Energy transfer from fluorescein dye dispersed with CdS nanoparticles as evidenced by emission spectrum measurements

Abstract Cadmium Sulphide (CdS) nanoparticles show very interesting optical properties due to quantum confinement effects, that make them useful for biomedical labelling, optoelectronic devices, etc. In this work we show that when CdS nanoparticles are dispersed in organic dyes, the optical properties of the dyes change considerably. We have synthesized CdS nanoparticles by co-precipitation method and characterized by XRD and TEM. Nanoparticles have been dispersed in aqueous solution of fluorescein dye and their absorption and photoluminescence (PL) spectra were recorded. The intensities of PL spectra and the peak wavelength of emission shifted remarkably from the spectra of corresponding pure dye solution. The observed shifts are attributed to the band structure modification by the formation of chemical complex when dye molecules get adsorbed onto nanoparticle surfaces. FRET mechanism is responsible for the rapid quenching of dye fluorescence.