Peroxidase-like activity of MoS2 nanoflakes with different modifications and their application for H2O2 and glucose detection.

MoS2 nanoflakes (MoS2 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 MoS2 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 MoS2 NFs, Cys functionalized MoS2 NFs exhibited a high catalytic activity toward H2O2 in the presence of TMB or ABTS. Zeta potential and Michaelis-Menten analyses implied that the electrostatic force induced affinity or repulsion between the MoS2 NFs and substrates, as well as surface modifications of the MoS2 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-MoS2 NFs containing H2O2 and ABTS, and the catalytic reaction could occur because the Cys on the surface of the MoS2 NFs served as an electron transfer bridge between H2O2 and ABTS. Based on this finding, we also established a platform for colorimetric detection of H2O2 and glucose using Cys-MoS2 NFs as a peroxidase substitution. The limit of detection (LOD) was determined to be 4.103 μmol L-1 for H2O2, 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 MoS2 NFs, and paves the way for enzyme-like nanomaterials to be used for medical diagnosis.