Multimodal microscope system for hyperspectral imaging of scattering directionality and Raman excitation spectroscopy

Abstract

Plasmonic nanostructures enable the strong localization of an electromagnetic field, which allows them to be used for enhancing Raman signals. This property has a range of applications in various fields, from detecting small quantities of substances to studying the interactions between compounds and metals. Although the general mechanism of Raman signal enhancement by metal nanoparticles is accepted, details related to the interaction of the nanoparticle with the molecule are still unexplained because of its complexity. A versatile, high‐resolution microscope system is required to investigate the spectroscopic properties of nanoparticles and the Raman signals enhanced by them. This study describes a multifunctional microscope system designed for comprehensive microspectroscopic analysis of plasmonic nanostructures functionalized with chemicals. The integrated system combines various excitation and detection modalities, enabling hyperspectral Raman mapping, Rayleigh (dark‐field) scattering hyperspectral mapping, and angular scattering and emission mapping in defocused mode. The flexibility in excitation wavenumber choice ensures optimal measurement efficiency and the ability to perform all measurements as a function of excitation. We demonstrate the system's capabilities using malachite green deposited on gold nanorods, showcasing the surface‐enhanced Raman scattering (SERS) excitation profiles and scattering directionality defocused imaging using the hyperspectral imaging of the angular distribution of Raman scattering technique. This integrated microscope system promises to advance the study of plasmonic nanostructures and their interactions with chemical compounds at the single‐particle level. The construction of a multimodal Raman microscopic system that enables hyperspectral imaging of the angular distribution of Raman scattering and dark‐field scattering, as well as Raman excitation profiles, is presented. The capabilities of the system are demonstrated by studying the surface‐enhanced Raman scattering of malachite green deposited on gold nanorods.