Fabrication of highly luminescent CdS nanocrystal/polyelectrolyte composite from aqueous solution

CdS/polyelectrolyte nanocomposites were prepared by using thiol-stabilized CdS nanocrystals and poly(diallyldimethylammonium chloride) in aqueous medium. The colloidal solution displayed the typical weak orange emission, which has been attributed to recombination processes at the crystallite surface. When CdS nanocrystals were introduced in a polyelectrolyte matrix, their luminescence was increased. In addition, higher intensity and whitish luminescence was observed in CdS/polyelectrolyte composite, in which a Zn excess was added during the CdS synthesis. The absorbance spectra display a resolved peak around 374 nm, corresponding to CdS electronic transition between conduction and valence band in quantum confined state. Raman spectroscopy show vibrational modes corresponding possibly to low dimensional CdS and ZnS around 600 cm^-1 and 575 cm^-1, respectively.