Novel Electrochemical Measurements on Nanoparticle Ensembles and Actual Single Nanoparticle

The research work in this dissertation is focused on the study of the semiconductor nanoparticles (NPs) for photo conversion of light into electricity. Semiconductor nanoparticles are used not only for photo conversion but also in medicine, environmental pollution removal, material preparations, cosmetics, etc. The main goal of this work is to establish a protocol to capture and study the reaction kinetics of the single semiconductor NP. We have studied cadmium selenide (CdSe) quantum dots and TiO2 NPs suspended in a neat methanol solution as a model system where the methanol gets photooxidized into formaldehyde. The methanol oxidation to formaldehyde is a two-electron process. The particles of quantum dots get agglomerated under illumination which is evident by the current size of the photocurrent obtained in the scale > 1 pA. This observation is also consistent with the stability of the particles in methanol suspension under constant illumination and the collision frequency. We have detected formaldehyde, the product of photooxidation of methanol by FTIR, and quantified the formaldehyde by ESI-MS. We also studied the change in temperature in the vicinity of the ultramicroelectrode (UME) under constant laser illumination. It is very important to study the change in temperature because it can have a significant effect on electron transfer rate. In the last chapter, we studied TiO2 NPs suspended in methanol solution by nano-impact study under laser illumination. The particles were spiked into the solution after turning on the laser and were captured on the UME which was evident by the current steps in i-t traces. We further carried out the surface modification of the electrode and captured an actual single particle of TiO2