The additive effect of zwitterion and nano-particles on ion dissociation in polyelectrolytes

To realise the battery potential of gel polyelectrolytes greater ion dissociation, ultimately leading to higher conductivities, must be achieved. Higher conductivities will result through increasing the ion-dissociating properties of the gel polyelectrolyte. The poor degree of ion dissociation arises as the active ion tends to remain in close proximity to the backbone charge. Nano-particle inorganic oxides, and zwitterionic compounds have been shown to act as dissociation enhancers in certain polyelectrolyte systems. In an attempt to further increase ion dissociation the addition of both TiO₂ nano-particles and a zwitterionic compound based on 1-butylimidazolium-3-N-(butanesulphonate) were added to the gel polyelectrolyte system poly (Li-2-acrylamido-2-methyl-1-propane sulphonate-co-N,N′-dimethylacrylamide), poly(Li-AMPS-co-DMAA) to determine if a synergistic effect occurs. Two different solvents were used to determine the breadth of applicability of the additive effect. The use of both dissociators resulted in the maximum ionic conductivity being achieved at lower nano-particle concentrations when compared to an identical system without zwitterion.     

Performance of a single-phase hybrid and nanocomposite polyelectrolyte in classical electrochromic devices

In this paper, we discuss the high stability of a single-phase hybrid polyelectrolyte (SPHP) and nanocomposite hybrid polyelectrolyte (NHP) in a large electrochromic (EC) device (5 cm × 10 cm) mounted with different electrodes. The electrochromic device (K-glass/FTO/WO₃/SPHP/CeO₂-TiO₂/FTO/K-glass—ECI, K-glass/FTO/WO₃/NHP/CeO₂-TiO₂/FTO/K-glass—ECII,) exhibited excellent color and bleach reversibility, high coloration efficiency (CE) (>35 cm²/C) from the first cycle up to more than 60,000 CA cycles, and a maximum constant rate of deintercalation/intercalation (O_out/Q_in = 1). Also, the life time of the EC device with Nb₂O₅:Mo (K-glass/FTO/Nb₂O₅:O/SPHP/CeO₂-TiO₂/FTO/K-glass—ECIII) was prolonged to up to more than 10,000 cycles with a fairly stable coloration efficiency (around 19 cm²/C) and O_out/Q_in = 1. The SPHP and NHP were tested in a large EC device with different configurations to evaluate its successful performance. In conclusion, its remarkable behavior and high stability render this material an excellent candidate for application in EC devices.     

On the effects of the sol-gel synthesis parameters on textural and structural characteristics of TiO2

The effects of alcohol/alkoxide, water/alkoxide molar ratios, acid addition, type of solvent, reaction temperature and calcination temperature on textural, structural and morphological characteristics of TiO₂ were studied. The results show that surface area, pore size distribution and crystalline phases were very sensitive to preparation conditions.     

Photocatalytic activity of metal ion (Fe or W) doped titania

Iron or tungsten-doped nano TiO₂ were successfully synthesized from TiCl₄. All of the samples showed anatase phase of TiO₂. For the iron-doped TiO₂, Iron ion was well dispersed in the TiO₂ lattice. However, tungsten-doped TiO₂ formed 12-tungstate with anatase TiO₂. As the concentration of tungsten increased, 12-tungstate disappeared. The photocatalytic oxidation of acetaldehyde was evaluated to examine the photocatalytic characteristics of metal-doped TiO₂. Because of the surface containing metal oxide or metal precursors at high concentration metal ion, increasing the concentration of W or Fe ion decreased the reactivity. The reaction rate was drastically increased after 300 °C heat treatment. Furthermore, the photocatalytic activity of iron- or tungsten-doped TiO₂ was higher than that of synthesized pure TiO₂ and commercial TiO₂.     

Reversible transformation between the isolated and the bidentately bound sulfate ion in sulfate promoted metal oxides

A new experimental result of thermally treating ammonium sulfate-titanium oxide (AS-TiO₂) is reported. The results strongly suggest the reversibility of the transformation between the isolated and the bidentately bound sulfate ion involved in the sites responsible for the acidity and the catalytic activity of sulfate promoted metal oxides. On the basis of the results a scheme for the reversible transformation is suggested.     

Effect of TiO2 addition on the microstructures,mechanical and dielectric properties of porous Si3N4-based ceramics

Porous Si₃N₄-based ceramics with different TiO₂ contents were prepared by gas pressure sintering method. The effects of TiO₂ addition ranging from 0 to 25?wt-% on the phase compositions, microstructures, mechanical performance and dielectric properties were investigated. The addition of TiO₂ significantly promoted the density which increased from 1.64 to about 2.3?g?cm^?3. The mechanical properties of porous Si₃N₄-based ceramics with TiO₂ addition decreased first and then increased with the increase of TiO₂ content, and the flexural strength and elastic modulus are more than 167.4?MPa and 72.8?GPa, respectively, which were higher than that of the Si₃N₄ ceramic without TiO₂ addition. With the increase of TiO₂ content, both the dielectric constant and dielectric loss increased, and the dielectric constant enhanced obviously. These results suggested that the TiO₂ was beneficial for the improvement of mechanical properties and dielectric constant of porous Si₃N₄-based ceramics.     

The Effect of a Changing Lean Gas Composition on the Ability of NO2 Formation and NOx Reduction over Supported Pt Catalysts

Three model catalysts (Pt/Al₂O₃, Pt/TiO₂, Pt/V₂O₅/TiO₂) were examined in regard to their NO₂ formation ability under a changing lean gas composition. The results show that the NO to NO₂ oxidation function as well as the NO _x reduction under lean gas conditions is affected by a change in the lean gas atmosphere. The NO oxidation activity also decreased with time, for Pt/Al₂O₃ and Pt/TiO₂, and a possible explanation may be platinum oxide formation. This deactivation was not observed for Pt/V₂O₅/TiO₂.     

Effect of Ag addition on the properties of Pd–Ag/TiO2 catalysts containing different TiO2 crystalline phases

Anatase and rutile TiO₂ were used for preparation of the TiO₂ supported Pd and Pd–Ag catalysts for selective hydrogenation of acetylene. It was found that Pd/TiO₂-anatase exhibited higher acetylene conversion and ethylene selectivity than rutile TiO₂ supported ones. However, addition of Ag to Pd/TiO₂-anatase catalyst resulted in lower ethylene selectivity while that of Pd/TiO₂-rutile increased. It is suggested that Ag addition suppressed the beneficial effect of the Ti³⁺ sites presented on the anatase TiO₂ during selective acetylene hydrogenation whereas without Ti³⁺, Ag promoted ethylene selectivity by blocking sites for over-hydrogenation of ethylene to ethane.     

Characterization of Supported NiSO4 and Effect of TiO2–ZrO2 Composition on Catalytic Activity for Acid Catalysis

A series of catalysts, NiSO₄/TiO₂–ZrO₂ having different TiO₂–ZrO₂ composition, for acid catalysis was prepared by the impregnation method using an aqueous solution of nickel sulfate. The addition of TiO₂ to ZrO₂ improved the surface area of the catalyst and enhanced its acidity remarkably because of the formation of new acid sites through the charge imbalance of Ti–O–Zr bonding. The binary oxide, TiO₂–ZrO₂ calcined above 600 °C resulted in the formation of crystalline orthorhombic phase of ZrTiO₄. Therefore, NiSO₄/TiO₂–ZrO₂ calcined at 500 °C exhibited a maximum catalytic activity for acid catalysis, and then the catalytic activity decreased with the calcination temperature. The correlation between catalytic activity and acidity held for both reaction, 2-propanol dehydration and cumene dealkylation. NiSO₄ supported on 50TiO₂–50ZrO₂ (TiO₂/ZrO₂ ratio = 1) among TiO₂–ZrO₂ binary oxides exhibited the highest catalytic activity for acid catalysis.     

Prediction of a highly sensitive molecule sensor for SOx detection based on TiO2/MoS2 nanocomposites: a DFT study

First principles calculations within density functional theory have been carried out to investigate the adsorptions of SO_x (x?=?1, 2) molecules on TiO₂/MoS₂ nanocomposites in order to fully discover the gas sensing capabilities of TiO₂/MoS₂ composite systems. The van der Waals interactions were included to obtain the most stable geometrical structures of TiO₂/MoS₂ nanocomposites with adsorbed SO_x molecules. SO_x molecules preferentially interact with the doped nitrogen and fivefold coordinated titanium sites of the TiO₂ anatase nanoparticles because of their higher activities in comparison with the other sites. The results presented include structural parameters such as bond lengths and bond angles and energetics of the systems such as adsorption energies. The variation of electronic structures are discussed in view of the density of states and molecular orbitals of the SO_x molecules adsorbed on the nanocomposites. The results show that the adsorption of the SO_x molecule on the N-doped TiO₂/MoS₂ nanocomposite is energetically more favorable than the adsorption on the undoped one, implying that the nitrogen doping helps to strengthen the interaction of SO_x molecules with TiO₂/MoS₂ nanocomposites. These calculated results thus provide a theoretical basis for the potential applications of TiO₂/MoS₂ nanocomposites in the removal and sensing of harmful SO_x molecules.     

Effects of orientation and substrate on ion transport in fluoride heterostructures grown by molecular beam epitaxy

Ion conductor heterostructures of BaF₂ and CaF₂ with various spacings have been prepared by molecular beam epitaxy (MBE) technique as reported previously by Sata et al. [Nature 408 (2000) 946]. In this paper, we are especially interested in the effects of orientation and substrate on the conductivity. Four kinds of substrates have been investigated (Al₂O₃(0 1 2), Al₂O₃(0 0 6), MgO(1 1 1), and MgO(1 1 0)), generating [1 1 1] and [1 0 0] oriented heterostructures with smooth surfaces. The samples have been investigated by ac impedance, dc polarization techniques, X-ray diffraction (XRD) and atomic force microscopy (AFM). The polarization measurements confirm that electronic effects are minor and the conductivity is ionic. The substrate itself causes a space charge effect which adds to the overall conductance as a constant contribution and is of the order of the effect of a single CaF₂/BaF₂ interface (or less), and hence totally negligible if the number of CaF₂/BaF₂ interfaces is high. Variation of the substrate’s surface chemistry leads to a conductivity variation that is exactly opposite to the case of cation adsorption, and thus suggests F⁻ adsorption as defect inducing mechanism at the Al₂O₃/BaF₂ interface. The dominating contribution of the CaF₂/BaF₂ interfaces is approximately independent of the orientation, hence, favoring a fluoride ion transfer from one to the other phase rather than a charge accumulation at the interfacial core, in full agreement with the conclusions of Sata et al. [Nature 408 (2000) 946].     

Photocatalytic oxidation of ethylene to CO2 and H2O on ultrafine powdered TiO2 photocatalysts: Effect of the presence of O2 and H2O and the addition of Pt

The complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O has been achieved on ultrafine powdered TiO₂ photocatalysts and the addition of H₂O was found to enhance the reaction. The photocatalytic reaction has been studied by IR, ESR, and analysis of the reaction products. UV irradiation of the photocatalysts at 275 K led to the photocatalytic oxidation of C₂H₄ with O₂ into CO₂, CO, and H₂O. The large surface area of the photocatalyst is one of the most important factors in achieving a high efficiency in the photocatalytic oxidation of C₂H₄. The photoformed OH species as well as O ₂ ⁻ and O ₃ ⁻ anion radicals play a significant role as a key active species in the complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O. Interestingly, small amount of Pt addition to the TiO₂ photocatalyst increased the amount of selective formation of CO₂ which was the oxidation product of C₂H₄ and O₂.     

The effects of firing conditions on the properties of electrophoretically deposited titanium dioxide films on graphite substrates

Thick anatase films were fabricated on graphite substrates using a method of anodic aqueous electrophoretic-deposition using oxalic acid as a dispersant. Thick films were subsequently fired in air and in nitrogen at a range of temperatures. The morphology and phase composition were assessed and the photocatalytic performance was examined by the inactivation of Escherichia coli in water. It was found that the transformation of anatase to rutile is enhanced by the presence of a graphite substrate through reduction effects. The use of a nitrogen atmosphere allows higher firing temperatures, results in less cracking of the films and yields superior bactericidal performance in comparison with firing in air. The beneficial effects of a nitrogen firing atmosphere on the photocatalytic performance of the material are likely to be a result of the diffusion of nitrogen and carbon into the TiO₂ lattice and the consequent creation of new valence band states.     

Potentiometric SO2 gas sensor based on a thick film of Ca2+ ion conducting solid electrolyte

A planar miniaturized SO₂ sensor based upon a thick film of Ca²⁺ ion conductor-CaO·0.6MgO·6Al₂O₃ (CMA) with a Na₂SO₄ auxiliary electrode and a Pt/O₂ reference electrode was fabricated and tested. The thick film was fabricated by screen-printing CMA ink on an alumina substrate and then fired at 1823 K. The solid electrolyte was interfaced with a sodium sulphate auxiliary phase containing Pt paste and the sensor showed a good SO₂ response at 873–1073 K. The electromotive force (emf) values obtained were linearly dependent upon the logarithm values of SO₂ concentration in a range of 10–500 ppm. Both the electrodes were exposed to the same test gas thus eliminating the need to separate the electrode chambers.     

TiO2 nanotube arrays annealed in CO exhibiting high performance for lithium ion intercalation

Anatase titania nanotube arrays were fabricated by means of anodization of Ti foil and annealed at 400 °C in respective CO and N₂ gases for 3 h. Electrochemical impendence spectroscopy study showed that CO annealed arrays possessed a noticeably lower charge-transfer resistance as compared with arrays annealed in N₂ gas under otherwise the same conditions. TiO₂ nanotube arrays annealed in CO possessed much improved lithium ion intercalation capacity and rate capability than N₂ annealed samples. At a high charge/discharge current density of 320 mA g⁻¹, the initial discharge capacity in CO annealed arrays was found to be as high as 223 mAh g⁻¹, 30% higher than N₂ annealed arrays, ∼164 mAh g⁻¹. After 50 charge/discharge cycles, the discharge capacity in CO annealed arrays remained at ∼179 mAh g⁻¹. The improved intercalation capacity and rate capability could be attributed to the presence of surface defects like Ti-C species and Ti³⁺ groups with oxygen vacancies, which not only improved the charge-transfer conductivity of the arrays but also possibly promoted phase transition.     

TiO2/ZnO Supported on Sepiolite: Preparation,Structural Characterization,and Photocatalytic Degradation of Flumequine Antibiotic in Aqueous Solution

In this study, TiO₂, ZnO, TiO₂/ZnO (Ti/Zn), and TiO₂/ZnO/Sep (Ti/Zn/Sep) catalysts have been synthesized using sol–gel and chemical precipitation method. Their photocatalytic performances have been compared using Flumequine (FLQ) antibiotic. X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), N₂-adsorption, and the determination of a zero point charge has been used to characterize the synthesized catalysts. The degradation studies showed that the catalytic efficiency of Ti/Zn/Sep is higher than that for other catalysts. The operational parameters such as pH, initial FLQ concentration, and catalyst dosage were evaluated. UV–vis and high-resolution mass spectroscopy (HRMS) analyses were used to determine the degradation efficiency and products. ZnO played a major role in the FLQ degradation process, and sepiolite contributed to adsorption of FLQ on the catalyst surface enormously. The catalysts exhibited 11%, 23%, 63%, and 85% degradation efficiency for ZnO, TiO₂, Ti/Zn, and Ti/Zn/Sep in the decomposition of FLQ, respectively.     

Effect of M-doping (M = Fe,V) on the photocatalytic activity of nanorod rutile TiO2 for Congo red degradation under the sunlight

Nanorods TiO₂, Fe-TiO₂ (3 and 2 at.% Fe), V-TiO₂ (5 at.% V) were prepared by a low temperature method and characterized by powder X-ray diffraction, thermal analysis, transmission electron microscope and BTE surface area analysis. The as-prepared samples were evaluated as catalysts for photodegradation of Congo red aqueous solution under the sunlight. Nanorods Fe-doped TiO₂ shows higher adsorption and also higher photocatalytic degradation of Congo red solution compared to pure nanorods TiO₂ rutile. A higher activity is obtained when the amount of doped Fe is 2 at.%, compared to 3 at.%. However, nanorods V-TiO₂ does not show neither adsorption nor photodegradation activity of Congo red solution.     

Comparison of the killing effects between nitrogen-doped and pure TiO2 on HeLa cells with visible light irradiation

The killing effect of nitrogen-doped titanium dioxide (N-TiO₂) nanoparticles on human cervical carcinoma (HeLa) cells by visible light photodynamic therapy (PDT) was higher than that of TiO₂ nanoparticles. To study the mechanism of the killing effect, the reactive oxygen species produced by the visible-light-activated N-TiO₂ and pure-TiO₂ were evaluated and compared. The changes of the cellular parameters, such as the mitochondrial membrane potential (MMP), intracellular Ca²⁺, and nitrogen monoxide (NO) concentrations after PDT were measured and compared for N-TiO₂- and TiO₂-treated HeLa cells. The N-TiO₂ resulted in more loss of MMP and higher increase of Ca²⁺ and NO in HeLa cells than pure TiO₂. The cell morphology changes with time were also examined by a confocal microscope. The cells incubated with N-TiO₂ exhibited serious distortion and membrane breakage at 60 min after the PDT.