Structure, thermal stability, and optical properties of boron modified nanocrystalline anatase prepared by chemical vapor synthesis
TL;DR: Boron modified nanocrystalline anatase titania powders with boron contents varying from 0.5 to 6.2% were synthesized by a chemical vapor synthesis process as mentioned in this paper.
Abstract: Boron modified nanocrystalline anatase titania powders with boron contents varying from 0.5 to 6.2 wt % were synthesized by a chemical vapor synthesis process. High temperature x-ray diffraction studies revealed that the anatase powders containing more boron were more stable at higher temperatures. When present in small quantities (about 0.5 wt % or less), boron went into the structure of titania and lowered the direct band gap to 3.41 eV. On the other hand, higher boron contents resulted in smaller anatase crystallite sizes and partially offset the redshift. However, the excess boron formed boron oxide which probably coated the surface of the nanoparticles/crystallites resulting in improved high temperature stability of the anatase phase.
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24 May 2011
14 citations
TL;DR: An efficient microwave supported synthesis, with a reaction time of only one and a half minute, to prepare boron-modified titania nanocrystals TiO2:(B), was developed as discussed by the authors.
Abstract: An efficient microwave supported synthesis, with a reaction time of only one and a half minute, to prepare boron-modified titania nanocrystals TiO2:(B), was developed. The nanocrystals were obtaine...
11 citations
Cites background from "Structure, thermal stability, and o..."
...Previous literature studies [19] demonstrated that anatase containing boron, at least at the surface of the nanocrystals, has peculiar characteristics in bricks: boron favours the persistence of the anatase phase when thermal treatments are performed [19]....
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24 May 2011
5 citations
TL;DR: In this paper, the adsorption and reaction of N2O and CO on the modified N + Fe/TiO2 (101) surface (M-S(101)) of anatase were investigated.
Abstract: First principles density functional theory calculations were carried out to investigate the adsorption and reaction of N2O and CO on the modified N + Fe/TiO2 (101) surface (M-S(101)) of anatase. The adsorption energies of N2O on M-S(101) and CO/M-S(101) were obtained. The mechanisms of the conversion of CO and N2O to CO2 and N2 were proposed and the photocatalytic involvement was described. The calculations indicated that the process described here happened only on doped Fe atoms and the possibility of a photocatalytic cycle was discussed assuming electron scavenging by the codoping of Fe and N atoms.
2 citations
01 Jan 2015
TL;DR: In this article, an efficient microwave supported synthesis, with a reaction time of only one and a half minute, to prepare boron-modified titania nanocrystals TiO2:(B), was developed.
Abstract: An efficient microwave supported synthesis, with a reaction time of only one and a half minute, to prepare boron-modified titania nanocrystals TiO2:(B), was developed. The nanocrystals were obtained by hydroly‐ sis of titanium tetraisopropoxide (TTIP) together with benzyl alcohol and boric acid, and the approach did not need surfactants use and a final calcination step. The produced TiO2:(B) nanocrystals were characterized in detail by low magnification Transmission Electron Microscopy (TEM), Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), X-Ray Diffractometry (XRD), and a Micro Raman Spectroscopy. One of the obtained samples was then tested as an additive in various amounts in a typical aluminosilicate refractory composition. The effects of these additions in bricks were evaluated, according to UNI EN 196/2005, in terms of thermo-physical and mechanical properties: diffusivity, bulk density, apparent density, open and apparent porosity and cold crushing strength. Bricks’ microstruc‐ ture was analysed by Scanning Electron Microscopy (SEM) and energy dispersion spectroscopy (EDS). The bricks obtained with nanoadditives presented improved mechanical characteristics with respect to the typical aluminosilicates, presumably because of a better compac‐ tion during the raw materials’ mixing stage.
1 citations
Cites background from "Structure, thermal stability, and o..."
...Previous literature studies [19] demonstrated that anatase containing boron, at least at the surface of the nanocrystals, has peculiar characteristics in bricks: boron favours the persistence of the anatase phase when thermal treatments are performed [19]....
[...]
References
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TL;DR: Film and powders of TiO2-x Nx have revealed an improvement over titanium dioxide (TiO2) under visible light in optical absorption and photocatalytic activity such as photodegradations of methylene blue and gaseous acetaldehyde and hydrophilicity of the film surface.
Abstract: To use solar irradiation or interior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Films and powders of TiO 2- x N x have revealed an improvement over titanium dioxide (TiO 2 ) under visible light (wavelength 2 has proven to be indispensable for band-gap narrowing and photocatalytic activity, as assessed by first-principles calculations and x-ray photoemission spectroscopy.
11,402 citations
TL;DR: In this article, the optical constants of amorphous Ge were determined for the photon energies from 0.08 to 1.6 eV, and the absorption is due to k-conserving transitions of holes between the valence bands as in p-type crystals.
Abstract: The optical constants of amorphous Ge are determined for the photon energies from 0.08 to 1.6 eV. From 0.08 to 0.5 eV, the absorption is due to k-conserving transitions of holes between the valence bands as in p-type crystals; the spin-orbit splitting is found to be 0.20 and 0.21 eV in non-annealed, and annealed samples respectively. The effective masses of the holes in the three bands are 0.49 m (respectively 0.43 m); 0.04 m, and 0.08 m. An absorption band is observed below the main absorption edge (at 300 °K the maximum of this band is at 0.86 eV); the absorption in this band increases with increasing temperature. This band is considered to be due to excitons bound to neutral acceptors, and these are presumably the same ones that play a decisive role in the transport properties and which are considered to be associated with vacancies. The absorption edge has the form: ω2ϵ2∼(hω−Eg)2 (Eg = 0.88 eV at 300 °K). This suggests that the optical transitions conserve energy but not k vector, and that the densities of states near the band extrema have the same energy-dependence as in crystalline Ge. A simple theory describing this situation is proposed, and comparison of it with the experimental results leads to an estimate of the localization of the conduction-band wavefunctions.
8,184 citations
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.
4,241 citations
TL;DR: In this article, a novel and simple method for preparing highly photoactive nanocrystalline F-doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution.
Abstract: A novel and simple method for preparing highly photoactive nanocrystalline F--doped TiO2 photocatalyst with anatase and brookite phase was developed by hydrolysis of titanium tetraisopropoxide in a mixed NH4F−H2O solution. The prepared F--doped TiO2 powders were characterized by differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV−vis absorption spectroscopy, photoluminescence spectra (PL), transmission electron microscopy (TEM), and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results showed that the crystallinity of anatase was improved upon F- doping. Moreover, fluoride ions not only suppressed the formation of brookite phase but also prevented phase transition of anatase to rutile. The F--doped TiO2 samples exhibited stronger absorption in the UV−visible range with a red shift in the band gap transition. The photocatalytic activity of F--doped TiO2 powders prep...
2,074 citations