Comparative Study of the Morphology, Aggregation, Adherence to Glass, and Surface-Enhanced Raman Scattering Activity of Silver Nanoparticles Prepared by Chemical Reduction of Ag⁺ Using Citrate and Hydroxylamine

Abstract

Two different silver colloids were prepared by chemical reduction of silver nitrate with trisodium citrate and hydroxylamine hydrochloride to compare their characteristics in relation to their possible use in surface-enhanced Raman scattering (SERS) spectroscopy. The morphology and plasmon resonance of the single nanoparticles and aggregates integrating these colloids were characterized by means of UV-vis absortion spectroscopy and scanning electron microscopy, revealing important differences between each type of nanoparticle as concerns their physical properties. These metallic systems also manifested differences in the aggregation and the adherence to glass surfaces, revealing significant differences in the chemical surface properties of these nanoparticles. SERS and surface-enhanced IR also indicated the presence of interference bands which can overlap the spectra of the analyte, mainly in the case of the citrate colloid. All these differences have an important influence on the applicability of these nanostructured systems in SERS. In fact, the enhancement factor and spectral pattern of the SERS obtained by using alizarin as a molecule probe are different.

Enhancement of FITC Fluorescence by Silver Colloids and Silver Island Films

“…The layer of citrate anions prevents aggregation of nanoparticles. This procedure leads to obtaining nanoparticles, which are approximately spherical and uniform in size and stable during several weeks [24,25].…”

Surface-Enhanced Raman Scattering of 4-Aminothiophenol Adsorbed on Silver Nanosheets Deposited onto Cubic Boron Nitride Films

“…22 However, the crystal faces of {100}, {110} and {311} with high free energies easily appear on edges, corners, and protuberances, in small proportions. 20,21 It has been reported that the enhancement of the Raman signal encountered in SERS arises mainly from so-called "hot spots" in various metallic nanostructures, and the "hot spots" exist on sharp protrusions and sites between two particles in proximity.…”

Silver substrates for surface enhanced Raman scattering: Correlation between nanostructure and Raman scattering enhancement

“…3,4 Thus, SERS substrates could be used for non-invasive biological assays, 5 biosensing, 6 or environmental analysis 7 with high sensitivity. Several methods have been commonly employed to fabricate SERS-active substrates, e.g., the immobilization of colloidal nanoparticles on solid surfaces 8,9 or lithographic techniques. 10,11 The use of patterned templates exploiting the self-assembly capabilities of block co-polymer thin films has also been explored.…”