Synthesis of Ag-Loaded TiO<Subscript>2</Subscript> Electrospun Nanofibers for Photocatalytic Decolorization of Methylene Blue

Titanium dioxide (TiO₂) is one of the excellent photocatalysts used for degradation of environmetal pollutants. In this work, 2.5, 5.0 and 7.5 wt.% of silver (Ag)-loaded TiO₂ nanofibers of mean size 52–134 nm were synthesized by electrospinning method. These electrospun nanofibers were calcined at 500 °C to enable the transformation of Rutile (R) phase to Anatase (A), elimination of reaction moieties from the TiO₂ matrix and subsequently formation of Ag clusters. The effect of Ag loading on the morphology, crystal structure, phase transformation, and band gap of these electrospun nanofibers have been characterized by scannining electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), raman spectroscopy and UV-visible spectroscopy. These nanofibers exhibited a red-shift in the absorbance edge and a significant enhancement of light absorption in the wavelength range of 250–550 nm. These electrospun nanofibers were investigated for photodecomposition of methylene blue (MB), and photocatalytic decolorization rates were determined by pseudo-first-order equation. The rate constants for the pure and those of 2.5, 5.0, and 7.5 wt% Agloaded TiO₂ nanofibers were computed to be 0.1439 min^-1, 0.1608 min^-1, 0.1876 min^-1, and 0.2251 min^-1 respectively.     

Polyaniline-doped TiO<Subscript>2</Subscript>/PLLA fibers with enhanced visible-light photocatalytic degradation performance

A simple and practical strategy has been developed for preparing polyaniline(PANi)-doped TiO₂/poly(l-lactide) (P@TiP-C) fibers by a combination of coaxial-electrospinning and in-situ polymerization. The TiO₂/PLLA composite fibers with TiO₂ located on the surface were fabricated by coaxial-electrospinning, with PLLA as the core phase and a dispersion of TiO₂ particles, a well-known photocatalyst, in the sheath phase. The aniline monomers were also located in the core phase and in-situ polymerized by ammonium persulfate (APS) after electrospinning. SEM images show that TiO₂ particles were located on the surface of PLLA fibers. Photocatalytic degradation tests show that the P@TiP-C fibers exhibit enhanced photocatalytic activity for degradation of methyl orange under visible light, likely due to the synergistic effect of PANi and TiO₂.     

Multifunctional modification of wool fabric using graphene/TiO<Subscript>2</Subscript> nanocomposite

In this study, a new finishing technique is introduced through treatment of wool fabric with graphene/TiO₂ nanocomposite. Graphene oxide/titanium dioxide nanocomposite first applied on the wool fabric by hydrolysis of titanium isopropoxide in graphene oxide suspension and then this coating chemically converted by sodium hydrosulfite to graphene/TiO₂ nanocomposite. The homogenous distribution of the graphene/TiO₂ nanocomposite on the fiber surface was confirmed by field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray mapping. X-ray diffraction patterns proved the presence of titanium dioxide nanoparticles with a crystal size of 127 Å on the treated wool fabric. Also, the defect analysis based on X-ray photoelectron spectroscopy (XPS) established the composition of the nanocomposite. Other characteristics of treated fabrics such as antibacterial activity, photo-catalytic self-cleaning, electrical resistivity, ultraviolet (UV) blocking activity and cytotoxicity were also assessed. The treated wool fabrics possess significant antibacterial activity and photo-catalytic self-cleaning property by degradation of methylene blue under sunlight irradiation. Moreover, this process has no negative effect on cytotoxicity of the treated fabric even reduces electrical resistivity and improves UV blocking activity.     

Electrospun in-situ hybrid polyurethane/nano-TiO<Subscript>2</Subscript> as wound dressings

By combining the organic-inorganic hybridization, wet phase inversion, and electrospinning, novel electrospun polyurethane (PU) membranes with in-situ generated nano-TiO₂ were prepared, which satisfied the requirements of an ideal wound dressing. The morphology of the PU-TiO₂ mats and the cross sectional morphologies of the membranes were characterized by a scanning electron microscopy (SEM). The average diameter of the individual fibers obtained from the solutions was 341±12 nm. SEM micrographs with higher magnification further showed that the in-situ generated TiO₂ particles were well-separated and dispersed homogeneously in the membranes. The average sizes of TiO₂ particles were increased from 31 to 57 nm, with the increase of nano-TiO₂ concentration. The water vapor transmission rates (WVTRs) of the membranes were in the range of 373.55–3121.86 g/m²·d and decreased gradually with the increase of nano-TiO₂ concentration. The water absorption of various PU membranes was in the range of 210.90–397.98 % which was enough to prevent wound beds from exudate accumulation. Shake flask testing indicated that the PU membrane exhibited antibacterial efficiency against Pseudomonas aeruginosa (Ps. aeruginosa) and Staphylococcus aureus (S. aureus) due to in-situ generated of nano-TiO₂. These electrospun nanofibrous membranes also had no toxic effect and showed good and immediate adherence to L929 cells.     

Coloration and Decoloration of Textiles Using a TiO<Subscript>2</Subscript> Composite Pigment

A colorable pigment was prepared by dye adsorption onto titanium dioxide and subsequent silane coating. The effects of pH value, dye concentration, and adsorption times on dye adsorption were discussed. Large adsorption capacity of an anionic dye was obtained at pH value of 2 and the adsorption process was well described by the Langmuir isotherm model. Good dyeability and color fastness of pigment dyed fabric were achieved in the normal life cycle under sunlight. The decoloration of pigment was realized through photocatalytic degradation of dye molecules by titanium dioxide under ultraviolet irradiation when reusing the pigment dyed textiles after disposal. The new absorption peaks in the FTIR spectrum at 2924.95 cm^-1, 1714.91 cm^-1, 1461.17 cm^-1, and 1289 cm^-1 verified silane modification. Silane modification improved fixation of dyes onto the pigment and immobilization of pigments onto substrates. The close attachment of silane coating layer to titanium dioxide was conducive to photodegradation of dye molecules in the pigment.     

Fabrication and characterization of nano Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filled PVA:NH<Subscript>4</Subscript>SCN electrolyte nanofibers by electrospinning

Present paper reports a method of preparing polymer composite electrolyte nanofiber mat using polyvinyl alcohol (PVA), ammonium thiocynate (NH₄SCN) salt, and aluminium oxide (Al₂O₃) nano particles based on electrospinning technique. Two-stage process of preparation of nanofibers, namely, preparation of nano particles filled PVA electrolyte gel solution followed by its electrospinning has been used. The so obtained nanofibers have been characterized by XRD, DSC, SEM, and Conductivity measurements. XRD patterns affirm the formation of nanocomposite while SEM pictures reveal formation of fibers on a nano scale format (300–800 nm). Fibers of the electrolytes are seen to be thermally stable. Ionic conductivity of electrolyte fiber is seen to improve in the presence of nano filler at room temperature with a maximum at 5.31×10⁻³ Scm⁻¹ for 4 wt% filler concentration, which is comparable to that for corresponding dried gel electrolyte films.     

Electrospun titanium dioxide nanofibers: Fabrication,properties and its application in photo-oxidative degradation of methyl orange (MO)

In this study, we synthesed two kind of TiO₂ nanomaterial (nanoparticles and nanofiber) for photocatalitic degradation of methyl orange (MO) as pollutant. TiO₂ nanoparticles were synthesized by sol-gel technique using titanium (IV) isopropoxide as precursor. Polyvinyl acetate (PVAc)/TiO₂ hybrid nanofibers were fabricated by combining sol-gel process with electrospinning technology, which consisted of PVAc as organic segment and TiO₂ as inorganic part. Crystalline phase of TiO₂ nanomaterials was investigated by X-ray diffraction (XRD). The XRD results show that the TiO₂ nanomaterials crystallize in anatase with some rutile phase and these consist of titanium dioxide nano-crystals. The surface structures of TiO₂ nanomaterials were examined using scanning electron microscopy (SEM). SEM scanning revealed that the nanoparticle and nanofibrous structure was formed. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the chemical structures of the PVAc/TiO₂ hybrid nanofibers. The FTIR analysis indicated the newly formed associated hydrogen bond because of the hybrid effect between PVAc and TiO₂ sol. Finally, The photooxidative decomposition of methylene blue by using the titania nanomaterials was examined and compared.     

Effect of UV irradiation on cellulase degradation of cellulose acetate containing TiO<Subscript>2</Subscript>

Cellulose acetate (CA) films containing anatase type titanium dioxide (TiO₂) nanoparticles were prepared by solution casting. The film surface was modified by UV irradiation using a grid type UV irradiator. The UV irradiation caused slight increase in photodegradation of the CA films with TiO₂ compared to the CA film alone. However, CA films irrespective of TiO₂ content did not show a significant enzymatic degradation by a cellulase fromAspergillus niger without UV irradiation. Upon UV irradiation, the biodegradability remarkably improved even in the CA film without TiO₂. The irradiation of CA films decreased both the water contact angle and the degree of substitution (DS) implying the decrease in acetyl groups of the CA film surface due to the photo-scission of the acetyl group and photooxidation, resulting in more facile biodegradation of the surface film layer. The substantial enhancement in biodegradation of the UV irradiated CA film containing TiO₂ was attributed to the increased hydrophilicity, lowered DS and zeta potential due to the photoscission and the photooxidation effect of UV light. Also the increased surface area of the CA film due to the photocatalysis of TiO₂ particles may encourage the facile biodegradation.     

Nano-TiO<Subscript>2</Subscript> based multilayer film deposition on cotton fabrics for UV-protection

Nano-TiO₂ based multilayer nanocomposite films were fabricated on cationically modified woven cotton fabrics by layer-by-layer molecular self-assembly technique. Cationization process was used to obtain cationic surface charge on cotton fabrics. Attenuated total reflectance Fourier transform infrared spectroscopy analyses were used to verify the presence of cationic surface charge and multilayer films deposited on the fabrics. Scanning electron microscope micrographs of poly(sodium 4-styrene sulfonate)/TiO₂, nano polyurethane/TiO₂, and TiO₂/poly(diallyldimethylammonium chloride) multilayer films deposited on cotton fabrics were taken. With nano-TiO₂ based multilayer film deposition, the protection of cotton fabrics against UV radiation is enhanced. The UV protection durability of the self-assembled multilayer films deposited on the cotton fabrics was analyzed after 10 and 20 washing cycles at 40 °C for 30 min. Air permeability and whiteness value analysis were performed on the untreated and multilayer film deposited cotton fabrics. The effect of layer-by-layer deposition process on tensile strength properties of the warp and weft yarns was determined.     

Preparation and UV-protective property of PVAc/ZnO and PVAc/TiO<Subscript>2</Subscript> microcapsules/poly(lactic acid) nanocomposites

The poly(vinyl acetate) (PVAc)/zinc oxide (ZnO) microcapsule and PVAc/titanium dioxide (TiO₂) microcapsule were synthesized via in-situ emulsion polymerization method. The PVAc/ZnO microcapsule and PVAc/TiO₂ microcapsule were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis(TG), transmission electron microscopy (TEM), and UV-visible spectroscopy (UV-vis). Effect of PVAc/ZnO microcapsule and PVAc/TiO₂ microcapsule on properties of poly(lactic acid) (PLA) was evaluated by UV-vis, SEM and mechanical properties test. The results showed that the addition of PVAc/ZnO and PVAc/TiO₂ microcapsules as a UV-blocking additive could significantly enhance UV-blocking property of PLA/PVAc/ZnO microcapsule composites and PLA/PVAc/TiO₂ microcapsule composites compared with pure PLA, PLA/ZnO composites and PLA/TiO₂ composites. The mechanical properties of PLA/PVAc/ZnO microcapsule composites were better than those of PLA/ZnO composites due to good dispersability and compatibility of PVAc/ZnO microcapsule in PLA matrix. Also, the mechanical properties of PLA/PVAc/TiO₂ microcapsule composites were better than those of pure PLA and PLA/TiO₂ composites. This study demonstrates the great potentials of the intrinsically UV shield additive PVAc/ZnO and PVAc/TiO₂ microcapsules in the application of high performance matrix resin and composite material.     

Load of Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript> Particles on Sulfonated Polyphenylene Sulfide Superfine Fibre with High Visible-light Photocatalytic Activity

Ag₃PO₄ was loaded on sulfonated polyphenylene sulfide (SPPS) superfine fibre by a facile precipitation method. Both the structure and properties of the as-synthesized Ag₃PO₄/SPPS composites were characterized via XRD, SEM, EDS, XPS, FTIR, and UV-vis. The photocatalytic performance of Ag₃PO₄/SPPS composites was investigated via degradation of Methylene blue(MB) solution under visible light irradiation. The degradation results revealed that the photocatalytic activity of Ag₃PO₄/SPPS composites was greatly enhanced by the incorporation of Ag₃PO₄ with SPPS superfine fibre. For concentrations of AgNO₃ and Na₂HPO₄ solutions of 0.3 M and 0.06 M in the preparation process, the Ag₃PO₄/SPPS composite showed higher photocatalytic activity under visible light irradiation.     

Spherical Bacterial Cellulose/TiO<Subscript>2</Subscript> Nanocomposite with Potential Application in Contaminants Removal from Wastewater by Photocatalysis

Contaminants are often found in aquatic environments, for instance, heavy metals, dyes, parasites, pesticides, hormones and pharmaceuticals. Therefore, large amounts of these contaminants reaches wastewater via industrial and domestic effluents, causing major concern to human health. Heterogeneous photocatalysis is a technique for removing these contaminants in order to achieve better efficiency in water treatment. Then, bacterial cellulose (BC) produced in an agitated culture can form spherical bodies composed of nanofibers with high specific surface area. Moreover, Titanium dioxide (TiO₂) is a semiconductor containing high photocatalytic activity capacity. Thus, the main objective in this work was to produce spherical BC/TiO₂ nanocomposites for contaminants removal from wastewater by photocatalysis process. The incorporation of TiO₂ nanoparticles in the spherical BC matrix was performed by ex situ and in situ methods. In addition, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used as tools of morphological, chemical and thermal characterizations of the nanocomposites. Besides, photocatalysis tests were performed in order to evaluate the removal efficiency of methylene blue from aqueous solutions. The results of these tests exhibited a percentage of methylene blue removal of 70.83 and 89.58 % after 35 minutes for spherical BC/TiO₂ nanocomposites both, in situ and ex situ, respectively. Therefore, these results demonstrated that BC/TiO₂ to be a low cost material with high capacity of contaminants removing and a great potential for industrial applications.     

Preparation of TiO<Subscript>2</Subscript>-coated ZnO Nanoparticles and Their Effect on the UV Absorption of a Poly(vinyl alcohol) Composite Film

Titanium oxide (TiO₂) and zinc oxide (ZnO) composite structured nanoparticles were prepared by combining a sol-gel process and a solvothermal method. Titanium (IV) isoproxide (TTIP), used as a TiO₂ precursor, was dissolved in a colloidal ZnO nanoparticle solution synthesized by the sol-gel method, and TiO₂ was synthesized via solvothermal synthesis onto the ZnO nanoparticles. The effects of reaction conditions such as pH, reaction temperature, and reaction time on the morphology of the composite nanoparticles and the ultraviolet (UV) absorbance of their polymer composite films were investigated. The UV absorption of the poly(vinyl alcohol) (PVA) composite film with TiO₂-coated ZnO nanoparticles was higher than that of the TiO₂, ZnO, and ZnO-coated TiO₂ composite films. The reaction pH was found to have the strongest influence on the UV absorbance of the PVA/(TiO₂/ZnO) composite film. A pH of 7.0, reaction temperature of 250 °C, and reaction time of 24 h were the optimum conditions for UV absorption.     

In situ loading TiO<Subscript>2</Subscript> and its photocatalysis and UV resistance on cotton fabric

Anatase TiO₂ nanoparticles was in-situ formed on the cotton fabric by using tetrabutyl titanate (TBT) as a precursor through the normal pressure hydrothermal method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV visible spectra (UV-VIS), ATR-IR were used as the characterization techniques. Photocatalytic performance of TiO₂ on the fabric surface was evaluated by methylene blue (MB), 4 kinds of the common living stains and three dyes under ultraviolet and visible light radiation. XRD analysis found that the TiO₂ loaded on the fabric was mainly anatase crystalline phase with particle size of 6.4 nm. SEM observed that a large number of nano TiO₂ particles are distributed on the fabric surface. UV-VIS test indicated that theTiO₂-coated fabric possessed an obvious absorption for ultraviolet. ATR-IR analysis indicated that the nano-TiO₂ possesses a strong affinity with the hydroxyl group of the cotton fabric, and the soaping tests showed that the TiO₂ was firmly bonded with the fabrics. The treated fabrics have good degradation ability for MB aqueous solution, and could degrade azo, anthraquinone and phthalocyanine dyes. The order of degradation of the common life stains was: pepper oil> tea > coffee > soy sauce.     

Electrospun poly(tetrafluoroethylene) nanofiber membranes from PTFE-PVA-BA-H<Subscript>2</Subscript>O gel-spinning solutions

As a kind of high-performance fibers, PTFE fiber has been widely used in many fields because of its unique characteristics. In this study, the poly(tetrafloroethylene) (PTFE) nanofibers manufactured by electrospinning method was reported. The gel-spinning solution of poly(tetrafluoroethylene)/poly(vinyl alcohol)/boric acid (PTFE/PVA/BA), which was prepared by the gel process of the mixture of PTFE, PVA, BA and redistilled water, was electrospun to form PTFE/PVA/BA composite nanofibers. After calcinating, the PTFE nanofibers with diameters of 200 nm to 1000 nm were obtained. The fibers before and after calcinating were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), FT-IR spectrum analysis and X-ray photoelectron spectroscopy (XPS), respectively, and the mechanical and hydrophobic properties of the fibers were also investigated. The results showed that the PTFE nanofiber membranes could be electrospun effectively used the gel-spinning solution of PTFE/PVA/BA, and may realize the applications in the fields of high-temperature filtration, catalyst supports, battery separator and so on.     

Effects of silver content and morphology on the catalytic activity of silver-grafted titanium oxide nanostructure

As titanium oxide is a well-known photocatalyst, we investigated the effects of silver content and nanostructural morphology on the photocatalytic degradation of two dyes, methylene blue and rhodamine B. Two nano-formulations were utilized, including nanofibers and nanoparticles. Silver-grafted titanium oxide nanofibers were synthesized using the electrospinning of silver nitrate/titanium isopropoxide/poly(vinyl acetate) sol-gel. The nanoparticulate form was obtained by calcination of a ground powder prepared from the same electrospun sol-gel. The results affirmed the advantage of the silver-grafted titanium oxide nanostructures over the silver-free ones. Increasing the silver content in the nanofibers led to increases in their surface area, which is an important parameter in heterogeneous catalytic chemical reactions. Therefore, the results strongly suggest the use of silver-grafted titanium oxide in a nanofibrous form. These results further support utilizing Agloaded titanium oxide nanofibers as a photocatalyst.     

Preparation and characterization of inner-pressure hollow fiber composite membrane via two-way coating technique for CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> separation

High-selectivity inner-pressure hollow fiber composite (HFC) membrane for CO₂/CH₄ separation was prepared through the Two-way coating (TWC) technique. The blends of poly(vinylamine) (PVAm)/polyvinyl alcohol (PVA) were coated onto porous hollow fiber polysulfone (PSF) ultrafiltration (UF) membrane with an effective membrane area of 0.4 m². The effects of fabrication parameters on the permselectivity of the resultant HFC membrane were investigated and the optimum preparation conditions were obtained as follows: coating time for 30 min and air blowing time for 30 min after the coating. The prepared HFC membrane showed the typical characteristic of fixed carrier membrane with a high selectivity of CO₂ and CH₄: the separation factor of CO₂/CH₄ (40 vol% CO₂ at 25 °C and 0.2 MPa) was 36.6 and the CO₂ permeability was 56.3 GPU. Field emission scanning electron microscopy (FESEM) images indicated that the HFC membrane prepared by TWC technique had a uniform coating layer along the whole hollow fiber. Membrane permselectivity showed almost no difference between different membrane sections. The HFC membrane showed a good stability during the continuous testing process of 540 h. And the HFC membrane preserved at 30 °C and 40 % humidity exhibited a good durability with a basically unchanged separation factor after 30 days.     

Hard Surface-adhesive Properties of TiO<Subscript>2</Subscript> Nanoparticles-encapsulated Microparticles Prepared by Spray Drying and Surface Coating Method

The aim of this study is to compare hard surface-adhesive properties of TiO₂ nanoparticles (TNPs)-encapsulated microparticles prepared by spray drying and surface coating method. Thus, TNPs were encapsulated with chitosan by spray drying and poly(L-lysine) by surface coating method, which were selected as positively charged materials. And then, the TNPs-encapsulated microparticles were investigated by particle surface properties and adhesion properties on hydroxyapatite (HAP) surface as model for hard surface-adhesion. The characteristics of TNPs-encapsulated Chitosan microcapsules (CM) and TiO₂ nanoparticles coated with cationic poly(L-lysine) polymer (TNPs-PLL) were determined with scanning electron microscope (SEM) image and zeta-potentials. The hard surface-adhesive properties on HAP surface were confirmed with SEM and whitening test. The zeta-potentials of TNPs and HAP were negative, -13 mV and -18 mV respectively, while TNPsencapsulated CM, and TNPs-PLL of positively charged polymers were positive, 13 mV and 57 mV respectively. Whitening test was carried out on model surface when shaking the samples. TNPs-PLL were adhered to HAP surface very much more than those of TNPs-encapsulated CM. Also, the change value of whiteness of the HAP surface treated with TNPs-PLL is large evidently, compared with TNPs-encapsulated CM.     

Rapid fabrication and optimization of silk fibers supported and stabilized MnO<Subscript>2</Subscript> catalysts

We report on the in situ synthesis and stabilization of manganese dioxide (MnO₂) onto four different silk yarns (mulberry, tasar, muga and eri silks). A new ultrasound-assisted procedure was used to reduce permanganate (MnO₄ ^?) and yielded MnO₂ nanoparticles (NPs) on/in the different silk fibers. Using a factorial design we assessed the influence of the silk type, manganese precursor concentration, sonication time, and temperature. The results indicated no measurable effect of the process parameters on the silk structures, but significant correlation with the rate of degradation of methylene blue (MB) and the fraction of permanganate consumed. Further optimization of the factorial model identified the optimal process conditions for each silks: mulberry (150 min sonication, 20 mM permanganate), eri (360 min, 10 mM), tasar (150 min, 10 mM) and Muga (20 min, 10 mM). The operational stability (successive catalysis) of the optimum hybrids showed good performance over 5 cycles and most importantly reduced direct dye absorption relatively to dye oxidation. Overall, we found that all silks could template the formation and stabilization of different MnO₂ polymorphs and yielded catalytic instead of stoichiometric hybrid fibers.     

Experimental study on dyeing technical PET yarns having different TiO<Subscript>2</Subscript> contents

TiO₂ contents in yarns can influence color yield so that dyeing quality of industrial poly ethylene terephthalate (PET) yarns can be improved through the adjustment of TiO₂ contents. To evaluate the dyeing performance of color yield, the chips which included the different TiO₂ contents of 330, 550, and 1,100 ppm respectively were used to produce the yarns of different TiO₂ content by a spin-draft machine. The physical and structural properties of the yarns were measured to investigate effect of the TiO₂ contents on them. Dye uptake and dyeing rate were also evaluated using a colorimeter to compare the yarns having different TiO₂ contents. The experimental results showed that there were no appreciable variation in physical and structural properties among the yarn samples and no difference were observed among the dyed fabric samples with regard to dyeing uptake and dyeing rate. However, the color yield of dyed fabrics increased as TiO₂ contents decreased in the yarns especially when the fabric samples were dyed to pale shade. The physical reasoning could be proposed on why the yarns having low TiO₂ contents appeared to have higher color yield after dyeing.