Morphological changes and covalent reactivity assessment of single-layer graphene oxides under carboxylic group-targeted chemistry

Acid–base titrations were used to assess the covalent reactivity of carboxylic groups on single-layer graphene oxides (SLGO) or hydrazine-reduced analogues (SLGR) when treated with thionyl chloride and subsequent coupling to amines. Reflux with aggressive solvents led to size reduction and folding of individual sheets as well as loss of carboxylic groups, substantially so for SLGR. Room temperature treatment of SLGO with a carbodiimide collapsed the sheets into star-like clusters, which exhibited poor subsequent reactivity with amines. Ultimately, conventional chemical treatment of carboxylic groups on SLGO leads to morphological changes and reduced reactivity, which may potentially limit their use.