Structure–Property Analysis of Bimetallic Plasmonic Nanoparticles Using Correlative Optical and Electron Microscopy

Bimetallic plasmonic nanomaterials offer unique opportunities for tailoring optical and catalytic functionality through controlling the composition and structure. Their performance arises from the interplay between a plasmonic host metal and a functional secondary component, yet disentangling how alloying and morphology influence their optical response remains challenging, particularly when their optical properties are commonly measured on the bulk scale. Here, we present a systematic single-particle study of Ag and AgPt nanoparticles (NPs) with varying shapes and platinum contents, all measured under identical conditions on a single carbon-coated TEM grid. Using a correlative imaging approach that integrates dark-field microscopy, single-particle scattering spectroscopy, scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS), we directly link structural and compositional features to optical behavior at the individual particle level. Our data set includes Ag and Ag_1–xPt_x (x = 0.02, 0.035, and 0.1) nanospheres, nanodiscs, and triangular nanoparticles (TNPs), with the AgPt NPs synthesized via galvanic replacement. The same-grid configuration enables a one-to-one tracking of particle identity across optical and structural modalities, thereby avoiding artifacts from sample-to-sample variability. We observe composition- and geometry-dependent changes in plasmonic response, confirmed by finite element method (FEM) simulations, which demonstrate how alloying and morphology modulate optical scattering. This work establishes a robust and accessible framework for resolving structure–property relationships in bimetallic plasmonic nanostructures in the context of energy conversion applications. By enabling controlled comparative measurements across compositions and morphologies, our approach provides insights into nanoscale plasmonic tuning and supports the rational design of next-generation bimetallic materials.