Fe<sup>3+</sup>-doped Anatase TiO<sub>2</sub> with d–d Transition, Oxygen Vacancies and Ti<sup>3+</sup> Centers: Synthesis, Characterization, UV–vis Photocatalytic and Mechanistic Studies
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Bibliographic record
Abstract
The current work emphasizes the preparation, characterization, recyclability, stability, and mechanistic study of nanosized Fe 3+ -doped TiO 2 photocatalyst. The structural, optical, and photocatalytic properties of undoped and doped TiO 2 were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N 2 absorption–desorption, UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS), Raman and UV–visible spectroscopy. XRD analysis showed that prepared powders with different iron content (200, 100, 50, and 25 molar ratios) consisted of only anatase phase. FTIR study confirmed the chelation of acetate with titanium precursor through the bidentate bridge mode; as a result, the condensation pathways are effectively altered by the acetate ligands favoring the formation of the anatase phase, this result gives further confirmation to the XRD analysis. A decrease in charge carrier recombination rate and the presence of oxygen vacancies and related Ti 3+ centers in the prepared photocatalysts were confirmed through PL and EPR spectroscopic studies. XPS results have indicated the presence of dopant electronic states (Fe 3+, Fe 2+ and Fe 4+ ), which could be due to substitution of Fe 3+ ions in-place of Ti 4+ in the crystal lattice. UV–vis DRS spectrum showed that undoped TiO 2 exhibits an absorption edge in the UV region, the position of which was shifted toward the visible region on incorporation of Fe 3+ into it. This red shift of the optical absorption in doped TiO 2 was the outcome of d–d transition of Fe 3+ ( 2 T 2g → 2 A 2g, 2 T 1g ) and the charge transfer transition between interacting iron ions (Fe 3+ + Fe 3+ → Fe 4+ + Fe 2+ ). These Fe 3+ 3d states in addition to oxygen vacancies and Ti 3+ centers create band states, thereby favoring the electronic transition to these levels and resulting in narrowing of TiO 2 band gap. A direct confirmation is the increase in the magnitude of Urbach energy with the lowering in the band gap of Fe 3+ -TiO 2 . The production of hydroxyl radicals (OH – + h + → OH • ) which are the main scavengers for the photogenerated holes (h + ) was monitored by a PL technique using terephthalic acid (TA). The observed trend was TFe 50 > TFe 100 > TFe 25 > TFe 200 > TiO 2, implying that the TFe 50 powder produced an enhanced amount of OH • radicals under light irradiation, which helps in its highest photocatalytic activity against the degradation of methylene blue and 4-chlorophenol under UV and visible light irradiation.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it