A CoPt Graphitic Nanozyme-based Colorimetric Sensing Platform for Determination of Ascorbic Acid in Food

Ascorbic acid (AA) is an important food-derived nutrient, which plays a critical role in regulating redox metabolism in the human body. Consequently, the development of a simple, rapid, and reliable method for determining AA content in food is of significant importance. In recent years, nanozyme-mediated colorimetric sensing strategy has attracted considerable attention and emerged as a research hotspot in the field of rapid AA detection. This approach combines the advantageous features of nanozymes including low cost, high catalytic activity, good stability, and scalable production with the practical benefit of colorimetric analysis which allows visual detection without specialized instrumentation. However, most existing nanozymes achieve optimal catalytic performance only under acidic conditions, where their stability is often substantially reduced. This limitation poses a significant barrier to advancing the field. In this work, an ultra-stable CoPt graphitic nanozyme (CoPt@G) with high oxidase-like (OXD) activity was synthesized via chemical vapor deposition (CVD) to construct a colorimetric sensor for AA detection. The sensor displayed a good linear response within the AA concentration range of 3–50 μmol/L and a detection limit (S/N=3) of 0.87 μmol/L. It also demonstrated good anti-interference ability. Spike-and-recovery tests performed in commercial grape juice and fresh cabbage juice yielded satisfactory recoveries, confirming the method′s reliability. This study presented a synthesis strategy for ultra-stable nanozymes and established a straightforward, rapid colorimetric method for AA detection, offering a promising analytical tool for dietary nutrition assessment and informed food choices.