Collaborative Research: Interfacial Excitation Transfer in Hybrid Metal/Chalcopyrite Plasmonic Nanostructures

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry Professors Reinhard and Dennis from Boston University and Northeastern University will investigate charge and energy transfer between metal nanostructures and semiconductor nanocrystals through single particle spectroscopy. The chosen metal (gold and silver) and semiconductor (chalcopyrite, CuFeS2) nanomaterials both support collective charge oscillations that provide opportunities for very efficient coupling between them under resonant conditions. The lineshape of the scattering spectra of individual hybrid structures containing both metal nanoparticles and semiconductor nanocrystals will be analyzed to characterize direct charge and energy transfer between the building blocks. Optimization of these transfer processes has the potential to result in enhanced photocatalytic activity for the hybrid nanomaterials, which will be tested experimentally. Improved photocatalytic materials have important societal relevance, for instance in solar energy conversion and waste water remediation. The research of this project will be enriched by educational and outreach components. For instance, a Nano Workshop (Boston University) and a Quantum Dot Bootcamp (Northeastern University) will be developed to introduce interested high school teachers and inner-city high school students to the concepts and science underlying this research project. Plasmon dephasing in noble metal nanostructures generates hot charge carriers that are of interest in a wide range of applications, including photoconversion and photocatalysis. Unfortunately, hot electrons and holes recombine rapidly in noble metal nanostructures, severely limiting their potential for applications. Hybrid structures comprising noble metal nanoparticles and semiconductor nanocrystals may increase the lifetime of the reactive charge carriers by charge separation, but extraction of the hot charge carriers competes with their rapid thermalization, limiting the efficiency of the process. Hybrid nanostructures that produce excited charge centers in the semiconductor through direct energy and/or charge transfer without a priori generation of hot charge carriers in the metal hold great potential to increase the generation of long-lived reactive species. Chalcopyrite nanocrystals sustain quasi-static resonances in the visible, which provides unique opportunities for enhancing direct charge and energy transfer in hybrid structures in which noble metal and chalcopyrite building blocks are resonantly coupled. This project will use single particle spectroscopy to quantify interfacial plasmon dephasing as a measure of direct excitation transfer in metal/chalcopyrite hybrid systems with correlated electron microscopy to elucidate the composite structure/function relationship on a single-particle scale. Hybrid systems containing building blocks whose collective resonances show different degrees of energetic overlap will be used to test the hypothesis that resonant coupling between the building blocks enhances direct excitation transfer. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.