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We have investigated the electronic structure changes and the origin of the enhanced optical properties of N-doped anatase TiO2 using first-principles density-functional theory calculations. To determine the band gap variations induced by N-doping, we developed a new approach to locate the effective valence band maximum (VBM) by characterizing the degree of localization of the N-induced states in the band structures of various N-doped TiO2 systems. Our calculations show that the band gap variations are largely affected by the local bonding structures and doping concentration of the substitutional N atoms. As the N content is up to certain level, some local bonding structures can indeed cause band gap reduction due to the formation of band-like delocalized states above the VBM of TiO2, while other local bonding configurations may simply form localized impurity states in the band gap. Accordingly, the N-induced localized and delocalized electronic states can exist simultaneously to contribute to the enhanced optical properties of anatase TiO2. Our computational approach also provides a new way to investigate the band gap engineering of other wide band gap semiconductor material systems. [ABSTRACT FROM AUTHOR]

In this paper, we report anatase and rutile titanium oxide (TiO2) nanoparticulate thin films fabricated on silica and Indium Tin Oxide (ITO) substrates using femtosecond pulsed laser deposition (fs-PLD). Depositions were carried-out at substrate temperatures of 25 °C, 400 °C and 600 °C from anatase and rutile phase target materials. Effect of substrate temperature on the surface morphology, microstructural, optical, and electrical properties of these films were systematically investigated by using various range of measurements such as scanning electron microscopy, (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Ultraviolet–visible-near infrared (UV–Vis–NIR) spectroscopy, and Hall Effect measurements. It is observed that the TiO2 thin films surface are predominated with nanoparticulates of diameter less 35 nm, which constitute about ~ 70%; while the optical bandgaps and electrical resistivity decrease with increasing substrate temperature. A mixed-phase (anatase/rutile) TiO2 thin film was produced at a substrate temperature of 400 °C when samples are fabricated with anatase and rutile target materials. The results of this study indicate that the structural and crystallinity, optical, and electrical properties can be controlled by varying fs-PLD process parameters to prepare TiO2 thin films, which are suitable for applications in photovoltaics, solar cells, and photo-catalysis. [ABSTRACT FROM AUTHOR]

Copyright of Journal of University of Anbar for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The article presents the results of research on titanium dioxide synthesized by a sol-gel method that is an easy process enabling the control of the shape and size of particles The purpose of this article is to examine titanium dioxide nanoparticles and thin films deposited by an atomization method. Design/methodology/approach: Titanium dioxide sol was synthesized by using titanium isopropoxide as a precursor. Optical properties were measured by a UV-Vis spectrometer. Structural studies were performed by Raman spectroscopy. Qualitative analysis was performed by the EDS. Surface morphology of nanoparticles and thin films was performed by the SEM technique. Findings: The sol-gel method allows the formation of uniform nanoparticles and thin films of titanium dioxide. The atomization method is a successful method for the deposition of sol to the surface of substrates. Research limitations/implications: The next step in the research will be to investigate the obtained thin films in dye-sensitized solar cells as a semiconductive layer. Practical implications: Unique properties of produced titanium dioxide nanostructural materials have caused the interest in them in such fields as optoelectronics, photovoltaics, medicine and decorative coatings. Originality/value: Titanium dioxide thin films and nanoparticles were synthesized using the sol-gel method and then deposited by the atomization method. [ABSTRACT FROM AUTHOR]

Thermal annealing effects on structural and optical properties of TiO2-SiO2 binary thin films deposited on glass substrate were studied. X-ray diffraction was used to investigate the crystal structure of as-deposited and annealed films at different temperatures (300, 500, 600) °C. The XRD pattern of annealed film at 600 °C showed a growth of anatase TiO2 structure at 24.95∘. The surface of binary thin films were scanned by the optical microscope and revealed the crack reduction with increasing annealing temperature up to 600 °C. The thickness of binary thin films were derived from spectroscopic ellipsometry data and it was found that the thickness increased linearly with increasing the annealing temperature from room temperature to 600 °C. From the UV-Vis spectrophotometer the optical constants were studied and the optical band gap energies (Eg) were estimated. The results indicated that the annealing leads to an increase in the absorbance and decrease the transmittance. This can be ascribed to the slight increase in crystallite size of the films with increasing temperature. The optical energy gaps of binary thin films were direct and indirect, and both were decreased with increasing the annealing temperature which can be attributed to the homogeneous and regular dispersion of Ti and Si atoms in the mixed films and the formation of Ti-O-Si bond. [ABSTRACT FROM AUTHOR]

TiO2 nanotube arrays (NTs) have been prepared by anodic oxidation and the oxidation voltages are 20, 30, 40 and 50 V, respectively. Microstructure, chemical composition and optical property of the TiO2 NTs were investigated. XRD and Raman spectra analysis show that the good crystal performance of TiO2 NTs obtained at the above voltages. The obtained samples are mainly composed of morphology nanotube arrays and TiO2 NTs are emerged at lower oxidation voltages. The Ti and O surface atom ratio for the sample prepared at 30 V is estimated about 1:2.14. UV-Visible absorption spectra analyses indicate that absorption edge appears slight blue shift phenomenon when the oxidation voltage rises and the absorption intensity decreases at the same time. The calculated optical band gaps for all samples are close to the standard value 3.2 eV of TiO2. [ABSTRACT FROM AUTHOR]

Understanding the effect of a porous TiO2 nanolayer on the optical scattering and absorption through electrospun fibers is of great importance for the design and development of advanced optical extinction materials. Based on electrospinning and controllable self-assembly techniques, pure electrospun poly(vinylidene fluoride) (PVDF) fibers and TiO2-coated ones with different self-assembly cycles were prepared. The effect of TiO2 self-assembly cycles on surface parameters, e.g., thickness, assembled content, and porosity of the TiO2 nanolayer were determined by scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. With an increase in the self-assembly cycles, the TiO2-coated electrospun PVDF fibers presented rougher surfaces and greater average diameters. According to the characterized surface parameters, the effects of the controllable self-assembly on the optical refractive index, absorption index, and infrared extinction were investigated to increase the optical properties of electrospun PVDF fibers. The results indicated that an increase of almost 120-130 cm-1 in infrared extinction could be achieved through the controllable self-assembly with only 5.7 wt. % assembled TiO2 content. This is highly efficient when compared with other coating modes. We believe that this study could give some positive guidance in the design of TiO2-coated electrospun fibers for improving their surface and optical properties. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of optical properties of cubic titanium dioxide (TiO2) using Orthogonalized Linear Combinations of Atomic Orbitals (OLCAO) basis set under the framework of Density Functional Theory (DFT). Many optical properties such as refractive index, extinction coefficient, reflectivity, absorption coefficient, photoconductivity, and loss coefficient have been studied and analyzed thoroughly. From the analysis of optical properties, it is seen that, cubic TiO2 supports interband transition between states. Reflectivity of pyrite structure TiO2 lies within IRvisible - UV region due to which it qualifies for coating industry. Furthermore, the results are compared with previous theoretical as well as with experimental results. It is found that DFT based simulation produces results which are close approximation to experimental results. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Physics is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present research, we use a first principles calculation to investigate the electronic structure and optical properties of Mo-, Pt- and Rh-doped rutile TiO2. The results indicate that the band gap of the Mo-, Pt-, and Rh-doped systems decreases to 1.758, 0.906, and 0.971 eV, respectively, compared with the 1.968 eV band gap of intrinsic TiO2, which is due to the hybridization of the doped atom d and O p orbital electrons, resulting in the formation of an impurity level and enhanced conductivity. The charge-difference density maps show that the covalence is enhanced in the region around Ti atoms for Mo- and Pt-doped systems, whereas Rh doping has little effect on the covalence. Based on these results, the bond population is 0.42, 0.28, and 0.27 for Mo–O, Pt–O, and Rh–O bonds, respectively. In the absorption spectrum, the peaks of the doped systems decrease significantly and redshift. Compared with the Mo-doped system, the Rh- and Pt-doped systems have lower static dielectric constant and dielectric loss in the low-energy region, which is promising for fascinating applications in microelectronic components. [ABSTRACT FROM AUTHOR]

Anatase TiO2 thin films with high optical modulation, better reversibility, fast switching time, and enhanced coloration efficiency were prepared by nebulized spray pyrolysis technique. X-ray diffraction study confirmed the formation of anatase phase TiO2 in the present work. This inference was substantiated from the Raman active modes of A1g, 2 B1g, and 3 Eg corresponding to O-Ti-O bond in TiO2. The PL emission peak observed at 400 nm is corresponds to the indirect transition (X1b → Γ3) from the conduction band to the valence band. The average reflectance of TiO2 thin films was varied from 31 to 20%. The electrochemical study revealed the excellent performance of TiO2 films with high optical modulation (ΔT = 61%), fast switching kinetics (tb = 1.6 s, tc = 2.4 s), good coloration efficiency (100 cm2 C−1), and better reversibility (86%). The efficient electrochromic behavior of films may be due to the smooth microstructure nature, which provides an easy pathway for the diffusion and charge transfer process of Li+ ions in TiO2 film matrix. The fast transfer of Li+ ion was realized from the electrochemical impedance spectroscopic measurement. [ABSTRACT FROM AUTHOR]

The titanium dioxide (TiO2) is synthesized by sol-gel method using titanium-tetra-iso-propoxide (TTIP) as a starting material, and deposited on the pre-cleaned glass substrate using spin coating technique at optimized parameters. Energy dispersive X-ray (EDX) spectroscopy confirms successful TiO2 growth. The optical properties concerning the transmission and absorption spectra show 85% transparency and 3.28 eV wide optical band gap for indirect transition, calculated from absorbance. The exponential behavior of absorption edge is observed and attributed to the localized states electronic transitions, curtailed in the indirect band gap of the thin film. The film reveals decreasing refractive index with increasing wavelength. The photoluminescence (PL) study ascertains that luminescent properties are due to the surface defects. [ABSTRACT FROM AUTHOR]

In the present work, hydrothermal method was followed to synthesize Undoped and Dy3+ doped TiO2 nanoparticles. The as-prepared pure and doped nanoparticles were investigated by the characterization techniques, as such X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy dispersive X-ray analysis (EDAX), Ultraviolet–Visible (UV–Vis) spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), and Dielectric Spectroscopy. The crystallography and grain size have been studied using XRD and TEM Analysis. X-ray diffraction and energy dispersive X-ray spectroscopy results showed that the as prepared nanoparticles were without any impurity. With the doping of Dysprosium ion, the grain size increases. UV–Visible Spectra reveals the optical properties and the optical band gap calculated using Kubelka- Munk plot was found to be 3.45 eV for pure TiO2 and decreases to 3.39 eV due to doping. The results indicate that the size of the nanoparticles increases with decreasing bandgap when dopant added. The development of the anatase phase TiO2 is affirmed by XRD and FT-IR. The Dielectric properties and A.C Conductivity measurements along with frequency were done for synthesized samples. [ABSTRACT FROM AUTHOR]

SnO2 doped TiO2 materials have received considerable attention due to their high dielectric permittivity (on the order of 10,000) and low loss factor (< 0.1) over a broad temperature/frequency range. In this work, a SnO2–TiO2 nanocomposite was successfully synthesized by a single solvent process. The synthesized samples were characterized by X-ray diffraction, high resolution scanning electron microscopy, UV–Vis spectroscopy, photoluminescence and impedance analysis. The high dielectric permittivity of SnO2 doped TiO2 has been attributed to a special defect-dipole structure. Such dielectric behavior has been observed in this work in hydrogen-reduced TiO2–SnO2 crystals, where the colossal dielectric permittivity and the low loss factor of ~ 0.1 exist in the temperature range of 20–300 °C (and frequency at 10 ~ 105 Hz). Based on the investigations on the phase microstructures, the elemental valences, impedance spectroscopy and dielectric response, the colossal dielectric permittivity of the hydrogen-reduced TiO2–SnO2 crystals was thought to be associated with the electronic relaxation polarization mechanism. This research further revealed that the weak-binding electron is the most critical factor for the high dielectric permittivity in TiO2–SnO2 system, while a special defect-dipole structure may not be a preliminary determinant. [ABSTRACT FROM AUTHOR]

TiO2/Cu/TiO2 (TCT) multilayers were deposited by dc pulsed magnetron sputtering on glass substrates for the possible use as transparent conducting oxide (TCO). The thicknesses of copper (Cud) interlayers were 0, 8, 10, 12, 13 and 15 nm. The changes in structural, optical and electrical properties of the TCT multilayers have been investigated as a function of Cud. XRD examination revealed that, all studied TCT multilayers have rutile TiO2 crystalline structure with different orientations, whereas no peaks have been indexed for the Cu. The refractive index (at 650 nm) of the TCT multilayers decreased from 2.39 to 1.90 and the optical band gap values decreased from 3.77 ± 0.02 to 3.66 ± 0.02 eV as the thickness of the Cu interlayer increased from 8 to 15 nm. It has been found that the electrical resistivity of TCT multilayers decreased from 1.4 × 10−4 to 3.2 × 10−5 Ω cm with increasing Cu interlayer thickness from 8 to 15 nm. The TCT film with 10 nm Cu interlayer has a sheet resistance of 13.7 Ω/sq, an average transmittance value of 87.1% (in the wavelength ranging from 500 to 800 nm) and highest figure of merit value of 1.84 × 10−2 Ω−1. Accordingly it can be considered as superlative TCT film which can be potentially used as transparent conductor electrode for solar cells and other optoelectronic applications. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of the rare earth metal atom-doped anatase TiO2 have been investigated systematically via density functional theory calculations. The results show that TiO2 doped by Ce or Pr is the optimal choice because of its small band gap and strong optical absorption. Rare earth metal atom doping induces several impurity states that tune the location of valence and conduction bands and an obvious lattice distortion that should reduce the probability of electron–hole recombination. This effect of band change originates from the 4f electrons of the rare earth metal atoms, which leads to an improved visible light absorption. This finding indicates that the electronic structure of anatase TiO2 is tuned by the introduction of impurity atoms. [ABSTRACT FROM AUTHOR]

The aim of the study was the production of thin composite nanofibrous mats PAN/TiO2nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO2nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO2rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer. [ABSTRACT FROM PUBLISHER]

The synthesis of nanotubes and faceted nanocrystals of titanium dioxide doped with alkali metals cations has been performed. It has been established that TiO nanotubes with lengths of up to 100 nm and thicknesses of 50-500 nm obtained by solvothermal synthesis have an anatase structure in the direction of crystal growth. Faceted TiO particles with sizes of 80-150 nm doped with Na and K cations (2-7 at % calculated to a yield of TiO yield) preserve the anatase structure, whereas doping with Li induces the formation of a mixture of anatase and rutile. An analysis of the diffuse reflectance spectra showed that dopants had an insignificant effect on optic properties of TiO nanoparticles. The high activity of these catalysts is explained by a decrease in the rate of recombination of charge carriers, rather than by the increase of their photo-generation yield. [ABSTRACT FROM AUTHOR]

TiO2 nanotube (TNT) structures were grown perpendicular to fluorine-doped tin-oxide-coated glass substrates by anodic oxidation of titanium films. The morphology, crystal structure and optical properties of the TNTs were shown to be dependent on the thickness of the titanium film, which acts as an electrode in electrochemical anodization. Field emission scanning electron microscopy measurements revealed that an increase in titanium thickness from 1.5 to 2.7 µm caused a considerable increase in both inner diameter and tube length, which in turn increases the porosity and the physical surface of the TNTs per unit area. Grazing-incidence small-angle scattering was used to infer the statistical lateral ordering of the TNTs over macroscopic length scales. X-ray diffraction data show an increase in the texture coefficient for the (004) plane as well as the I004/ I101 intensity ratio with titanium film thickness. All these factors lead to a significant improvement in the photoluminescence intensity from titania nanotubes, which is about five times more than from titania nanoporous materials under similar circumstances. [ABSTRACT FROM AUTHOR]

Nanosized Titania was prepared through a microwave assisted continuous flow method. Initially, the samples were characterized by XRD, TEM, BET, FTIR, UV-Visible and photoluminescence (PL) spectroscopy. Then the effect of titanium-n-butaoxide (TBO, Ti precursor) concentration on the physicochemical of Titania was investigated. X-ray diffraction spectra confirmed the formation of phase pure anatase phase of TiO with particle size of 5.87 nm. TEM images showed a slight transformation in the particle size but no substantial alteration in the particle morphology was observed. The optical bandgap studies revealed a red shift for TiO in this work. PL spectroscopy indicated a decrease in the surface defects. The size of the particles showed an enhancement to 8.31 nm from 5.87 nm while surface area measurements revealed a reduction to 191.65 from 289.17 mg on increasing the TBO concentration from 37 to 150 mmol. We perceive that TiO synthesised in this study may be a potential source for sensing and have optoelectronic applications. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation on the optical properties of the TiO2and TixCyOznanopowders, produced by the pulsed plasma chemical method. Pulsed plasma chemical synthesis is realized on the laboratory stand, including a plasma chemical reactor (6 l) and TEA-500 electron accelerator. The parameters of the electron beam are as follows: 400–450 keV electron energy, 60 ns half-amplitude pulse duration, up to 200 J pulse energy, and 5 cm beam diameter. In TiO2sample, obtained using the pulsed plasma chemical method, the particles can be divided into two groups: 100–500 nm large spherical particles and tiny complex particles (sized less than 100 nm). For TixCyOz sample, the morphology of the particles is mainly presented with irregular fragment shape. The average size of the particles is ranged from 200 to 300 nm. The band gap for all synthesized samples is within 2.94–3.35 eV. [ABSTRACT FROM AUTHOR]

Water is regarded as a poor absorber of solar energy. This affects the efficiency of solar thermal systems. The addition of nanoparticles to heat transfer fluids used in solar thermal systems can enhance their optical properties. These new-generation heat transfer fluids are known as nanofluids. The present study investigates the stability and optical properties of three nanofluids, including aluminum oxide (13 nm and <50 nm) and titanium dioxide (21 nm) nanofluids. The stability of the nanofluids was observed through a photo-capturing method and zeta potential measurements. Ultraviolet-visible (UV-Vis) spectrophotometer was used to measure the absorbance and transmittance of the prepared nanofluids. The effect of factors such as type of particle, type of surfactant, and pH of the solution on the optical properties of the nanofluids was also investigated. We found that the titanium dioxide nanofluid had better optical properties but lower stability compared to aluminum oxide nanofluids. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO) ultrathin films with different thicknesses below 20 nm were grown by atomic layer deposition (ALD) on silicon substrates at 300 °C. Spectroscopic ellipsometry (SE) measurements were operated to investigate the effect of thickness on the optical properties of ultrathin films in the spectra range from 200 to 1000 nm with Forouhi-Bloomer (F-B) dispersion relation. It has been found that the refractive index and extinction coefficient of the investigated TiO ultrathin film increase while the band gap of TiO ultrathin film decreases monotonically with an increase in film thickness. Furthermore, with the purpose of studying the temperature dependence of optical properties of TiO ultrathin film, the samples were annealed at temperature from 400 to 900 °C in N atmosphere. The crystalline structure of deposited and annealed films was deduced by SE and supported by X-ray diffraction (XRD). It was revealed that the anatase TiO film started to transform into rutile phase when the annealing temperature was up to 800 °C. In this paper, a constructive and effective method of monitoring the phase transition in ultrathin films by SE has been proposed when the phase transition is not so obvious analyzed by XRD. [ABSTRACT FROM AUTHOR]

Pure and Nb doped TiO (TNO) thin films were deposited onto glass substrates by RF magnetron sputtering technique using a Nb and TiO mixture powder target at room temperature to explore the possibility of producing sputtered TNO films by a low cost process. The effect of Nb doping on the structure, morphology, optical and electrical properties of the prepared films was studied by systematically varying the Nb content from 2 to 6 wt%. GXRD results show that the deposited films mainly possess rutile phase with the (110) orientation. Raman spectra confirm that the deposited films are predominantly rutile phase. Surface roughness increases with the increase of Nb doping concentration , which may be attributed to the structural changes in the film due to the incorporation of Nb into the TiO lattice. Optical transmittance in the visible range reaches 85 % for the undoped films then it decreases as the doping content increases. Doping by niobium resulted in a slight increase in the optical band gap energy of the films due to the Burstein-Moss effect. The resistivity measurement of TNO films reveals that the Nb doping improves the electrical conductivity of the deposited films compared to the undoped one. The best value was observed for films deposited at 4 wt% Nb. [ABSTRACT FROM AUTHOR]

In this study, the optical properties of a TiO2 photocatalyst were enhanced with various impregnations of Er3+ and Ni2+ separately, using the impregnation method as photocatalysts for the direct solar photolysis degradation of chloroxylenol. The synthesized Er3+/TiO2 and Ni2+/TiO2 catalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), metal mapping, and ultraviolet visible (UV–Vis) spectroscopy. The results showed that the Er3+/TiO2 and Ni2+/TiO2 nano-particles have the same structures of TiO2 nano-particles with little difference in particle size. The Er3+ and Ni2+ ions were well-distributed on the TiO2 surface, and it was found that the maximum band gap decreased from 3.13 eV for intrinsic TiO2 to 2.63 eV at 1.8 wt % Er3+/TiO2 and to 2.47 eV at 0.6 wt % for Ni2+/TiO2. The initial concentration of chloroxylenol, catalyst loading, and pH of the solution are the most important factors affecting the solar photocatalytic degradation efficiency that were optimized using Design Expert software (version 6.0.10, Minneapolis, MN, USA, 2003). The results showed that the optimal conditions for chloroxylenol degradation include a pH of 4, TiO2 loading at 3 g/L, and a chloroxylenol concentration of 50 mg/L. These conditions resulted in a degradation efficiency of 90.40% after 60 min of direct solar irradiation, wherein the solar energy recorded during a clear sunny day is 1000 W/m2. However, some experiments were conducted on a semi-cloudy day to cover all weather stated and to study the degradation kinetics. During semi-cloudy day experiments, using Er3+/TiO2 and Ni2+/TiO2 with a solar irradiation activity of 600 W/m2 for a 60 min exposure at optimal conditions increased the degradation efficiency from 68.28% for intrinsic TiO2 to 82.38% for Er3+/TiO2 and 80.70% for Ni2+/TiO2. [ABSTRACT FROM AUTHOR]

Anatase TiO2nanospheres having a high degradation efficiency are prepared through hydrothermal method employing titanium (IV) isopropoxide as precursor. The effects of hydrothermal temperature on structural, morphological and optical properties of TiO2nanospheres are investigated. X-ray diffraction (XRD) results show that, the TiO2nanospheres crystallise in the anatase phase, the tetragonal crystal system. The crystallite size increases with the increase in hydrothermal temperature and the values are in the range of 10–19 nm. On the other hand, the spherical particles evenly distributed on the surface are observed in the scanning electron microscope (SEM) images. The band gap of the nanospheres is determined from the reflectance spectra using Kubelka–Munk function. The band gap energy decreases from 3.189 (2) to 3.023 (5) eV with the increase in hydrothermal temperature. The decrease in band gap values well agree with the XRD results of higher crystallite size and enhanced crystallinity. The removal of Congo red dye under dark condition varies with the hydrothermal temperature and it is maximum for the higher crystallinity anatase TiO2synthesised at 160 °C having a lower band gap of 3.023 (5) eV. Maximum efficiency of 96.9% and rate constant value of 0.01413 g mg−1min−1are observed for the sample hydrothermally synthesised at 160 °C. [ABSTRACT FROM AUTHOR]

Graphene and TiO were synthesized using electrochemical exfoliation and co-precipitation methods, respectively. An ex situ approach was adopted for the graphene/TiO composites. The conformation of graphene in the TiO samples was examined through X-ray diffraction. Optical properties of the as-synthesised composites such as optical absorption, extinction coefficient, refractive index, real dielectric constant, imaginary dielectric constant, dissipation factor, and optical conductivity were measured using UV-Vis spectroscopy. The varying concentration of graphene in TiO affects the optical properties which appear different for 10 wt.% as compared to 5 wt.% graphene/ TiO composite. The composites exhibit an absorption peak at 300 nm with a decrease in band gap for 10 wt.% as compared to 5 wt.% graphene/TiO composite. The maximum optical conductivity for the graphene/TiO composite of 10 wt.% was found to be 1.86·10 Ω·m at 300 nm. [ABSTRACT FROM AUTHOR]

The self-cleaning properties of the TiO/SiO double-layer films prepared by sol-gel method were investigated. Thin films were prepared by spin coating onto glass and then thermally treated at different temperatures, and characterized using X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy, and UV-visible spectroscopy. The cross-sectional structure of the films was observed by FESEM. The surface roughness of the films was characterized by AFM. The root mean square surface roughness of the thin films was below 2 nm, which should enhance their optical transparency. The photo-induced hydrophilicity of the films was evaluated by water contact angle measurement in air. The photocatalytic activity of the films was studied by the photocatalytic degradation of methylene blue under UV light irradiations. The TiO/SiO double-layer thin films are plausibly applicable to developing self-cleaning materials in various applications such as windows, solar panels, cement, and paints. [ABSTRACT FROM AUTHOR]

A simple chemical technique has been used to prepare core-shell extender pigments based on Nigerian indigenous clays as core and titanium dioxide as shell. The prepared core-shell extender pigments were characterized using X-ray fluorescence and scanning electron microscopy. The physico-chemical properties of these extender pigments were also evaluated according to ASTM measurements. The study showed that the prepared core-shell pigments were nontoxic and environmentally friendly. They are of low cost and can be incorporated in semi-gloss paints, paper, rubber, and plastic composites without much effect on the volume. The characteristics of these pigments showed that they combine the properties of both their precursors, and have the potential to overcome their disadvantages, e.g., low hiding power of clays and photochemical activity of titanium dioxide. [ABSTRACT FROM AUTHOR]

An anatase TiO2 photoanode with a novel three-dimensional nest-like structure was prepared directly on a transparent conductive glass substrate through hydrothermal cycles by three times. First, an unidirectional banded structure film was prepared by a facile hydrothermal method. And then, with the time of hydrothermal cycle increased, part of nanobelts were ruptured into a lot of small polyhedrons, but they still maintained a trend of the previous connection, and some fine nanobelts were interweaved in small polyhedrons. Finally, we successfully prepared a film with a novel 3D nest-like structure, and it had all the characteristics of the hierarchitectures. It had better photoelectric properties than the film with fewer times of hydrothermal cycle. Its photoelectric conversion efficiency reached 3.81%, which is due to a large dye adsorption amount, rapid electronic transmission, and superior light scattering and more electrons transmission paths. An anatase TiO2 photoanode with nanobelt structure was directly prepared on the transparent conductive glass substrate through hydrothermal method, with the time of hydrothermal cycle increased, the novel three-dimensional nest-like structure was formed. Its photoelectric conversion efficiency reached 3.81%, which was due to a large dye adsorption amount, rapid electronic transmission, superior light scattering and more electron transmission paths. [ABSTRACT FROM AUTHOR]

In recent years, titanium dioxide (TiO2) has been commonly applied in the production of photoactive concrete materials capable of degrading a wide range of air contaminant such as nitric oxide (NO), VOC etc. It was confirmed that the photocatalytic activity of TiO2 can be further enhanced by modifying the photocatalyst with non-metals such as In recent years, titanium dioxide (TiO2) has been commonly applied in the production of photoactive concrete materials capable of degrading a wide range of air contaminant such as nitric oxide (NO), VOC etc. It was confirmed that the photocatalytic activity of TiO2 can be further enhanced by modifying the photocatalyst with non-metals such as nitrogen (N) or carbon (C). In view of this finding, several concrete/ TiO2 composites consisting of commercial concrete and raw anatase TiO2 (supplied by Grupa Azoty Zakłady Chemiczne 'POLICE' S.A., Poland), previously modified with ammonia [N source] and/or 2-propanol [C source] have been manufactured. For reference, the additional concrete samples were prepared, containing unmodified TiO2 and commercial titania P25 (Evonik). The NO degradation properties of prepared photoactive concrete materials were evaluated using laboratory test set-up. The measurements were conducted under constant temperature and humidity conditions, using ultraviolet light irradiation. Significant NO removal was recorded for the TiO2/ concrete composites containing N and/or C co-modified titania. The results were related to the improved photocatalytic activity of modified photocatalysts and probable, partial NO reduction to N2, via the selective catalytic reduction process catalysed by TiO2. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of Mn-S co-doped anatase TiO2 were calculated using the plane-wave-based ultrasoft pseudopotential density functional method within its generalized gradient approximation (GGA). The calculated results show that the band gap of Mn-S co-doped TiO2 is larger than that of the pure TiO2, and two impurity bands appear in the forbidden band, one of which above the valence band plays a vital role for the improvement of the visible light catalytic activity. The Mn-S co-doped anatase TiO2 could be a potential candidate for a photocatalyst because of its enhanced absorption ability of visible light. [ABSTRACT FROM AUTHOR]

Cu-loaded titania nanotube arrays (Cu/TNAs) were prepared by photodeposition of copper on the surface of titania nanotube arrays (TNAs) using copper nitrate as copper source. The resulting samples were characterized by field-emission scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and ultraviolet-visible spectroscopy. The Cu/TNAs showed a tube diameter of 40–90 nm and wall thickness of 20–30 nm. The photocatalytic activities of the prepared photocatalysts were evaluated by the photodegradation of methylene blue (MB) and the production of hydrogen under xenon light illumination. The results showed that Cu/TNAs sample exhibited better photocatalytic activity than the TNAs due to the strong synergistic interactions between titania and copper. This work demonstrated a feasible method to fabricate an effective, reproducible and inexpensive photocatalyst for hydrogen evolution and environmental applications. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of S- and/or Ce-(co)doped anatase titanium dioxide (TiO2) are investigated using density functional theory plus U (DFTU) calculations. The optimized total energy suggests that TiO2 codoping by Ce and S favours the configuration of one substitutional Ce atom occupied on a Ti site with one substitutional S atom either on its nearest neighboring O or Ti site. The calculated results show that all doping configurations exhibit remarkable red-shift and excellent photocatalytic properties compared with pure TiO2. These reinforced features can mainly be ascribed to the appearance of S states in the top of valence band (VB) and Ce states in the bottom of conduction band (CB) as well as the contribution from the increasing octahedral dipole moments. The synergetic effects of cationic Ce and anionic S can extend optical absorption edge, which results in higher absorption coefficient in the visible light region than that of the anionic S monodoping and cationic Ce monodoping case; in the same time, decreasing the codoping concentration leads to reduced optical absorption. Additionally, Ce and S as cations incorporating into TiO2 lattices can induce stronger redox potential with a lower defect formation energy under O-rich condition compared with other doping systems. [ABSTRACT FROM AUTHOR]

Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO2(B). The mesoporous TiO2 materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO2(B) exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy. [ABSTRACT FROM AUTHOR]

Wide gamut light emitting diodes using quantum dot-silicone film protected by atomic layer deposited TiO2 film were demonstrated. The core/shell QDs with multi-emission peaks were synthesised by a one-pot approach, in which the emission wavelength and colour composition were in situ adjusted during the synthetic process. [ABSTRACT FROM AUTHOR]

Thin layers of titanium dioxide were fabricated by direct inkjet patterning of a reverse micelles sol-gel composition onto soda-lime glass plates. Several series of variable thickness samples were produced by repeated overprinting and these were further calcined at different temperatures. The resulting layers were inspected by optical and scanning electronic microscopy and their optical properties were investigated by spectroscopic ellipsometry in the range of 200-1000 nm. Thus the influence of the calcination temperature on material as well as optical properties of the patterned micellar titania was studied. The additive nature of the deposition process was demonstrated by a linear dependence of total thickness on the number of printed layers without being significantly affected by the calcination temperature. The micellar imprints structure of the titania layer resulted into significant deviation of measured optical constants from the values reported for bulk titania. The introduction of a void layer into the ellipsometric model was found necessary for this particular type of titania and enabled correct ellipsometric determination of layer thickness, well matching the thickness values from mechanical profilometry. [ABSTRACT FROM AUTHOR]

The present work aims to study the synthesis, morphology and optical properties of TiO/CNT nanocomposite. TiO/CNT nanocomposite powder were synthesized by sol-gel method using TiCl as a precursor in ethanol solution containing CNTs as a support. The prepared samples were characterized by scanning electron microscopy, powder X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopic techniques. The results show that TiO nanoparticles covered a homogenous layer on the surface of purified CNTs. Moreover, applying CNTs as a support can significantly change the morphology and band gap energy of TiO nanoparticles. [ABSTRACT FROM AUTHOR]

Recent studies specify that designated nanofluids may increase the proficiency of direct absorption solar thermal collectors. To determine the efficiency of nanofluids in solar applications, their capability to change light energy to thermal energy must be identified (i.e., the absorption spectrum of the solar material). In view of that, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (200– 1100 nm). In the first decade of nanofluid research, most of the focus was on measuring and modeling the fundamental thermophysical properties of nanofluids (i.e., thermal conductivity, density, viscosity, and convection coefficients). Lately, considerable focus is given to the fundamental optical properties of nanofluids. However, the effect of particle size, shape, and volume fraction of nanoparticles as well as alternation of the base fluids, which can significantly affect scattering and absorption, have not been addressed to date in the literature. In this study, the effects of size and concentration of TiO2nanoparticles on the extinction coefficient were analyzed using the Rayleigh approach. The results show that smaller particle size (<20 nm) has a nominal effect on the optical properties of nanofluids. Volume fraction is linearly proportionate to the extinction coefficient. Considering a nanoparticle size of 20 nm, almost 0% transmissivity is obtained for wavelengths ranging from 200 to 300 nm. However, a sudden increase of 71% in transmissivity is noted from 400 nm, gradually increasing to 88% and becoming similar to that of water at 900 nm. Promising results are observed for volume fractions below 0.1%. [ABSTRACT FROM AUTHOR]

The simple co-precipitation route was used to couple commercial TiO2 anatase nanopowder with nickel ferrite (NiFe2O4). The morphology and the crystalline structure of composite nanoparticles were characterised by TEM, N2 adsorption-desorption, XRD and Rietveld refinement, XPS and XAS. The optical and magnetic properties were investigated. After co-precipitation NiFe2O4 nanoparticles, composed of spinel ferrite crystal phase, were formed on the surface of TiO2 anatase nanopowder. The TiO2/NiFe2O4 composite oxide demonstrated large specific surface area, high visible light absorption efficiency and efficient charge carrier separation, compared to pristine anatase TiO2 or pristine NiFe2O4, representatively. The obtained TiO2/NiFe2O4 composite oxides, with different nickel ferrite contents (5, 10, 25, 50 and 75 wt%) showed decent visible light photocatalytic efficiency, up to three times higher than pure anatase or pure NiFe2O4. However, TiO2/NiFe2O4 composite oxides did not demonstrate high magnetic properties. [ABSTRACT FROM AUTHOR]

Antireflection coating (ARC) prepared by a wet process is beneficial for low cost fabrication of photovoltaic cells. In this study, we investigated optical properties and morphologies of spin-coated TiO2 ARCs on alkaline textured single-crystalline silicon wafers. Reflectance spectra of the spin-coated ARCs on alkaline textured silicon wafers exhibit no interferences and low reflectance values in the entire visible range. We modeled the structures of the spin-coated films for ray tracing numerical calculation and compared numerically calculated reflectance spectra with the experimental results. This is the first report to clarify the novel optical properties experimentally and theoretically. Optical properties of the spin-coated ARCs without interference are due to the fractional nonuniformity of the thickness of the spin-coated ARCs that cancels out the interference of the incident light. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) polymer solar cells with Ag and titanium dioxide were fabricated to improve the PV performance by increasing the amount of Ag in TiO2(by 3, 5, 7, and 10%). Sol–gel method was used to obtain amorphous or crystalline form of titanium dioxide layers. The solar cells with poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester active layer in two various positions of titanium dioxide in device were tested. Higher PV performance was received by introducing TiO2with 5% of Ag between ITO and PEDOT:PSS in device and by heating the layer at 130 °C. The viscosity of applied PEDOT:PSS strongly influences the values of power conversion efficiency of the constructed polymer devices with titanium dioxide. [ABSTRACT FROM AUTHOR]

Indium tin oxide (ITO) and titanium dioxide (TiO) anti-reflective coatings (ARCs) were deposited on a (100) P-type monocrystalline Si substrate by a radio-frequency (RF) magnetron sputtering. Polycrystalline ITO and anatase TiO films were obtained at room temperature (RT). The thickness of ITO (60 to 64 nm) and TiO (55 to 60 nm) films was optimized, considering the optical response in the 400- to 1,000-nm wavelength range. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). The XRD analysis showed preferential orientation along (211) and (222) for ITO and (200) and (211) for TiO films. The XRD analysis showed that crystalline ITO/TiO films could be formed at RT. The crystallite strain measurements showed compressive strain for ITO and TiO films. The measured average optical reflectance was about 12% and 10% for the ITO and TiO ARCs, respectively. [ABSTRACT FROM AUTHOR]

In this study pure and aluminum (Al) doped TiO2 films were prepared by using sol-gel spin coating process. The structural, surface morphological and optical properties of these films have been investigated. X-ray diffraction (XRD) with a Cu-Kα irradiation was used to identify the phase structures of the films. Optical properties of undoped and Al-doped TiO2 films were determined by using UV-VIS spectrophotometer and its attachment of diffuse reflectance. Transmittance and reflectance values of the films were measured in the wavelength range of 350-700 nm. The optical parameters (band gap, refractive index, etc.) of the films were then calculated based on these data. The results show that optical bandgap the film is effectively enhanced by Al doping. The results open an approach to create a new semiconductor material for the engineering applications especially for gas sensing and photocatalytic applications. [ABSTRACT FROM AUTHOR]