Glutathione-stabilized silver nanoparticles as colorimetric sensor for Ni2+ ion

We report herein the synthesis of glutathione-stabilized silver nanoparticles (GSH-Ag NPs) in water media and colorimetric assay of Ni2+ with GSH-Ag NPs. GSH-Ag NPs were characterized by IR spectroscopy, ultraviolet-visible spectroscopy (UV–vis), transmission electron microscopy (TEM). The freshly synthesized GSH-Ag NPs are yellow in color due to the intense surface plasmon absorption band. In the presence of Ni2+, the yellow GSH-Ag NPs solution turns to a deep orange color accompanying the broadening and red shifting of surface plasmon absorption band. However, the sensitivity of GSH-Ag NPs towards other representative transition-metal ions (Zn2+, Co2+, Cd2+, Mn2+, Hg2+, Cu2+), alkali metal ions (Li+, Na+, K+) and alkaline earth metal ions (Mg2+, Ca2+, Sr2+, Ba2+) can be negligible, except Co2+ having a modest interference. Also the effect of the concentration of Ni2+ to the silver nanoparticles was considered and the limit of detection for Ni2+ by GSH-Ag NPs is 7.5 × 10−5 mol L−1. Meanwhile, an interesting phenomenon that 1,2-ethylenediamine can make the aggregated nanoparticles redispersed was observed, and possible mechanism of the response of the aggregated GSH-Ag NPs to 1,2-ethylenediamine is discussed.