Peroxidase-like activity of MoS 2 NFs was enhanced by cysteine modification which is beneficial to the detection of glucose and H 2O 2 and a new catalytic mechanism was proposed.
MoS 2 nanoflakes (MoS 2 NFs) with a diameter of ∼390 nm were obtained by a facile one-pot hydrothermal method and the NFs exhibited intrinsic peroxidase-like activity. After being modified by commonly used biocompatible surfactants including polyethyleneimine (PEI), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), and cysteine (Cys), the peroxidase-like catalytic activities of MoS 2 NFs were investigated by using 3,3′,5,5′-tetramethylbenzidine (TMB) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) as chromogenic substrates. Compared to the polymer modified MoS 2 NFs, Cys functionalized MoS 2 NFs exhibited a high catalytic activity toward H 2O 2 in the presence of TMB or ABTS. Zeta potential and Michaelis–Menten analyses implied that the electrostatic force induced affinity or repulsion between the MoS 2 NFs and substrates, as well as surface modifications of the MoS 2 NFs played a key role in the catalytic reactions. Notably, a new peroxidase-like catalytic reaction mechanism was proposed based on the formation of a transient state of Cys–MoS 2 NFs containing H 2O 2 and ABTS, and the catalytic reaction could occur because the Cys on the surface of the MoS 2 NFs served as an electron transfer bridge between H 2O 2 and ABTS. Based on this finding, we also established a platform for colorimetric detection of H 2O 2 and glucose using Cys–MoS 2 NFs as a peroxidase substitution. The limit of detection (LOD) was determined to be 4.103 μmol L −1 for H 2O 2, and the linear range (LR) was from 0 to 0.3 mmol L −1. The LOD for glucose was 33.51 μmol L −1 and the LR was from 0.05 to 1 mmol L −1, which is suitable for biomedical diagnosis. This work provides a new insight into the catalytic mechanism of peroxidase-like MoS 2 NFs, and paves the way for enzyme-like nanomaterials to be used for medical diagnosis.