石墨烯/离子液体再分散在水中的分子光谱研究

Study on Redispersibility in Water of Graphene/AmimCl Solutioninvestigated by Molecular Spectroscopy

液相法剥离石墨可制备结构完善性能优异的石墨烯片,与石墨烯表面能相近的有机溶剂如NMP和DMF等常被用作液相剥离剂。然而,石墨烯片层间强的π—π相互作用使其极易在水中发生不可逆的聚集,抑制液相剥离制备的石墨烯溶液在水中的分散性及其与水溶性高分子的复合制备。因此,使用一种简单绿色环保的溶剂,通过机械剥离石墨制备能够稳定再分散在水中的石墨烯溶液对其实际加工应用具有重大意义。1-甲基-3-烯丙基咪唑氯盐离子液体(AmimCl)是一种新型高效的绿色溶剂,其表面能与石墨烯相近,可用作剥离和稳定石墨烯的溶剂,且与水可任意比例互溶。本文在未经任何处理的离子液体AmimCl中直接超声剥离石墨制备石墨烯/AmimCl溶液,并运用Raman和UV-Vis光谱技术考察了其在水中的再分散性及其稳定性。其中,Raman光谱研究结果表明,再分散在水中的石墨烯干燥后为几个片层的堆积,即石墨烯在水中并未发生明显的聚集;UV-Vis光谱结果显示,石墨烯/AmimCl在水中能够长时间均匀稳定分散,这显著增加了石墨烯的实际应用范畴且为其与水溶性高分子的复合提供可能。

The graphene sheets with perfect structure and excellent properties can be obtained via liquid-phase exfoliation of graphite flakes,organic solvents such as NMP,DMF and so on,having the surface tension similar with the surface energy of graphite,can be used as dispersion media.However,because of the strongπ—πinterface interaction between graphene sheets,the graphene sheets are irreversibly aggregated,which limits their dispersibility in water and the further fabrication of composite with water-soluble polymers.Therefore,it is of great significant to prepare the graphene sheets redispersed in water using liquid-phase exfoliation of graphite flakes with a green and environmentally friendly solvent.1-methyl-3-allyl imidazolium chloride(AmimCl),a new and highly efficient green solvent,can be used to exfoliate graphite and make the graphene sheets stable due to their similar surface energy;also,it is freely miscible with water.In this work,the graphene/AmimCl solution has been prepared by exfoliation of graphite in AmimCl,their redispersibility and stability has been studied by Raman and UV-Vis spectroscopy.The results from Raman spectra indicate that there are less than five layers of graphene sheets redispersed in water,and the graphene/AmimCl solution can be stably dispersed in water for a long time via the UV-Vis spectra,which can definitely raise the practical application and provide the possibility of preparing the composites with water-soluble polymers.