Modulating the properties of g-C3N4 through two-step annealing and ionic-liquid gating.

We reported a novel strategy by the combination of two-step annealing treatment and ionic-liquid gating technology for effectively regulating the properties of g-C3N4, especially largely reducing the recombination rate of the electron-hole pairs, with evidenced by the remarkable reduction of photoluminescence (PL) intensity. Firstly, graphitic carbon nitrides with typical layered structure were obtained by annealing melamine with temperature above 500°C. Further annealing at 600°C with much longer time (from 2 hours to 12 hours) were found to effectively reduce the imperfections or defects, and thus the PL intensity (49% reduction). Secondly, by post-treating annealed sample with ionic liquid, the PL were found to be further reduced, mainly due to the passivation of charged defect centers by ionic liquid. Additionally, applying an external electric field in an ionic liquid (IL) environment significantly enhance charged defect passivation. The ionic liquid gating resulted in a larger bandgap and further reduced PL intensity. This study demonstrates a new approach for defect passivation, providing insights and strategies for modulating properties of advanced materials such as g-C3N4. .