Dual-functional oxygen-/nitrogen-rich gold nanostars enabled by inter-/intraparticle aggregation: Ultrasensitive Cr(VI) detection and rapid removal

Abstract

Accidental leakage of hexavalent chromium (Cr(VI)) ions caused by natural disasters or operational failures frequently exceeds the regulatory discharge limits and poses severe environmental and health risks. Such incidents highlight the urgent need for highly sensitive, real-time detection and rapid removal technologies. Herein, we present oxygen−/nitrogen-rich gold nanostars (O/N-rich GNS) as a dual-function nanoplatform capable of real-time colorimetric detection of Cr(VI) ions, with strong Cr(VI) binding that facilitates aggregation-based signal amplification. The O/N-rich surface facilitates the monolayer chemisorption of Cr(VI) ions, contributing to rapid aggregation and enhanced optical response. The rate constant for the reaction between O/N-rich GNS and Cr(VI) is 0.277 min−1, significantly higher than those of previously reported adsorbents. The star-shaped morphology promotes inter- and intraparticle interactions with Cr(VI) ions, leading to the formation of milli-scale aggregates that induce a distinct color change, enabling ultrasensitive detection down to 90.12 nM—significantly outperforming conventional analytical techniques. These interactions also simplify post-adsorption recovery. The O/N-rich GNS exhibit high Cr(VI) selectivity and removal efficiency (>98.91%) in simulated industrial wastewater containing 36 coexisting ions while maintaining stable performance under acidic conditions and temperature conditions. This multifunctional nanoplatform provides a practical and sensitive approach for rapid Cr(VI) monitoring in complex aqueous environments. This multifunctional nanoplatform provides a practical and scalable solution for the immediate response to Cr(VI) contamination, integrating rapid sensing and effective remediation for real-world environmental applications.