Black Phosphorus Quantum Dots with a Core–Shell Nanostructure as a Water-Based Lubrication Additive

The unique tribological characteristics of black phosphorus quantum dots (BPQDs) have recently attracted much attention. However, the long-term stable lubrication of BPQDs and prevention of degradation in ultrapure water remain huge challenges. Herein, BPQDs@silica (BPQDs@SiO2) core–shell materials were designed and synthesized. The BPQDs are uniformly distributed in the SiO2 shell. The as-prepared BPQDs@SiO2 as the water-based lubrication additive has remarkable lubricity, wettability, and stability. In particular, compared with the average coefficient of friction (COF) and wear rate of ultrapure water, those of BPQDs@SiO2, being a water-based lubrication additive, could be reduced by 45.7 and 83.0% at 10 N and 150 r/min, respectively. The lubrication mechanisms of BPQDs@SiO2 as a water-based lubrication additive were proposed based on the friction test and wear surface analysis. The excellent lubricity performances of BPQDs@SiO2 are owed to the polishing of the SiO2 shell, the extreme pressure property of the BPQD core, and the tribo-chemical reaction film. This investigation established a simple, convenient, and feasible method for using the BPQDs@SiO2 materials as a water-based lubrication additive. It is expected that BPQDs with a core-shell nanostructure will open up new ideas for the development of excellent lubricating nanomaterials.