The inset shows the corresponding plots of (αhν)1/2 as a function of photon energy. Fluorescence spectra of SA-coated TiO2 NPs in toluene and DMSA-coated TiO2 NPs in DI water with an excitation wavelength of 325 nm were recorded at room temperature and are shown in Figure 3a,b. The broad emission spectra which are observed from 400 to 500 nm arise from indirect bandgap and surface recombination processes SBI-0206965 cell line [15]. After multipeak Gaussian Ferrostatin-1 ic50 fitting of fluorescence spectra in Figure 3a,b, we found that Gaussian curves fit original curves
perfectly. The peak positions of Gaussian bands in Figure 4a are located at about 384, 407, 440, 480, and 525 nm, respectively. The peak positions of Gaussian bands in Figure 4b are located at about 394, 418,
445, 485, and 540 nm, respectively. All these peaks are red shifted due to the light-induced relaxation of polar molecules [16]. The prepared TiO2 NPs with high surface-to-volume ratio favor the existence of large quantities of oxygen vacancies. The observed fluorescence bands may be the result of emission from radiative recombination of self-trapped excitons localized within TiO6 octahedra and oxygen vacancies [17]. Oxygen vacancies have been considered as the most common defects and usually act as radiative centers in the luminescence processes [18]. The emission peak at about 384/394 nm is attributed to the emission of near bandgap transition of anatase. This is consistent with the E g calculated by UV measurement techniques (i.e., approximately 3.1 eV). The emission bands at 407 and 418 nm PF01367338 were ascribed to electron transition mediated by defect levels in the bandgap [19]. In addition, the signals observed in wavelength over range from 440 to 540 nm arise from the excitonic PL, which mainly results
from surface oxygen vacancies and defects. The peaks at 440 and 445 nm are attributed to band edge free excitons, and the other peaks at 480 and 485 nm corresponds to bound excitons [20]. Figure 4 Fluorescence spectra of TiO 2 NP. (a) Toluene-dispersible SA-coated NPs. (b) Water-dispersible DMSA-coated NPs. The fluorescence spectra are deconvoluted into Gaussian line shapes. The experimental data are shown in solid circles. The dashed lines correspond to the individual components by Gaussian fitting, and the solid lines represent the sum of individual fitting lines. Conclusions A facile route for the synthesis of TiO2 NPs through biphasic solvothermal interface reaction method has been reported. The XRD pattern of TiO2 NPs revealed the anatase structure. The average XRD crystallite size was calculated as 6.89 nm using the Scherrer formula. The optical studies showed that the bandgap is 3.1 eV. The results show that synthesized nanoparticles are monodispersed with long-term stability.
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