Enhancing the Fluorescence Activity of Graphitic Carbon Nitride Nanosheets by Eliminating the Active Defect States: Implications for Fluorescent Sensing and Biological Imaging

The fluorescence (FL) activity of graphitic carbon nitride nanosheets (CNNSs) is dependent on both their band gap and surface defect states. It is known that the band gap of CNNSs is difficult to tune; however, studies on the regulation of the FL activity of CNNSs by surface defect states are still few. Herein a facile strategy to enhance the FL activity of CNNSs is developed by alkali-mediated passivation of the active defect states (dangling bonds) on CNNSs. With alkali treatment, the active defect states of CNNSs are eliminated and replaced with the passivated −NH2 groups, leading to significant enhancement of the FL quantum yields. We believe that this work will promote an understanding of the structure–FL properties of CNNSs, advancing an understanding of the luminous mechanisms and the application of CNNSs in FL sensing as well as biological imaging.