The role of mild microwave irradiation in liquid-phase graphene oxide reduction toward aqueous dispersions and conductive films

ABSTRACT The scalable and sustainable production of high-quality, solution-processable graphene materials remains a central challenge in nanomaterial research. This study investigates the reduction of graphene oxide (GO) in aqueous dispersions using low-power microwave (MW) irradiation and conventional thermal reflux, comparing four common chemical reductants, ascorbic acid, glucose, hydrazine, and sodium borohydride, alongside a reductant-free route. MW irradiation at 200 W induces rapid deoxygenation and enhancement of sp 2 -domain signatures within seconds, whereas reflux requires extended heating to achieve comparable effects. XPS and Raman analyses reveal that MW treatment promotes a more uniform reduction across reductants and leads to significantly larger apparent crystallite sizes (L a ) than reflux. Importantly, although chemical reductants remain active under MW conditions, their influence on structural reorganization and electrical performance is considerably diminished, demonstrating that MW field itself governs defect elimination and sp 2 -domain enrichment under these mild aqueous conditions. The reductant-free MW route yields the highest conductivity (88.4 S/m for 150 nm films) and the largest sp 2 -domains among all samples. Combined spectroscopic, electrical, and electronic microscopy evidence supports a mechanism in which MW irradiation selectively removes highly defective, oxygen-rich, and sp 3 -hybridized regions rather than reconstructing the graphene lattice, thereby enriching the remaining framework in extended sp 2 networks. Overall, these results position mild MW irradiation as a rapid, and scalable strategy for producing structurally enhanced, water-dispersible rGO dispersions suitable for solution-processed graphene films.