Trace Level Colorimetric Hg2+ Sensor Driven by Citrus japonica Leaf Extract Derived Silver Nanoparticles: Green Synthesis and Application

In this report we demonstrate the use of Citrus japonica (CJ) leaf extract for the first time as biological liquid to work as capping as well as reducing agent for synthesizing extremely stable silver nanoparticles (AgNPs) from its precursor silver salt. Different parameters such as pH, speed of reaction, silver salt concentrations and leaf extract were optimized for the formation of CJ-AgNPs. CJ-AgNPs were then characterized through techniques like Ultra-violet visible (UV–Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), Zeta-potential analysis (ZPA) and dynamic light scattering (DLS). As-formed CJ-AgNPs were verified as highly sensitive, extremely selective, stable, economical, eco-friendly and rapidly responsive colorimetric sensor for Hg2+ detection based on color change in solution from yellow to brownish. The dynamic range of developed sensor worked linearly in the range of 0.3–7.3 µM with R2 value of 0.999 and limit of (LOD) and limit of quantification (LOQ) as 0.09 µM and 0.30 µM respectively. The sensor demonstrated negligible interference under the influence of ions like Mg2+, Zn2+, Cu2+, Co2+, Pb2+, Cd2+ and Fe2+ and corresponding anions. The developed sensor was successfully applied to detect Hg2+ at low level in some real water samples.