▎ 摘　　要

In this work, the gelation mechanism of graphene quantum dots (GQDs) into hydrogels is investigated using dynamic light scattering and ultraviolet-visible techniques. Hydrogels are prepared through the hydrothermal reduction of concentrated GQDs solutions (20-50 mg/mL) using L-ascorbic acid as the reducing agent. At early stages of the gelation process (first 2 h), J-type aggregation of GQDs results in the formation of particles with dimensions around 10 nm. As the gelation process proceeds, formation of larger particles through the aggregation of almost all GQDs results in slower dynamics and hindered Brownian motions in the solution. With the reduction of a majority of edge-carboxyl groups through six first hours of the hydrothermal process, a change in the self-assembly mechanism takes place (from J-type to H-type). A GQDs hydrogel, with an interconnected colloidal morphology and a very low density (similar to 0.009 g/cm(3)) can be obtained after 8 h of the hydrothermal process. The specific surface area of the prepared GQDs hydrogel, fabricated through the hydrothermal reduction of the 20 mg/mL GQDs precursor solution, is >1000 m(2)/g. Hydrogels and cryogels prepared using GQDs as the building units can be applicable where hyper-porous structures with large number of available sites are needed. (C) 2018 Elsevier B.V. All rights reserved.