Tunable plasmon properties of Fe2O3@Ag substrate for surface-enhanced Raman scattering

We introduce a new approach that combines the self-assembly and seeding methods for silver plating of the proposed Fe2O3@Au-seed substrate. By adjusting the silver plating time between 0 and 360 s, the optical resonance of the substrates clearly varied from visible to near-infrared. To investigate the potential of these substrates for use in surface-enhanced Raman scattering (SERS) applications, SERS spectra of thiophenol (TP), 4-aminothiophenol (PATP) and rhodamine 6G (R6G) were evaluated at three excitation wavelengths (532, 633 and 785 nm). Analysis of the SERS spectra clearly demonstrated that the SERS effect depends strongly on the nature of the substrate surface and the nature and electronic resonance of the probe molecules. The calculated enhancement factor (EF) of TP adsorbed onto an Fe2O3@Ag substrate was ∼107 following three laser excitations. More importantly, these SERS substrates can successfully be utilized for the detection of small molecules at very low concentrations (∼100 pg mL−1).