Two-dimensional FeP@C nanosheets as a robust oxidase mimic for fluorescence detection of cysteine and Cu2+

Abstract

In the past few years, the development of novel nanozymes with excellent performance has attracted increasing attention in biosensing. However, most of those nanozymes were found to possess peroxidase activity with the prerequisite of the presence of H₂O₂. In contrast, oxidase mimics can catalyze the oxidation of substrates without H₂O₂, delivering a higher signal-to-noise ratio than that of peroxidase mimics in practical applications. Herein, for the first time, two-dimensional (2D) nanosheets composed of iron phosphide embedded in a carbon matrix (FeP@C nanosheets) were found to demonstrate a robust oxidase-like property, different from those previously reported peroxidase mimics based on transition metal phosphides (TMPs). Based on this intriguing observation, the fluorescent substrate Amplex Red (AR) of peroxidase can be effectively oxidized by FeP@C nanosheets in the absence of H₂O₂. Benefiting from the oxidase-like enzymatic activity of the FeP@C nanosheets, a novel fluorescence sensing platform was developed for the detection of cysteine (Cys) and Cu²⁺. The outstanding performance of the 2D FeP@C nanosheets endows the proposed platform with superior sensitivity and selectivity compared to many previously reported approaches. Besides, the inherent features of simplicity, being label free, and low cost also allow this methodology to stand out among many other strategies, revealing its huge potential in practical analysis and detection applications.