Naked-Eye Detection of Mercury Ions from Morphological Transition of Silver Nanocubes: Tuning Sensitivity Using Co-Staining Agent

Abstract

A simple, low-cost and highly selective nanosensor was developed for naked-eye detection of mercury ions (Hg2+) based on Eosin/silver nanocubes (Eosin/AgNCbs). Silver nanocubes (AgNCbs) were synthesized by polyol assisted chemical method. HR-TEM result shows the formed AgNCbs have a mean diameter of 84±0.005 nM (diagonally measured) and edge length of 55±0.01 nM. XRD result confirms that the AgNCbs are single crystalline in nature with a phase structure of face centered cubic (FCC) of silver. On interaction of Hg2+, AgNCbs exhibits a color change from gray to black up to 16.67 μM of Hg2+ owed to the formation of solid like bimetallic complex of Ag/Hg amalgam. The selectivity of AgNCbs was evaluated with several other toxic metal ions including, Mg2+, Ba2+, Ca4+, Pb2+, Cd4+, Zn2+, Co2+, Cu2+, K+ and Ni2+ and found good selectivity towards Hg2+. The sensitivity of the AgNCbs sensor system was tuned by using Eosin as a co-staining agent. The Eosin/AgNCbs showed a limit of detection of 60±0.050 nM with the color change from orange to purple. The results suggests that the Eosin/AgNCbs nanosensor exhibits good selectivity, sensitivity, repeatability and rapid response, which could be explored for real-time detection of Hg2+ in environmental and biological samples.