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, con...
