Tuning of the hydrophilicity and hydrophobicity of nitrogen doped carbon dots: A facile approach towards high efficient lubricant nanoadditives

Nanosizing is considered as a promising approach for achieving better dispersibility of nanoparticles in mediums, while the regulation of their hydrophilicity and hydrophobicity is very important issue for wide application of nanoparticles. Herein, nitrogen-doped carbon dots (N-CDs) with hydrophilicity was prepared via namely “bottom-up” and exhibited excellent excitation-dependent maximum fluorescence at 480/560 nm, while a novel kind of liquid-like N-CDs with hydrophobicity was synthesized followed via covalent grafting stratagem and exhibited excellent excitation-dependent maximum fluorescence at 500/580 nm. Both hydrophilic and hydrophobic N-CDs exhibited favorable dispersion stability in polar and apolar mediums respectively and were used for the first time as friction-reducing and antiwear nanoadditives in selected PEG and PAO synthetic base oils for steel/steel contact, which offered great potential in lubricant field as demonstrated for the highly efficient carbon dots nano-additives in reducing both undesirable friction and wear.