Synthesis and Photocatalytic Properties of Hybrid Metal-Semiconductor Nanoparticles

Metal and semiconductor nanoparticles exhibit excellent light absorbing ability and size-tunable properties. When the two components are combined in one hybrid structure, effective charge separation could occur upon photoexcitation and the long-lived charge-separated state along the electrons or holes to transfer to molecules nearby; therefore, they can be employed to catalyze photochemical reactions. In our work, we developed a method to synthesize Ag-tipped CdS nanorods with varying lengths using a seed-mediated growth method. The length of the nanorods can be controlled by the ratio of the Ag and Cd/S precursors. The Ag-CdS nanorods were applied as photocatalyst for methyl orange degradation reaction and their catalytic activities were affected by their length. Specifically, rods of intermediate lengths showed higher degradation rates than the short and long ones. Steady-state and time-dependent fluorescence spectroscopy was used to measure photoluminescence (PL) spectra and decays of the Ag-CdS nanorods and rod-like CdS nanoparticles. The Ag-CdS nanorods exhibited broad, red-shifted PL spectra and much slower PL decays compared to that of the CdS nanoparticles. By fitting the PL lifetime distribution of the decay curves, we attributed the high photocatalytic activities of the intermate-length Ag-CdS nanorods to the higher probability of populating the charge-separated states than that of the short or long rods.