The Silver Nanorod Array SERS Substrates Available to Purchase

The fabrication of large area, uniform and high enhancement substrates for surface enhanced Raman scattering (SERS) based sensing is a bottle‐neck for practical applications of SERS. Recently using oblique angle deposition (OAD) method, we have fabricated silver nanorod arrays with SERS enhancement factor $>108,$ and SERS intensity variation <14%. The SERS spectra from those substrates have been demonstrated to be able to distinguish different viruses and virus strains, bacteria, microRNAs, or other chemical and biological molecules. We have performed a detailed characterization on those Ag nanorod substrates. The SERS enhancement factor depends strongly on the nanorod length and the fabrication conditions. For different deposition angle, there is an optimal nanorod length that gives the maximum enhancement. The SERS enhancement seems to directly depend on the reflectivity of the Ag nanorod substrates at the excitation wavelength regardless of the deposition angles and rod length. The SERS performance also depends strongly on the configurations of the excitation laser beam: the incident angle, the polarization, and the reflectance of the underlayer substrates. A simple modified Greenler’s model is proposed to qualitatively explain those effects. The possible origin for the high enhancement of the Ag nanorod substrates has been studied by placing the Raman probe molecules on different locations of the substrates, and we have found that the side surfaces of the nanorod arrays contributes more to the SERS enhancement compared to the ends. We propose that this is due to the anisotropic absorbance nature of the Ag nanorod substrates.