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Sharma M.,Bhopal University | Sharma M.,Indian Institute of Technology Bombay | Sharma A.B.,Bhopal University | Mishra N.,Bhopal University | Pandey R.K.,Barkatullah University
Materials Research Bulletin | Year: 2011

Cadmium selenide (CdSe) quantum dots were grown on indium tin oxide substrate using wet chemical technique for possible application as light emitting devices. The structural, morphological and luminescence properties of the as deposited thin films of CdSe Q-dot have been investigated, using X-ray diffraction, transmission electron microscopy, atomic force microscopy and optical and luminescence spectroscopy. The quantum dots have been shown to deposit in an organized array on ITO/glass substrate. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The effect of quantum confinement also manifested as a blue shift of photoluminescence emission. It is shown that the nanocrystalline CdSe exhibits intense photoluminescence as compared to the large grained polycrystalline CdSe films. © 2010 Elsevier Ltd. All rights reserved.

Faiyas A.P.A.,Indian Institute of Science | Vinod E.M.,Indian Institute of Science | Joseph J.,Bhopal University | Ganesan R.,Indian Institute of Science | Pandey R.K.,Bhopal University
Journal of Magnetism and Magnetic Materials | Year: 2010

Nanoparticles of Fe3O4 were synthesized by co-precipitation in an aqueous solution containing ferrous and ferric salts (1:2) at varying pH with ammonia as a base. It was found that the value of pH influences the reaction mechanism for the formation of Fe3O4. Furthermore, the addition of mercaptoethanol significantly reduced the crystalline size of Fe3O4 nanoparticles from 15.03 to 8.02 nm. X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles were ε-Fe2O3 or Fe3O4 phase. To further prove the composition of the product, as-prepared Fe3O4 were examined by X-ray photoelectron spectroscopy (XPS). Magnetic properties of the obtained particles were determined by vibrating sample magnetometer (VSM). Further analysis of the X-ray studies shows that while maintaining a pH value of 6 and 9 in a solution containing iron salts II and III ions produces ε-Fe2O3. Whereas a pH value of 11 produces magnetite (Fe3O4) phase. All of these results show that the pH has a major role in the observed phase formation of (Fe3O4) nanoparticles. © 2009 Elsevier B.V. All rights reserved.

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