Influence of reagents concentrations during synthesis for silver nanoparticles stability

Mettalic nanoparticles have outstanding optical, electronic and mecanical properties. Some of these properties comes from the interaction between eletromagnetic field in specific frequencies that can induct a ressonance oscilation of free surface electrons on nanoparticles which is called surface plasmonic ressonance (SPR). The obtainment of silver nanoparticles is based on a oxidation- redution reaction of a silver salt and a reduction agent, Sodium tetrahydridoborate – a powerful reduction agent which favors the reaction velocity making it higher and providing smaller particles when compared to weaker reduction agents. As a stabilizing agent for silver nanoparticles, polyvinil alcohol (PVA) was used. Although synthesis of silver nanoparticles is not new, stability is a crucial factor for a good aplicability of silver nanoparticles. On this purpose, a range of variables can influence silver nanoparticles stability such as concentration of silver nanoparticles and reduction agent, reaction temperature, the lasting of the reduction process, storage. In this work, the variation of silver salt, sodium tetrahydridoborate and PVA concentractions during nanoparticles synthesis were evalluated in order to understand their influence on silver nanoparticles stability. This was obtained through nanoparticles diameter analysis through transmission eléctron microscopy (TEM) and Ultraviolet and visible spectroscopy. Results show that smaller diameter nanoparticles are obtained when PVA is used as a stabilizing agent when compared to nanoparticles obtained with just silver nitrate and sodium tetrahydridoborate. Silver nanoparticles synthesized with higher concentration sodium tetrahydridoborate are smaller when compared to the ones obtained with a smaller sodium tetrahydridoborate concentration.