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Sudipta Bandyopadhyay

Bio: Sudipta Bandyopadhyay is an academic researcher from University of Calcutta. The author has contributed to research in topics: Magnetization & Doping. The author has an hindex of 21, co-authored 79 publications receiving 1389 citations. Previous affiliations of Sudipta Bandyopadhyay include Indian Association for the Cultivation of Science.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the electrical conductivity of ZnO films has been studied in order to elucidate the structural and electrical properties at low temperature, showing that zinc monoacetate is an intermediate product prior to the formation of zinc hydroxide.

168 citations

Journal ArticleDOI
TL;DR: In this paper, a transparent and conducting films of mixed oxides of zinc and zirconium have been prepared by sol-gel method and the optical bandgap was estimated from the reflectance and transmittance spectra.

132 citations

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TL;DR: The structural, optical and magnetic properties of the Zn1−xMnxO (0, <,x,<,0.05) thin films synthesized by solgel technique have been analyzed in the light of modification of the electronic structure and disorder developed in the samples due to Mn doping as mentioned in this paper.

114 citations

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TL;DR: In this paper, the optical transmission and reflection data for aluminum doped zinc oxide films have been analyzed and the optical absorption coefficient (α ) and hence the refractive index ( n ), extinction coefficient ( k ) and the band gap ( E g ) have been determined for these films using different methods.

87 citations

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TL;DR: In this article, single phase Mn doped ZnO samples have been synthesized by the solid-state reaction technique and all the samples were found to be ferromagnetic with clear hysteresis loops at room temperature and the maximum value for saturation magnetization (0.11μB/Mn atom) was achieved for 96h milled sample.

69 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, Tauc plots are fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called “Tauc” plots).
Abstract: One of the most frequently used methods for characterizing thin films is UV–Vis absorption. The near-edge region can be fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called “Tauc” plots). While the technique is powerful and simple, the accuracy of the fitted band-gap result is seldom stated or known. We tackle this question by refitting a large number of Tauc plots from the literature and look for trends. Nominally pure zinc oxide (ZnO) was chosen as a material with limited intrinsic deviation from stoichiometry and which has been widely studied. Our examination of the band gap values and their distribution leads to a discussion of some experimental factors that can bias the data and lead to either smaller or larger apparent values than would be expected. Finally, an easily evaluated figure-of-merit is defined that may help guide more accurate Tauc fitting. For samples with relatively sharper Tauc plot shapes, the population yields Eg(ZnO) as 3.276 ± 0.033 eV, in good agreement with data for single crystalline material.

765 citations

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TL;DR: In this article, the effect of key operational parameters on the photocatalytic performance in terms of the degradation and mineralization of dyes are discussed, in particular aiming at enhancing the degradation efficiency and activity in visible region as well as solar irradiation.
Abstract: Organic dyes are one of the largest groups of pollutants discharged into wastewaters from textile and other industrial processes. Owing to the potential toxicity of the dyes and their visibility in surface waters, removal and degradation of them have attracted considerable attention worldwide. A wide range of approaches have been developed, amongst which the heterogeneous photocatalysis involving zinc oxide (ZnO) emerges as a promising new route for water purification process. For the first time, we attempt to review and summarize the recent research on ZnO photocatalytic systems for organic dyes degradation. The photocatalysis on modified ZnO is also discussed, in particular aiming at enhancing the degradation efficiency and activity in visible region as well as solar irradiation. The effects of key operational parameters on the photocatalytic performance in terms of the degradation and mineralization of dyes are detailed. This review also highlights the utilization of multivariate analysis to d...

370 citations

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TL;DR: Al-doped zinc oxide (ZnO) thin films were prepared by chemical spray pyrolysis technique and structural analysis of the films revealed that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure with (0,0,2) preferred orientation.
Abstract: Al-doped zinc oxide (ZnO) thin films were prepared by chemical spray pyrolysis technique. The dopant concentration (Al/Zn at%) varied from 0 to 1.5 at%. Structural analysis of the films reveals that all the films are of polycrystalline zinc oxide in nature, possessing hexagonal wurtzite structure with (0 0 2) preferred orientation. The lattice constants calculated from the most prominent peaks are found to be in good agreement with the ICDD reference pattern: zinc oxide, 01-080-0074 (a = 3.2535 A and c = 5.2151 A). The sensing properties of the films towards methanol vapour are investigated for various concentrations of methanol in air at different operating temperatures in the range 200–350 °C. It is observed that compared to the undoped ZnO film, Al-doped films show higher sensitivity to methanol vapour. Among all the Al-doped films studied, the 0.5 at% Al-doped ZnO film shows the maximum response (∼44%) at 275 °C to 500 ppm of methanol vapour in air. Further, the films show fast response and recovery to methanol vapour at higher operating temperatures. The methanol-sensing mechanism of the film has been explained.

358 citations

Journal ArticleDOI
Xiao Li Cheng1, Hui Zhao1, Li-Hua Huo1, Shan Gao1, Jing-Gui Zhao1 
TL;DR: In this article, a powder and its thin film were characterized by X-ray diffractometer (XRD), atomic force microscopy (AFM) and IR spectra methods, which indicated that the ZnO particles crystallized in the wurtzite phase, which were well distributed in the films with the mean particle size of about 10nm.
Abstract: ZnO thin films were prepared by sol–gel dip coating method using zinc acetate dihydrate and 2-ethanolamine as the starting materials. The powder and its thin film were characterized by X-ray diffractometer (XRD), atomic force microscopy (AFM) and IR spectra methods. The results indicated that the ZnO particles crystallized in the wurtzite phase, which were well-distributed in the films with the mean particle size of about 10 nm. The IR spectra of the gel and powders annealed at different temperatures were investigated. It showed that the vibration bands of NH and mono-acetate diminished and the stretching mode of ZnO at 471 cm−1 appeared after the dried gel annealed at 500 °C for 1 h. The diameter, D of ZnO particles in the monolayer was also calculated from the optical spectroscopy curve, which is close to that obtained from AFM observation. The gas-sensing properties of the multi-layers for alcohols with different chain lengths were measured at room temperature. The thin films exhibited high sensitivity and rapid response–recovery characteristics to these gases. The film can detect methanol, ethanol and propyl alcohol vapor as low concentration as 1, 10, and 0.5 ppm, respectively.

355 citations