Optical Properties of Ag@TiO2 and CdS@TiO2 Core-Shell Nanostructures

Titanium hydroxyacylate has been used as a shell forming agent to form core shell nanostructures of Ag@TiO2 (10-40 nm core; 15 nm shell) and CdS@TiO2 (3 nm core; 1 nm shell) using the reverse micellar route. The low rate of hydrolysis of titanium hydroxyacylate appears to be responsible for the formation of TiO2 shell. A red shift of 25 nm was observed in the surface plasmon band of silver for Ag@TiO2 core shell structures (compared with that of silver nanoparticles) while blue shift of the absorption band CdS@TiO2 core shell nanostructures (compared to bare CdS nanoparticles) was observed. CdS@TiO2 shows a strong quantum confinement effect. Our studies clearly show an increase in the PL intensity of Ag@TiO2 which we rationalize based on the SERS effect of the Ag nanoparticle. No quenching was observed of the emission band of CdS for the CdS@TiO2 core shell nanostructures.