Sustainable Surface-Enhanced Raman Substrate with Hexagonal Boron Nitride Dielectric Spacer for Preventing Electric Field Cancellation at Au–Au Nanogap

Nanogaps between Au nanoparticles and Au substrates are the simplest systems that generate extremely high electric fields at hotspots for surface-enhanced Raman spectroscopy (SERS). However, the electric field cancellation at the hotspots in the systems can cause the reduction of Raman signal when two metallic materials are physically contacted due to the low concentration of analytes. Here, we propose an atomically thin hexagonal boron nitride (h-BN) shielding layer for Au substrates, which can be used as an insulating spacer to prevent electrical shorts at nanogaps. Experimental investigation of the SERS effect combined with theoretical studies by finite-difference time-domain simulations demonstrate that the Au NP/h-BN/Au substrate structure has excellent performance in electrical short prevention, thus facilitating ultrasensitive Raman detection. The outstanding chemical and thermal stability of h-BN allow the efficient recycling of the SERS substrate by protecting the Au surface during the removal of Au NPs and molecular analytes by chemical and thermal processes.