A smartphone-integrated CuFe aerogel nanozyme for rapid and visual detection of ascorbic acid in real samples

The development of highly active nanozymes for advanced bioanalysis has attracted considerable attention, yet significant challenges remain. Inspired by the structural features of natural oxidases with transition metal active sites, we designed a bimetallic CuFe aerogel with significantly enhanced oxidase-like activity for the facile and visual detection of ascorbic acid (AA). The incorporation of Fe into the Cu aerogel matrix resulted in a remarkable 7.8-fold increase in oxidase-like activity compared to pure Cu aerogel, as confirmed by comprehensive experimental analyses and theoretical calculations. Leveraging the inhibitory effect of AA on the Cu₆Fe aerogel-catalyzed oxidation reaction, we developed a rapid and sensitive colorimetric detection method, achieving a low detection limit of 0.1 μM. Furthermore, by integrating the Cu₆Fe aerogel with portable test strips and smartphone-based colorimetric analysis, we constructed a visual sensing platform capable of accurate and reliable AA quantification. The practical applicability of this platform was successfully demonstrated through the detection of AA in real-world samples, including fruits and commercial vitamin C beverages. This work not only provides a novel strategy for designing highly active metal aerogel-based nanozymes but also opens new avenues for their application in visual sensing and point-of-care diagnostics.