Spectroelectrochemical Investigation of the Charge Carrier Kinetics of Gold-Decorated Cadmium Chalcogenide Nanorods

The interfacial transfer of charge carriers across the semiconductor nanoparticle/electrolyte boundary is an elementary process for applications such as photoelectrochemical sensing and photocatalysis. This mechanism is investigated for systems based on complex shaped semiconductor and metal-semiconductor nano-heteroparticles. In the present work the influence of the presence of a CdSe domain within the CdS nanorod as well as the influence of gold domain decoration is investigated spectroelectrochemically. Therefore, the mentioned nanoparticles are linked to transparent indium tin oxide (ITO) glass slides via (3-mercaptopropyl)trimethoxysilane (MPTMS). This preparation yields sub-monolayers of the particles. External photocurrent quantum efficiency spectra are measured in the range from λ=350–650 nm. Intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) measurements are applied to the samples in order to reveal and explain the differences of the electrochemical kinetics between the four different particle types (CdS, CdSe/CdS, CdS−Au, and CdSe/CdS−Au nanorods). We demonstrate that the presence of gold domains affects the carrier dynamics of various involved processes. An equivalent circuit model is derived and fitted to the impedance data to explain changes of the kinetics in the system