Growth, optical, and wettability properties of iron modified titania and ferropseudobrookite thin films

Abstract

Iron (Fe)-modified titanium dioxide, Fe–TiO2, thin films with molar ratios Fe:Ti = 1:360, 1:60, and 1:30 and Fe-pseudobrookite, FeTi2O5 (molar ratio Fe:Ti = 1:2), were grown by the sol-gel process using acid-catalyzed solutions prepared with titanium isopropoxide and iron(III) chloride hexahydrate as Ti and Fe precursors, respectively. The layers were deposited by dip-coating onto soda–lime glasses and (100)-Si substrate wafers, and their chemical composition, crystal structure, and surface morphology were investigated in detail. For the low Fe-doped samples, the experimental results clearly indicate the formation of Fe–O–Ti heterolinkages. The films have an amorphous structure and high flatness surfaces if grown onto glass substrates. On the contrary, if grown onto (100)-Si substrates, they exhibit a granular structure (domain size ∼12 nm) made of a solid solution of Fe3+ ions within the anatase TiO2 lattice. For coatings with the molar ratio Fe:Ti = 1:2 (high Fe content), morphological investigations show the formation of wrinkled surfaces characterized by dendritic structures. X-ray diffraction measurements confirm the formation of nanocrystallites (domain size ∼15 nm) of pure, single-phase orthorhombic FeTi2O5. Wettability measurements conducted on amorphous low Fe-doped TiO2 samples revealed superhydrophilic properties with a surface–water contact angle <1°, whereas optical absorption and reflectance measurements yield bandgap widening and narrowing. A bandgap narrowing occurs with the formation of oxygen vacancies and of Ti3+ levels, but if the concentration of oxygen vacancies and Ti3+ levels increases, more electron donors are generated, which shift the Fermi level to the conduction band. This widening of the bandgap (blue shift) can be explained by the Burstein–Moss effect. The correlation of the large optical bandgap (3.61 < Eg < 3.74 eV) and the wettability results are interpreted and discussed with the presence of oxygen vacancies and Ti3+ and Fe3+ sites in the TiO2 matrix.

Photoelectrochemical and Electrochemical Activity of Anodic Semitransparent Aligned and Spaced Titania Nanotubes Formed out of Titanium–Silver Alloys

“…In the case of the spaced TNT materials, the increase in the density of states can be attributed to the presence of structural defects. In fact, the Burstein–Moss effect originating from defects in the titania matrix was reported by Ferrara et al…”

“…In the case of the spaced TNT materials, the increase in the density of states can be attributed to the presence of structural defects. In fact, the Burstein−Moss effect originating from defects in the titania matrix was reported by Ferrara et al 42 The overall chemical composition of the TNT materials prepared from the Ti and TiAg films was examined in detail by XPS analysis. There are no significant differences in the highresolution XPS spectra of Ti 2p, O 1s, C 1s, F 1s, and Ag 3d recorded for all of the prepared TNT materials out of the TiAg alloys.…”

Laser-Treated MXene as an Electrochemical Agent to Boost Properties of Semitransparent Photoelectrode Based on Titania Nanotubes

“…The calculated band gap energy values were found to be 3.39, 3.26, 3.06, 2.95, and 2.82 eV for TNT, TiCl 4 @TNT, 1M-TiCl 4 @TNT, 2M-TiCl 4 @TNT, and 3M-TiCl 4 @TNT samples, respectively. The presence of Ti 3+ donor states in the synthesized TiO 2 /Ti 3 C 2 T x heterostructure (Figure b) can effectively explain the narrowing of the band gap. , …”

“…The presence of Ti 3+ donor states in the synthesized TiO 2 /Ti 3 C 2 T x heterostructure (Figure 4b) can effectively explain the narrowing of the band gap. 93,94 Figure 9 shows the photoluminescence (PL) spectra of the prepared samples. PL measurements were performed to provide information about the rate of electron−hole recombination in the prepared semiconductor materials.…”