Photocatalytic and magnetic titanium dioxide/polystyrene/magnetite composite hybrid polymer particles

Novel multifunctional titanium dioxide (TiO₂)/polystyrene/magnetite composite hybrid polymer particle dispersions with TiO₂ nanoparticles in the surface and magnetite nanoparticles encapsulated inside the polymer matrix were produced by Pickering miniemulsion polymerization in one single step. Whereas TiO₂ nanoparticles were used to impart photocatalytic functionality and colloidal stability, magnetite nanoparticles were incorporated to allow an easy extraction for recovery and reuse of the composite multifunctional particles. The morphology of the composite particles was assessed by scanning transition electron microscopy (STEM) and energy‐dispersive X‐ray spectroscopy (EDX). The paramagnetism of the particles was analyzed using a SQUID magnetometer and their photocatalytic activity was assessed by degrading methylene blue (MB) solutions under UV light and by recovering and reusing of the particles in five consecutive cycles. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3350–3356     

Photocatalytic activity and biodegradation of polyhydroxybutyrate films containing titanium dioxide

This study aims to evaluate the photocatalytic activity and biodegradation of polyhydroxybutyrate (PHB) films containing titanium dioxide (TiO₂). Nanosized TiO₂ photocatalysts were immobilized onto PHB film to overcome the difficulty of the recovery process. PHB is a suitable base material as it is naturally biodegradable and is produced from renewable resources. The photocatalytic degradation of organic compounds, photocatalytic sterilization activity and biodegradation rate in garden soil of PHB-TiO₂ composite films were investigated. After an hour under solar illumination, 96% of methylene blue solution was decolorized. The antibacterial activity against Escherichia coli (E. coli) using PHB-TiO₂ composite film exhibited enhanced photocatalytic sterilization activity over time. As for the ability to biodegrade, PHB-TiO₂ composite films placed on soil surface with no direct solar illumination showed slower degradation rate compared to those receiving direct solar illumination. Interestingly, the latter composite films showed faster degradation rates compared to pure PHB films indicating that the degradation is mainly due to photocatalytic activity. PHB-TiO₂ composite films buried in soil generally showed slower degradation rates compared to pure PHB films and were dependent on the soil microbial activity.     

Photocatalytic activity enhancement in doped titanium dioxide by crystal defects

Visible light sensitive Fe(3+) and Ce(4+) co-doped nano TiO(2) photocatalyst has been prepared by a modified aqueous sol-gel method and the activity has been measured in terms of degradation of MB dye. Both dopants shifted the absorption profile of TiO(2) to the visible region and improved activity. Fe(3+) ions trapped the charge carriers due to the stable electronic configuration and improved their separation. Ce(4+) ions, which were mainly located at the grain boundaries, cause dislocations by bending the valence and conduction bands of TiO(2) and prevent the recombination of photoexcited electrons and holes. The co-doped TiO(2) compositions exhibited higher photocatalytic activity than that of pure titania and commercially available Degussa P25 under visible light by utilising the individual and synergistic contributions of Fe(3+) and Ce(4+) dopants, respectively.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.     

Tin oxide-surface modified anatase titanium(IV) dioxide with enhanced UV-light photocatalytic activity

[Sn(acac)(2)]Cl(2) is chemisorbed on the surfaces of anatase TiO(2)via ion-exchange between the complex ions and H(+) released from the surface Ti-OH groups without liberation of the acetylacetonate ligand (Sn(acac)(2)/TiO(2)). The post-heating at 873 K in air forms tin oxide species on the TiO(2) surface in a highly dispersed state on a molecular scale ((SnO(2))(m)/TiO(2)). A low level of this p block metal oxide surface modification (~0.007 Sn ions nm(-2)) accelerates the UV-light-activities for the liquid- and gas-phase reactions, whereas in contrast to the surface modification with d block metal oxides such as FeO(x) and NiO, no visible-light response is induced. Electrochemical measurements and first principles density functional theory (DFT) calculations for (SnO(2))(m)/TiO(2) model clusters (m = 1, 2) indicate that the bulk (TiO(2))-to-surface interfacial electron transfer (BS-IET) enhances charge separation and the following electron transfer to O(2) to increase the photocatalytic activity.     

Preparation of anatase phase titanium dioxide film by non-aqueous electrodeposition

The electrodeposition–annealing route to fabricating thin film of the promising photocatalyst material anatase-titanium dioxide (anatase-TiO₂) has been studied. The sample was deposited with a solution of N,N-dimethylformamide containing titanium compound by controlled-potential technique. SEM image showed the annealed sample at 600 °C for 1 h under air provided a continuous film with a thickness of ca. 350 nm. In this sample, X-ray photoelectron spectrum corresponding to the Ti 2p peak assigned to a chemical bond of TiO₂ and X-ray diffraction peaks assigned to the anatase phase were observed, respectively. Electrochemical oxidation in sodium sulfate solution on this annealed film was enhanced in the presence of UV light radiation. These results confirm the successful synthesis of photocatalytic anatase-TiO₂ film by the electrodeposition and annealing process.     

Photocatalytic activity of titanium dioxide nanoparticles produced by methods of high-energy physical dispersion

Photocatalytic activity of titanium dioxide nanoparticle samples under study is almost uncorrelated with their phase composition and, in particular, with the content of the anatase phase. The photocatalytic activity depends on the annealing temperature of the nanoparticles. The photocatalytic activity is positively affected by an ultrasonic radiation of the nanoparticles. The highest photocatalytic activity, comparable with that of the AEROXIDE P25 reference nanopowders, is observed for nanoparticles produced by a method of electrical explosion of wires.     

Relative brookite and anatase content in sol-gel-synthesized titanium dioxide nanoparticles

Sol-gel synthesis of titania typically produces a mixture of brookite and anatase. Rietveld refinements were used to systematically track the brookite content and particle size as functions of synthetic variables. Results demonstrate that brookite content and anatase particle size decrease with decreasing Ti/H(2)O ratios. In syntheses at pH 3, the addition of HCl resulted in increased amorphous content compared to samples synthesized using HNO(3). Similar amorphous contents were observed for particles prepared at pH 6-9. Hydrothermal aging for 4 h at 200 degrees C of sol-gel products containing substantial amorphous titania resulted in higher brookite content than did hydrothermal aging of sol-gel products containing little to no amorphous titania. Finally, dialysis prior to hydrothermal aging appeared to inhibit phase transformation from brookite to anatase in aged materials. Results presented demonstrate that considerable control over the relative anatase and brookite contents can be achieved through control of synthetic variables.     

Photocatalytic activity of titanium dioxide modified with thiourea under the action of visible light

Photocatalyst powders were synthesized from nanosized titanium dioxide crystals modified by sintering with thiourea (TU). The powders contained anatase crystals of various sizes. TU-TiO₂ powders absorbed visible light to produce an oxidizer (oxidizing iodide) and a reducing agent (reducing tetranitromethane). The activity of TU-TiO₂ correlated with the size of nanocrystals. The photocatalytic activity of TU-TiO₂ was suggested to be related to impurity states appearing during modification in the forbidden band of TiO₂.     

Photocatalytic,phosphorus-doped,anatase oxide layers applicable to titanium implant alloys

Titanium alloys provide excellent corrosion resistance and favorable mechanical properties well suited for a variety of biomaterial applications. The native oxide surface on titanium alloys has been shown to be less than ideal and surface modification is often needed. Previously, an optimized anodization process was shown to form a porous phosphorus-enhanced anatase oxide layer on commercially pure Ti grade 4. The anodized layer was shown to improve osseointegration and to reduce bacteria attachment when photocatalytically activated with UVA preillumination. The primary objective of the present study was to create a similar phosphorus-enhanced anatase oxide layer on series of titanium alloys including commercially pure Ti grade 4, Ti-6Al-7Nb, Ti-6Al-4V ELI, alpha + beta Ti-15Mo, beta Ti-15Mo, and Ti-35Nb-7Zr-5Ta. Phosphorus-enhanced anatase oxide layers were formed on each titanium substrate. Anatase formation was shown to generally increase with oxide thickness, except on substrate alloys containing niobium. Phosphorus uptake was shown to be dependent on the titanium alloy chemistry or microstructure. Anodized layers formed on beta-structured titanium alloys revealed the lowest phosphorus uptake and the most nanosized surface porosity. A methylene blue degradation assay showed anodized layers on commercially pure Ti and both Ti-15Mo alloys to exhibit the highest levels of photocatalytic activity. Given the range of mechanical properties available with the commercially pure Ti and Ti-15Mo alloys, the results of this study indicate the benefits of phosphorus-enhanced anatase oxide coatings may be applicable to a wide variety of biomaterial applications.     

Photocatalytic degradation of 1,5-naphthalenedisulfonate on colloidal titanium dioxide

Photocatalytic degradation of 1,5-naphthalenedisulfonate (NDS) was investigated by monitoring the absorption and emission spectral changes, chemical oxygen demand, total organic carbon (TOC) content as well as pH and sulfate concentration. Intermediates formed during the irradiation were also detected by liquid chromatographic-mass spectrometric analysis. The results obtained by the applied analytical techniques clearly indicate that the initial step of degradation is oxygenation (hydroxylation) of the starting surfactant resulting in the formation of an 8-hydroxy derivative, although desulfonation and some mineralization, that is, decrease of TOC indicating carbon dioxide generation, also take place at this stage. Further oxygenation and desulfonation lead to the destruction of the diaromatic naphthalene system, then to ring fission, producing diols, aldehydes, and carboxylic acids on the side-chains. A tentative scheme involving possible pathways of degradation is proposed, taking the intermediates detected by mass spectrometry into consideration. On the basis of the results of quantum chemical calculations, the most possible points of attack by HO radical were identified, supplementing the MS results, and elucidating the initial oxidation step in the degradation of NDS and the benzenesulfonate (BS) intermediate. Thus, in the case of NDS para position is favored for hydroxylation, while for BS, formation of the ortho-hydroxy derivative is preferred.     

Kinetics of heterogeneous photocatalytic decomposition of monuron over anatase titanium dioxide powder

The photocatalytic degradation of Monuron (3-(4-chlorophenyl)-1-1-dimethylurea) in aqueous TiO₂ dispersions irradiated in the near-UV region has been investigated by using a Pyrex batch photoreactor. The Monuron and total organic carbon concentrations were determined; several reaction intermediates were also identified using HPLC. The influence on the degradation kinetics of the initial Monuron concentration, of the TiO₂ concentration, and of the initial pH of dispersion was studied. A pseudo-first order kinetics of Langmuir-Hinshelwood type was found to satisfactorily describe the Monuron degradation. The mineralization of the pollutant was virtually complete in the 3–9 pH range while at pH = 1.0 and 11.0 only a partial mineralization was reached even after a long irradiation time. The quantum yield values of Monuron degradation were determined by measuring the photon flow transmitted by the dispersion and applying a macroscopic photon balance on the photoreactor. The quantum yields were found to increase by increasing the pH of the dispersion.     

Photocatalytic activity of polyvinyl borate/titanium dioxide composites for UV light degradation of organic pollutants

In this study, it is aimed to prepare polyvinyl borate (PVB)/titanium dioxide (TiO₂) composites through the condensation reaction of polyvinyl alcohol and boric acid in the presence of TiO₂ nanoparticles. The scope of this study contains the photocatalytic activity of the prepared composites with varying TiO₂ content from 0 to 35 wt.% for the degradation of methylene blue in aqueous medium under UV light irradiation. The structure and morphological properties of the prepared composites were studied with FTIR, TGA, EDX, SEM and TEM analyses. The photocatalytic activity of the prepared samples was analyzed by UV-Vis spectrophotometer measurements. In parallel with TiO₂ content up to 30 wt.%, the photocatalytic activity of PVB/TiO₂ composites was enhanced and the composites exhibited higher discoloration rate of the model dye, methylene blue.     

Low-cost synthesis of titanium dioxide anatase nanoclusters as advanced materials for hydrogen photoproduction

Research on Chemical Intermediates - Sub-nm titanium dioxide (TiO2) clusters are synthesized via the hydrolysis of TiCl4 in order to produce clean and surfactant-free oxide surfaces. By controlling...     

Non-isothermal kinetics in mixtures of barium carbonate and titanium dioxide (anatase)

The complexes AgL (L = theobromine, 1,3,8-trimethylxanthine and 3,8-dimethylxanthine) Hg₂L·NO₃ (L = 3,8-dimethylxanthine and 1,3,8-trimethylxanthine) and Hg₂C₂(NO₃)₂ (C = caffeine), were prepared in aqueous and HNO₃ medium. These complexes were characterized by IR, ¹H-NMR, TG, DTG and DSC techniques.     

Enhanced photocatalytic reduction of Cr(VI) by manganese-doped anatase titanium dioxide

Nano-TiO₂ is frequently used as an optimal photocatalyst, since it is nontoxic, low cost, and environmentally friendly, especially for its photocatalytic oxidation action. However, its photocatalytic reducing action has not been widely researched. In this study, TiO₂ doped with different concentrations of manganese was prepared by the sol–gel method and characterized using different techniques to analyze the surface structure, phase composition, and surface elements of the different materials. To investigate the photocatalytic activity, Mn–TiO₂ was used for photocatalytic reduction of Cr(VI). Moreover, various organic pollutants were added to determine whether they enhanced the photocatalytic reduction of Cr(VI). The experiments indicated that the presence of Mn in TiO₂ could enhance its photocatalytic reduction action, especially at 0.02 % molar ratio. Manganese ions doped in TiO₂ behaved as electron accumulation sites. In addition, pH value, and photocatalyst dosage were investigated to analyze their effects on the photocatalytic reduction action. The results show that lower pH value improved the efficiency of photocatalytic reduction; there were no significant changes in the photocatalytic reduction rate with dosage above 1.0 g/L. In the presence of different electron donors (organic pollutants as hole scavengers), the photocatalytic reduction of Cr(VI) was generally improved. In short, manganese-doped TiO₂ exhibited improved photocatalytic reduction activity, especially in cooperation with various organics.     

Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

Photocatalytic degradation of dimethyl terephthalate in aqueous suspensions of titanium dioxide

The photocatalytic degradation of dimethyl terephthalate (DMT, 1) has been investigated in aqueous suspensions of titanium dioxide (TiO2) by monitoring the depletion of Total Organic Carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation kinetics were studied using different parameters such as pH, substrate and photocatalyst concentration, a different kind of titanium dioxide and the presence of electron acceptors such as H2O2, KBrO3 and (NH4)2S2O8 in addition to molecular oxygen. The photocatalytic activity was better for Degussa P25 as compared to the other photocatalysts. From the obtained kinetic data a detailed account of the influence of various parameters on the degradation rate for the mineralization of the compound is given. The degradation products were analyzed using the GC/MS technique and probable pathways for the formation of different products have been proposed.