TiO2 Fibers Research Articles

Phase Controlling of TiO2 Fibers by Adjusting Precursor Pre-Hydrolysis and Calcined Process Towards Enhanced Photocatalysis

Phase Controlling of TiO₂ Fibers by Adjusting Precursor Pre-Hydrolysis and Calcined Process Towards Enhanced Photocatalysis

Photocatalytic Activity of Biomorphic TiO2 Fibers Obtained by Ultrasound-Assisted Impregnation of Cellulose with Titanium Polyhydroxocomplexes

An ultrasound-assisted biotemplate method for producing biomorphic fibrous titanium oxide (TiO2) is reported. Wood pulp in the form of sheets was used as a biotemplate, and a solution of titanium hydroxocomplexes as a precursor. On completing the impregnation, the samples were dried and calcined at temperatures of 300–1000 °C. The process of obtaining fibrous TiO2, as well as its structure and textural properties, was investigated by DSC/TG analysis, X-ray diffraction, scanning electron microscopy, and nitrogen adsorption/desorption, while photocatalytic activity was studied using Rhodamine B dye degradation by UV irradiation. It is shown that the phase composition, textural and sorption characteristics of the biomorphic TiO2 samples essentially depend on the biotemplate annealing temperature. The TiO2 sample obtained at 600 °C is a mixture of anatase and rutile (with a ratio of 72 and 28%, respectively) and possesses the highest surface area, adsorption capacity, and photocatalytic activity with respect ...

Novel Synthesis of Plasmonic Ag/AgCl@TiO2 Continues Fibers with Enhanced Broadband Photocatalytic Performance

The plasmonic Ag/AgCl@TiO2 fiber (S-CTF) photocatalyst was synthesized by a two-step approach, including the sol-gel and force spinning method for the preparation of TiO2 fibers (TF), and the impregnation-precipitation-photoreduction strategy for the deposition of Ag/AgCl onto the fibers. NaOH aqueous solution was utilized to hydrolyze TiCl4, to synthesize TF and remove the byproduct HCl, and the produced NaCl was recycled for the formation and deposition of Ag/AgCl. The surface morphology, specific surface area, textural properties, crystal structure, elemental compositions and optical absorption of S-CTF were characterized by a series of instruments. These results revealed that the AgCl and Ag0 species were deposited onto TF successfully, and the obtained S-CTF showed improved visible light absorption due to the surface plasmon resonance of Ag0. In the photocatalytic degradation of X-3B, S-CTF exhibited significantly enhanced activities under separate visible or UV light irradiation, in comparison to TF.

Preparation and Characterization of Pd Modified TiO2 Nanofiber Catalyst for Carbon–Carbon Coupling Heck Reaction

TiO2 fibers were prepared through electrospinning of poly methyl methacrylate (PMMA) and titanium isopropoxide (TIP) solution followed by calcination of fibers in air at 500°C. Cetyltrimethylammonium bromide (CTAB) protected palladium nanoparticles (Pd NPs) prepared through reduction method were successfully adsorbed on the TiO2 nanofibers (NF). Combined studies of X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) indicated that the synthesized Pd/TiO2 had anatase. BET indicated that the synthesized TiO2 and Pd/TiO2 had a surface area of 53.4 and 43.4 m2/g, respectively. The activity and selectivity of 1 mol% Pd/TiO2 in the Heck reaction have been investigated towards the Mizoroki-Heck carbon–carbon cross-coupling of bromobenzene (ArBr) and styrene. Temperature, time, solvent, and base were optimized and catalyst was recycled thrice. 1H NMR and 13C NMR indicated that stilbene, a known compound from literature, was obtained in various Heck reactions at temperatures between 100°C and 140°C but the recyclability was limited due to some palladium leaching and catalyst poisoning which probably arose from some residual carbon from the polymer. The catalyst was found to be highly active under air atmosphere with reaction temperatures up to 140°C. Optimized reaction condition resulted in 89.7% conversions with a TON of 1993.4 and TOF value of 332.2 hr−1.

Novel heterostructured InN/TiO2 submicron fibers designed for high performance visible-light-driven photocatalysis

InN phase was successfully integrated into TiO2 fiber, which greatly improved its visible-light photocatalytic property.

Fabrication of Photocatalytic Paper Using TiO2 Nanoparticles Confined in Hollow Silica Capsules.

TiO2 nanoparticles (NPs) encapsulated in hollow silica spheres (TiO2@HSSs) show a shielding-effect that can insulate photocatalytically active TiO2 NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO2@HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO2@HSS, which has an ample void space between inner TiO2 NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO2@HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO2@HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO2@HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO2 NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO2 and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

Vapor-phase polymerized poly(3,4-ethylenedioxythiophene) (PEDOT)/TiO2 composite fibers as electrode materials for supercapacitors

Vapor-phase polymerized poly(3,4-ethylenedioxythiophene) (PEDOT)/TiO2 composite fibers were fabricated and applied as the supercapacitor electrode materials. TiO2 fibers were prepared as substrates for the vapor-phase polymerization process, by electrospinning and calcination in air. The symmetric supercapacitor cells assembled with the resulting composites were studied by a series of electrical measurements including cyclic voltammetry, charge-discharge characterization and electrochemical impedance spectroscopy. To further understand the capacitive behavior, the band gap energy of the composite fibers and the specific surface area of TiO2 fibers calcined at varied temperatures were measured. The highest specific capacitance of PEDOT on TiO2 fibers to date, 87.9Fg−1, was achieved with the composite fibers prepared by vapor-phase polymerization at 50°C on the TiO2 fibers calcined at 550°C. The pseudocapacitance and the reversibility of PEDOT were improved in comparison to other PEDOT/TiO2 binary composites.

Advanced Fabrication of Chemically Bonded Graphene/TiO2 Continuous Fibers with Enhanced Broadband Photocatalytic Properties and Involved Mechanisms Exploration.

In this article, a novel route for the synthesis of graphene/TiO2 continuous fibers (GTF) using force-spinning combined with water vapor annealing method is reported for the first time. The morphology, structure and optical properties of the composite were fully characterized. With a single step of heat treatment process using steam at ambient conditions, we were able to initiate a series of chemical reactions, such as reduction of graphene oxide (GO), crystallization of TiO2, formation of C-Ti bond, and introduction of oxygen vacancies into TiO2. The incorporation of graphene in TiO2 fibers facilitated bandgap narrowing and improved photo-induced charge separation in the photocatalyst. As a result of synergistic effects, TiO2 fibers-2 wt% graphene (2%GTF) showed the highest photocatalytic activities in the degradation of X-3B under UV irradiation, superior to the benchmark photocatalyst P25. Under visible light irradiation, the same catalyst was about 4 times more efficient compared to pure TiO2 fibers (PTF). A detailed study of involved active species (in particular, ·, h+ and ·OH) unraveled the mechanism regarding photocatalysis.

EFFECT OF POLYVINYLPYRROLIDONE AND FABRICATION PARAMETERS ON ELECTROSPUN TITANIUM OXIDE NANOFIBRES’ DIAMETER

Electrospinning is the most versatile and cost effective technique to produce titanium oxide (TiO2) nanofibres. An ethanolic solution containing titanium tetraisopropoxide, polyvinylpyrrolidone and acetic acid was loaded in the syringe to produce TiO2 nanofibres. In the present work, a custom-made electrospinning system was developed to investigate the fabrication and solution effects to the diameter of electrospun TiO2 fibres. The fabrication parameters were applied voltage (kV), flow rate (ml/hr) and tip to collector distance (cm). In addition, the effect of varying the weightage of polymer carrier on electrospun TiO2 nanofibres was investigated. The surface morphology of the fibres was examined with scanning electron microscope (SEM) and further analysed with the aid of JMicroVision. The significance of the influencing parameters was observed from high to low order as PVP content > tip to collector distance > applied voltage > flow rate. In conclusion, the parameters of applied voltage (15 kV), flow rate (1 ml/hr), tip to collector distance (10 cm) and PVP content (6 wt. %) are able to produce uniform TiO2 nanofibres.

Mechanical Properties and Phase Transformations in Resistance Spot Welded Dissimilar Joints of AISI409M/AISI301 Steel

Objectives: This paper is about the mechanical characters of biaxial braided carbon fiber nanocomposites. Methods/Statistical Analysis: Hand layup technique is used for fabrication of biaxial braided fiber nanocomposites. Seven samples have been prepared with Unfilled, TiO2 (1, 3 & 5wt %) and Nanoclay (1, 3 & 5 wt %). The above nanoparticles were mixed in the epoxy resin using magnetic stirrer. Mechanical properties (tensile, flexural and impact) were carried out. Findings: The experimental outcomes showed that the mechanical characterization of unfilled biaxial braided fiber nanocomposite material was lower than the TiO2 (1, 3 & 5wt %) and nanoclay (1, 3 & 5 wt %) biaxial braided fiber nanocomposite materials. 3wt% TiO2 and 3wt% nanoclay composite materials showed better improvement in the mechanical characters. However, 3wt% nanoclay composite material showed very excellent improvement in the mechanical characters than 3wt% TiO2. This is due to nanoclay particles have higher strength and higher modulus than TiO2 particles. Application/Improvements: The developed biaxial braided fiber nanocomposite materials were used in the field of aeronautics, automotive and space recreation products because of their excellent properties, light weight, corrosion resistance, high energy absorption and excellent strength characteristics.

Enhanced visible-light responsive photocatalytic activity of N-doped TiO2 thoroughly mesoporous nanofibers

Improving the photocatalytic efficiency of TiO2 semiconductor is crucially important and highly desired for its practical applications. In the present work, aiming to broaden the photoresponse window and limit the photocatalyst aggregation, we reported the exploration of N-doped TiO2 thoroughly mesoporous nanofibers with high purity in morphology via a foaming-assisted electrospinning strategy. The foaming agents and urea were introduced in the raw materials to create the mesopores and incorporate the N dopants into the conventional solid TiO2 nanofibers, respectively, which could be accomplished simultaneously over one-step calcination process. The synergetic combination of N dopants and one-dimensional mesoporous nanostructure allow the TiO2 fibers to exhibit significantly enhanced visible-light photocatalytic activity toward the Rhodamine B and hydrogen evolution, as compared to those of N-doped solid and intrinsic thoroughly mesoporous counterparts, suggesting their promising applications in water purification and energy supply.

Synthesis of TiO2 and ZnO nano and submicrometric fibers by solution blow spinning

Nano and submicrometric fibers of TiO2 and ZnO were produced for the first time by solution blow spinning (SBS). High surface area, homogenous, crack free TiO2 and ZnO fibers were successfully spun, as confirmed by BET surface area, X ray diffraction (XRD), transmission electron (TEM) and scanning electron (SEM) microscopy studies. TiO2 and ZnO fibers presented mean diameters ranging from 300nm to 600nm and from 200nm to 550nm, respectively. SBS proved to be an efficient method of producing metal-oxide semiconductor nano and submicrometric fibers at high output rates when compared other fiber spinning techniques.

Shedding light on precursor and thermal treatment effects on the nanostructure of electrospun TiO2 fibers

Electrospinning technique was employed for the synthesis of different TiO2 samples, starting from titanium oxysulfate and titanium n-butoxide (TNBT) as precursors. The electrospun fibers, obtained after optimization of starting solutions, were either calcined in air at 450 °C or treated in 50 mbar of pure oxygen at 450 °C. The main goal was to obtain TiO2 fibers constituted by crystallites with size lower than 10 nm (size largely reported in literature for this kind of synthesis) in the anatase form. Before thermal treatment, the morphology of the fibers was characterized by Scanning Electron Microscopy (SEM); after thermal treatment TiO2 morphological and structural properties were determined by Transmission Electron Microscopy (TEM) as well as by high resolution (HR-) TEM and X-ray Diffraction (XRD).TiO2 prepared with TNBT precursor and treated in oxygen at 450 °C gave the best results in terms of crystalline phase (pure anatase) and particle size (about 5 nm). Moreover, HR-TEM analysis of the fibers obtained from TNBT before thermal treatment revealed that the precursor crystallization occurred already at room temperature during the electrospinning process, giving rise to nucleation germs for the subsequent growth of TiO2 crystallites during the thermal treatment. On the contrary, samples prepared by electrospray and by simple solvent evaporation at room temperature of the solution with the same TNBT precursor did not give the same promising results in terms of crystalline phase and particle size.

The role of ruthenium photosensitizers in the degradation of phenazopyridine with TiO2 electrospun fibers

Abstract There has been increased interest in titanium dioxide (TiO2) fibers as a photocatalyst for the degradation of persistent organic and biopharmaceutical toxins in the environment. The photocatalytic efficiency of TiO2 fibers is typically limited to UV irradiation due to its semiconductor bandgap. TiO2 fibers have been prepared and adsorbed the visible photosensitizer cis-dichlorobis(2,2′-bipyridyl-4,4′-dicarboxylic acid)ruthenium (II) (Ru(dcbpyH2)2Cl2) on the surface in order to absorb from 300 to 800 nm in the visible spectrum and drive photocatalysis. This dye fiber material has been applied to the degradation of 2,6-pyridinediamine,3-(phenylazo) monohydrochloride or phenazopyridine (PAP) as a model biopharmaceutical waste. The Ru(dcbpyH2)2Cl2–sensitized fibers degrade PAP under UV and visible irradiation following a first order reaction rate. The rate constants for PAP degradation in visible light when using bare TiO2 fibers and dye-sensitized TiO2 fibers were 0.014 ± 0.001 min−1 and 0.012 ± 0.001 min−1 respectively, showing little change. Under UV irradiation, the rate decreased from 0.032 ± 0.003 min−1 and 0.012 ± 0.002 min−1. These results suggest that the major pathway for the degradation of PAP may occur through the valence band.

Ultrafast charge separation dynamics in opaque, operational dye-sensitized solar cells revealed by femtosecond diffuse reflectance spectroscopy.

Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and –690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded.

Producing Nano-Porous TiO<sub>2</sub> Fibers by Electrospinning with Phase Separation

TiO2 photocatalyst plays an important role in the degradation of sewage and cleaning the air. nanoporous TiO2 fibers have excellent photocatalytic properties due to their high porosity and specific surface area. Based on DMF and alcohol as solvent, nanoporous TiO2 fibers were produced by electrospinning with phase separation. The spinning dope advance rate, DMF/alcohol ratio and calcination temperature were investigated on the influence of micro-structure, porous structure, phase composition and photocatalytic performance of the nanoporous TiO2 fibers. It showed that nanoporous anatase TiO2 fibers had surface pores at 20nm by 550°C calcination. And when the proportion of DMF and alcohol was 1:3, the BET Surface Area of nanoporous TiO2 fibers was 40.75m2/g. They get photocatalytic degradation rate of 85.2% to 20mg·L-1 methyl orange solution after 35 min.

Extrusion-based Integrative Chemistry: Generation and applications of inorganic fibers

Abstract In this review we depict how fibers can be obtained by combining sol-gel and polymer chemistry with extrusion processes acting as an external shaping mode. Thanks to this Integrative Chemistry-based synthetic path, it was possible to organize nano-building blocks such as V2O5 ribbons and ZnO nanorods on a greater length scale yielding highly anisotropic fibers. It has been demonstrated that when aligning a whole population of nano-building block objects along a single main axis, collective properties were obtained, thereby enhancing their sensing, mechanical or photonic properties. This method can be extended toward fiber morphogenesis by using isotropic nanoparticles such as TiO2, and can be scaled-up toward the one-step generation of several hundred meter long fibers with both high surface to volume ratio and high surface roughness. Specifically, when addressing photocatalytic-based VOC pollutant degradation, these TiO2 fibers appear to be outstanding candidates regarding both pollutant degradation and associated mineralization (production of water and carbon dioxide).

Investigation of photocatalytic performance of TiO2 network and fiber geometries

In typical photocatalytic processes slurry reactors are used in which catalyst particles have to be separated from the solution after the process ends which means much higher time and costs. Hence, immobilizing process is carried out on the catalyst to overcome this problem. In this work, fiber and network geometries were produced by particle precipitation on substrates. The obtained structures were characterized by XRD, SEM, and Brunauer–Emmett–Teller analyses. Photocatalytic performance of the samples was investigated by methyl orange degradation and also by hydrogen generation from water/methanol splitting. From the SEM images, the size range of the TiO2 particles in the network geometries were 20–60 nm. The nanoparticles had covered the surface of the substrate uniformly. Removal of the cellulose substrate by heat treatment yielded hollow TiO2 fibers with diameters of 0.5–1μm and lengths of 30 μm. The rate constant of the dye degradation reaction using powder catalyst was 0.0118 min−1. However, the rate constants for fiber and network geometries were 0.0057 and 0.0083 min−1 respectively. The amount of hydrogen generated from different catalysts was determined to be in the following order: powdery > network > fiber.

Photocatalytic activity of TiO2 polycrystalline sub-micron fibers with variable rutile fraction

TiO2 polycrystalline sub-micron fibers can be used as photocatalysts for the degradation of a variety of organic molecules. Here we report on the optimization of these fibers for decontaminating pharmaceutical agents in aqueous medical waste streams. Mixed-phase TiO2 fibers have been prepared via a sol–gel technique followed by electrospinning and calcination. By adjusting the calcination temperature, the rutile phase fraction in TiO2 fibers can be tuned relative to the anatase phase from 0% to 100%. The effect of rutile phase fraction on grain size and specific surface area as well as their subsequent influences on the photocatalytic activity was investigated. An optimal grain size in post-calcined TiO2 fibers was found to be critical to balance the e−/h+ volume recombination, surface recombination rate, and charge diffusion rate. The photocatalytic activities of the post-calcined TiO2 fibers with different rutile fractions were measured by monitoring the decreasing concentration of phenazopyridine in aqueous solution under UV illumination using UV–vis absorption spectroscopy. Post-calcined TiO2 fibers composing of 38wt% rutile and 62wt% anatase exhibited the highest initial degradation rate constant of 0.044min−1. This optimal photocatalytic activity can be attributed to the combined influences of the fibers' phase composition, surface area and grain size.

A transparent TiO2–C@TiO2–graphene free-standing film with enhanced visible light photocatalysis

A transparent TiO2–C@TiO2–graphene free-standing film with graphene wrapped flower-like TiO2 particles on C–TiO2 fibers is synthesized for visible light photocatalysis.