Facile and efficient colorimetric detection of cadmium ions in aqueous systems using green-synthesized gold nanoparticles

Contamination of food and water by heavy metals, especially cadmium (Cd), poses a significant threat to humans and ecological systems. Here, we focus on the development of a simple, cost-effective, and selective colorimetric sensing system for Cd2+ ions using green-synthesized gold nanoparticles (GNPs). We used Annona muricata fruit pulp extract (AMPuE) to prepare highly stable GNPs (AMPuE-GNPs). Peerless optoelectronic properties of AMPuE-GNPs were employed for both spectroscopic and paper-based sensing of Cd2+ ions in spiked samples (e.g., water and kinnow juice). These GNPs displayed a selective response for Cd2+ over various metal chloride forms (Al3+, Ba2+, Co2+, Fe2+, Hg2+, In2+, K+, Li+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Pt2+, Sn2+, and Zn2+). The estimated detection limits of Cd in water samples using GNP-based spectroscopic and paper-based sensors were 1.13 x 10(-10) and 4.45 x 10(-8) M, respectively. GNPs prepared via a green synthesis method yielded more sensitive and selective results than those prepared chemically.