White Nanozymes with Enhanced Alkaline Phosphatase-Mimicking Activity and Selective Inhibition Effect: Enzyme-Free Colorimetric Test Strip of Pesticide

The development of nanozymes with minimized color interference and target-specific recognition capability represents a critical advancement in colorimetric test strip. Here, white nanozymes are facilely synthesized by coordination polymerization. The optimization of surfactant modification endowed these nanozymes with enhanced alkaline phosphatase (ALP)-like activity by a larger specific surface area, and electrostatic interactions. Notably, the ALP-like activity of the nanozyme can be specifically inhibited by emamectin benzoate (EMB) rather than other pesticides. A reversible uncompetitive inhibition mechanism is systematically investigated at both enzymological and molecular levels, establishing a framework for studying nanozyme-small molecule interactions. Further, an EMB test strip is developed. Crucially, the whiteness of nanozyme effectively minimized nanozyme-induced background interference and shows a whitening effect on the paper substrate of test strip, significantly enhancing the visibility of colorimetric signal. Due to EMB-specific recognition, high ALP-like activity, and the whiteness of nanozyme, the developed nanozyme-based test strip demonstrated excellent selectivity, high sensitivity, and reliable performance for the real-time detection in real samples. This work not only demonstrates the seamless integration of white nanozymes with colorimetric test strips, but also provides a promising solution for developing enzyme-free, visual, and rapid detection platforms by screening highly specific nanozyme recognition elements for commercial pesticides.