Singlet-Triplet Energy Inversion in Carbon Nitride Photocatalysts

Arianna Actis; Michele Melchionna; Giacomo Filippini; Paolo Fornasiero; Maurizio Prato; Mario Chiesa; Enrico Salvadori

doi:10.1002/anie.202313540

Singlet-Triplet Energy Inversion in Carbon Nitride Photocatalysts

Angew Chem Int Ed Engl. 2023 Nov 27;62(48):e202313540. doi: 10.1002/anie.202313540. Epub 2023 Oct 23.

Authors

Arianna Actis¹, Michele Melchionna², Giacomo Filippini², Paolo Fornasiero^{2

3}, Maurizio Prato^{2

4

5}, Mario Chiesa¹, Enrico Salvadori¹

Affiliations

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.
³ ICCOM-CNR URT, Via Licio Giorgieri 1, 34127, Trieste, Italy.
⁴ Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo Miramon 194, 20014, Donostia San Sebastián, Spain.
⁵ Basque Fdn Sci, Ikerbasque, 48013, Bilbao, Spain.

PMID: 37801043
DOI: 10.1002/anie.202313540

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.

Keywords: Carbon Nitride; EPR Spectroscopy; Photochemistry; Time-Resolved EPR; Triplet State.

Abstract

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