Synthesis and Characterization of silver colloidal nanoparticles and their application in surface enhanced Raman spectroscopy

Silver colloids were produced by chemical reduction of silver salt (silver nitrate, AgNO₃) solution. As a reducing agents trisodium citrate, sodium borohydride, ascorbic acid, PVP (Polyvinylpyrrolidone) and glucose were used. The characters of silver nanoparticles were investigated using UV-Vis spectrophotometer, dynamic light scattering (DLS), zeta (ζ) potential measurements and scanning electron microscopy. The as prepared silver nanoparticles were used in SERS measurements of pyridine. The best enhancement of the signal was achieved using sample reduced and stabilized with citrate, with the particle size of approximately 40 nm and non-uniform distribution. As aggregating agents NaNO₃, KCl and KBr in different concentrations were tested. The Raman signal for pyridine was enhanced even more with the addition of sodium borohydride instead of other aggregating agents. Addition of borohydride had the largest impact to sample stabilized with DEAE-dextran which consists of large (0.5 μm) as well as very small silver nanoparticles. The mixture colloid-borohydride-pyridine was stable for hours.