ZnO–Co₃O₄ Nanofibers/MXene Composite with Peroxidase-Like Activity for Ascorbic Acid Detection

The growing concern about nutrient-rich diets and health monitoring has motivated the search for simple, fast, and effective methods for detecting important nutrients in foodstuffs. In this scenario, colorimetric detection using nanostructures presenting enzymatic properties (nanozymes) has gained prominence due to its experimental simplicity and low cost. In this work, zinc oxide–cobalt oxide electrospun nanofibers (ZnO–Co 3 O 4 NFs) were combined with titanium carbide (Ti 3 C 2 T x ) MXene for the colorimetric detection of ascorbic acid. The nanocomposite (ZnO–Co 3 O 4 NFs/Ti 3 C 2 T x ) presented peroxidase-like activity with a high affinity for the chromogenic substrate 3,3,5,5-tetramethylbenzidine and fast reaction kinetics. Taking advantage of the catalytic properties of the developed nanocomposite, ascorbic acid was detected with high sensitivity (the limit of detection was 0.58 μmol L –1 ) and selectivity, even in the presence of common interferents. The colorimetric sensor even detected ascorbic acid in orange juice, revealing its potential to be used as a reliable and sensitive portable method for food analysis.