Synthesis of TiO2−xNy/Ag‐PbMoO4 Composite and Their Photocatalytic Activity Under Simulated Solar Light Irradiation

TiO_2?xN_y/Ag‐PbMoO₄ composite were synthesized by sonochemical method. The results revealed that the band‐gap energy absorption edge of TiO_2?xN_y/Ag‐PbMoO₄ composite was shifted to a longer wavelength as compared to TiO₂, TiO_2?xN_y, PbMoO_4, and Ag‐PbMoO₄. The TiO_2?xN_y/Ag‐PbMoO₄ composite showed the enhanced photocatalytic activity for degradation of indigo carmine dye (ICD) under simulated solar light irradiation. The TiO_2?xN_y/Ag‐PbMoO₄ composite exhibited the highest percentage (95.4%) of degradation of ICD and the highest reaction rate constant (0.0244 min^?1) in 2 h. The results suggested that a good combination of Ag and TiO_2?xN_y nanoparticles has great influence on the photocatalytic behavior of PbMoO₄.     

Preparation of aerochitin‐TiO2 composite for efficient photocatalytic degradation of methylene blue

An aerochitin–titania (TiO₂) composite was successfully synthesized and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and N₂ adsorption isotherms. The photocatalytic activity of the composite was investigated on the degradation of the model organic pollutant, methylene blue (MB) dye, under UV irradiation. The aerochitin–TiO₂ composite showed excellent adsorptive and photocatalytic activity with a degradation degree of 98% for MB. The first‐order rate constants for the photodegradation MB by TiO₂ nanoparticles and aerochitin–TiO₂ composite were found to be (3.49 ± 0.04) × 10^?3 and (1.82 ± 0.02) × 10^?2 min^?1. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45908.     

Antimicrobial properties of silver nanoparticles synthesized by bioaffinity adsorption coupled with TiO2 photocatalysis

BACKGROUND: On the basis of effective bioaffinity adsorption of Ag⁺, silver nanoparticles (Ag NPs) were synthesized on the surface of chitosan‐TiO₂ adsorbent (CTA) by TiO₂ photocatalysis for crystal growth. RESULTS: Among the microstructure characterizations of the resulting silver nanoparticles‐ loaded chitosan‐TiO₂ adsorbent (Ag‐CTA), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X‐ray (EDX) revealed the formation of metallic Ag on the CTA, which was further confirmed by the surface plasmon resonance of Ag NPs in the UV‐visible absorption spectrum. The underlying mechanism behind the formation of Ag NPs on the CTA by TiO₂ photoreduction was studied by Fourier transform infrared (FTIR) spectroscopy. The distinctive feature of Ag‐CTA after adsorption was the highly efficient antimicrobial activity in inactivating different test strains. In the case of Escherichia coli, 1.50 mg 1.67 wt% Ag‐CTA could totally inhibit 1.0–1.2 × 10⁷ colony forming units (CFU) in 100 mL nutrient medium, which was superior to that previously reported. CONCLUSIONS: CTA effectively adsorbed the precious metal ion Ag⁺ onto active imprinting sites on the adsorbent and then exerted efficient antimicrobial effects against diverse microbes. This research will be useful for designing a novel CTA‐based wastewater treatment for multi‐functional performance. Copyright © 2010 Society of Chemical Industry     

Dielectric Properties of Ba0.8Ca0.2TiO3–Bi(Mg0.5,Ti0.5)O3–NaNbO3 Ceramics

Ceramics in the system 0.45Ba_0.8Ca_0.2TiO₃–(0.55?x)Bi(Mg_0.5Ti_0.5)O₃–xNaNbO₃, x = 0–0.02 were fabricated by a conventional solid‐state reaction route. X‐ray powder diffraction indicated cubic or pseudocubic symmetry for all samples. The parent 0.45Ba_0.8Ca_0.2TiO₃–0.55Bi(Mg_0.5Ti_0.5)O₃ composition is a relaxor dielectric with a near‐stable temperature coefficient of relative permittivity, ε_r = 950 ± 10% across the temperature range 80°C–600°C. Incorporation of NaNbO₃ at x = 0.2 extends the lower working temperature to ≤25°C, with ε_r = 575% ± 15% from temperatures ≤25°C to >400°C, and tan δ < 0.025 from 25°C to 400°C. Values of dc resistivity ranged from ~10⁹ Ω·m at 250°C to ~10⁶ Ω·m at 500°C. The properties suggest that this material may be of interest for high‐temperature capacitor applications.     

Fabrication of high performance silicon nitride ceramics with TiO2 additive by annealing process

The high performance Si₃N₄ ceramic was prepared firstly for TiO₂, Y₂O₃ and MgO as pressureless sintering additives. Si₃N₄ ceramic with relative density of 99.6% and flexural strength of 785 ± 23.3 MPa could be obtained with 3 mol% TiO₂ and sintered at 1800 °C for 2 h. After annealing at 1700 °C, the facture toughness of sample of 1 mol% TiO₂ increased from 8.31 ± 0.28 MPa m^1/2 to 9.84 ± 0.16 MPa m^1/2. The flexural strength of sample of 2 mol% TiO₂ increased from 707 ± 26 MPa to 981 ± 16 MPa, thermal conductivity increased from 57.8 W/(m·K) to 68.49 W/(m·K). The XRD results showed that the ratio of I₁₀₁/I₂₁₀ and grain height reached to 1.84 and 5 μm of the sample of 3 mol% TiO₂, respectively. The present investigation revealed that the three-dimensional array of highly oriented crystalline Si₃N₄ micro rods could be prepared which array on the homogeneous substrates by using TiO₂ as agent. This phenomenon may propose a method that the mechanical properties the Si₃N₄ ceramics added TiO₂ can be improved significantly after annealing process.     

A multifunctional Ag/TiO2/reduced graphene oxide with optimal surface-enhanced Raman scattering and photocatalysis

A multifunctional Ag/TiO₂/reduced graphene oxide (rGO) ternary nanocomposite was prepared by a one-step photochemical reaction with TiO₂ and Ag nanoparticles successively deposited on reduced graphene oxide. The structure, morphology, composition, optical, and photoelectrochemical properties of Ag/TiO₂/rGO were investigated in detail. Meanwhile, the ternary nanocomposite possessed much higher adsorption capacity to organic dyes compared with bare TiO₂ and binary Ag/TiO₂, which would help to its use for surface-enhanced Raman scattering detection and photocatalytic degradation. Due to the charge transfer between rGO and organic dyes and enhanced electromagnetic mechanism of Ag, Ag/TiO₂/rGO nanocomposites as surface-enhanced Raman scattering substrates demonstrated dramatically improved sensitivity and good uniformity. The detection limit of rhodamine 6G (R6G) was as low as 10⁻⁹ mol/L, and the relative standard deviation values of the intensities remained below 5%. Most importantly, the synergistic coupling effect of three components extended the photoresponse range and accelerated separation of the electron-hole pairs, leading to greatly improved photocatalytic activity under simulated sunlight. The maximum rate constant (k, 0.06243 min⁻¹) of Ag/TiO₂/rGO was 50 and four times higher than that of TiO₂ and Ag/TiO₂, respectively.     

A hybrid Ag/TiO2 nanoarray-based in situ charge transfer toward multi-functional active-platform

Designing an efficient heteronanostructure array for surface-enhanced Raman scattering (SERS) to enable ultrasensitive and reproducible detection of analytes and degrading organic contaminants provides new perspectives for chemical and biological detection at trace levels and environmental remediation. Here, we design and fabricate a heterostructure consisting of Ag nanoparticles (NPs) in-situ grown on high-density arrays of vertical TiO₂ nanorods (NRs) (denoted Ag/TiO₂ NRs). As a result, compared with pristine TiO₂ NRs, the as-obtained Ag/TiO₂ NR substrate possesses a SERS activity for detecting rhodamine 6G (R6G) with a detection limit as low as 10⁻¹² M and an enhancement factor up to 1.2 × 10¹⁰. In addition, the substrate exhibits the highest degradation rates of R6G of 82% under illumination with visible light and an excellent self-cleaning effect under UV-assisted light. Such remarkable enhanced efficacy of the binary Ag/TiO₂ NRs nanocomposites may be attributed to the i) appropriate band alignment based on the synergistic effect of Ag decorated on TiO₂ NRs; ii) a large adhesion area and the localized surface plasmon resonance (LSPR) of Ag; and iii) high-density and engineering hotspots in the active platform. These properties make the heterostructure Ag/TiO₂ NR platform promising candidate for detecting analytes and photocatalytic applications.     

Degradation studies of CI Reactive Blue 19 on biodegraded cellulosic fabrics via liquid chromatography‐photodiode array detection coupled to high resolution mass spectrometry

When textile substrates biodegrade in landfills, the fate of textile colorants is unknown, and potentially poses an ecotoxic threat. In this study, we developed a systematic analytical method to evaluate the biodegradation of reactive dyes, the most common class of dye applied to cotton fabrics. The cotton fabrics were dyed with CI Reactive Blue 19 and biodegraded in soil in a laboratory‐controlled environment over intervals of 45 and 90 days. A dye isolation method using a low concentration of alkali (0.15% sodium hydroxide) was developed and applied (80°C for 1 hour) to isolate intact and degraded dye from the fabric samples. To quantify the intact dye isolated from the fabric samples, a quantification method was then developed using liquid chromatography‐photodiode array detection. The quantification method provided excellent linearity (R² = 0.9997 ± 0.0002), accuracy (% error = ?2% ± 4), precision (% coefficient of variation = 2% ± 4) and sensitivity (lower limit of quantification = 0.4 ± 0.2 µg/mL) for concentrations ranging from 1 to 50 µg/mL. After validation, the method was applied and showed a reduction of dye in biodegraded samples (after 45 and 90 days) compared with undegraded control samples (0 days). To characterise the isolated dye degradation product, quadrupole time‐of‐flight tandem mass spectrometry was utilised. Analysis showed that the degradation product was formed by losing a group from the intact hydrolysed form of the dye, creating a more hydrophobic degradation product compared with the intact hydrolysed form of dye.     

Photocatalytic hydrogen production by Au–MxOy (MAg,Cu, Ni) catalysts supported on TiO2

Au–M_xO_y (MAg, Cu, Ni) nanoparticles supported on TiO₂–P25 were prepared by the deposition–precipitation method and were evaluated for the photocatalytic water splitting reaction for hydrogen production, using a mixture of water–methanol (1:1). The combinations of Au–Cu₂O/TiO₂ and Au–NiO/TiO₂ effectively increased the hydrogen production (2064 and 1636 μmol·h^− 1·g^− 1) obtained by Au/TiO₂ (1204 μmol·h^− 1·g^− 1). The higher photoactivities achieved by Au–Cu₂O and Au–NiO nanoparticles deposited on TiO₂ were attributed to an enhancement of the electron charge transfer from TiO₂ to the Au–M_xO_y systems and the effect of surface plasmon resonance of gold nanoparticles.     

Visible light induced self-cleaning performance of iron-doped TiO2 nanoparticles for surface applications

This study aimed to enhance the visible light photosensitivity of TiO₂ nanoparticles for self-cleaning applications by doping with Fe³⁺. Nanocrystalline undoped and Fe-doped TiO₂ (Ti_1 − xFe_xO₂, x = .01–.04) were synthesized via sol–gel method. The results demonstrated that Fe-doped TiO₂ nanoparticles exhibited visible light sensitivity and self-cleaning properties. An increased Fe concentration resulted in a red shift in the absorption band edge. Fe_0.03-doped TiO₂ with an average particle size of ∼21 nm, a crystallite size of ∼12 nm, and a band gap of ∼2.86 eV showed the highest photocatalytic activity (60% methylene blue degradation) and super-hydrophilicity (water droplet contact angle 9°) under visible light radiation. These findings highlight the potential of Fe-doped TiO₂ nanoparticles as a promising material for self-cleaning applications.     

Direct grafting poly(methyl methacrylate) from TiO2 nanoparticles via Cu2+‐amine redox‐initiated radical polymerization: An advantage of monocenter initiation

Cu²⁺ can oxidize amines to generate radicals to initiate radical polymerization of electron‐deficient monomers under mild conditions. Here, CuSO₄‐catalyzed redox‐initiated radical polymerizations of methyl methacrylate from amino‐functionalized TiO₂ nanoparticles (TiO₂‐NH₂ nanoparticles) was performed to prepare TiO₂ nanoparticles grafted with poly(methyl methacrylate) (TiO₂‐g‐PMMA hybrid nanoparticles) in dimethylsulfoxide or N,N‐dimethylformamide at 90°C. Infrared spectroscopy, thermogravimetric analysis, and X‐ray photoelectron spectroscopy confirmed the presence of the grafted PMMA and the grafting yield was about 50 wt%. Microscopy and particle‐size analysis indicated that TiO₂‐g‐PMMA nanoparticles had a good affinity to organic media. Because only aminyl radical (? NH?) on TiO₂ nanoparticles formed in Cu²⁺‐amine redox‐initiation step, there was no free PMMA chains formed during polymerization. Thus, our protocol provides a facile strategy to prepare inorganic/organic hybrid nanoparticles via one‐pot Cu²⁺‐amine redox‐initiated free radical polymerization. POLYM. ENG. SCI., 55:735–744, 2015. © 2014 Society of Plastics Engineers     

Facile Preparation of Linear Polyurethane from UPy‐Capped Poly(dl‐Lactic Acid) Macrodiol

Linear polyurethanes based on poly(dl ‐lactic acid) (PDLLA) macrodiol are promising materials in tissue engineering, yet their synthesis requires rigorous control on various parameters. A facile way to prepare linear polyurethanes by capping the PDLLA macrodiol (M _n = 4536) with 2‐ureido‐4[1H]‐pyrimidone (UPy) is reported. The obtained low‐molecular‐weight UPy‐capped polyurethane can form flexible, stretchable, and hydrophobic supramolecular films due to the strong and unidirectional quadruple hydrogen bonding of UPy dimers. Tensile tests, shape recovery, and self‐healing observations indicate that, compared with conventional PDLLA macrodiol‐based linear polyurethane (M _n = 48840 and PDI = 1.8), the UPy‐capped polyurethane films have comparable mechanical properties (tensile modulus: 900 ± 38 MPa; ultimate strength: 9.6 ± 0.8 MPa) yet significantly better shape memory and self‐healing properties. These results suggest that the UPy‐capped polyurethane might become an alternative for conventional linear polyurethane as a new biomedical material.     

Hydrothermal preparation of Ag-TiO2 nanostructures with exposed {001}/{101} facets for enhancing visible light photocatalytic activity

Nano-composite materials of Ag nanoparticles dispersed TiO₂ nanocubes with exposed {001}/{101} crystal faces were fabricated mainly via a flexible one-step method of hydrothermal treatment with different content of Ag from 1 up to 3 mol%. Prepared photocatalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. These analysis was carried out for understanding the contribution of different content of silver for enhancing the photocatalytic activity of TiO₂ nanocubes. Prepared silver nanoparticles had small particle size and grafted to the {101} crystal face of TiO₂ with the role of template control agent and linking agent. The photocatalytic performance of Ag-TiO₂ nanocubes were researched via Rhodamine B dye removal under visible light irradiation ( ≧420 nm). Ag-TiO₂ composite materials with the content of 2 mol% Ag showed the best photocatalytic activity for degradation of Rhodamine B, which was five times more than bare TiO₂ and associated with the localized surface plasmon resonance (LSPR) propelled effect. The mechanism by which silver enhanced the photocatalytic activity of TiO₂ was also demonstrated.     

Titania/gum tragacanth nanohydrogel for methylene blue dye removal from textile wastewater using response surface methodology

The aim of this study was to statistically evaluate the capability of a prepared TiO₂/gum tragacanth hydrogel as a photocatalyst for the removal of methylene blue dye molecules from contaminated solutions. In this regard, TiO₂ nanoparticles were sonicated in gum tragacanth and the final hydrogel was prepared by the addition of glutaraldehyde as a crosslinking agent. Response surface methodology was employed as a mathematical and statistical tool to describe the system by a polynomial equation that relates the removal efficiency to selected variables (time, pH, initial dye concentration and photocatalyst dosage). The significance and adequacy of the model were confirmed by high coefficient of determination (R²) and adjusted R² values (>93%). The system was optimized at an initial dye concentration of 9.37 mg L^?1, pH of 9.02, time of 124.34 min and photocatalyst dosage of 0.13 g L^?1 using the response optimizer with an efficiency of 88.86%. A kinetic study of photocatalytic decoloration indicated that the pseudo‐second‐order model was well fitted to the experimental data. © 2018 Society of Chemical Industry     

Morphological and thermal properties of photodegradable biocomposite films

Biocomposites containing ultraviolet (UV) radiation absorbing inorganic nanofillers are of great interest in food packaging applications. The biodegradable polylactide (PLA) composite films were prepared by solvent casting method by incorporating 1 wt % of titanium dioxide (TiO₂) and Ag‐TiO₂ (silver nanoparticles decorated TiO₂) nanoparticles to impart the photodegradable properties. The films were exposed to UV radiation for different time periods and morphology of the composite films before and after UV exposure were investigated. The results showed that homogenous filler distribution was achieved in the case of Ag‐TiO₂ nanoparticles. The thermal properties and thermomechanical stability of the composite film containing Ag‐TiO₂ nanoparticles were found to be much higher than those of neat PLA and PLA/TiO₂ composite films. The scanning electron microscopy and X‐ray diffraction studies revealed that the photodegradability of PLA matrix was significantly improved in the presence of Ag‐TiO₂ nanoparticles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The Nanocrystalline SnO2–TiO2 System—Part I: Structural Features

The phases present and their crystal structure and microstructure in the nanocrystalline SnO₂–TiO₂ system were studied in the compositional range Sn_1?xTi_xO₂ (0.0 ≤ x ≤ 0.9). There is an apparent increase in the solubility limits in the solid solution compared to bulk crystalline SnO₂–TiO₂. No two phase region was observed with increasing TiO₂ content. Electron energy loss spectroscopy, infrared spectroscopy (FTIR), and X‐ray diffraction (XRD) of the nanopowders showed that the apparent increase in solubility is related to the systematic Ti⁴⁺ segregation on the particle surface (surface excess) at the SnO₂‐rich side, avoiding the nucleation of a second phase even at high Ti⁴⁺ contents. Is this finding in accord with Raman spectra, which suggest localized Ti‐rich sites in the absence of a second crystalline phase. Ti⁴⁺ surface excess is also lead to a modification of the surface hydroxyls and a decrease in the crystallite size of the nanoparticles (with a concomitant increase in surface area), with expected implications to catalytic and sensorial properties of these nanoparticles.     

Effect of Ba Nonstoichiometry in Bax(Zr0.8Y0.2)O3−δ on Population of 5‐Coordinated Y

The local environments of Y in the Y‐substituted BaZrO₃ of the starting compositions of Ba_x(Zr_0.8Y_0.2)O_3?δ (x = 0.97, 1.0, 1.03, and 1.06) were analyzed by ⁸⁹Y magic angle spinning NMR spectroscopy. The result showed a strong population dependence of 5‐coordinated Y³⁺ ions mostly at the B site on the Ba contents. The enhancement of Ba contents by 9 at% (from 0.97 to 1.06 in the starting Ba contents) in a nominal composition increased the amount of 5‐coordinated Y³⁺ ions from 35% ± 7% to 49% ± 5%, suggesting the importance of maximizing the Ba contents to populate more oxygen vacancies which is related to the concentration of protons incorporated during the hydration process. The wide variation in the lattice parameter of yttrium‐substituted BaZrO₃ perovskite materials in previous reports was reinterpreted with the variation in the Ba contents resulting from the evaporation of BaO during the sintering processes. Y³⁺ ions were confirmed to replace mainly the Zr⁴⁺ ions, as expected, and a tendency of oxygen vacancy clustering near the Y³⁺ ions was discussed.     

Effect of silver (Ag) ions irradiation on the structural,optical and photovoltaic properties of Mn doped TiO2 thin films based dye sensitized solar cells

Dye sensitized solar cell (DSSC) is an emerging energy harvesting tool which converts direct sunlight into electrical energy. These cells have much better properties in contrast with silicon based solar cells because of their flexible nature, light weight, low cost, environment friendly nature, and involvement of a simple manufacturing process. Since, a photoanode is the backbone of DSSC, we synthesized a pure and 1% manganese (Mn) doped titanium dioxide (TiO₂) films by sol-gel method which are irradiated with silver (Ag) ions at two different concentrations (2 × 10¹⁴ and 4 × 10¹⁴) ions-cm^?2. X-ray diffraction revealed that Mn doping followed by Ag irradiation transformed TiO₂ from pure anatase to rutile phase. Ultraviolet–visible spectroscopy exposed the reduction in band gap of TiO₂ film during this doping and irradiation process. Therefore, absorption is enhanced with red shift in UV-range. When these films are used as a photoanode in DSSC, 1% Mn doped TiO₂ film exposed with Ag at the concentration of (2 × 10¹⁴) ions-cm^?2 exhibited maximum efficiency of 2.40%.     

A comparative study between epoxy/Titania micro‐ and nanoparticulate composites thermal and mechanical behavior by means of particle–matrix interphase considerations

The aim of the present study is to examine and compare the thermal and mechanical properties of epoxy resin/TiO₂ particle microcomposites (0.2 μm) and nanocomposites (21 nm). Composite materials consisting of epoxy resin reinforced with different amounts of TiO₂ microparticles (1, 5, 10, 15, and 20% wt) and TiO₂ nanoparticles (0.5%, 1%, 3%wt) were prepared. The thermal and mechanical properties of the manufactured composites were investigated and compared through differential scanning calorimetry (DSC) and three‐point bending tests (3PB). Lipatov's Theory was then applied on the DSC results, thus leading to the calculation of the particle‐matrix interphase thickness which was correlated to experimental findings. The glass transition temperature (T_g) of the materials was obtained and the effect of the grain size on the measured T_g values was investigated. The data obtained from DSC tests for both micro‐ and nanoinclusions when normalized with respect to the specific surface area of the particles, resulted in a single continuous curve describing the normalized phase transition enthalpy variation with filler weight fraction. POLYM. ENG. SCI., 58:1146–1154, 2018. © 2017 Society of Plastics Engineers     

TiO2 nanofibers assembled on graphene-silver platform as a visible-light photo and bio-active nanostructure

The heterogeneous titanium oxide-reduced graphene oxide-silver (TiO₂/RGO/Ag) nanocomposites were successfully prepared by incorporation of two dimensional (2D) RGO nanosheets and spherical silver nanoparticles (NPs) into the 1D TiO₂ nanofibers. The novel TiO₂/RGO/Ag nanocomposites were synthesized by loading TiO₂ nanofibers, prepared via electrospinning technique, on the RGO/Ag platform. The resulting nanocomposites have been characterized using various techniques containing transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultra-violet-visible (UV–vis) spectroscopy. Microscopic studies clearly verified the existence of TiO₂ nanofibers with Ag NPs on the surface of RGO sheet and formation of TiO₂/RGO/Ag nanocomposites. Moreover, the results of UV–vis spectroscopy demonstrated that TiO₂/RGO/Ag nanocomposites extended the light absorption spectrum toward the visible region and significantly enhanced the visible-light photocatalytic performance of the prepared samples on degradation of rhodamine B (Rh. B) as a model dye. It was found that, incorporation of 50 µl RGO/Ag into the TiO₂ nanofibers lead to a maximum photocatalytic performance. Also, the improvement of the inactivation of Escherichia coli (E. coli) bacteria under visible-light irradiation was revealed by introduction of RGO/Ag into the TiO₂ matrix. The significant enhancement in the photo and bio-activity of TiO₂/RGO/Ag nanocomposites under visible-light irradiation can be ascribed to the RGO/Ag content by acting as electron traps in TiO₂ band gap.