Generation of hot spots with silver nanocubes for single-molecule detection by surface-enhanced Raman scattering.

This paper presents a simple strategy for the formation of surface-enhanced Raman scattering (SERS) hot spots, or regions with extraordinary large electric-field enhancements, by depositing a silver nanocube on a metal substrate. Our experimental and theoretical results show that hot spots form at the corners of a nanocube in contact with the substrate and the hot spots derived from a single silver nanocube are capable of detecting SERS from a single molecule. By varying the electrical property of the substrate, and the distance between the nanoparticle and the substrate, we show that the substrate can dramatically affect the SERS from a supported nanoparticle. In addition, by comparing the SERS for nanocubes and nanospheres of similar sizes, we show that this effect is also sensitive to the shape of the supported nanoparticle, and enhancement factors of 9.7×10 and 2.1×10 were obtained for a nanosphere and a nanocube on a metal substrate, respectively. This new approach requires minimum fabrication efforts and offers great simplicity for the formation of robust and fully accessible hot spots, providing an effective SERS platform for single-molecule detection.