Enhancement of Raman signal from analytes on ultrathin Au and AuCu alloy nanowire network substrates

Network of ultrathin Au and AuCu alloy nanowires of diameter ∼3.5 nm were used to design novel substrates for surface-enhanced Raman spectroscopy (SERS) for detection of ppm level of analyte molecule, Rhodamine 6 G. The ultrathin morphology and geometry of the wire network resulted in a 20-fold enhancement in the signal as compared to a substrate with Au or AuCu particles of the same concentration. Raman signal enhancement on AuCu nanowire array has been found to be higher than on Au nanowire array. This observation has been corroborated by theoretical simulations as well. The effect of excitation wavelength on the enhancement has been studied for different analyte molecules on Au and AuCu nanowire ensemble as the SERS substrate. The effect of polarization of the laser source with respect to the anisotropic bunch of nanowires on the Raman signal was also studied.