Silver nanoparticles with different thiol functionalization: An opposite optical behaviour in presence of hg(ii)

Abstract

We synthesized two different functionalized silver nanoparticles (AgNPs) in water, starting from silver nitrate, as Ag(I) ions precursor, and sodium borohydride, as reduction agent. The first system was capped with sodium 3-mercapto-1-propansulfonate (3MPS), while L-Cysteine and citrate stabilized the other system. We characterized both systems by UV-Vis absorption spectroscopy and transmission electron microscopy (TEM). We tested their optical response to several heavy metal ions monitoring the Localized Surface Plasmon Resonance (LSPR) band. In particular, these two systems have an opposite optical behaviour in presence of Hg(II) ions as contaminants. In the case of AgNPs-L-Cysteine/citrate, the plasmonic band shifted to higher wavelengths affording a linear behaviour and LOD, in the range from 1 to 7.5 ppm and 600 ppb, respectively; whereas, the AgNPS-3MPS peak shifted to lower wavelengths with a linear range from 0 to 5 ppm and a LOD of 240 ppb for Hg(II). A preliminary hypothesis about the interaction mechanism between AgNPs and Hg(II) ions is discussed.