An efficient and eco-friendly solution-chemical route for preparation of ultrastable reduced graphene oxide suspensions

We describe a facile and eco-friendly solution approach to chemically reduce graphene oxide (GO) to high-quality graphene using nontoxic inexpensive reductants. The reduction process and mechanism of a group of eco-friendly reductants were systematically studied. These reductants perform quite differently in terms of reduction rate (l-ascorbic acid [l-AA]>d-fructose>sucrose>glucose>sodium sulfite), density of small sp² domains (l-AA>sodium sulfite>glucose>sucrose>d-fructose), degree of reduction (l-AA>glucose>d-fructose>sodium sulfite>sucrose), and stability of the reduced GO suspension (l-AA>d-fructose>sucrose>glucose>sodium sulfite). l-AA shows the highest reducing ability, achieving the largest extent of reduction after 10 min in the presence of ammonia. Both residual oxygen functionalities and the adsorbed oxidization products of l-AA on the graphene surface are responsible for stabilizing the reduced GO suspension over several months.