A rapid and sensitive smartphone colorimetric sensor for detection of ascorbic acid in food using the nanozyme paper-based microfluidic chip

Ascorbic acid is very important to human health because of its excellent antioxidant effect. Developing sensitive and on-site detection methods is therefore in high demand. In this work, a portable paper-based colorimetric sensor with a smartphone platform with an ultrahigh sensitivity has been designed for on-site and quantitative analysis of ascorbic acid based on AuNPs nanozyme activity. The developed excellent peroxidase-like nanozymes, could effectively catalyze the oxidation of chromogenic substrates by H2O2. Herein, the AuNPs nanozyme activity are embedded on paper pieces to construct paper-based microfluidic chips for visual detection. Meanwhile, a smartphone platform is integrated for the signal readout. Using ascorbic acid as an analyte model, the proposed paper-based analysis platform shows a reliable and sensitive detection of ascorbic acid with a low detection limit of 0.406 μmol/L. The platform also works well in various real samples. This analysis method is facile in design, showing a great application potential for on-site and mass screening of ingredients in the environment and in foods.