Author
Shailaja Mahamuni
Other affiliations: Southern Illinois University Carbondale, University of Maryland, College Park
Bio: Shailaja Mahamuni is an academic researcher from Savitribai Phule Pune University. The author has contributed to research in topics: Quantum dot & Photoluminescence. The author has an hindex of 30, co-authored 98 publications receiving 3537 citations. Previous affiliations of Shailaja Mahamuni include Southern Illinois University Carbondale & University of Maryland, College Park.
Papers published on a yearly basis
Papers
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TL;DR: In this article, the authors investigated the effect of confinement on optical phonons of different symmetries in the nanoparticles of zinc oxide with wurtzite structure using Raman spectroscopy.
Abstract: Effect of confinement is investigated on optical phonons of different symmetries in the nanoparticles of zinc oxide with wurtzite structure using Raman spectroscopy. An optical phonon confinement model is used for calculating the theoretical line shapes, which exhibit different asymmetric broadening and shifts, depending on the symmetries of phonon and their dispersion curves. The best fit to the data is found for particle diameters consistent with those estimated using x-ray diffraction.
438 citations
TL;DR: In this article, a method for the synthesis of stable, OH free zinc oxide quantum dots, using an electrochemical route, was reported, and the optical properties of these quantum dots were studied at room temperature, by taking the optical absorption and luminescence spectra.
Abstract: We report a novel method for the synthesis of stable, OH free zinc oxide quantum dots, using an electrochemical route. The optical properties of these quantum dots were studied at room temperature, by taking the optical absorption and luminescence spectra. The band gap luminescence is predominant in ZnO quantum dots synthesized by the present technique, while the green defect induced luminescence, typical of ZnO, is strongly quenched. The role of defects in photoluminescence emission is discussed.
299 citations
TL;DR: In this article, size effects in cupric oxide nanocrystals, synthesized using a novel electrochemical route, having average diameters of about 4 and 6 nm, are probed by x-ray photoelectron spectroscopy.
Abstract: Size effects in cupric oxide nanocrystals, synthesized using a novel electrochemical route, having average diameters of about 4 and 6 nm, are probed by x-ray photoelectron spectroscopy. Cu---O bond ionicity was found to increase with reduction in nanocrystallite size. Formation of pure CuO phase was confirmed from x-ray diffraction, infrared spectrophotometry and photoelectron spectroscopy. This report also disproves the earlier conjecture that nanometer sized CuO phase is unstable below 25 nm.
272 citations
TL;DR: Cuprous oxide quantum particles as small as 2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochemical route Quantum confinement effects are evident from a blueshift in the optical absorption as discussed by the authors.
Abstract: Cuprous oxide quantum particles as small as 2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochemical route Quantum confinement effects are evident from a blueshift in the optical absorption The optical absorption spectra of Cu2O nanoparticles of different sizes are discussed Structural analysis by x-ray diffraction as well as electron diffraction shows the nanoparticles to be cubic and single phased Cu2O X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface of Cu2O core nanoparticles
270 citations
TL;DR: In this paper, a significantly narrower size distribution of ZnS nanocrystals than reported in earlier published results was obtained, and band gap luminescence was observed in mercaptoethanol capped ZnSRs.
Abstract: Optical measurements on ZnS nanoclusters have been carried out to investigate surface effects along with quantum size effects. ZnS nanocrystals have been synthesized in the range of 1.5–2.5 nm, using different chemical methods as well as electronic passivating procedures. The size of nanoparticles has been estimated from empirical pseudopotential calculations. We have obtained a significantly narrower size distribution of ZnS nanocrystals than reported in earlier published results. We observed band gap luminescence in mercaptoethanol capped ZnS nanocrystals. Effects of various defect levels on the luminescent behavior of ZnS nanoparticles have been examined
191 citations
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TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...
10,260 citations
TL;DR: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد لماش VB و ) رگید اب لاقتنا VB (CO2) .
Abstract: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .
2,055 citations
TL;DR: The prospects of LHP NCs for optoelectronic applications such as in television displays, light-emitting devices, and solar cells are surveyed, emphasizing the practical hurdles that remain to be overcome.
Abstract: Semiconducting lead halide perovskites (LHPs) have not only become prominent thin-film absorber materials in photovoltaics but have also proven to be disruptive in the field of colloidal semiconductor nanocrystals (NCs). The most important feature of LHP NCs is their so-called defect-tolerance—the apparently benign nature of structural defects, highly abundant in these compounds, with respect to optical and electronic properties. Here, we review the important differences that exist in the chemistry and physics of LHP NCs as compared with more conventional, tetrahedrally bonded, elemental, and binary semiconductor NCs (such as silicon, germanium, cadmium selenide, gallium arsenide, and indium phosphide). We survey the prospects of LHP NCs for optoelectronic applications such as in television displays, light-emitting devices, and solar cells, emphasizing the practical hurdles that remain to be overcome.
1,595 citations
TL;DR: It is demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size, and it is proposed that both the abrasiveness and the surface oxygen species of ZNO nanoparticle promote the biocidal properties of ZngN nanoparticles.
1,352 citations
TL;DR: The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation and a narrowing bandgap can be confirmed by the enhancement of the photocurrent response when theZnO was irradiated with visible light.
Abstract: Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO2 as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation.
1,213 citations