3D Hotspots Platform for Plasmon Enhanced Raman and Second Harmonic Generation Spectroscopies and Quantitative Analysis

Abstract Constructing plasmonic hotspots in metal nanostructures is essential for plasmon‐enhanced spectroscopies (PESs), but their application in quantitative analysis is a long‐standing challenge. Herein, highly uniform, reproducible, stable, and sensitive 3D hotspots platform substrates are assembled on hydrophobic silicon wafers using a drop of solution containing silica coated surface plasmon resonance (SPR) active nanoparticles (NPs). Plasmon‐enhanced second harmonic generation (PESHG) and surface‐enhanced Raman scattering (SERS) experimental signals increase sharply with the increase of droplet evaporation time, which is attributed to the rapid increase of 3D hotspots generated by gradual decrease of distance between adjacent NPs. Compared with 3D bare metal NP substrate, 3D metal shell‐isolated nanoparticles (SHINs) substrate demonstrates much more stable PESHG and SERS signals attributing to the protecting SiO₂ shells. Besides that, uniform distribution of 3D “hotspots” on the hydrophobic substrate can facilitate the quantitative analysis of an analyte using SERS. Experimental and theoretical results demonstrate that the 3D hotspots platform has the potential to be developed as a plasmon‐enhanced substrate for linear and nonlinear spectroscopies with practical sensing applications.