Label free colorimetric assay for selective and sensitive detection of exceedingly noxious Cd2+ ions based on Heliotropium indicum leaf extract mediated gold nanoparticles and its application in real sample analysis

Abstract

Environmental pollution derivated from organic toxins and toxic metals is becoming a dangerous factor in universal because of their destructive effects on human health and ecological system. Cadmium is one of the most hazardous and toxic heavy metal to human health and environmental safety. Herein we are reporting a new simple, cost-effective, label free and environment friendly colorimetric assay for recognition of Cd2+ ions using Heliotropium indicum leaf extract mediated gold nanoparticles. Formation of HI-AuNPs were well characterized by using various spectroscopic analysis such as UV-Visible, TEM, FTIR, EDX, SAED, XRD, FE-SEM, AFM, DLS, Zeta Potential and XPS. The synthesized AuNPs revealed a SPR peak at 539 nm, having spherical shape with 22.24 nm size. The HI-AuNPs probe exhibited extremely selective, sensitive quick colorimetric response towards Cd2+ ions with a visible colour change from red to bluish black (within 12 sec). It was assured that aggregation induced sensing mechanism was responsible for colorimetric phenomenon. The detection limit was found to be 5.35 pM, which was far less than the WHO and US-EPA recommended level. In addition, any other metal ions even Zn2+ can not interfere in this experiment, though Zn2+ and Cd2+ possess similar chemical properties. Besides, this proposed method was successfully applied for determination of Cd2+ ions in practical purpose such as real sample analysis. The results designated that this simple, cost-effective, label free, environment friendly, selective and sensitive sensing approach has good potential activity in real applications also.