Time, aging and optical absorption of silver particles obtained by chemical reduction

The present work is focused on obtaining silver nanoparticles by chemical reduction of silver nitrate through sodium borohydride. As well as, sodium citrate was used as a reducing/stabilizing agent at a temperature of 0ºC in distilled water. Measurements of their optical properties were performed using UV-VIS Spectrophotometer. The absorption spectrum obtained shows a band around 400 nm, indicating the formation of Ag nanoparticles. The peak of the surface plasmon resonance in the absorption spectrum of the silver colloid solution shows an absorption maximum in the range of 382-402 nm, even a color change in the colloid was observed. Comparing Mie's theory of light scattering and experimental results show the size of the silver nanoparticles (approximately, 2-20nm). It was found that the shift of the plasmon peak is related to the color change of the silver colloid for different aging times.