Challenges in semiconductor single-entity photoelectrochemistry

It is challenging to study the single semiconductor nanocrystal electrochemistry and photoelectrochemistry. The photocatalytic processes, such as the oxidation of methanol and iodide, that result from the electron-hole pair formed within a nanoparticle (NP) allow the detection of discrete current transient events assigned to single entities. Photocatalytic current amplification allows detection of collisions between the semiconductor NPs and the ultramicroelectrode that produce current transient. Staircase responses and blips in the i vs. t response indicate that irreversible and reversible NP/electrode interactions result depending on the experimental conditions. Dye sensitization increases the photocurrent magnitude of ZnO and TiO2 with respect to bare TiO2 NPs. The microelectrodes used are Pt, TiO2/Pt, TiO2/Au, and F-doped SnO2.