A comparison of enhancement factors for surface-enhanced Raman scattering using visible and near-infrared excitations

We investigated enhancement factors for surface-enhanced Raman scattering from p-aminobenzoic acid (PABA) on different silver and gold substrates using visible (632.8 nm) and near-infrared (NIR) (1064 nm) excitations. The results indicated that the use of NIR excitation provided larger enhancements (about 10-100 times) than those obtained using the visible excitation. The enhancement factors for the PABA on the silver coated alumina, silver island, gold-coated alumina, and gold island are 2.7×106, 4.3×105, 3.0×104, and 6.0×103, respectively, with the NIR excitation, and are 4.6×104, 4.7×103, 1.2×103, and 6.0×102, respectively, with the visible excitation.