04/08/2024
By Kwok Fan Chow
Date: Wednesday, April 10, 2024
Time: 12:00 to 1:00 pm
Location: Olney 518
Speaker: Prof. Wei-Shun Chang, Department of Chemistry and Biochemistry, UMass Dartmouth
Abstract:
Gold nanoparticles possess unique optical properties as a result of surface plasmon resonances. Plasmonic nanostructures have been explored for various applications, including photocatalysis, nanoscale sensing, photovoltaic devices, bioimaging, and therapeutics. Photoexcitation of surface plasmon resonances generates high-energy carriers or thermal energy that drive chemical reactions. The efficiency of hot carrier and heat generation are regulated by the morphologies of the plasmonic structures. However, the size and shape heterogeneities always appear in the chemically synthesized nanoparticles and impede the detailed structure-function relationship of the nanostructures when characterized by the conventional ensemble measurements. Single-nanoparticle spectroscopy resolves the obstacles of sample heterogeneity to obtain more information that is inaccessible by the ensemble measurements. In this talk, I will present the technique developed in my lab to explore plasmonic photocatalysis at the single-particle level. Measuring the scattering spectra of single nanoparticles provides information about electron transfer at the nanoparticle-substrate interface and the redox reaction on nanoparticles. We have observed efficient electron transfer between gold nanorods and carbon thin films and molecular adsorbates to potentially promote plasmonic catalysis. The capping ligand, polyvinylpyrrolidone, of gold nanorods induces charge separation at the gold-polyvinylpyrrolidone interface and enhances Au+3 reduction for thirteen times under photoexcitation. A detailed mechanism for ligand-induced plasmonic photocatalysis will be discussed. These results provide insight into the design of plasmonic photocatalysts.