Perovskite mesoporous LaFeO₃ with peroxidase-like activity for colorimetric detection of gallic acid

Gallic acid (GA) holds great potential in anti-cancer, anti-mutagenesis and as antioxidant. Thus its quantification is essential for quality control of GA-based drugs and health-care products, as well as for ensuring appropriate usage in human body. We developed a facile colorimetric method of GA determination, in which perovskite LaFeO₃ worked as nanozyme to catalyze oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and GA as inhibitor to prevent occurrence of the reaction. LaFeO₃ was synthesized by simple hydrothermal tactic and subsequent calcination, and appears as microspheres with mesopores on the surface. The steady-state kinetic study demonstrated that the mesoporous LaFeO₃ microspheres owned higher affinity and larger maximum initial velocity (V_max) for both TMB and H₂O₂ compared with natural horseradish peroxidase. Colorimetric analysis of GA was established based on its reducing property to measure GA in a dynamic range of 0.6∼36 μM, as well as a low detection limit of 0.4 μM (S/N = 3). In addition, the sensing system withstood interference of various interfering species and behaved well in monitoring actual samples including green tea, diet tea and pharyngitis tablets. With all these merits, the colorimetric sensor is expected to serve as a facile device for analysis of other substances.