Peroxidase-like activity of MoS 2 nanoflakes with different modifications and their application for H 2 O 2 and glucose detection.

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 ₂ O 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 ₂ O 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 ₂ O ₂ and ABTS. Based on this finding, we also established a platform for colorimetric detection of H ₂ O 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 ₂ O 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.