Carbon Dots with Spatially‐Mediated‐N/S‐Co‐Doping Enabling One‐Year Stable Lubricant with Oil Leakage Detection Capability

Abstract The dispersion stability of nano‐lubricating additives is crucial for the shelf life of lubricant and its practical applications. Nitrogen–sulfur co‐doped carbon dots (N,S@CDs) via a one‐step hydrothermal method with nitropyrene and thiourea as raw materials are hereby presented. The N and S elements are selectively distributed throughout the entire carbon skeleton with a doping amount of 22.6 at%. The as‐synthesized N,S@CDs exhibit excellent dispersion stability in PEG200 and maintain stability for over one year. The experiment results indicate that N,S@CDs significantly improve the anti‐wear and friction reduction properties of PEG200, while the friction coefficient is reduced from 0.25 to 0.09 with 1.5 wt% N,S@CDs addition, and the wear volume, depth, and width are reduced by 68%, 52%, and 57%, respectively. The good lubrication performance is attributed to N,S@CDs excellent dispersion stability, enhanced filling and polishing effects, and complex tribochemical reactions caused by heteroatom doping to form a stable protective film on the worn surface. Furthermore, the as‐prepared N,S@CDs exhibit intrinsic fluorescence intensity in PEG200 with the photoluminescence quantum yield (PLQY) of 12.5% and remain fluorescent stable during the long‐term friction process, therefore the N,S@CDs have a potential application prospect in non‐destructive detection of oil leakage via fluorescence labeling method.