A colorimetric and visual assay is described for the herbicide aminotriazole (ATZ). It is based on the etching of gold nanorods (AuNRs) by iodine which is formed on oxidation of iodide via H2O2. Longitudinal etching of the AuNRs occurs quickly and is accompanied by a color change from dark blue to red. In the absence of ATZ and the presence of active catalase (CAT), H2O2 is quickly decomposed into water, and the AuNRs will not be etched. In the presence of ATZ, CAT is partially deactivated, and this affects the amount of available H2O2 and, consequently, of the iodine. Hence, the color is significantly changed. The color changes can be easily detected with bare eyes. The assay has a linear response in the 5 to 70 μM concentration range, with a detection limit of 1.3 μM and high selectivity for ATZ. It was applied to the determination of ATZ in water and food samples. Graphical abstract A multicolor colorimetric method is developed for aminotriazole (ATZ) detection based on catalase (CAT) deactivation-dependent longitudinal etching of gold nanorods (AuNRs). The color signals can be visually identified. Good detection performances and capability for evaluating ATZ level in water and food samples is demonstrated.
Keywords: Aminotriazole; Bare eye detection; Catalase; Colorimetric assay; Etching; Food sample; Gold nanorods; Herbicide testing; Iodine; Visual detection.