纯水中氧化石墨烯的超声裁剪及机理研究

采用超声在纯水中对氧化石墨烯(GO)进行裁剪, 研究了超声时间对GO片层尺寸、 官能团种类和含量的影响, 探讨了超声裁剪GO的机理. 用原子力显微镜(AFM)和透射电子显微镜(TEM)对产物进行观测, 结果表明, 随着超声时间延长, GO片层平均直径从2000 nm减小至200 nm. 红外光谱(FTIR)、 X射线光电子能谱(XPS)及热分析结果表明, 随着超声时间延长, GO的含氧官能团种类没有变化, 但是GO含氧官能团总量逐渐升高, 其中环氧基团含量逐渐下降, 羧酸基团含量变化不大, 酮基基团含量先下降后升高, 羟基基团含量先升高后下降, 醚氧基团含量逐渐升高. 基于上述结果, 提出了超声裁剪GO的机理: 超声空化现象形成的剪切力使GO的碳碳键、 环氧、 酮基基团断裂, GO片层尺寸变小; 在超声诱导下水分子形成的羟基自由基和氢自由基与片层上断裂形成的碳自由基结合生成羟基或醚氧基团, 未发生水解的碳自由基形成新的碳碳键, 长时间的超声作用还会使羟基基团发生断裂并转化成酮基基团. 利用超声在纯水中裁剪GO的条件温和, 不使用其它化学试剂, 可以有效控制GO片层尺寸, 是一种具有应用前景的二维材料裁剪技术.

Cutting Process and Mechanism of Graphene Oxide Sheets in Water by Ultrasonic†

Graphene oxide ( GO) sheets were cut into smaller pieces in water by ultrasonic. The effects of treatment time on the GO sheets’ size and GO surface groups were investigated. Moreover, the mechanism of cutting process was discussed. The results indicate that the diameter of GO sheets decreases from 2000 nm to 200 nm with increasing treatment time. The species of GO surface groups do not change after ultrasonic treat-ment. However, with increasing treatment time, the content of epoxy groups decreases, the content of carbox-ylate groups changes little, the content of ketone groups firstly decreases and then increases, the content of hy-droxyl groups firstly increases and then decreases, and the content of ether oxygen groups increases. The ultra-sonic cavitation leads to the break of carbon-carbon bonds, epoxy groups and ketone groups, which fractures the GO sheets. After that, the hydroxyl radical and hydrogen radicals formed from water react with carbon radi-cals of GO to form new carbon-carbon bonds and ether oxide or hydroxyl groups. The hydroxyl groups convert into ketone groups under long time ultrasonic treatment. The cutting process of GO by ultrasonic can be procee-ded under mild conditions without other chemicals, which is a promising technology for cutting two-dimension-al materials.