Hexagonal boron nitride nanosheet Film-Veiled Ag nanoparticles for ultrasensitive and long-term stable SERS substrates under visible and UV excitation

A versatile surface-enhanced Raman spectroscopy (SERS) substrate capable of responding to excitation by both visible and ultraviolet (UV) lasers is challenging. Herein, an ultrasensitive and long-term stable SERS substrate suitable for both visible and UV excitation is realized by a structure of hexagonal boron nitride (hBN) nanosheet film-veiled Ag nanoparticles (hBN/Ag substrate). Utilizing the hBN/Ag substrate, the detection limit for crystal violet (CV) under a 532 nm laser is remarkably low at 1.0 × 10^-15 M; adenine, a biomarker, can be detected under UV excitation (a 325 nm laser) with a low limit of 1.0 × 10^-7 M. The hBN/Ag substrate provides abundant electromagnetic (EM) hotspots and multiple charge transfer paths under both 532 nm and 325 nm lasers. This cooperation of EM and chemical enhancement confers ultrasensitive and versatile SERS performance to the substrate. Furthermore, the hBN/Ag substrate demonstrates excellent reproducibility and stability even after 6 months in air, maintaining the SERS intensity of CV at over 86 % of that on the freshly prepared substrate, with a relative standard deviation of 6.57 %. These results indicate that the hBN/Ag substrate can be employed in visible and UV SERS for widespread and practical applications.