Logic-gate assisted colorimetric platform based on α-sulfophenylacetic acid functionalized gold nanoparticles for ultrasensitive detection and removal of Cr(III) and Cr(VI)

Chromium contamination in aquatic systems represents a major environmental and public health concern due to the high toxicity and mobility of its hexavalent species. In this work, α-Sulfophenylacetic acid functionalized gold nanoparticles (α-SPAA-AuNPs) were developed as a dual-functional colorimetric platform for the selective detection and removal of chromium ions in aqueous media. The functionalized nanoparticles enable ultrasensitive sensing of Cr(III) and Cr(VI) through analyte-induced aggregation, producing a distinct color transition resulting from localized surface plasmon resonance changes. By integrating Cr(VI), Cr(III), ethylenediaminetetraacetic acid (EDTA), and ascorbic acid (AA) as chemical inputs, molecular logic gate operations including AND, OR, and INHIBITOR were successfully constructed. The proposed sensing system exhibited excellent selectivity toward chromium species over other competing metal ions. The limits of detection were determined to be 15.6 ppb for Cr(III) and 20.8 ppb for Cr(VI) after reduction with AA. The sensing mechanism is attributed to coordination interactions between chromium ions and the carboxyl functional groups of α-Sulfophenylacetic acid on the nanoparticle surface, leading to nanoparticle aggregation. Furthermore, the platform demonstrated practical applicability through successful analysis of environmental water samples including drinking water, tap water, and lake water, highlighting its potential for environmental monitoring and remediation of chromium contamination.