Portable colorimetric detection of copper based on enhanced peroxidase-like activity of MoO 3 nanobelts

, thereby catalyzing the oxidation of the 3,3',5,5'-tetramethylbenzidine (TMB) substrate with a colorimetric response. To enhance the analytical reliability and practical applicability, we employed a portable optical device for colorimetric signal analysis and a smartphone-based red-green-blue (RGB) colorimetric analysis platform. These methods show high sensitivity, with detection limits of 4.61 nM (colorimetry), 6.35 nM (portable device), and 9.91 nM (RGB analysis), significantly below the U.S. EPA regulatory limit (20 μM). Validation using real samples (wheat and corn) confirms the platform's robustness in environmental monitoring and food safety applications, offering a cost-effective, rapid and simple method for copper detection.