Photoinduced Paramagnetic Centers in Nanocomposites Formed by Titanium Dioxide and Myristic Acid

An electron paramagnetic resonance (EPR) study has been carried out on the hybrid layered nanocomposite formed by TiO₂ and myristic acid. The samples were characterized by means of X-ray diffraction (XRD), thermogravimetric analysis, solid-state NMR, scanning electron microscopy (SEM), spectral absorbance (UV–vis), and Raman and infrared spectroscopy (FTIR). X-band continuous wave (CW)-EPR was used to investigate the photoinduced paramagnetic species generated in the nanocomposite by UV irradiation at 365 nm in vacuum and in ambient atmosphere and characterized spectroscopically at 90 K. Various paramagnetic species were identified and characterized by their Hamiltonian parameters. They include disordered isolated Ti³⁺ centers, dimeric units producing S = 1 triplet species, and superoxide radicals, (ROO•), whose concentrations were monitored as a function of temperature and annealing times during the course of well-defined temperature cycling protocols.