A smartphone-integrated colorimetric sensing platform for the detection of tannic acid in beverages using folic acid-functionalized copper nanoclusters nanozyme

Abstract

In the present work, we describe a straightforward method for the synthesis of highly luminescent folic acid-functionalized copper nanoclusters (FA–CuNCs) using folic acid as a stabilizing agent and hydrazine hydrate as a reducing agent. In the presence of hydrogen peroxide (H₂O₂), the FA–CuNCs drive the oxidation of 3,3′,5,5′-tetramethyl benzidine (TMB) to its blue oxidized state (oxTMB), demonstrating good peroxidase-like activity. Adding tannic acid (TA) dramatically inhibits its catalytic activity making it possible to create a rapid, colorimetric sensing platform for TA. The proposed sensor exhibited notable sensitivity, achieving a low detection limit of 88.5 nM and a wide linear range from 2.00 × 10⁻⁷ to 4.00 × 10⁻⁶ mol dm⁻³, showing good selectivity against common interfering ions and biomolecules. This method was made considerably simpler and more portable by combining the colorimetric visibility with RGB color variation analysis based on a smartphone. Furthermore, the successful detection of TA in actual tea and coffee samples validated the method for practical applications. This portable, straightforward, cost effective and selective approach has a lot of potential for practical uses in environmental monitoring and food safety.