N-doped TiO<Subscript>2</Subscript> applied in low-temperature-based dye-sensitized solar cells

With urea as nitrogen source, N-doped TiO₂ powders were synthesized and fabricated for low-temperature dye-sensitized solar cells (DSSCs) by the method of doctor-blade, and the highest temperature of the whole process was 120 °C. SEM, TEM, XRD, DRS, and XPS were used to analyze the microstructure of the N-doped TiO₂ powders. EIS, Bode plot, UV–Vis and I–V were employed to measure the photovoltaic performance of the DSSCs. The maximum photoelectric conversion efficiency (η) was 5.18 % when the amount of the doped nitrogen was 4 %, and, when compared with the η of 4.22 % for pure TiO₂, the short circuit current was increased by 22.2 % and the efficiency was increased by 22.7 %. It has been shown that the doped nitrogen could effectively suppress TiO₂ crystal phase transition from anatase to rutile, and decrease the size of particles. Therefore, the increased photoelectric conversion efficiency of the N-doped TiO₂-based DSSC was ascribed to the more suitable crystal phase, sizes and inner structure.     

Efficient electrochromic performance of anatase TiO2 thin films prepared by nebulized spray deposition method

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 A_1g, 2 B_1g, and 3 E_g corresponding to O–Ti–O bond in TiO₂. The PL emission peak observed at 400 nm is corresponds to the indirect transition (X_1b?→?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 (t _b ?=?1.6 s, t _c ?=?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.     

Band-gap energy estimation from diffuse reflectance measurements on sol–gel and commercial TiO<Subscript>2</Subscript>: a comparative study

A comparison of the band gap energy estimated from UV–vis reflectance spectra of TiO₂ powders prepared by sol–gel route versus commercial TiO₂ powders, nanopowder, bulkpowder and P25 is reported. The experimental results obtained from the optical absorption spectra were reported for all the TiO₂ samples. Graphic representations were used to calculate E_g: absorbance versus λ; F(R) versus E; (F(R) hν)ⁿ versus E, with n = ½ for an indirect allowed transition and n = 2 for a direct allowed transition. From the results, it could be seen that E_g strongly varied according to the equation used for the graphic representation. Differences in E_g up to 0.5 eV for the same semiconductor depending on the transition chosen were observed. Accurate E_g estimation in the four semiconductors studied was obtained by using the general equation α (hν) ≈ B (hν ? E_g)ⁿ (where α ~ F(R)) and indirect allowed transition.     

Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Al-doped TiO<Subscript>2</Subscript> photoanode

In this work, we have prepared Al-doped TiO₂ nanoparticles via a hydrothermal method and used it for making photoanode in dye-sensitized solar cell (DSSC). Material characterizations were done using XRD, AFM, SEM, TEM and EDAX. XPS results reveal that Al is introduced successfully into the structure of TiO₂ creating new impurity energy levels in the forbidden gap. This resulted in tuning of the conduction band of TiO₂ and reduced charge recombination which led to better current conversion efficiency of DSSC. Greater dye loading and enhanced surface area was obtained for Al-doped TiO₂ compared to un-doped TiO₂. I-V analysis, EIS and Bode plots are employed to evaluate photovoltaic performance. The short-circuit current density (J _sc) and efficiency (η) of cell employing Al-doped TiO₂ photoanode were extensively enhanced compared to the cell using un-doped TiO₂. The optical band gap (E _g) for Al-doped and un-doped TiO₂ was obtained as 2.8 and 3.2 eV, respectively. J _sc and η were 13.39 mAcm^?2 and 4.27%, respectively, under illumination of 100 mWcm^?2 light intensity when thin films of 1% Al-doped TiO₂ was employed as photoanode in DSSC using N719 as the sensitizer dye. With the use of un-doped TiO₂ as photoanode under similar conditions, J _sc 5.12 mAcm^?2 and η 1.06% only could be obtained. The maximum IPCE% obtained with Al-doped TiO₂ and un-doped TiO₂ was 67 and 38% respectively at the characteristic wavelength of dye (λ _max = 540 nm). The EIS analyses revealed resistive and capacitive elements that provided an insight into various interfacial processes in terms of the charge transport. It was observed that Al-doping reduced the interfacial resistance leading to better charge transport which has improved both photocurrent density and conversion efficiency. Higher electron mobility and fast diffusion resulting in greater charge collection efficiency was obtained for Al-doped TiO₂ compared to the un-doped TiO₂. Using the Mott–Schottky plot, the donor density was calculated for un-doped and Al-doped TiO₂. The work demonstrated that the Al-doped TiO₂ is potential photoanode material for low-cost and high-efficiency DSSC.     

Molecular mechanism of propane oxidative dehydrogenation on surface oxygen radical sites of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/TiO<Subscript>2</Subscript> catalysts

Minimum energy pathways of propane oxidative dehydrogenation to propene and propanol on supported vanadium oxide catalyst VO _x /TiO₂ were studied by periodic discrete Fourier transform (DFT) using a surface oxygen radical as the active site. The propene formation pathway was shown to consist of two consecutive hydrogen abstraction steps. The first step includes C_β–H bond activation of propane followed by the formation of a surface hydroxyl group V–O _t H and a propyl radical n-C₃H₇. This step with the activation energy E* = 0.56 eV (54.1 kJ/mol) appears to be rate-determining. The second step involves the reaction of the bridging O _b oxygen atom with the methylene C–H bond of propyl radical n-C₃H₇ followed by the formation of a hydroxylated surface site HO _t –V⁴⁺–O _b H and propene. The initial steps of the C–H bond activation during propane conversion to propanol and propene by ODH on V⁵⁺–(O _t O _b )^? active sites are identical. The obtained results demonstrate that participation of surface oxygen radicals as the active sites of propane ODH makes it possible to explain relatively low activation energies observed for this reaction on the most active catalysts. The presence of very active radical species in low concentration seems to be the key factor for obtaining high selectivity.     

Mechanistic study of Ce-modified MnO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/TiO<Subscript>2</Subscript> catalysts with high NH<Subscript>3</Subscript>-SCR performance and SO<Subscript>2</Subscript> resistance at low temperatures

A series of Ce–MnO _x /TiO₂ catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH₃ at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO _x /TiO₂ catalyst showed the highest activity and best resistance to SO₂ poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H₂-temperature-programmed reduction (TPR), and NH₃-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO _x /TiO₂ catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO₂ poisoning resistance of the 0.07Ce–MnO _x /TiO₂ catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO _x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH₃ and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism.     

Physical and photoelectrochemical characterizations of SrWO<Subscript>4</Subscript> prepared by thermal decomposition. Application to the photo electro-oxidation of ibuprofen

We have reported the semi conducting and photoelectrochemical properties of SrWO₄ prepared by chemical route. The phase purity is confirmed by X-ray diffraction and the oxide is characterized by scanning electron microscopy, diffuse reflectance, and electrochemical impedance spectroscopy. SrWO₄ crystallizes in the scheelite structure with an average crystallite size of 378 ± 6 nm. The Raman spectrum gives an intense peak at 920 cm^?1 assigned to A _g mode while the infrared analysis confirms the hexagonal coordination of tungsten. The UV-visible spectroscopy shows an indirect optical transition at 2.60 eV. SrWO₄ exhibits n-type conduction by oxygen deficiency, confirmed by the chrono-amperometry and the intensity potential J(E) curve shows a small hysteresis. The Mott-Schottky plot gives electrons density of 5.72 × 10¹⁸ cm^?3 and a flat band potential of 0.27 V_SCE, indicating that the conduction band derives mainly from W⁶⁺: 6s orbital. The electrochemical impedance spectroscopy (EIS), measured in the range (1–10⁵ Hz), shows the predominance of the bulk contribution with a dark impedance of 38 kΩ cm². As application, the ibuprofen is degraded by electrocatalysis on SrWO₄ with a conversion rate of 42%. An improvement up to 77% has been obtained by electrophotocatalysis under UV light; the conversion follows a first order kinetic with a rate constant of 2.32 × 10^?4 min^?1.     

Cooperation among N,F and Fe in tri-doped TiO<Subscript>2</Subscript> photocatalyst

TiO₂ photocatalysts tri-doped with N, F and Fe were synthesized by a sol–gel method. The cooperation of N, F and Fe in tri-doped TiO₂ was verified by monitoring NH₃ decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and by the simulation based on the density functional theory (DFT). The results from NH₃ decomposition revealed that the cooperation of N, F and Fe broadened the optical response of TiO₂ to the visible light range and also enhanced the photocatalytic activity of TiO₂ under UV light. The reusability of the tri-doped TiO₂ sample after three cycles under UV and visible light irradiation was very good. XRD patterns and SEM and HRTEM images indicated that the tri-doped sample was nanometric anatase with a small amount of rutile with an average particle size of 18 nm. Tri-doping with N, F and Fe suppressed the phase transition from anatase to rutile and also resulted in some more lattice defects. XPS analysis showed that the N, F and Fe atoms were doped into the TiO₂ lattice. UV–Vis absorption spectra of the tri-doped TiO₂ showed that its optical absorption edge was moved up to 640 nm and its UV absorption was also enhanced. The DFT results confirmed that the cooperation of Fe 3d and N 2p orbits narrowed the band gap of TiO₂ and the F 2p orbit broadened the upper valence bands. The synergistic electron density around N, F and Fe in tri-doped TiO₂ was capable of enhancing the photochemical stability and reusability of TiO₂.     

Non-isothermal crystallization kinetics of Ti<Subscript>20</Subscript>Zr<Subscript>20</Subscript>Hf<Subscript>20</Subscript>Be<Subscript>20</Subscript>(Cu<Subscript>50</Subscript>Ni<Subscript>50</Subscript>)<Subscript>20</Subscript> high-entropy bulk metallic glass

The crystallization transformation kinetics of Ti₂₀Zr₂₀Hf₂₀Be₂₀(Cu₅₀Ni₅₀)₂₀ high-entropy bulk metallic glass under non-isothermal conditions are investigated using differential scanning calorimetry. The alloy shows two distinct crystallization events. The activation energies of the crystallization events are determined using Kissinger, Ozawa and Augis–Bennett methodologies. Further, we observe that similar values are obtained using the three equations. The activation energy of the initial crystallization event is observed to be slightly small as compared to that of the second event. This implies that the initial crystallization event may have been easier to be occurred. The local activation energy (E(x)) maximizes in the initial stage of crystallization and keeps dropping in subsequent crystallization process. The non-isothermal crystallization kinetics are further analyzed using the modified Johnson–Mehl–Avrami (JMA) equation. Further, the Avrami exponent values are observed to be 1.5 < n(x) < 2.5 for approximately the entire period of the initial crystallization event and for most instances (0.1 < x < 0.6) of the second crystallization event, which implies that the mechanism of crystallization is significantly controlled by diffusion-controlled two- and three-dimensional growth along with a decreasing nucleation rate.     

Selective catalytic oxidation of ammonia into nitrogen and water vapour over transition metals modified Al<Subscript>2</Subscript>O<Subscript>3</Subscript>, TiO<Subscript>2</Subscript> and ZrO<Subscript>2</Subscript>

Copper or iron supported on commercially available oxides, such as γ-Al₂O₃, TiO₂ (anatase) and monoclinic tetragonal ZrO₂ (mt-ZrO₂) were tested as catalysts for selective catalytic oxidation of ammonia into nitrogen and water vapour (NH₃-SCO) in the low temperature range. Different commercial oxides were used in this study to determine the influence of the specific surface area, acidic nature of the support and crystalline phases as well as of the type of species and aggregation state of transition metals on the catalytic performance in selective ammonia oxidation. Copper modified oxide supports were found to be more active and selective to nitrogen than catalysts impregnated with iron. Activities of both transition metal modified samples decreased in the following order: mt-ZrO₂, TiO₂ (anatase), γ-Al₂O₃. Quantitative total ammonia conversion was achieved with the Cu/ZrO₂ catalytic system at 400°C. Characterisation techniques, e.g. H₂-temperature programmed reduction, UV-VIS-diffuse reflectance spectroscopy, suggest that easily reducible copper oxide species are important in achieving high catalytic performances at low temperatures.     

Microstructure of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> hybrid electrospun nanofibers and their application in dye degradation

SiO₂/TiO₂ hybrid nanofibers were prepared by electrospinning and applied for photocatalytic degradation of methylene blue (MB). The phase structure, specific surface area, and surface morphologies of the SiO₂/TiO₂ hybrid nanofibers were characterized through thermogravimetry (TG), X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), etc. XRD measurements indicated that doping of silica into TiO₂ nanofibers can delay the phase transition from anatase to rutile and decrease the grain size. SEM and BET characterization proved that silica doping can remarkably enhance the porosity of the SiO₂/TiO₂ hybrid nanofibers. The MB adsorption capacity and photocatalytic activity of the SiO₂/TiO₂ hybrid nanofibers were distinguished experimentally. It was found that, although increased silica doping content could enhance the MB adsorption capacity, the intrinsic photocatalytic activity gradually dropped. The SiO₂ (10 %)/TiO₂ composite nanofibers exhibited the highest MB degradation rate, being superior to SiO₂ (20 %)/TiO₂ or pure TiO₂.     

On the role of TiO<Subscript>2</Subscript> nanoparticles on thermal behavior of flexible polyurethane foam sandwich panels

A series of flexible polyurethane foam (FPUF) and monolithic polyurethane (PU) sandwich panels reinforced with different contents of TiO₂ nanoparticles (0, 0.5 and 1 mass%) have been successfully prepared by compression molding process at room temperature. The influence of TiO₂ nanoparticles on the thermal properties of PU matrix has been investigated by thermogravimetric and dynamic mechanical thermal analysis (DMTA). The morphology of porous structure of FPUF sandwich panels has been characterized by scanning electron microscopy. The presence of TiO₂ nanoparticles as reinforcement has improved the thermal properties of the FPUF and PU sandwich panel samples. It has been observed that FPUF and PU sandwich panel reinforced with 1 mass% of TiO₂ nanoparticles possessed the highest enhancement in thermal properties in all accomplished thermal tests. The DMTA results for the FPUF and PU sandwich panel reinforced with 1 mass% of TiO₂ nanoparticles indicated that the storage modulus and loss modulus have increased about 1.22 and 1.25 times, 1.5 and 1.55 times, respectively, compared to pure samples. Furthermore, the glass transition (T _g) obtained from the damping factor (tanδ) curves has increased 2 and 1 °C for FPUF and PU sandwich panels, respectively.     

Thermal analysis of heat-treated silver fir wood and larval frass

Glasses having composition 5Li₂O–5ZnO– xBi₂O₃ –(90 ? x) P₂O₅ (x = 5, 10, 15, 20 and 25 mol%) were prepared by the normal melt quenching technique. Nanocomposite glass containing bismuth phosphate BiPO₄ nanocrystals was obtained, which can be attributed to homogeneous nucleation process. The formation of BiPO₄ nanocrystals was confirmed and characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, optical absorption (UV–Vis) and micro-hardness studies. The morphological analysis by XRD and TEM microscopy showed the formation of hexagonal BiPO₄ nanocrystals, and its estimated nanocrystalline sizes were found to be varying from 5.35 to 11.53 nm depending on the Bi₂O₃ concentrations. The density (ρ) and molar volume (V _m) were also determined and found to be in compositional dependence. Glass transition temperature (T _g) and glass crystallization temperature (T _c) were obtained and found to be increased (from 240.0 to 337.2 °C) with increasing Bi₂O₃ up to 20 mol% and then decreased (from 337.2 to 331.8 °C) due to the structural changes in the glass network. Effect of BiPO₄ content on the optical properties had been investigated. From the UV–Vis spectra, it was observed that the fundamental absorption edge shifts toward lower wavelengths, i.e., blueshifts with increasing Bi₂O₃ mol% up to 20 mol%, and then shifts toward higher wavelengths, i.e., redshifts beyond 20 mol%. It was also observed that the obtained E _opt (for indirect and direct transitions) increases with gradual increase in Bi₂O₃ content up to 20 mol% and then decreases beyond 20 mol%. This may be due to the introduction of Bi cations into the glass network as a network former up to 20 mol% causing a decrease in ΔE values, beyond 20 mol%, the introduction of Bi ions into the glass network interstitially leads to increase the values of ΔE. The optical properties of the present nanocrystallized glasses showed a quantum size dependence, in which the optical band gap energy (E _opt) was changed as a function of BiPO₄ nanocrystalline sizes.     

Chitosan-modified TiO<Subscript>2</Subscript> as photocatalyst for ethanol reforming under visible light

This work reports the reforming of bio-ethanol on chitosan–TiO₂ hybrid photocatalysts at ambient temperature. The influence of chitosan composition on the photocatalytic performance of chitosan–TiO₂ hybrid was studied. The hybrids were characterized by CHN elemental analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the preparation variables used for the incorporation of chitosan on TiO₂ promoted changes in the morphology, superficial area, crystal size and porosity of the photocatalyst, affecting the band gap of this semiconductor and consequently the reactivity of the chitosan–TiO₂ hybrids. The catalysts were evaluated for hydrogen production from ethanol under visible light. It was demonstrated that the calcination temperature of 623 K and a chitosan content of 20% were the most appropriate preparation conditions and the resulting product displays a pore size of 1.9 nm, crystal size of 11.3 nm, BET area of 178 m² g^?1 and band gap of 2.92 eV. The calcination temperature of 623 K and incorporation of 20% of chitosan obtained the same results in the conversion rate of hydrogen in comparison to the pure TiO₂ P25.     

Structural and textural features of TiO<Subscript>2</Subscript>/SAPO-34 nanocomposite prepared by the sol–gel method

This paper focuses on the synthesis of nanocomposite materials, TiO₂/SAPO-34, using the sol–gel method, which involves preparing a mixture between as-synthesized or calcined SAPO-34 zeolite and TiO₂ gel under hydrothermal crystallization and then calcining it at 400 °C for the formation of the TiO₂ anatase phase. The structural and textural features of the obtained materials were determined by various physico-chemical techniques such as thermogravimetric analysis, X-ray diffraction, scanning electronic microscopy, nitrogen sorption at 77 K, energy dispersive X-ray analysis and ultraviolet–visible spectrometry. The DRX results showed that calcination at 400 °C of the mixture between the calcined SAPO-34 and TiO₂ gel led to the collapse of the original framework of zeolite, but formed the anatase TiO₂ in a nano-spherical morphology; however, the use of as-synthesized SAPO-34 supports provides a mixture phase between SAPO-34 and TiO₂ anatase after calcination. The photocatalytic properties of the SAPO-34/TiO₂ and TiO₂-type materials were tested for the removal of methylene blue (MB) dye. The MB degradation proved to increase as a function of contact time, catalyst mass and the initial concentration of MB.     

Synthesis and Characterization of Spindle-Like TiO<Subscript>2</Subscript> Nanostructures and Photocatalytic Activity on Methyl Orange and Methyl Blue Dyes Under Sunlight Radiation

Spindle-like TiO₂ nanostructures was prepared by a simple one pot solvothermal method followed by calcination at 400 °C for 3 h. The sample was characterized using various techniques such as X-ray diffractometer, transmission electron microscopy, Fourier transform infrared spectroscopy and UV–Vis absorption spectroscopy. The crystal structure of TiO₂ nanostructure was measured by X-ray diffractometer. According to the XRD result, the peaks in the sample can be indexed to anatase phase of TiO₂. The morphological characterization of TiO₂ sample was examined by transmission electron microscopy. The synthesized sample consisted of spindle-like shape with size in the range of 50–70 nm. The band gap value of Spindle-like TiO₂ nanostructures is 2.92 eV, which is lower than that of bulk TiO₂ of 3.2 eV. The FTIR bands observed at 493, 443 and 428 cm^?1 confirms the presence of TiO₂. The Spindle-like TiO₂ nanostructures showed photodegradation ability for methyl orange and methyl blue dye. The reuse evaluation of the Spindle-like TiO₂ nanostructures showed that their photocatalytic activity had good durability.     

Poly(Styrene Sulfonate)/Poly(Allylamine Hydrochloride) Encapsulation of TiO<Subscript>2</Subscript> Nanoparticles Boosts Their Toxic and Repellent Activity Against Zika Virus Mosquito Vectors

Green fabricated nanoparticles often need to be encapsulated and stabilized, to ensure uniform dispersion in the aquatic environment and relevant larvicidal activity over time. However, recent research showed that nanoencapsulation processes led to a reduction of nanoparticle larvicidal efficacy. We used an extract of Argemone mexicana to reduce TiO₂ nanoparticles, which were then capped with PSS/PAH (poly(styrene sulfonate)/poly(allylamine hydrochloride)). The toxic and repellent potential of the nanoparticles were compared to elucidate their potential effects against the Zika virus vector Aedes aegypti. Nanoparticles were characterized by biophysical methods including UV–Vis, EDX and FTIR spectroscopy, SEM, TEM, XRD and DLS analyses. In larvicidal and pupicidal experiments, TiO₂ nanoparticles achieved LC₉₀ values from 41.648 (larva I), to 71.74 ppm (pupa). Nanoencapsulated TiO₂ achieved LC₉₀ values from 39.16 (I), to 69.12 ppm (pupa). In adulticidal experiments, LC₉₀ of TiO₂ nanoparticles on Ae. aegypti was 10.31 ppm, while LC₉₀ of nanoencapsulated TiO₂ was 9.54 ppm. At 10 ppm, the repellency towards Ae. aegypti was 80.43% for TiO₂ nanoparticles, and 88.04% for nanoencapsulated TiO₂. This research firstly highlighted the promising potential of PSS/PAH encapsulation, leading to the production of highly effective titania nanostructures, if compared to titania nanoparticles synthesized with eco-friendly routes without further stabilization.     

Degradation of ofloxacin by UVA-LED/TiO<Subscript>2</Subscript> nanotube arrays photocatalytic fuel cells

The degradation of ofloxacin (OFX) at low concentration in aqueous solution by UVA-LED/TiO₂ nanotube arrays photocatalytic fuel cells (UVA-LED/TiO₂ NTs PFCs) was investigated. TiO₂ nanotube arrays (TiO₂ NTs) photoanode prepared by anodization-constituted anatase–rutile bicrystalline framework. The results indicated that the degradation efficiency of OFX by UVA-LED/TiO₂ NTs PFC was significantly enhanced by 14.3% compared with UVA-LED/TiO₂ NTs photocatalysis. The pH affected the degradation efficiency markedly; the highest degradation efficiency (95.0%) and the pseudo-first-order reaction rate constant k value (0.049 min^?1) were achieved in neutral condition (pH 7.0). The degradation efficiency increased with the increasing concentration of dissolved oxygen (DO) in the UVA-LED/TiO₂ NTs PFC. The main reactive species of OFX degradation are positive holes (h⁺) and superoxide ion radicals (O ₂ ^·? ) in a DO sufficient condition. Furthermore, the possible pathways of OFX degradation were proposed.     

Biosynthesis and Photocatalytic Properties of SnO<Subscript>2</Subscript> Nanoparticles Prepared Using Aqueous Extract of Cauliflower

This work reports the biosynthesis of Sn(OH)₂ using aqueous extract of fresh cauliflower (Brassica oleracea L. var. botrytis), and the subsequent preparation of SnO₂ nanoparticles at two different annealing temperatures of 300 and 450 °C for 2 h. The obtained SnO₂ nanoparticles were denoted as S1 and S2 for the samples prepared at 300 and 450 °C, respectively. XRD analysis identified rutile tetragonal phase of SnO₂ nanoparticles and TEM results gave a quasispherical and spherical morphologies for S1 and S2 respectively of the size range 3.62–6.34 nm. The optical properties were studied with UV–vis and photoluminescence (PL) spectroscopies, and the nanoparticles showed blue shift in their absorption edges. The observed emission peak in the PL spectra found around 419 nm is attributable to oxygen vacancies and defects. Photocatalytic activities of the nanoparticles (S1 and S2) were studied using methylene blue (MB) under ultraviolet light irradiation and the results reveal 91.89 and 88.23% degradation efficiency of MB by S1 and S2 respectively over a period of 180 min.     

Dye-Sensitized Solar Cell Utilizing TiO<Subscript>2</Subscript> Nanostructure Films: Effect of Synthesis Temperature

This paper is concerned with a study of the influence of synthesis temperature on the properties of TiO₂ films and the performance of dye-sensitized solar cell (DSSC). The TiO₂ film samples synthesized via liquid phase deposition for 5 h at various temperatures, namely, 40, 50, 60, 70 and 80°C. It was found that the morphological shape of the film changes with growth temperature. The optical absorption increases with growth temperature. However, the photoluminescence decreases with growth temperature. These TiO₂ samples were applied in a DSSC of ITO/TiO₂/electrolyte/platinum. The DSSC utilizing the sample grown at 40°C demonstrated the highest photovoltaic parameters with the J_sc, and η of 1.40 mA cm^–2 and 0.44% respectively. This is due to the smallest grain size of TiO₂ films and the smallest bulk resistance of the device.