Spectral Properties of AOT-Protected CdS Nanoparticles: Quantum Yield Enhancement by Photolysis

Absorption and steady-state emission spectra and time-resolved luminescence decays have been recorded for CdS nanoparticles prepared using the reverse-micelle method. Spectra were collected in hexane solution, with the surfactant AOT as stabilizer. The emission spectra of these particles are characteristic of trap-state emissions, being broad and red-shifted from the absorption-edge onset. Quantum yields for CdS particles prepared with w 0 's of 3−7 ( w 0 = [H 2 O]/[AOT]) are low (∼1−4%) and are not size dependent. CdS nanoparticles with w 0 = 4 were irradiated at the maximum of the first absorption peak. Irradiation resulted in a red shift and overall decrease in intensity of the absorption spectra, a red shift and increase in intensity of the emission spectra, an increase in the apparent lifetimes, and an increase in the quantum efficiency. Final quantum yields range from ∼9 to 13%.