PROBING HOT-ELECTRON SPATIAL AND TEMPORAL KINETICS IN COMPOSITIONALLY VARYING BIMETALLIC ALLOY SYSTEM

Farheen khurshid^1*, Jeyavelan Muthu¹, Ya-Ping Hsieh², Mario Hofmann¹

¹Physics, National Taiwan University, Taipei, Taiwan
²Institute of Atomic and Molecular Sciences, IAMS, Sinica, Taipei, Taiwan

* Presenter:Farheen khurshid, email:nkhursheed412@gmail.com

Bimetallic plasmonic nanoparticles enable tuning of the optical response and chemical stability by composition variation. Understanding the spatial and temporal kinetics of hot electrons in compositionally varying plasmonic bimetallic alloy nanoparticles is of paramount importance, as it unlocks unprecedented opportunities for tailoring their performance. So far first-principle techniques, such as ab initio time-dependent density-functional theory can be used to investigate hot-carrier processes in compositionally varying alloy systems, but are challenging to apply to experimentally relevant systems due to the limitations of conventional fabrication methods. In this study, we utilized a novel gradient mask approach to develop compositionally varying continuous bimetal alloy (Au-Ag) nanostructures on a single substrate and explore the intricate dynamics of hot electrons within plasmonic bimetallic alloy nanoparticles with varying compositions. We explore the spatiotemporal evolution of hot electrons, tracking their movement and interactions at the nanoscale. By employing cutting-edge experimental techniques, including ultrafast spectroscopy and high-resolution scanning electrochemical microscopy, we unravel the complex interplay between nanoparticle composition, and the generation of hot electrons and demonstrate that the hot electron sweet spot optimized to be at a composition of Au0.35-Ag0.65 and this prediction was confirmed by the in situ photocatalytic SERS experiments. Further investigation by Local electrochemical spectroscopy reveals a minimized flat-band potential and charge transfer resistance as a result of suppressed bend bending at this ratio, which is the origin of this sweet spot. Computational simulations complement our experimental findings, providing a comprehensive picture of hot electron transfer kinetics.
In conclusion, the research emphasizes the critical role of investigating hot electron spatial and temporal kinetics in compositionally varying plasmonic bimetallic alloy nanoparticles. Our findings open new horizons for the design and engineering of tailored nanomaterials with enhanced functionality for a diverse range of applications.

Keywords: Composition, Gradient, Bimetal, Plasmons, Hot-electron