Oligochitosan stabilized silver nanodispersions as a promising basis for SERS substrates

Abstract

New nanodispersions of silver particles stabilized by oligomeric chitosans have been synthesized. The synthesis was controlled by electronic absorption spectroscopy and the particle size (from 30 to 90 nm) was measured by dynamic light scattering. The formation of ring-shaped deposits on glass slides from these dispersions was studied. It was proposed to use the obtained nanodispersions and ring-shaped deposits based on them as substrates for Raman spectroscopy. A specific modification of the synthesis protocol of the nanodispersions was carried out in order to obtain larger nanoparticles (90 nm) with a small thickness (2–5 nm) of the oligochitosan shell, which does not limit the measurement of the signal of small amounts of analytes. It is shown that SERS substrates based on modified nanodispersions allow obtaining a well resolved Raman spectrum of an analyte (Rhodamine 6 G) deposited on the substrate at a low concentration (10⁻⁸ M). Thus, the developed solid SERS substrates can be used for the analysis of trace amounts of chemicals in analytical applications.