Experimental and statistical analysis of dielectric barrier discharge plasma effect on sonochemically TiO2 coated cotton fabric using complete composite design

A single step ultrasonic biosynthesis method was used to synthesize and coat TiO₂ nanoparticles onto DBD plasma functionalized raw cotton. Titanium isopropoxide was reduced with aloe vera plant extract into TiO₂ nanoparticles. The effect of DBD plasma treatment on self-cleaning property of TiO₂ coated fabric was optimized statistically by using a complete composite design. To induce functional groups on the cotton fabric surface, the fabric was pre-treated with DBD plasma over various periods of time. The plasma exposure time, molarity of solution and ultrasonication time were optimized using complete composite design package. TiO₂ nanoparticles revealed spherical shape and anatase phase with average crystallite size of 10.46 nm. The statistically optimized plasma exposure time, molarity and sonication time was 7 min, 0.80 and 75 min, respectively. The plasma activation of fabric significantly improved the adsorption, tensile strength and self-cleaning ability of TiO₂ coated fabric.     

Ultrasound with low intensity assisted the synthesis of nanocrystalline TiO2 without calcination

A novel method has been developed for the preparation of nano-sized TiO₂ with anatase phase. Nanoparticles with diameter about 6 nm were prepared at a relatively low temperature (75 °C) and short time. The synthesis was carried out by the hydrolysis of titanium tetra-isopropoxide (TTIP) in the presence of water, ethanol, and dispersant under ultrasonic irradiation (500 kHz) at low intensity. The results show that variables such as water/ethanol ratio, irradiation time, and temperature have a great influence on the particle size and crystalline phases of TiO₂ nanoparticles. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV–vis spectroscopy.     

Combined ultrasonic and gamma-irradiation to prepare TiO2@PET-g-PAAc fabric composite for self-cleaning application

The grafting of polyacrylic acid (PAAc) onto the fabric of Poly(ethyleneterephthalate) (PET) was loaded with TiO₂ by a mixture sonication of TiO₂ dispersed in AAc dissolved in acetone solvent. Ultrasonic irradiation was utilized as a tool for a good dispersion of TiO₂ onto the PET fabric. The grafted PET fabrics with acrylic acid AAc monomer were successfully obtained using gamma-ray induced graft polymerization, the degree of grafting PET-g-PAAc fiber was 105%. The chemical compositions and crystal structure of grafted TiO₂@PET-g-PAAc fabrics were characterized by ATR-FTIR and XRD. It was found that loading of PET fiber with in TiO₂ particles showing the formation of anatase and rutile as performed by XRD. The thermal property of TiO₂@PET-g-PAAc was investigated by differential thermal analysis (DTA). The obtained result indicated the thermal property of the grafted TiO₂@PET-g-PAAc was increased. Image of scanning electron microscope (SEM) indicated the good adherent and good distribution of PAAc and TiO₂ with PET fabric. The self-cleaning property of TiO₂@PET-g-PAAc has been evaluated by using three kinds of dyes as models.     

A robust super-paramagnetic TiO2:Fe3O4:Ag nanocomposite with enhanced photo and bio activities on polyester fabric via one step sonosynthesis

High intensity ultrasound was used for the synthesis and simultaneous deposition of TiO₂:Fe₃O₄:Ag nanocomposites on polyester surface providing a feasible route for imparting magnetic and enhanced antibacterial and self-cleaning activities with controllable hydrophilicity/hydrophobicity at low temperature. Synergistic impact of sonochemistry and physical effects of ultrasound originating from implosive collapse of bubbles were responsible for the formation and adsorption of nanomaterials on the fabric surface during ultrasound irradiation. The increase in photocatalytic activity of TiO₂ was obtained attributing to the co-operation of iron oxide and silver nanoparticles nucleated on TiO₂ surface boosting the electron–hole pair separation and prolonging their recombination rate. The process was further optimized in terms of reagents concentrations including Fe²⁺/TiO₂ and Ag/TiO₂ molar ratios using central composite design in order to achieve the best self-cleaning property of the treated fabric. The magnetic measurements indicated the super-paramagnetic behavior of the treated fabric with saturation magnetization of 4.5 (emu/g). Findings suggest the potential of the proposed facial method in producing an intelligent fabric with durable multi-functional activities that can be suitable for various applications including medical, military, bio-separation, bio-sensors, magneto graphic printing, magnetic screens and magnetic filters.     

The super-hydrophobic IR-reflectivity TiO2 coated hollow glass microspheres synthesized by soft-chemistry method

The super-hydrophobic and IR-reflectivity hollow glass microspheres (HGM) was synthesized by being coated with anatase TiO₂ and a super-hydrophobic material. The super-hydrophobic self-cleaning property prolong the life time of the IR reflectivity. TBT and PFOTES were firstly applied and hydrolyzed on HGM and then underwent hydrothermal reaction to synthesis anatase TiO₂ film. For comparison, the PFOTES/TiO₂ mutual-coated HGM (MCHGM), PFOTES single-coated HGM (F-SCHGM) and TiO₂ single-coated HGM (Ti-SCHGM) were synthesized as well. The MCHGM had bigger contact angle (153°) but smaller sliding angle (16°) than F-SCHGM (contact angle: 141.2°; sliding angle: 67°). Ti-SCHGM and MCHGM both showed similar IR reflectivity with ca. 5.8% increase compared with original HGM and F-SCHGM. For the thermal conductivity, coefficients of F-SCHGM (0.0479 W/(m K)) was basically equal to that of the original HGM (0.0475 W/(m K)). Negligible difference was found between the thermal conductivity coefficients of MCHGM-coated HGM (0.0543 W/(m K)) and Ti-SCHGM (0.0546 W/(m K)).     

Ultrasound irradiation based in-situ synthesis of star-like Tragacanth gum/zinc oxide nanoparticles on cotton fabric

Application of natural biopolymers for green and safe synthesis of zinc oxide nanoparticles on the textiles is a novel and interesting approach. The present study offers the use of natural biopolymer, Tragacanth gum, as the reducing, stabilizing and binding agent for in-situ synthesis of zinc oxide nanoparticles on the cotton fabric. Ultrasonic irradiation leads to clean and easy synthesis of zinc oxide nanoparticles in short-time at low-temperature. FESEM/EDX, XRD, FT-IR spectroscopy, DSC, photocatalytic activities and antimicrobial assay are used to characterize Tragacanth gum/zinc oxide nanoparticles coated cotton fabric. The analysis confirmed synthesis of star-like zinc oxide nanoparticles with hexagonal wurtzite structure on the cotton fabric with the average particle size of 62 nm. The finished cotton fabric showed a good photocatalytic activity on degradation of methylene blue and 100% antimicrobial properties with inhibition zone of 3.3 ± 0.1, 3.1 ± 0.1 and 3.0 ± 0.1 mm against Staphylococcus aureus, Escherichia coli and Candida albicans.     

A comparative DFT study of adsorption and catalytic performance of Au nanoparticles at anatase and brookite TiO2 surfaces

We have compared the adsorption properties of small Au_n (n = 1–8) nanoparticles on the defect-free (stoichiometric) and defective (partially reduced) brookite TiO₂(210) and anatase TiO₂(101) surfaces using density functional theory calculations. The interaction between Au atoms and anatase TiO₂(101) was determined to be quite weak and small Au_n particles grown at defects (O vacancies) prefer extended 2D structures. By contrast, dispersion and 3D configurations appear to be favored at brookite TiO₂(210) for Au_n nanoparticles due to their strong interaction. Calculations of CO oxidation at Au_n (n = 6–8) particles supported at defective brookite TiO₂(210) show that occurrence of protruding low-coordinated Au atoms is essential for favorable CO adsorption and subsequent reaction with O₂. In particular, the configuration of the Au_n nanoparticles can determine the energetics in the formation of active Au atoms, and their mobility also affects the reaction between CO and O₂ (or O).     

The preparation and characterization of nanoparticle TiO2/Ti films and their photocatalytic activity

Nanoparticle TiO₂/Ti films were prepared by a sol–gel process using Ti(OBu)₄ as raw material, the as-prepared film samples were also characterized by TG-DTA, XRD, TEM, SEM, XPS, DRS, PL, SPS and EFISPS testing techniques. TiO₂ nanoparticles experienced two processes of phase transition, i.e. amorphous to anatase and anatase to rutile at the calcining temperature range from 450 to 700 °C. TiO₂ nanoparticles calcined at 600 °C had similar composition, structure, morphology and particle size with the internationally commercial P-25 TiO₂ particles. Thus, the conclusion that 600 °C might be the most appropriate calcining temperature during the preparation process of nanoparticle TiO₂/Ti film photocatalysts could be made by considering the main factors such as the properties of TiO₂ nanoparticles, the adhesion of nanoparticle TiO₂ film to Ti substrate, the effects of calcining temperature on Ti substrate and the surface characteristics and morphology of nanoparticle TiO₂/Ti film for the practice view. The Ti element mainly existed on the nanoparticle TiO₂/Ti(3) film calcined at 600 °C as the chemical state of Ti⁴⁺, while O element mainly existed as three kinds of chemical states, i.e. crystal lattice oxygen, hydroxyl oxygen and adsorbed oxygen with increasing band energy. Its photoluminescence (PL) spectra with a peak at about 380 nm could be observed using 260 nm excitation, possibly resulting from the electron transition from the bottom of conduction band to the top of valence band. The PL peak position was nearly the same as the onset of its diffuse reflection spectra (DRS) and surface photovoltage spectroscopy (SPS), demonstrating that the effects of the quantum size on optical property were greater than that of the Coulomb and surface polarization. The PL spectra with two peaks related to the anatase and rutile, respectively, could be observed using the excited wavelength of 310 nm. Weak PL spectra could be observed using the excited wavelength of 450 nm, resulting from surface states. In addition, during the experimental process of the photocatalytic degradation phenol, the photocatalytic activity of nanoparticle TiO₂/Ti film with three layers calcined at 600 °C was the highest.     

Sonosynthesis of nano TiO2 on wool using titanium isopropoxide or butoxide in acidic media producing multifunctional fabric

This study presents a novel idea to prepare nanocrystalline structure of TiO₂ under ambient pressure at 60–65 °C using in situ sonochemical synthesis by hydrolysis of either titanium isopropoxide or titanium butoxide in an acidic aqueous solution. The nano titanium dioxide coated wool fabrics possess significant antibacterial/antifungal activity and self-cleaning property by discoloring Methylene blue stain under sunlight irradiation. This process has no negative effect on cytotoxicity and tensile strength of the sonotreated fabric even reduces alkaline solubility and photoyellowing and improves hydrophilicity. More titanium isopropoxide or titanium butoxide as a precursor led to higher photocatalytic activities of the treated fabrics. Also introducing more ethanol improved the adsorption of TiO₂ on the wool fabric surface leading to enhanced photocatalytic activity. EDS and XRD patterns, SEM images, X-ray mapping confirmed the presence of nano TiO₂ particles on the fabric surface. The role of both solvent and precursor concentrations on the various properties of the fabric was investigated and the optimized conditions were obtained using response surface methodology.     

Preparation and photocatalytic activity of bicrystal phase TiO2 nanotubes containing TiO2-B and anatase

Bicrystal phase TiO₂ nanotubes (NTS) containing monoclinic TiO₂-B and anatase were prepared by the hydrothermal reaction of anatase nanoparticles with NaOH aqueous solution and a heat treatment. Their structure was characterized by XRD, TEM and Raman spectra. The results showed that the bicrystal phase TiO₂ NTS were formed after calcining H₂Ti₄O₉·H₂O NTS at 573 K. The bicrystal phase TiO₂ NTS exhibit significantly higher photocatalytic activity than the single phase anatase NTS and Dessuga P-25 nanoparticles in the degradation of Methyl Orange aqueous solution under ultraviolet light irradiation, which is attributed to the large surface and interface areas of the bicrystal phase TiO₂ NTS.     

Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation

In this research, Fe-doped TiO₂ nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10 wt%) were prepared by a sol–gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1 eV. Photocatalytic results indicated that TiO₂ had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO₂ nanoparticles. Among the samples, Fe-1 wt% doped TiO₂ nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.     

Simple one-step ultrasonic synthesis of anatase titania/polypyrrole nanocomposites

In this work, hybrid nanocomposites based on anatase titania:polypyrrole (TiO₂:PPy) were directly obtained from a simple, one-step, ultrasonic (UT)-assisted synthesis. The properties of these crystalline nanocomposites were compared with those of others fabricated using cold (Cold)-assisted synthesis without any UT assistance, which required a hydrothermal treatment (HT) to yield crystalline anatase titania in the nanocomposite (TiO₂:PPy) at low temperature (130 °C) and in a short time (3 h). The SEM results demonstrated that the UT-assisted synthesis is a feasible method to obtain anatase TiO₂:PPy nanocomposites with controlled morphology using low energy. The Fourier transform infrared (FT-IR) bands of the crystalline nanocomposites exhibited a shift with respect to neat components, which was attributed to the strong interaction between the secondary amine groups (N–H) of PPy and the oxygen from TiO₂. The acceptable absorption in the visible region (λ_max = 670 nm) indicates that these nanocomposites are good candidates for harvesting energy in solar cells. Devices based on these nanocomposites were built to evaluate their electrical properties. An increase in the photocurrent was observed for the devices prepared with the nanocomposites from the UT-assisted synthesis.     

TiO2 chemical vapor deposition on Si(111) in ultrahigh vacuum: Transition from interfacial phase to crystalline phase in the reaction limited regime

The interaction between the metal organic precursor molecule titanium(IV) isopropoxide (TTIP) and three different surfaces has been studied: Si(111)-(7 × 7), SiO_x/Si(111) and TiO₂. These surfaces represent the different surface compositions encountered during TTIP mediated TiO₂ chemical vapor deposition on Si(111). The surface chemistry of the titanium(IV) isopropoxide precursor and the film growth have been explored by core level photoelectron spectroscopy and x-ray absorption spectroscopy using synchrotron radiation. The resulting film morphology has been imaged with scanning tunneling microscopy. The growth rate depends on both surface temperature and surface composition. The behavior can be rationalized in terms of the surface stability of isopropoxy and isopropyl groups, confirming that growth at 573 K is a reaction limited process.     

Phase growth control in low temperature PLD Co: TiO2 films by pressure

This paper reports on the structural and optical properties of Co-doped TiO₂ thin films grown onto (0001)Al₂O₃ substrates by non-reactive pulsed laser deposition (PLD) using argon as buffer gas. It is shown that by keeping constant the substrate temperature at as low as 310 °C and varying only the background gas pressure between 7 Pa and 70 Pa, it is possible to grow either epitaxial rutile or pure anatase thin films, as well as films with a mixture of both polymorphs. The optical band gaps of the films are red shifted in comparison with the values usually reported for undoped TiO₂, which is consistent with n-type doping of the TiO₂ matrix. Such band gap red shift brings the absorption edge of the Co-doped TiO₂ films into the visible region, which might favour their photocatalytic activity. Furthermore, the band gap red shift depends on the films’ phase composition, increasing with the increase of the Urbach energy for increasing rutile content.     

Synthesis of nanocomposites of iron oxide/gold (Fe3O4/Au) loaded on activated carbon and their application in water treatment by using sonochemistry: Optimization study

This paper focuses on the finding best operational conditions using response surface methodology (RSM) for Rhodamine123 (R123) and Disulfine blue (DSB) dyes removal by ultrasound assisted adsorption onto Au-Fe₃O₄ nanoparticles loaded on activated carbon (Au-Fe₃O₄ NPs-AC). The influences of variables such as initial R123 (X₁) and DSB concentration (X₂), pH (X₃), adsorbent mass (X₄) and sonication time (X₅) on their removal were investigated by small central composite design (CCD) under response surface methodology. The significant variables and the possible interactions among variables were investigated and estimated accordingly. The best conditions were set as: 4 min, 4.0, 0.025 g, 13.5 and 26.5 mg L⁻¹ for sonication time, pH, adsorbent weight, initial R123 and DSB concentration, respectively. At above conditions, the adsorption equilibrium and kinetic follow the Langmuir isotherm and pseudo-second-order kinetic model, respectively. The maximum monolayer capacity (Q_max) of 71.46 and 76.38 mg g⁻¹ for R123 and DSB show sufficiency of model for well presentation of experimental data.     

Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination

Through an ultrasound assisted method, TiO₂/WO₃ nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO₂/WO₃ nanoparticles matches well with that of pure monoclinic WO₃ and rutile TiO₂ nanoparticles. TEM images show that the prepared TiO₂/WO₃ nanoparticles consist of mixed square and hexagonal shape particles about 8–12 nm in diameter. The photocatalytic activity of TiO₂/WO₃ nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO₂/WO₃ nanoparticles exhibits a higher degradation rate constant (6.72 × 10⁻⁴ s⁻¹) than bare TiO₂ nanoparticles (1.72 × 10⁻⁴ s⁻¹) under similar experimental conditions.     

Anatase TiO2 nanocrystals prepared by mechanochemical synthesis and their photochemical activity studied by EPR spectroscopy

Anatase TiO₂ has been prepared by mechanochemical synthesis using TiOSO₄·xH₂O and Na₂CO₃ as starting reactants. The reaction was performed in high-energy ball mill using steel and corundum jars, respectively. The final products were obtained by annealing the milled powder in the temperature range of 300–700 °C and subsequently by washing out the water-soluble byproduct Na₂SO₄·xH₂O. When steel jars were used, the annealing in the range of 300–600 °C led to anatase. For products milled in corundum, the stability of anatase increased up to 700 °C. Transition electron microscopy (TEM) showed that crystallites with a size in the range of 20–50 nm with equiaxed morphology were obtained after milling in corundum and annealing at 600 and 700 °C. The process of photoinduced reactive hydroxyl radical generation in aerated aqueous titania suspensions was studied by EPR spectroscopy using spin trapping technique. The presence of iron impurities in the samples milled in steel substantially decreases the radical formation. The rate of radical formation is substantially affected by particle size development of TiO₂ nanopowders. The product milled in corundum and annealed at 700 °C outperforms more than twice the photochemical activity of TiO₂ Degussa P25 standard.     

Ultrasonic synthesis and photocatalytic characterization of H3PW12O40/TiO2 (anatase)

A novel H₃PW₁₂O₄₀/TiO₂ (anatase) composite photocatalyst was prepared by a high-intensity ultrasonic method using a lower temperature (80 °C) and was characterized by XRD and FT-IR. Its photocatalytic activity, using solar light, was evaluated through the degradation of organic dye methylene blue (MB) in aqueous. When MB solution (50 mg/l, 200 ml) containing H₃PW₁₂O₄₀/TiO₂ (anatase) (0.4 g) was degraded by solar irradiation after 90 min, the removal of concentration and TOC of MB reached 95% and 73%, respectively. The photocatalyst activity of H₃PW₁₂O₄₀/TiO₂ (anatase) was much higher than TiO₂ which was prepared in the same way. H₃PW₁₂O₄₀/TiO₂ remained efficient after five repeated experiments.     

Nanocomposite fabric formation by electrospinning and electrospraying technologies

Electrospraying and electrospinning processes were employed for the production of nanocomposite material of polymer nanofibers blended with nanoparticles. The diameter of polymer nanofibers made of PVC, PSU or nylon was smaller than 500 nm. Metal oxide nanoparticles of TiO₂, MgO, and Al₂O₃ of the size 20–100 nm suspended in methanol were deposited on the polymer nanofibers. Three configurations of electrospray/electrospun nozzles used for the nanocomposite production were tested: 1. simultaneous electrospraying during the electrospinning process, 2. electrospraying onto the same rotating drum after the electrospinning is completed, and 3. electrospraying onto the electrospun mat removed from the drum and placed onto a heated table.     

Development of the IR laser pyrolysis for the synthesis of iron–doped TiO2 nanoparticles: Structural properties and photoactivity

The preparation of TiO₂-based nanoparticles of closely controlled sizes and purity gives rise to considerable interest in the frame of environmental applications, e.g. in photocatalysis. When nanoparticles instead of their bulk counterpart are used the synthesis method plays a fundamental role in defining specific structural properties. Between the different gas-phase synthesis techniques, the CO₂ laser pyrolysis is a versatile method allowing for the preparation of nanostructures of various chemical compositions. Here we demonstrate that pure and Fe–doped TiO₂ nanoparticles with rather low Fe concentration may be prepared by applying the sensitized IR laser pyrolysis to a gas mixtures containing titanium tetrachloride, air and iron pentacarbonyl (vapors). The structures of TiO₂-based particles were systematically investigated by X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy, selected area electron diffraction and X-ray Photoelectron Spectroscopy. Depending on the synthesis parameters, the nanoparticle system contains mixtures of anatase and rutile, with a preponderance of the anatase phase. Higher rutile proportion was found in the iron-doped samples. Mean particle diameters of around 14 nm and 12 nm were estimated for undoped and doped anatase titania, respectively. From UV–Vis diffuse reflectance spectra, higher absorbance and red shifted absorption were evidenced at higher amount of doped iron. Preliminary evaluation tests of the UV photoactivity of samples were performed by using the scanning electrochemical microscopy for determining the evolution of the oxygen consumption in the presence of IV-chlorophenol. They show that the undoped nano titania samples perform better than the reference P25 Degussa sample. A drop of the nano-titania photoactivity as a consequence of Fe doping was observed. Possible reasons of this effect are tentatively discussed.