Synthesis of Amphiphilic Graphene Quantum Dots and Their Sustained Release Effect on L-Menthol

Amphiphilic alkyl amine functionalized graphene quantum dots (AA-GQD) were synthesized by one-step thermal decomposition with citric acid and linear alkyl amine as raw materials. The results showed that the alkyl carbon chain length had a great effect on the surface activity of AA-GQD. When the dodecylamine was used as the functional reagent, the surface tension of the dodecylamine functionalized graphene quantum dots(DA-GQD) was reduced to 30.8 mN/m, which was close to that of the typical anionic surfactant sodium dodecyl benzene sulfonate. DA-GQD was then used as a solid particle emulsifier to stabilize L-menthol in water Pickering emulsion. The formed emulsion had high stability with the average particle size of emulsion being about 10 mu m. After the emulsion was cooled to room temperature, crystals were precipitated. The precipitate was filtered and dried to obtain the DA-GQD loaded with L-menthol. The effect of DA-GQD on the release behavior of menthol was studied by means of hot air sweeping. It was found that the time required for the complete release of menthol in the 1.0%DA-GQD loaded sample was 4.6 times and 9.2 times that of menthol in the mixed sample and the blank sample, respectively. The above results show that DA-GQD has a significant sustained release effect on L-menthol. GQDs contain rich functional groups such as hydroxyl group and carboxy group that might interact strongly with L-menthol , resulting in improved release behavior of the loaded sample.