Abstract
Although emulsion applications of microscale graphene sheets have attracted much attention recently, nanoscale graphene platelets, namely, graphene quantum dots (GQDs), have been rarely explored in interface science. In this work, we study the interfacial behaviors and emulsion phase diagrams of hydrophobic-functionalized graphene quantum dots (C18-GQDs). Distinctive from pristine graphene quantum dots (p-GQDs), C18-GQDs show several interesting surface-active properties including high emulsification efficiency in stabilizing dodecane-in-water emulsions. We then utilize the C18-GQDs as surfactants in miniemulsion polymerization of styrene, achieving uniform and relatively small polystyrene nanospheres. The high emulsification efficiency, low production cost, uniform morphology, intriguing photoluminescence, and extraordinary stability render C18-GQDs an attractive alternative in surfactant applications.
Highlights
In Pickering emulsions, the solid particles play a key role at the interface of two immiscible phases to prevent the coalescence by generating a mechanically robust monolayer [1]
Comparing with p-graphene quantum dots (GQDs), the low resolution/contrast of TEM image of C18GQDs might be due to the functionalization of edge of graphene sheets, which were observed in other polymer functionalized GQDs [27, 35]
We demonstrated that octadecyl grafted graphene quantum dots (C18-GQDs) surfactants could be used as effective emulsifiers for stabilizing Picking emulsions as well as for miniemulsion polymerization
Summary
In Pickering emulsions, the solid particles play a key role at the interface of two immiscible phases to prevent the coalescence by generating a mechanically robust monolayer [1]. This field received widespread scientific interests for developing stable Pickering emulsions/foam [2,3,4], double emulsions [5,6,7,8], liquid marbles, and superhydrophobic barriers [9, 10]. Pristine GO nanosheets could not stabilize the styrene droplets in aqueous phase due to high hydrophilicity of GO, the hydrophobic modification by adsorbing PS oligomers on GO surface led to the nascent nuclei formation and continuous Pickering emulsion polymerization successfully. Due to the limited hydrophobicity introduced by thermal reduction, the
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