(70i) One-Step Fabrication of Amphiphilic Graphene Quantum Dots As pH-Responsive Pickering Emulsifier

Pickering emulsions have attracted considerable interest, which are stabilized by inorganic nanoparticles. Carbon-based nanoparticles have low cytotoxicity, chemical inertness, cost-effectiveness, and biocompatibility. In this work, we developed a facile one-step bottom-up method to synthesize modified graphene quantum dots (C-GQDs) surfactant with controllable wettability. Pristine GQDs fabricated by bottom-up method using citric acid are hydrophilic due to a large of oxygen-containing groups. By introducing hydrophobic functional groups, such as alkane chain, improve hydrophobicity. The results from attenuated Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicate that dodecyl alkane chain was introduced on the GQDs surface. The different values of water contact angle for two sides of GQDs (WCA) indicate. The sizes of nanoparticles were investigated by Transmission Electron Microscope (TEM) and Atomic Force Microscope (AFM). These results indicate these C-GQDs lateral size is about 20 nm, the C-GQDs are few-layer. And C-GQDs could form stable Pickering emulsion under neutral conditions. Meanwhile the emulsion could be rapid responsive and reversible by pH due to the suspend carboxyl groups. When added little acid solution in to emulsion, emulsion could be demulsified without shaking. And then added based solution, the solution could be re-emulsified. These results indicate great potential for application in enhanced oil recovery, emulsion polymerization, sensor and catalyst.