DFWM study of thin films containing surface-modified CdS nanoparticles

Degenerate four-wave mixing (DFWM) was used as a technique to estimate the third-order optical susceptibility, χ(3) (−ω; ω, −ω, ω), of thin films prepared from cadmium sulfide (CdS) colloidal solutions. The formation of CdS films on a substrate, without any change in the particle size, enhanced the quantum yield of an excitonic band by removing a large number of surface traps. This film showed a large χ(3) value near ~ 10−7 esu around the exciton resonance at room temperature. This was possibly brought about by an effective surface passivation as well as a high CdS microcrystallite concentration.