Electrochemical Trimming of Graphene Oxide Affords Graphene Quantum Dots for Fe³⁺ Detection

Graphene-based fluorescent nanomaterials, including graphene nanoribbons (GNRs), graphene nanosheets (GNSs), and graphene quantum dots (GQDs), face application challenges due to the lack of efficient preparation routes. In this work, a facile electrochemical trimming route has been developed to prepare GNRs, GNSs, and GQDs from graphene oxide (GO) nanosheets by regulating the electrochemical reaction time. The formation mechanism of these nanomaterials is proposed to be the adsorption of hydroxyl and oxygen radicals onto the fragile points of large nanosheets, followed by the destruction of the GO nanosheets into small pieces. The as-prepared nanomaterials exhibit excellent fluorescence properties, and density functional theory calculations indicate that their energy gaps decrease gradually as the size of the nanomaterials increases. Especially, GQDs with diameters of 1–5 nm exhibit excitation wavelength-independent and pH-sensitive photoluminescence performances. Subsequently, the usage of the GQDs for the detection of ferric ions (Fe3+) in aqueous systems is thoroughly investigated, and a high sensitivity and selectivity with a low detection limit of about 0.23 μM have been realized successfully.