimentally demonstrated, whereas there are very few reports on this mechanism with rare earth doping. All-pure and Gd-doped CeO2 NPs are synthesized using a coprecipitation method and characterized using X-ray diffraction (XRD), absorption spectroscopy, surface-enhanced Raman Spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). The effect of Gd-doping on properties of CeO2 is discussed along with defects and oxygen vacancies generation. The XRD confirms the incorporation of Gd3+ at the Ce3+/Ce4+ site by keeping the crystal structure same. The average particle size from transmission electron microscopy (TEM) images is in the range of 5-7 nm. The XPS spectra of Ce 3d, O 1s, and Gd 4d exhibits the formation of oxygen vacancies to maintain the charge neutrality when Ce4+ changes to Ce3+. The gradual increase in hydrogen production is observed with increasing Gd concentration. The observed results are in good correlation with the characterization results and a mechanism of water splitting is proposed on the basis of analyses. The absorption spectra reveal optical band gap (2.5-2.7 eV) of samples, showing band gap narrowing leads to desired optical absorbance and photoactivity of NPs.

63 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis, characterization, optical and magnetic properties of Co-doped ZnO nanocrystals have been investigated using the Sol-gel technique, and an appreciable blue shift in the absorption spectrum was observed, which indicates that the Co doping in ZnOs leads to systematic increase in the band gap with dopant concentration.

62 citations

Journal ArticleDOI
TL;DR: In this article, the influence of Co doping on the structural, optical and magnetic properties of TiO 2 has been investigated in terms of broadening of peaks and small shift of Raman scattering modes, which is caused by the generation of defects such as vacancies and interstitials.

60 citations


Cited by
More filters
01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations

20 Dec 1998

360 citations

Journal ArticleDOI
TL;DR: In this article, a coprecipitation method was used to synthesize ZnO nanoparticles and the crystalline sizes of synthesized samples were calculated from powder XRD patterns, which were found to decrease with the increase of cobalt content.
Abstract: Zn1–xCoxO (x = 0, 0.05, 0.10, and 0.15) nanoparticles (NPs) were synthesized by a coprecipitation method. The crystalline sizes of synthesized samples were calculated from the powder XRD patterns, which were found to decrease with the increase of cobalt content. The FT-IR spectra confirmed the Zn–O stretching bands at 468, 456, 452, and 461 cm–1 for the respective ZnO NPs. SEM images demonstrated the distinct flowerlike morphology. The photoluminescence spectra of all the samples exhibited a broad emission in the visible range. XPS studies were carried out for Zn0.90Co0.10O NPs. The carriers (donors) bound on the Co sites were observed from the micro-Raman spectroscopic studies. The pure and Co-doped ZnO NPs showed significant changes in the M–H loop where the diamagnetic behavior of ZnO changes to ferromagnetic nature when doping with Co. Oxygen vacancies and zinc interstitials were found to be the main reasons for room-temperature ferromagnetism in the Co-doped ZnO NPs with the support of the results ob...

316 citations

Journal ArticleDOI
TL;DR: This review highlights different strategies for effectively introducing oxygen vacancies in titanium oxide-based nanomaterials, as well as a discussion on the positions of oxygen vacancies inside the TiO2 band gap based on theoretical calculations.
Abstract: TiO2 and other titanium oxide-based nanomaterials have drawn immense attention from researchers in different scientific domains due to their fascinating multifunctional properties, relative abundance, environmental friendliness, and bio-compatibility. However, the physical and chemical properties of titanium oxide-based nanomaterials are found to be explicitly dependent on the presence of various crystal defects. Oxygen vacancies are the most common among them and have always been the subject of both theoretical and experimental research as they play a crucial role in tuning the inherent properties of titanium oxides. This review highlights different strategies for effectively introducing oxygen vacancies in titanium oxide-based nanomaterials, as well as a discussion on the positions of oxygen vacancies inside the TiO2 band gap based on theoretical calculations. Additionally, a detailed review of different experimental techniques that are extensively used for identifying oxygen vacancies in TiO2 nanostructures is also presented.

258 citations

01 Jan 1988
TL;DR: An abstract should state briefly the purpose of the research, the principal results and major conclusions, and non-standard or uncommon abbreviations should be avoided.
Abstract: A concise and factual abstract is required. The abstract should state briefly the purpose of the research, the principal results and major conclusions. An abstract is often presented separately from the article, so it must be able to stand alone. For this reason, References should be avoided, but if essential, then cite the author(s) and year(s). Also, non-standard or uncommon abbreviations should be avoided, but if essential they must be defined at their first mention in the abstract itself.

209 citations