• Puja Chawla

      Articles written in Bulletin of Materials Science

    • Effect of solvent-induced structural modifications on optical properties of CdS nanoparticles

      Puja Chawla Geeta Sharma S P Lochab Nafa Singh

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      We have investigated the effects of solvent used during synthesis on structural and optical properties of CdS quantum dots. Different methods of synthesis for the production of CdS quantum dots are presented. These are:

      wet chemical co-precipitation in non-aqueous medium (i.e. methanol);

      wet chemical co-precipitation in aqueous medium (deionized water) and

      solid state reaction.

      It is demonstrated that the use of methanol as solvent leads to a strong enhancement of PL intensity of CdS quantum dots for use in optoelectronic devices.These products were characterized by X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The change in bandgap with size-quantization was investigated by UV-VIS absorption spectroscopy. CdS nanocrystals prepared in non-aqueous medium have narrow size distribution than those prepared in aqueous medium and solid state reaction. Phase transformation of CdS nanocrystals from a cubic to hexagonal structure was observed in methanol solution. The formation of CdS/Cd(OH)2 nanostructure was also confirmed using X-ray diffraction pattern. This suggests that the strong enhancement of the PL intensity may have originated from the remarkable reduction of non-radiative recombination process, due to surface defects of quantum dots. The red shift of the Raman peaks compared to that for bulk CdS may be attributed to optical phonon confinement.

    • Burstein Moss effect in nanocrystalline CaS : Ce

      Geeta Sharma Puja Chawla S P Lochab Nafa Singh

      More Details Abstract Fulltext PDF

      The nanocrystalline CaS : Ce nanophosphors are synthesized by wet chemical co-precipitation method. The particles possess an average size of 10 nm as calculated using Debye–Scherrer formula. The particle size and the crystalline nature of the formed nanoparticles are confirmed by TEM micrograph. The optical studies are carried out using UV–Vis absorption spectroscopy. The absorption edge is found to show blue shift with increasing cerium concentration. The shift may be attributed to Burstein Moss effect.

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