A smartphone sensing colorimetric detection of ascorbic acid in fruit samples based on Cu₂Fe(CN)₆@PVP nanozyme

Prussian blue analogue nanozymes (PBANZs) have been widely employed in the colorimetric detection of various organic small molecules due to their peroxidase-like activity. However, the practical applications of PBANZ are limited by its narrow operating pH range, insufficient catalytic activity, and poor stability. In this study, we synthesized a novel Cu₂Fe(CN)₆@PVP PBA nanozyme (Cu-PBANZ) using polyvinylpyrrolidone (PVP) as a capping ligand. This novel Cu-PBANZ not only exhibited enhanced peroxidase-like activity and improved stability under near-neutral conditions but also demonstrated higher sensitivity and a broader linear range in the detection of hydrogen peroxide (20-4000 μM, LOD 5 μM) and ascorbic acid (10-2000 μM, LOD 3.9 μM). Besides, a smartphone-based platform was developed for detecting AA content in fruits, achieving a detection limit of 7.8 μM. Both UV-Vis spectrophotometry and smartphone-based colorimetry were validated with recovery rates of 95.1 %-106.7 % and 94.8 %-108.9 %, respectively. This study proposed a promising biosensor incorporating Cu-PBANZ for rapid colorimetric detection of AA in fruits using a smartphone.