Department of Chemistry PChem Seminar 10/22/21

About the event

PChem Seminar, Friday, 10/22/21, at 4:10 in Fulmer 150

Speaker:       Dr. Liane Moreau

Assistant Professor

WSU Department of Chemistry

Title: Mapping the effects of physical and chemical reduction parameters on local atomic distributions within bimetallic nanocrystals

Abstract: Bimetallic metal nanoparticles are of broad interest due to their unique optical and catalytic properties which provide hybrid characteristics in comparison to monometallic counterparts. Associated properties in AgAu particles have typically been attributed to the presence of Ag-Au bonds, which follow the assumption that miscibility favors homogeneous alloy formation. This assumption is problematic, in that thermodynamics does not necessarily favor Ag-Au mixing, and necessitates the atomic-scale characterization of synthesized particles in order to accurately correlate observed properties with atomic scale distributions of the separate metal species.

Presented work includes a systematic investigation of how the parameters that control metal ion reduction affect the atomic scale distribution of Ag and Au within bimetallic nanocrystals. Given the substantial differences in redox properties between these two metals, we explore the hypothesis that reduction kinetics can be applied to tune the atomic scale incorporation and distribution of Ag and Au within synthesized particles. In particular, the roles of Ag:Au atomic ratio, the ratio of reducing agent to metal and the volume of reducing agent introduced (low, concentrated volume vs. larger, dilute volume) will be discussed. The synthetic space is thoroughly investigated using electron microscopy (TEM) and small angle X-ray scattering (SAXS) to probe effects on particle morphology, X-ray fluorescence (XRF) to elucidate incorporation ratios of Ag vs. Au, X-ray absorption spectroscopy (XAFS) to map coordination environments and consider alloy homogeneity vs. clustering and UV-vis spectroscopy to consider how the aforementioned parameters affect the optical properties of the resulting constructs. Overall, we find that reduction parameters indeed contribute to the atomic scale distribution of species within bimetallic nanocrystals, leading to the proposal of ways in which such particles can best be optimized for use as optical sensors and catalytic substrates.