CAREER: Developing Low-Cost Computational Models for the Photoexcited Dynamics of Noble Metal Nanoclusters

With this CAREER award, Rebecca Gieseking of Brandeis University is supported from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop computational models to understand the interactions of light with metal nanoclusters. Metal nanoclusters have the potential to revolutionize solar energy technologies by harnessing light to produce chemical fuels because they support plasmons, which are collective oscillations of the electrons that enable the nanoclusters to strongly absorb light.

Understanding, controlling, and manipulating the plasmon properties is key to improving the efficiency of solar energy storage. Dr. Gieseking and her research group are developing accurate models with low computational costs to understand the decay processes after metal nanoclusters absorb light.

They are using these models to understand how these decay processes change as a function of nanocluster size, shape, and composition to design metal nanoclusters with controllable decay time scales for efficient solar energy storage. Dr. Gieseking is also developing new computational chemistry laboratory exercises throughout the chemistry curriculum to introduce undergraduates to the field and deepen their understanding of important chemical properties.

Beyond her research contribution, Dr. Gieseking is engaged in promoting the participation of women and underrepresented minorities in chemistry through recruiting research students, mentoring through ChemWMN (Chemistry Women Mentoring Network), and participating in Brandeis’s outreach to local schools.

Dr. Rebecca Gieseking and her research group are developing nonadiabatic molecular dynamics (NAMD) models based on semi-empirical methods to understand the photoexcited dynamics of metal nanoclusters (NCs). Atomically precise noble metal NCs are strong absorbers that can be tuned by changing the NC size and shape, and the excited-state dynamics vary from excitonic (indicating discrete excited states) to plasmonic (reflecting a near-continuum of states).

Dr. Gieseking is parametrizing semi-empirical quantum mechanical (SEQM) methods in an effort to accurately reproduce the excited-state potential energy surfaces of Ag and Au NCs and utilizing NAMD codes for surface-hopping simulations of the dynamics. This project aims to advance the state of knowledge in plasmon-enhanced hot-electron chemistry by (i) providing a novel low-cost computational model for the atomistic excited-state dynamics of noble metal NCs and (ii) revealing structure-property relationships that affect the excited-state dynamics, which can be used to tailor NCs for applications in photocatalysis and other solar energy technologies.

These methods aim to provide fundamental insight into the transition from excitonic to plasmonic behavior and refine existing quantum mechanical definitions of plasmons by using dynamics. If successful, these studies will make important strides toward the vision of using SEQM methods to harness plasmonic hot electrons for photocatalysis of industrially important reactions.

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.