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This book deals with the synthesis, properties and applications of titanium dioxide (TiO2) which is a naturally occurring oxide of the element titanium. In nature these oxides are found in well-known minerals such as Rutile, Anatase and Brookite. However, it is most commonly extracted from titanium tetrachloride by carbon reduction and re-oxidization. Alternatively, it may be processed from another oxide called ilmenite, which is subjected to reduction with sulphuric acid to achieve pure titanium dioxide.

The coupling behaviour of H.sup.+ and trace elements in rutile has been studied using in situ polarised Fourier transform infrared (FTIR) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. H.sub.2 O contents in rutile can be precisely and accurately quantified from polarised FTIR measurements on single grains in situ. The benefits of this novel approach compared to traditional quantification methods are the preservation of textural context and heterogeneities of water in rutile. Rutile from six different geological environments shows H.sub.2 O contents varying between â¼ 50-2200 µg g.sup.-1, with large intra-grain variabilities for vein-related samples with H.sub.2 O contents between â¼ 500 and â¼ 2200 µg g.sup.-1 . From FTIR peak deconvolutions, six distinct OH absorption bands have been identified at â¼ 3280, â¼ 3295, â¼ 3324, â¼ 3345, â¼ 3370, and â¼ 3390 cm.sup.-1 that can be related to coupled substitutions with Ti.sup.3+, Fe.sup.3+, Al.sup.3+, Mg.sup.2+, Fe.sup.2+, and Cr.sup.2+, respectively. Rutile from eclogite samples displays the dominant exchange reactions of Ti.sup.4+ â Ti.sup.3+, Fe.sup.3+ + H.sup.+, whereas rutile in a whiteschist shows mainly Ti.sup.4+ â Al.sup.3+ + H.sup.+ . Trace-element-dependent H.sup.+ contents combined with LA-ICP-MS trace-element data reveal the significant importance of H.sup.+ for charge balance and trace-element coupling with trivalent cations. Trivalent cations are the most abundant impurities in rutile, and there is not enough H.sup.+ and pentavalent cations like Nb and Ta for a complete charge balance, indicating that additionally oxygen vacancies are needed for charge balancing trivalent cations. Valance states of multivalent trace elements can be inferred from deconvoluted FTIR spectra. Titanium occurs at 0.03 0/00-7.6 0/00 as Ti.sup.3+, Fe, and Cr are preferentially incorporated as Fe.sup.3+ and Cr.sup.3+ over Fe.sup.2+ and Cr.sup.2+, and V most likely occurs as V.sup.4+ . This opens the possibility of H.sup.+ in rutile as a potential indicator of oxygen fugacity of metamorphic and subduction-zone fluids, with the ratio between Ti.sup.3+ - and Fe.sup.3+ -related H.sup.+ contents being most promising.

Supports can widely affect or even dominate the catalytic activity, selectivity, and stability of metal nanoparticles through various metal-support interactions (MSIs). However, underlying principles have not been fully understood yet, because MSIs are influenced by the composition, size, and facet of both metals and supports. Using Ru/TiO 2 supported on rutile and anatase as model catalysts, we demonstrate that metal-support interfacial compatibility can critically control MSI modes and catalytic performances in CO 2 hydrogenation. Annealing Ru/rutile-TiO 2 in air can enhance CO 2 conversion to methane resulting from enhanced interfacial coupling driven by matched lattices of RuO x with rutile-TiO 2 ; annealing Ru/anatase-TiO 2 in air decreases CO 2 conversion and converts the product into CO owing to strong metal-support interaction (SMSI). Although rutile and anatase share the same chemical composition, we show that interfacial compatibility can basically modify metal-support coupling strength, catalyst morphology, surface atomic configuration, MSI mode, and catalytic performances of Ru/TiO 2 in heterogeneous catalysis. Supports can largely affect the catalytic performance of metal nanoparticles, but the underlying principles are not yet fully understood. Here the authors demonstrate that metal-support interfacial compatibility of Ru/TiO 2 can critically control the metal-support interaction modes and the catalytic performances in CO 2 hydrogenation.

The adsorption of common anions found in water can have a considerable impact on the surface state and optical characteristics of titanium dioxide (TiO2), which has an important impact on the photocatalytic nitrogen reduction reaction (NRR). This work utilizes density functional theory (DFT) computations to examine the electronic and optical characteristics of the TiO2 (001) surface under various anion adsorptions in order to clarify their influence on the photocatalytic NRR of TiO2. The modifications in the structure, optical, and electronic properties of TiO2 before and after anion adsorption are investigated. In addition, the routes of Gibbs free energy for the NRR are also evaluated. The results indicate that the adsorption of anions modifies the surface characteristics of TiO2 to a certain degree, hence impacting the separating and recombining charge carriers by affecting the energy gap of TiO2. More importantly, the adsorption of anions can increase the energy barriers for the NRR, thereby exerting a detrimental effect on its photocatalytic activity. These findings provide a valuable theoretical contribution to understanding the photocatalytic reaction process of TiO2 and its potential application of NRR in the actual complex water phase.

Anatase/rutile mixed-phase TiO2 nanoparticles were synthesized through a simple sol-gel route with further calcination using inexpensive titanium tetrachloride as a titanium source, which effectively reduces the production cost. The structural and optical properties of the prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis adsorption. The specific surface area was also analyzed by Brunauer–Emmett–Teller (BET) method. The anatase/rutile mixed-phase TiO2 nanocomposites containing of rod-like, cuboid, and some irregularly shaped anatase nanoparticles (exposed {101} facets) with sizes ranging from tens to more than 100 nanometers, and rod-like rutile nanoparticles (exposed {110} facets) with sizes ranging from tens to more than 100 nanometers. The photocatalytic activities of the obtained anatase/rutile mixed-phase TiO2 nanoparticles were investigated and compared by evaluating the degradation of hazardous dye methylene blue (MB) under ultraviolet light illumination. Compared to the commercial Degussa P25-TiO2, the mixed-phase TiO2 nanocomposites show better photocatalytic activity, which can be attributed to the optimal anatase to rutile ratio and the specific exposed crystal surface on the surface. The anatase/rutile TiO2 nanocomposites obtained at pH 1.0 (pH1.0-TiO2) show the best photocatalytic activity, which can be attributed to the optimal heterojunction structure, the smaller average particle size, and the presence of a specific exposed crystal surface. The enhanced photocatalytic activity makes the prepared anatase/rutile TiO2 photocatalysts a potential candidate in the removal of the organic dyes from colored wastewater.

We have studied the effects on the electronic band structure of rutile and anatase TiO2 impurified with the lanthanide Gd and Tb ions, by using first principles models. In order to consider the highly correlated effects of the lanthanide ions, as well as those of the TiO2 system, the GGA+U approach is used. We have found a series of band gap localized states coming from the 4f-orbitals of the lanthanide ions. At the same time, as we have obtained in previous work, we report the hybridization of the doping orbitals with the host Oxygen and Titanium states.

Rutile is a common accessory mineral that occurs in a wide spectrum of metamorphic rocks, such as in blueschists, eclogites, and granulites and as one of the most stable detrital heavy minerals in sedimentary rocks. The advent of rutile trace element thermometry has generated increased interest in a better understanding of rutile formation. This study documents important analytical advances in in situ LA-ICP-MS U/Pb geochronology of rutile: (1) Matrix matching, necessary for robust in situ dating is fulfilled by calibrating and testing several rutile standards (R10, R19, WH-1), including the presentation of new TIMS ages for the rutile standard R19 (489.5 +/- A 0.9 Ma; errors always stated as 2 s). (2) Initial common lead correction is routinely applied via Pb-208, which is possible due to extremely low Th/U ratios (usually < 0.003) in most rutiles. Employing a 213 nm Nd:YAG laser coupled to a quadrupole ICP-MS and using R10 as a primary standard, rutile U/Pb concordia ages for the two other rutile standards (493 +/- A 10 Ma for R19; 2640 +/- A 50 Ma for WH-1) and four rutile-bearing metamorphic rocks (181 +/- A 4 Ma for Ivrea metapelitic granulite; 339 +/- A 7 Ma for Saidenbach coesite eclogite; 386 +/- A 8 Ma for Fjortoft UHP metapelite; 606 +/- A 12 Ma for Andrelandia metepelitic granulite) always agree within 2% with the reported TIMS ages and other dating studies from the same localities. The power of in situ U/Pb rutile dating is illustrated by comparing ages of detrital rutile and zircon from a recent sediment from the Christie Domain of the Gawler Craton, Australia. While the U/Pb age spectrum from zircons show several pronounced peaks that are correlated with magmatic episodes, rutile U/Pb ages are marked by only one pronounced peak (at ca 1,675 Ma) interpreted to represent cooling ages of this part of the craton. Rutile thermometry of the same detrital grains indicates former granulite-facies conditions. The methods outlined in this paper should find wide application in studies that require age information of single spots, e.g., provenance studies, single-crystal zoning and texturally controlled dating.

Pure and Cu doped anatase/rutile mixed TiO2 nanomaterials were fabricated through sol-gel method. The obtained photocatalysts were characterized by XRD, SEM, TEM, XPS, PL and DRS, and the influences of Cu doping on the structure and photocatalytic property were studied. The results show that when the molar ratios of Cu/Ti are 1% and 2%, Cu doping promotes anatase → rutile phase transformation. When the molar ratio of Cu/Ti is 4%, the phase transformation is inhibited. Cu element coexists in the form of Cu+ and Cu2+, and Cu doping facilitates the separation of photogenerated electrons and holes. TEM image shows that copper oxides are dispersed on TiO2 particles surface, which significantly reduces the optical absorption of ultraviolet region. The photocatalytic experiment results show that the photocatalytic activity of Cu–TiO2 is lower than pure TiO2, and the higher doping concentration, the lower photocatalytic activity.

It is crucial to explore a facile synthesis of rutile TiO 2 nanorods anchored at carbon cloth at low temperature for applicable air purifier. Herein, antler-like TiO 2 rectangular bunched arrays were grown on carbon cloth by a hydrothermal method, and fluorine was doped into TiO 2 with solid diffusion of NH 4 F at 300 °C. Fluorine doping induces oxygen vacancies in TiO 2 , facilitating the charge transfer and providing more active sites for photocatalytic reactions. The F doped TiO 2 exhibits excellent photocatalytic oxidation of formaldehyde under UV and visible LED irradiation. UV–vis DRS and UPS results indicate that 3F-T@CC can harvest more visible light, and has the suitable energy band structure to generate hydroxyl radical and superoxide radical for the effective degradation of formaldehyde. EPR measurements prove the photogenerated superoxide radial ( · O 2 - ) and hydroxyl radical (·OH) are involved in oxidizing formaldehyde into CO 2 and H 2 O. Graphic Abstract Photocatalytic degradation of formaldehyde by fluorine doped rutile TiO 2 nanorod arrays on carbon cloth.