Fluorescence spectra of graphitic (g-C3N4) and spherical (s-C3N4) modifications of carbon nitride were measured as a function of green pulsed (6 ns-pulse) laser intensity. It was found that the intensity of the laser increases the maximum of the fluorescence shifts towards the anti-Stokes side of the fluorescence for s-C3N4 spherical nanoparticles. This phenomenon was not observed for g-C3N4 particles. The maximum of the anti-Stokes fluorescence in s-C3N4 nanoparticles was observed at 480 nm. The ratio of the intensity of the anti-Stokes peak (centered at 480 nm) to that of the Stokes peak (centered at 582 nm) was measured to be I484/582 = 6.4 × 10-3 at a low level of intensity (5 mW) of a green pulsed laser, whereas it rose to I484/582 = 2.27 with a high level of laser intensity (1500 mW).
Keywords: anti-Stokes; fluorescence; g-C3N4; s-C3N4.