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Catalysts 2018, 8(2), 47; https://doi.org/10.3390/catal8020047

EPR Investigations of G-C3N4/TiO2 Nanocomposites

1
Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, SK-812 37 Bratislava, Slovakia
2
Institute of Nanoscience and Nanotechnology, National Center for Scientific Research “Demokritos”, 153 43 Agia Paraskevi, Attikis, Greece
*
Author to whom correspondence should be addressed.
Received: 31 December 2017 / Revised: 19 January 2018 / Accepted: 23 January 2018 / Published: 26 January 2018
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Abstract

The g-C3N4/TiO2 nanopowders prepared by the annealing of melamine and TiO2 P25 at 550 °C were investigated under dark and upon UV or visible-light photoactivation using X- and Q-band electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra of powders monitored at room temperature and 100 K showed the impact of the initial loading ratio of melamine/TiO2 on the character of paramagnetic centers observed. For the photocatalysts synthesized using a lower titania content, the paramagnetic signals characteristic for the g-C3N4/TiO2 nanocomposites were already found before exposure. The samples annealed using the higher TiO2 loading revealed the photoinduced generation of paramagnetic nitrogen bulk centers (g-tensor components g1 = 2.005, g2 = 2.004, g3 = 2.003 and hyperfine couplings from the nitrogen A1 = 0.23 mT, A2 = 0.44 mT, A3 = 3.23 mT) typical for N-doped TiO2. The ability of photocatalysts to generate reactive oxygen species (ROS) upon in situ UV or visible-light photoexcitation was tested in water or dimethyl sulfoxide by EPR spin trapping using 5,5-dimethyl 1-pyrroline N-oxide. The results obtained reflect the differences in photocatalyst nanostructures caused by the differing initial ratio of melamine/TiO2; the photocatalyst prepared by the high-temperature treatment of melamine/TiO2 wt. ratio of 1:3 revealed an adequate photoactivity in both spectral regions. View Full-Text
Keywords: g-C3N4/TiO2; EPR spectroscopy; photoinduced processes g-C3N4/TiO2; EPR spectroscopy; photoinduced processes
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Dvoranová, D.; Mazúr, M.; Papailias, I.; Giannakopoulou, T.; Trapalis, C.; Brezová, V. EPR Investigations of G-C3N4/TiO2 Nanocomposites. Catalysts 2018, 8, 47.

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