Ultra-high quantum yield ultraviolet fluorescence of graphitic carbon nitride nanosheets

Graphitic carbon nitride (g-CN) nanosheets (CNNs) with an ultra-high quantum yield (80.1%) ultraviolet fluorescence (FL) were prepared. The effects of the lateral size and the polymerization temperature on the optical properties of CNNs have been studied. The ultraviolet FL was proved to have originated from the isolated melem units according to the density functional theory calculation and mass spectra. The obtained CNNs are further used as a pH probe due to the dependence of the FL signal on the pH of the solution.