1. Department of Chemistry and NIS Centre, University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy;2. Department of Chemical and Pharmaceutical, INSTM UdR, University of Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
Abstract:
Time-resolved EPR (TR-EPR) demonstrates the formation of well-defined spin triplet excitons in carbon nitride. This permits to experimentally probe the extent of the triplet wavefunction which delocalizes over several tri-s-triazine units. Analysis of the temperature dependence of the TR-EPR signal reveals the mobility of the triplet excitons. By employing monochromatic light excitation in the range 430–600 nm, the energy of the spin triplet is estimated to be ≈0.2 eV above the conduction band edge, proving that the triplet exciton lies above the corresponding singlet. Comparison between amorphous and graphitic forms establishes the singlet-triplet inversion as a general feature of carbon nitride materials.