Silver-chitosan and gold-chitosan substrates for surface-enhanced Raman spectroscopy (SERS): Effect of nanoparticle morphology on SERS performance

Abstract

The search for cost-effective methods for the fabrication of sensitive and selective surface-enhanced Raman spectroscopy (SERS) substrates has led to recent studies exploring the incorporation of biopolymers as the supporting scaffold or nanostructure stabilizer. In this paper, we report on the effect of the enhancing nanostructure morphology on the SERS performance of chitosan-containing substrates. For this work, silver nanospheres, silver nanocubes, gold nanospheres, and gold nanorods were synthesized and fully characterized; then, SERS substrates were prepared using all of the morphologies and chitosan with varying concentrations and molecular weight to also test the effect of the biopolymer on the SERS effect. This work showed that the chitosan film allows for trapping of analyte molecules and thus, higher Raman intensities. It was found that the chitosan concentration plays an important role in this effect. The fabricated substrates showed minimum values of detected concentration between 10−4 and 10−9 M using p-ATP as probe molecule, depending on the nanostructure morphology used, showing that the silver nanocubes lead to a higher sensitivity and Raman intensities enhancement compared to the other dispersions studied.