Amphiphilic sucrose-based carbon quantum dots as high-performance nanofluids for enhanced oil recovery

Carbon quantum dots (CQDs) have emerged as a promising class of nanocarbons owing to their ultrasmall dimensions and highly tunable surface properties. In this study, high-performance amphiphilic sucrose-based carbon quantum dots (s-CQDs) were successfully synthesized via a facile, one-step solvothermal method tailored for enhanced oil recovery (EOR) applications. The s-CQDs were prepared by reacting sucrose with dodecylamine at a 1:1 M ratio at 180 °C for 3 h. Comprehensive characterization (TEM, FT-IR, and XPS) confirmed the formation of monodisperse, quasi-spherical nanoparticles with an average core diameter of ∼4.1 nm, effectively functionalized with hydrophilic hydroxyl and amino groups alongside hydrophobic alkyl chains. The as-prepared s-CQDs exhibited robust thermal stability up to 180 °C, and their aqueous dispersions maintained excellent colloidal stability at temperatures up to 90 °C and in highly saline environments containing up to 7000 mg L −1 of NaCl or CaCl 2 . At a target concentration of 0.3 wt%, the s-CQDs reduced the surface tension of water to 29 mN m −1 and lowered the interfacial tension (IFT) between n-decane and deionized water to 4.3 mN m −1 , demonstrating pronounced interfacial activity. Stable n-decane/water emulsions were achieved at s-CQD concentrations exceeding 0.4 wt%, displaying outstanding long-term resistance to coalescence. Furthermore, the s-CQDs significantly altered the wettability of model oil-wet surfaces, successfully reversing the water contact angle from an initial 88.0° to a more water-wet 55.6°. Given their straightforward preparation, cost-effectiveness, and superior interfacial performance, these amphiphilic s-CQDs hold strong potential as an efficient and scalable nanofluid system for chemical EOR.