Temperature Evolution of Plasmonic Probes for Tip-Enhanced Raman Scattering

Abstract

This work delves into the processes leading to the evolution of nanofocusing plasmonic probes utilized in applications like tip-enhanced Raman spectroscopy, primarily under temperature growth. We identify stable crystallographic configurations of possible plasmonic tips that can withstand external influence, retain their original shape, and preserve their performance to enhance the local electromagnetic field under heat exposure. Employing molecular dynamics simulations, we study the behavior of plasmonic probes in the shape of sharp-edged gold nanotetrahedra as a case study. This makes it possible to observe the evolution of the shape and its impact on the light-concentrating performance of such probes. We identify the origin of shape instability and demonstrate that the migration of surface atoms from the tip area serves as the primary driver of shape variability in highly nonspherical plasmonic nanoparticles. By modeling the optical characteristics of the plasmonic probes utilizing the atomic discrete interaction model and finite element methods, we track alterations in the local electromagnetic field close to the apex of these gold nanotetrahedra at the plasmon resonance wavelength in the process of evolution. This analysis provides insight into the evolution of the field enhancement factor as the plasmonic tips degrade over time.