Selective colorimetric detection of trace chromium (III) based on silver nanoparticles aggregation via a domino-like reaction

Abstract

A simple method for measuring and tracking Cr3+, particularly in water, are crucial for environmental protection and avoiding serious health implications. Herein, we report the synthesis of mannose functionalized silver nanoparticles (Ag@mannose NPs) for naked eye detection of Cr3+ ions. The Cr3+-induced selective stimuli on the surface of Ag@mannose NPs promote aggregation, resulting in a colour change from yellow to purple, which can be assessed by absorption spectroscopy. Zeta potential investigation revealed that the surface charge of Ag@mannose NPs was altered in the presence of Cr3+, resulting in aggregation, as validated by dynamic light scattering and transmission electron microscopy. Cyclic voltammetry study shows that the NPs surface stabilized with mannose was oxidized in the presence of Cr3+, causing a domino-like effect that resulted in NPs aggregation and colour change. The interference study demonstrated the selectivity and sensitivity of Ag@mannose NPs to Cr3+ over other metal ions. Ag@mannose NPs can detect Cr3+ in a wide pH range of 3–9. The lowest Cr3+ concentration detected by the naked eye is 0.6 μM (39 μg/L), under the World Health Organization permissible limit of chromium (50 μg/L) in drinking water. Finally, the Ag@mannose NPs sensing ability was demonstrated by detecting Cr3+ in tap and sewage water with a good recovery percentage.