Abstract The active control of friction in oil-based lubricants was realized in the present study with the use of MoS 2 particle additives and the application of an electric field. By modifying the surface charging state of the MoS 2 particles, the dependence of potential-controlled boundary lubrication behavior on the electrical properties of the particles was demonstrated. For a diethyl succinate lubricant containing negatively charged MoS 2 particles, the coefficient of friction (COF) was reduced by 60–70% when a positive potential was applied to a lower friction pair of copper plates. After modification with poly(diallyldimethylammonium chloride), the particles were positively charged, and the COF was reduced with the application of a negative potential. The mechanisms underlying the potential control of the COF were investigated by observing the distributions of the particle additives and characterizing the tribofilms formed at different potentials. Most of the charged particles were locally concentrated near the opposite pole, and this was reversed when the electric field changed. For locally high concentrations of MoS 2 particles, a MoS 2 /MoO x tribofilm with a thickness of 100–500 nm and a loose structure formed on the lower friction pair, which significantly decreased the shear force during the friction process. Graphical Abstract
Yuanyuan Cai,Lingxi Niu,Xuan Liu,Yujiao Zhang,Zongmei Zheng,Lingxing Zeng,Aihua Liu
It is important to exploit highly efficient methods for detecting pollutants selectively and sensitively. Artificial enzymes are promising to replace natural enzymes with diverse functions for sustainable developments and various applications. However, it remains the challenge to develop novel mimic enzymes or multi-enzyme mimics for pollutant detection. Herein we report hierarchical porous MoS 2 particles prepared by a simple hydrothermal method, which demonstrated excellent sulfite oxidase (SuO x )-, nicotinamide adenine dinucleotide (NADH) oxidase- and superoxide dismutase-mimicking activities. In addition, the catalytic conditions for SuO x -like and NADH oxidase-like activities of MoS 2 were optimized. The catalytic mechanism of the NADH oxidase mimics is that O 2 involves in the oxidation of NADH, to generate O 2 .- intermediate and finally turn to H 2 O 2 , while SuO x mimics comes from that MoS 2 particles can effectively catalyze sulfite to reduce [Fe(CN) 6 ] 3- . Based on the excellent SuO x -like activity of MoS 2 particles, while phenol can inhibit the oxidation of sulfite, a phenol colorimetric sensor was explored with the dynamic range of 2–1000 μM and the limit of detection of 0.72 μM, applicable to detect phenol in effluents. Therefore, MoS 2 particles with the SuO x -like, NADH oxidase-like and SOD-like activities has broad application prospects in environmental monitoring and bio-analysis.
危险品化学品经营许可证（带存储）