Measuring the surface-enhanced Raman scattering enhancement factors of hot spots formedbetween an individual Ag nanowire and a single Ag nanocube

Abstract

This paper describes a systematic study of the surface-enhanced Raman scattering (SERS)activity of hot spots formed between a Ag nanowire and a Ag nanocube with sharp corners.We investigated two distinct dimer structures: (i) a nanocube having one sideface nearly touching the side face of a nanowire, and (ii) a nanocube having oneedge nearly touching the side face of a nanowire. The field enhancements for thedimers displayed a strong dependence on laser polarization, and the strongestSERS intensities were observed for polarization along the hot-spot axis. Moreover,the detected SERS intensities were dependent on the hot-spot structure, i.e.,the relative orientation of the Ag nanocube with respect to the nanowire’s sideface. When the dimer had a face-to-face configuration, the enhancement factorEFdimer was1.4 × 107.This corresponds to 22-fold and 24-fold increases compared to those for individual Ag nanowiresand nanocubes, respectively. Conversely, when the dimer had an edge-to-face configuration,EFdimer was4.3 × 106. These results demonstrated that the number of probe molecules adsorbed at thehot spot played an important role in determining the detected SERS intensities.EFdimer was maximized when the dimer configuration allowed for a larger number of probemolecules to be trapped within the hot-spot region.