Enhanced oxidase activity of platinum decorated graphitic carbon nitride for the colorimetric detection of ascorbic acid

Abstract

We present a sensitive colorimetric sensor based on platinum (Pt) nanoparticle-decorated graphitic carbon nitride (Pt@g-C3N4) for the detection of ascorbic acid (AsA) in real samples. Pt@g-C3N4 nanocomposites were synthesized through surface reduction of Pt ions on g-C3N4 dispersions, with their synthesis confirmed by various characterization techniques. The nanocomposites exhibited enhanced oxidase-like activity, particularly in the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). Utilizing AsA’s competitive inhibition of the oxidase activity, we developed a colorimetric assay for quantifying AsA in acetate buffer, commercially available tablets, and real samples such as orange and lemon juice. The sensor demonstrated a linear response in the 1–100 μM range, with a limit of detection of 0.28 μM. Additionally, we introduced a paper-based assay for on-site, naked-eye detection of AsA. This work offers a practical and cost-effective approach for monitoring AsA levels in various food and pharmaceutical products, with potential applications in health diagnostics and quality control. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.