Abstract
Plasmonic nanocavities exhibit exceptional capabilities in visualizing the internal structure of a single molecule at sub-nanometer resolution. Among these, an easily manufacturable nanoparticle-on-mirror (NPoM) nanocavity is a successful and powerful platform for demonstrating various optical phenomena. Exciting advances in surface-enhanced spectroscopy using NPoM nanocavities have been developed and explored, including enhanced Raman, fluorescence, phosphorescence, upconversion, etc. This perspective emphasizes the construction of NPoM nanocavities and their applications in achieving higher enhancement capabilities or spatial resolution in dark-field scattering spectroscopy and plasmon-enhanced spectroscopy. We describe a systematic framework that elucidates how to meet the requirements for studying light-matter interactions through the creation of well-designed NPoM nanocavities. Additionally, it provides an outlook on the challenges, future development directions, and practical applications in the field of plasmon-enhanced spectroscopy.