High-efficiency peroxidase mimics for fluorescence detection of H 2 O 2 and L-cysteine.

Enzyme-based sensing platforms have undergone rapid development in the field of diagnosis and bioanalysis. Here we present a novel fluorescent artificial enzyme-based detection strategy for L-cysteine (Cys) and H 2 O 2 by fabricating a series of Au-Ag bimetallic nanoparticles with peroxidase-like activity. Taking advantage of the enhanced performance of catalysts by optimizing the surface structure, the sensitive detection of Cys with an ultralow detection limit of 0.035 μM and accurate quantification in the range of 0.075-2 μM were achieved. It was revealed that the mechanism of the catalytic process on the Au-Ag surface follows the electron transfer mechanism rather than active species, that is the peroxidase-like catalysts work as electron transfer intermediates and the electron transfer efficiency will increase with the larger electron cloud density of active sites derived from the electronic synergistic effect between Au and Ag, contributing to the enhanced catalytic activity of peroxidase mimics. This finding could provide guidance for the structural design of high-activity peroxidase mimics.