Characterization of Electrodeposited Cu Interfaces Via Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy

Abstract

The advent of SERS created a new avenue for investigating interfacial phenomena by coupling the localized surface plasmon resonance (LSPR) of metal nanostructures to the inelastic scattering properties of molecules. Seeing a 104-fold enhancement in Raman signals, SERS scattering events were used to identify adsorbed molecules and substrate-surface structural conformations. But, even with the advent of SERs, Raman spectroscopy was still confined to LSPR active materials with roughened surfaces. However, recent technical modifications to SERS, such as shell-isolation and localized probe modes, have shown potential for the operando investigation of flat non-plasmon active single-crystal surfaces. Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) provides two parallel paths for electric field enhancement of non-plasmon active surfaces while minimizing chemical perturbations by encasing reporters in a chemically inert shell (Figure 1). This technique can be used to perform measurements before, during, and after electrodeposition to gain an understanding for changes at metal-solution interfaces under an applied bias. SHINERS serves as a great utility to not only understand surface adsorbates, but to also characterize how dynamic surfaces respond to surface adsorbates. The precarious nature of metastable surfaces (e.g. metallic Cu) make capturing surface information challenging, preventing accurate structure-activity assignments necessary to fully understand the system. The lack of techniques (operando, especially) capable of evaluating functional interfaces, vs model systems, has further inhibited understanding of surface phenomena. Breaking these limits, will enable novel findings that afford new understanding and strategies to develop refined interfaces and processes. Herein, we report the synthesis of Au@SiO2 core-shell nanoparticles and their application to track the state of interfacial phenomena on electrodeposited Cu surfaces (Figure 1).Figure 1. Electron microscopy images of Au-SiO2 nanoparticles (a) dispersed on Cu Trenches (b) for shell-isolated nanoparticle enhanced Raman spectroscopy (c) measurements to probe for surface adsorbates, which shows enhancement relative to the bare Cu surface (d). Figure 1