Shifting of fluorescence peak in CdS nanoparticles by excitation wavelength change.

CdS nanoparticles with different size are prepared by chemical bath deposition method. These particles show strong fluorescence at emission wavelength of 507 nm. It has been observed that this emission peak changes through a range of 147 nm, by varying the excitation wavelengths through 370-480 nm.The emission peak can thus be tuned by varying the excitation wavelengths. This peak emission wavelength shift is due to the selective excitation of vibronic levels in the surface state of the CdS nanoparticles.