Post-oxidation treated graphene quantum dots as a fluorescent probe for sensitive detection of copper ions

Highlights: • The oxidation degree of graphene quantum dots was increased by post-treatment. • Graphene quantum dots remain size and composition unchanged after post-treatment. • The post-treated graphene quantum dots showed a good responsivity of copper ions. Graphene quantum dots (GQDs) have been an ideal probe for copper ions detection due to its excellent optical properties, low toxicity and biocompatibility. However, most of GQDs prepared by present methods have low oxidation degree, which could hinder the complexation between copper ions and oxygen functional groups on the surface of GQDs. Therefore, we proposed a universal, mild and in situ post-treated approach for modifying GQDs obtained by any methods, which will increase the oxidation degree of GQDs without any other affect and its influence on the responsivity of copper ions.