A cost-effective nanoparticle-gap-film SERS sensor using graphene nanospacer by one-step transfer-free mechanical milling

Abstract

To develop operative surface-enhanced Raman spectroscopy (SERS) sensors, nanostructures with high signal enhancement and ease of production are highly desired. The SERS-active nanoparticle-gap-film (NGF) sandwich substrate using graphene as the gap nanospacer is of particular interest due to its strong local field enhancement associated with the atomically thin graphene gap. However, the complexity in fabricating such nanostructures, especially the often involved high-temperature and vacuum processes, ultimately hampers practical applications. Here, a simple and low-cost SERS-active NGF sensor is demonstrated in which a graphene-based nanospacer was prepared by a one-step transfer-free mechanical milling process under amiable conditions. Notably, the milling process can readily produce and deposit the graphene nanospacer in a single fabrication step onto the desired metal substrates. To further enhance SERS performance, shape-anisotropic triangular silver nanoprisms were introduced into the NGF system, which offered enhanced Raman gain compared to spherical silver nanoparticles. Using Rhodamine 6G as the probe, the NGF SERS sensors exhibited a high sensitivity with a low detection limit of 5 × 10−9M with an enhancement factor of 2.7 × 105. This study opens up a new route for the facile production of cost-effective graphene-based NGF substrates for various SERS sensing applications.