Glucono-delta-lactone controlled assembly of graphene oxide hydrogels with selectively reversible gel-sol transition

A generic approach to make the uniform graphene oxide (GO) hydrogels by using glucono-delta-lactone (GDL) as a hydrogel promoter has been put forward for the first time. Either in situ released multivalent metal ions (e. g. La3+, Co2+, Ni2+) or in situ protonized polyamine (e. g. polyethylenimine, melamine, polyamidoamine) molecules have assembled GO sheets into 3D hydrogel architectures with the assistance of the hydrolysis product of GDL. The permanent network and mechanical property of the resulting GO hydrogels have been studied by rheology investigation. The chemical composition and porous morphology of the resulting GO hydrogels have been revealed by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The microstructure of the resulting GO hydrogels has been investigated by Raman spectroscopy and X-ray diffraction. More interestingly, a reversible gel-sol transition initially triggered with the addition of the EDTA solution, depending on which additive (in situ released multivalent metal ions or in situ protonized polyamine molecules) is used for 3D assembly of the GO sheets, has been observed from the resulting GO hydrogels.