Luminescence study of bare and coated CdS quantum dots: Effect of SHI irradiation and ageing

Bare and silica coated CdS quantum dots are prepared following chemical route. Swift heavy ion (SHI) irradiation of the samples was carried out with 160 MeV Ni12+ ion beam with fluences 1012-1013 ions/cm2. Photoluminescence (PL) studies of all the samples were carried out with excitation wavelength 325 nm. The surface state emission is dominant in case of bare samples while e-h recombination is observed in case of coated samples. Red shift in the absorption response in the optical absorption spectra of bare samples reveal size enhancement of the quantum dots after irradiation. No such shift is observed for coated samples. The coated samples also exhibit enhanced photo stability.