This project aims to develop a methodology for selective detection of Hg(II) ions in water using silver nanoparticles as colorimetric and plasmonic sensor. For this purpose, we intend to synthesize silver nanoparticles, using sodium borohydride as reducing agent and the biopolymer chitosan as capping agent (AgNP-Chit), in aqueous medium. The colloidal solution of AgNP-Chit is going to be characterized using Ultraviolet-visible spectroscopy (UV-vis), to obtain the plasmon band. Scanning and transmission electron microscopy measures will also be carried out, to determine the particles' size, crystallinity, and morphology. When Hg(II) is in contact with Ag(0), the ion will reduce due to its higher reduction potential, while the silver will oxidize to Ag(I). Such phenomenon modifies AgNP's optical properties, resulting in a color change. Solutions of Hg(II), with control of their concentrations, it will be added in eppendorfs tubes containing fixed volumes of AgNP. This first test aims to investigate the limit of detection for Hg(II) and it will be monitored through sample's color change (colorimetric sensing) and UV-vis measurements (plasmonic sensing), evaluating modifications in the plasmon band of AgNP-Chit colloidal solution. A second test will be carried out in the same condition of the first one. However, others metallic ions, such as Fe(III), Ca(II), Cu(II), and Mg(II) will be present in the tubes with AgNP-Chit. In this experiment, it will be evaluate the selectivity of the test of detecting of Hg(II) by using AgNP-Chit in the presence of other metals.
News published in Agência FAPESP Newsletter about the scholarship: