Ultrasound-assisted preparation of CdSe nanocrystals in the presence of Polyvinyl alcohol as a capping agent

Nanosized Polyvinyl alcohol-capped CdSe particles were prepared via a simple and fast ultrasound-assisted technique through the reaction between aqueous solutions of cadmium acetate and sodium selenosulfate. The nanoparticles are characterized using X-ray diffraction (XRD), UV-Visible spectrophotometer, Scanning electron microscope (SEM), Energy dispersive X-ray (EDAX) analysis and Fourier transform infrared (FTIR) spectrometer. XRD pattern reveals that the nanoparticles are in well-crystalline cubic phase. The broadening of diffraction peaks indicated the formation of particles in the nanometer size regime. A shift in absorption peak is observed in the spectra near 544 nm due to quantum confinement effect. Particle sizes calculated from the X-ray diffraction studies agree fairly well with those estimated from optical absorption studies. The homogeneity of the sample could be controlled by adjusting the concentration of Polyvinyl alcohol. SEM images of a specific concentration of Polyvinyl alcohol for as-prepared CdSe nanocrystals show uniform particles distribution. The particle size is found to be less than 100 nm based on the observed SEM images and the reason of this mismatch is discussed. The calculated result from XRD and optical characterizations shows that the particles size is smaller than those observed in SEM images. The elemental analysis from EDAX shows that the average atomic percentage of Cd:Se was 50:50 showing that the prepared samples are exactly stoichiometric. (C) 2010 Elsevier Ltd. All rights reserved.