Preparation and enhanced off-resonance optical nonlinearities of CdS-capped gold nanoparticles embedded in BaTiO₃ thin films

A simple approach has been developed for the synthesis of Au@CdS core-shell nanoparticles by a direct self-assembling process. Stable Au@CdS composite colloids were prepared by thiourea, as a double-functional reagent that acted as the linkage agent between Cd²⁺ ions and gold nanoparticles. The CdS-capped gold composite nanoparticles were successfully integrated into BaTiO₃ films. A significant enhancement of third-order nonlinear optical susceptibility in the Au@CdS nanoparticles with core-shell structure is reported. To compare the effect of enhanced nonlinear response, single gold or CdS nanoparticles embedded in BaTiO₃ films were also prepared.