Identification of catechin species using a colorimetric and fluorescence dual-mode sensor array based on peroxidase-like PtNi bunched nanoparticles

The catechins in tea, as promoters of human health, have aroused widespread attention. Herein, a dual-signal mode (colorimetric and fluorescence) sensor array for catechin species fingerprinting was built based on PtNi bunched nanoparticles (PtNi-BNPs)-o-phenylenediamine (OPD)-H2O2 system. As we know, PtNi-BNPs catalyze the reaction between OPD and H2O2 to produce oxidized OPD (oxOPD) with both colorimetric (yellow) and fluorescent properties. As an antioxidant, catechins can inhibit the above reaction, resulting in a lighter color and reduced fluorescence intensity in their solution. Due to the varying inhibitory abilities of different catechins on their reactions, they produce unique colorimetric-fluorescence response patterns. These diverse responses were recorded and processed by linear discriminant analysis (LDA) and six catechin species were identified by the sensor array. Furthermore, our work provides a convenient method for simultaneous differentiation of catechins in mixtures and real samples. Such a sensor array with minimal sensor element and abundant signal outputs greatly saves cost and time, providing a powerful tool for the discrimination and assessment of catechins.