Easy and green synthesis of reduced graphite oxide-based hydrogels

We report an environmentally-friendly and easy to scale-up route to synthesize reduced graphite oxide (RGO) hydrogel by simple reduction of exfoliated graphite oxide (GO) with excess vitamin C (VC). Mono-layer graphene sheets self-assembling into a well-defined and interconnected 3D porous network through pi-pi interaction during gelation can be seen by scanning electron microscopy and atomic force microscopy images. The RGO hydrogels were further functionalized and the corresponding RGO/carbon nanotube or RGO/noble metal hybrid hydrogels were obtained after similar reduction or co-reduction when carbon nanotubes were added to and stabilized with GO sheets or when noble metal precursors were added and incorporated with GO sheets. Rheological performance and electrical conductivities of these RGO-based hydrogels were also investigated in this study. The residual VC retained in these hydrogels as a biofunctional component can be gradually released in a diffusion-controlled manner, which may endow these RGO-based hydrogels with a bio-functionality. Because encapsulated bioactive VC simultaneously occurs with the formation of these assemblies, the resulting RGO-based hydrogels may have great potential in use as transdermal systems for controlled delivery of VC, tissue engineering, biosensors, etc. (C) 2011 Elsevier Ltd. All rights reserved.