  Surface enhanced Raman spectroscopy (SERS) is a precise and non-invasive
analytical technique that is widely used in chemical analysis, environmental
protection, food processing, pharmaceutics, and diagnostic biology. However, it
is still a challenge to produce highly sensitive and reusable SERS substrates
with minimum fluorescence background. In this work, we propose the use of van
der Waals heterostructures of two-dimensional materials (2D materials) to cover
plasmonic metal nanoparticles to solve this challenge. The heterostructures of
atomically thin boron nitride (BN) and graphene provide synergistic effects:
(1) electrons could tunnel through the atomically thin BN, allowing the charge
transfer between graphene and probe molecules to suppress fluorescence
background; (2) the SERS sensitivity is enhanced by graphene via chemical
enhancement mechanism (CM) in addition to electromagnetic field mechanism (EM);
(3) the atomically thin BN protects the underlying graphene and Ag
nanoparticles from oxidation during heating for regeneration at 360 {\deg}C in
the air so that the SERS substrates could be reused. These advances will
facilitate wider applications of SERS, especially on the detection of
fluorescent molecules with higher sensitivity.
