Electrophoretic deposition of carbon nanotubes–hydroxyapatite nanocomposites on titanium substrate

Carbon nanotubes–hydroxyapatite (CNTs–HA) composites were synthesized, using an in situ chemical method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). HA particles were uniformly absorbed on the CNTs, with strong interfacial bonding. The CNTs–HA composites behaved like single composites when deposited on a titanium substrate by electrophoretic deposition (EPD). EPD was carried out at 10, 20 and 40 V, for 0.5 to 8 min at each voltage. Coating efficiency and weight increased with increasing deposition time, while the slope of the curves decreased, indicating a decrease in deposition rate. The CNTs–HA coating morphology was analyzed with scanning electron microscopy (SEM). The results revealed that decreasing the voltage used for deposition coatings could reduce cracking frequency. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that the deposition coatings protected the titanium substrate from corroding in simulated body fluid (SBF). In addition, in vitro cellular responses to the CNTs–HA coatings were assessed to investigate the proliferation and morphology of osteoblast cell line.     

Photocatalytic activity of β-MnO2 nanotubes grown on PET fibre under visible light irradiation

Development of visible light response semiconductor photocatalysts in degradation of organic compounds (pollutants) is one of the current research focuses due to the severe environmental pollution from various industrial and agricultural pollutants in water bodies. In this work, β-MnO₂ particles were successfully prepared by sol-gel method with potassium permanganate and manganese (II) sulphate as precursors. The transmission electron microscope/selected area electron diffraction analysis indicates that the particles were polycrystals with tubular structure. The photodegradation of Rhodamine B (RhB) solution using β-MnO₂ nanotubes under visible irradiation followed 1^st order kinetic with rate constant of 0.022 ± 0.003 min^?1 and photodegradation efficiency of 90.3% after 120 min under visible light irradiation. The N-deethylation was the dominant process in photodegradation of RhB dye by β-MnO₂ nanotubes as compared to cycloreversion process. By applying similar synthesis condition, the β-MnO₂ nanotubes were successfully synthesised on PET fibre. The photodegradation efficiency of RhB dye under circulation condition by β-MnO₂ nanotubes grown on PET fibre under visible light irradiation was 1.23 h^?1. The result suggests that β-MnO₂ nanotubes grown on PET fibre could be used as visible light-driven photocatalysts for wastewater purifier application.     

Photoreduction of Cr(VI) in water using Bi2O3–ZrO2 nanocomposite under visible light irradiation

Chromium(VI) is a common heavy metal pollutant and extensively used in variety of industrial processes. In the present study, bismuth oxide–zirconium oxide nanocomposite (Bi₂O₃–ZrO₂) was synthesized to improve photoreduction of Cr(VI) under visible light irradiation. The synthesized photocatalyst was characterized by UV-visible-diffuse reflectance spectroscopy (UV-vis-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (B.E.T) surface area analysis and photoluminescence spectroscopy (PL). Bi₂O₃–ZrO₂ was found to be more photoactive than Bi₂O₃, ZrO₂, TiO₂ and ZnO for the reduction of Cr (VI). The influences of various reaction parameters like the effect of catalyst concentration, initial Cr(VI) concentration and addition of inorganic salts on the photocatalytic activity have been investigated in detail. Meanwhile, the stability of Bi₂O₃–ZrO₂ was investigated by repeatedly performing Cr(VI) photoreducing experiments.     

Preparation of graphene–TiO2 nanocomposite and photocatalytic degradation of Rhodamine-B under solar light irradiation

GR–TiO₂ nanocomposite was prepared by simple chemical method using graphene oxide and titanium isopropoxide (Ti [OCH (CH₃)₂]₄) precursors. The crystalline nature of the composite was characterised by powder X-ray diffraction and the intercalation was explained by Raman spectroscopy. The morphology of the composite was analysed by field emission scanning electron microscopy. The elemental and quantitative measurement of the composite was determined by electron dispersive spectroscopy. The shape and size of the particle was measured by transmission electron spectroscopy and high resolution spectroscopy. The surface area and elemental composition of the composite was studied by using Brunauer–Emmett–Teller (BET) method and X-ray photoelectron spectroscopy. Photo-generated electrons were studied by photoluminescence spectra. The photocatalytic activity of nanocomposite was investigated by the degradation of Rhodamine-B (Rh-B) in an aqueous solution under solar light irradiation. The GR–TiO₂ demonstrates photocatalytic activity in the degradation with a removal rate of 98% under solar light irradiation as compared with pure TiO₂ (42%), graphite oxide (19%), and mechanical mixture GR + TiO₂ (60%) due to the increased light absorption intensity and reduction of electron–hole pair recombination with the intercalation of graphene and TiO₂. The results indicated that the GR–TiO₂ could be used as a catalyst to degrade Rh-B from coloured wastewater.     

Synthesis and photocatalytic performance of TiO<Subscript>2</Subscript> nanospheres–graphene nanocomposite under visible and UV light irradiation

In this article, we present a fast and simple method to produce TiO₂ nanospheres–graphene nanocomposite with high photocatalytic activity under visible and UV light irradiation. TiO₂ nanospheres were adsorbed on graphene in sol–gel process. First, titanium (IV) butoxide underwent hydrolysis in graphene oxide (GO) ethanol solution resulting in TiO₂ nanospheres deposition on GO. Next, the material was calcinated to generate the phase transition of TiO₂ into anatase and reduce GO to graphene. The detailed characterization of the material was performed via transmission electron microscopy, energy dispersive X-rays spectrometer, Fourier-transformed infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Interestingly, the band-gap energy of the prepared photocatalyst was drastically decreased in comparison with the commercial photocatalyst P25 from 3.05 to 2.36 eV. This influenced in the activation of the material under visible light and resulted in high photocatalytic activity in the process of phenol decomposition in visible and UV irradiation.     

Efficient photodegradation of dyes using light-induced self assembly TiO(2)/β-cyclodextrin hybrid nanoparticles under visible light irradiation

A novel β-cyclodextrin (β-CD) grafted titanium dioxide (TiO(2)/β-CD) was synthesized through photo-induced self assembly methods, and its structure was characterized. The TiO(2)/β-CD hybrid nanomaterial showed high photoactivity under visible light irradiation (λ ≥ 400 nm and/or λ ≥ 420 nm) and simulated solar irradiation (λ ≥ 365 nm). Photodegradation of Orange II followed the Langmuir-Hinshelwood kinetics model. The initial rate R(0) of Orange II degradation increased by 6.9, 2.6 and 1.9 times in the irradiation conditions of λ ≥ 420nm, λ ≥ 400nm and λ ≥ 365 nm, respectively. β-CD increased the lifetimes of the excited states of the unreactive guests and facilitated the electron transfer from the excited dye to the TiO(2) conduction band, which enhanced the dye pollutant degradation. Superoxide radicals were shown to be the main reactive species that caused the degradation of Orange II under visible irradiation.     

Surface structure and visible light photocatalytic activity of titanium–calcium hydroxyapatite modified with Cr(III)

The synthetic titanium–calcium hydroxyapatite (Ti–CaHap) particles were treated with different concentrations of aqueous Cr(NO₃)₃·9H₂O solution and the materials obtained were characterized by a variety of conventional techniques. The crystal structure and particle morphology of Ti–CaHap were essentially not altered by treating with Cr(III) solution. With increasing the Cr(III) concentration, the amount of Cr(III) in the products was increased and that of Ca(II) was decreased. XPS results revealed that the surface state of Cr of Ti–CaHap was trivalent. These facts allow us to infer that the Cr(III) was doped by substitution of surface Ca(II) of Ti–CaHap. Besides, IR results proved that increasing the Cr(III) concentration developed the surface Cr–OH band while the surface Ti–OH and P–OH bands of Ti–CaHap vanished. This imply that the formation of surface P–O-Cr(OH)₂ and Ti–O–Cr(OH)₂ groups, resulting the Cr(OH)₃-like layer on the surface of Ti–CaHap particles. The Cr(III)-doped Ti–CaHap possessed the absorption peaks at 446 and 623 nm in vis range in addition to the UV absorption of charge transfer transition of O^2? → Ti⁴⁺. The vis absorption peaks developed on raising the Cr(III) concentration. The photocatalytic decomposition of acetaldehyde into CO₂ over Cr(III)-doped Ti–CaHap was detected under vis irradiation and the activity was lowered by the formation of Cr(OH)₃-like layer on the particle surface.     

Potato starch-assisted green synthesis of nanoferrite and ferrite–semiconductor nanocomposites for effective visible light photocatalytic degradation of methylene blue

Journal of Materials Science - Biodegradable potato starch-assisted nanoferrite and ferrite–semiconductor nanocomposites have been synthesized by the co-precipitation method for the...     

Highly active Zr co-doped Ag–ZnO photocatalyst for the mineralization of Acid Black 1 under UV-A light illumination

The Zr co-doped Ag–ZnO (Zr–Ag–ZnO) was successfully synthesized by precipitation–decomposition method. The photocatalytic activity of Zr–Ag–ZnO was investigated for the degradation of Acid Black 1 (AB 1) in aqueous solution using UV-A light. Co-dopants shift the absorbance of ZnO, both in UV and visible region. Zr–Ag–ZnO is found to be more efficient than Ag–ZnO, Zr–ZnO, commercial ZnO, prepared ZnO, TiO₂–P25 and TiO₂ (Merck) at pH 9 for the mineralization of AB 1 under UV-A light. The influence of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of AB 1 has been analyzed. The mineralization of AB 1 has been confirmed by COD measurements. Mechanism of degradation by Zr–Ag–ZnO is proposed. The catalyst is found to be reusable.     

Photocatalytic degradation of dodecyl-benzenesulfonate over TiO2–Cu2O under visible irradiation

A series of TiO₂–Cu₂O mixed oxides were prepared by the hydrolysis of titanium butoxide and reduction of copper acetate with hydrazine. These composite oxides were characterized by X-ray diffraction (XRD), inductively coupled plasma spectrometry (ICP), high-resolution transmission electron microscopy (HRTEM), N₂ adsorption and UV–vis techniques. Photocatalytic degradation of dodecyl-benzenesulfonate (DBS) under visible irradiation was performed, and effects of composition of catalysts and reaction conditions were studied. It was observed that TiO₂–Cu₂O composite oxides exhibited better photocatalytic activity than Cu₂O or TiO₂ alone. Among these composite oxides, the 5%TiO₂–Cu₂O displayed the highest activity, and the degradation percentage of DBS and COD reached 97.3% and 65%, respectively. In addition, it was found that the decomposition of DBS followed the first-order kinetics and the adsorption of DBS followed the Langmuir model. Oxygen in solution played a vital role in the elimination of COD.     

A facile synthesis of supported amorphous iron oxide with high performance for Cr(Ⅵ) removal from aqueous solution under visible light irradiation

A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO_3)_3 supported on TiO_2,followed by low-temperature calcination. Scanning electron microscopy(SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), UV–vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO_2 were examined for photocatalytic reduction of Cr(Ⅵ). The experiments demonstrated that Cr(Ⅵ) in aqueous solution was more efficiently reduced using Fe_2O_3/TiO_2 heterogeneous photocatalysts than either pure Fe_2O_3 or TiO_2 under visible light irradiation. All TiO_2 supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(Ⅵ) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO_2 supported iron oxide samples with that supported on Al_2O_3 and ZrO_2. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably,iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO_2 was proposed as the source of photoactivity for Cr(Ⅵ) reduction.     

Polymerizable sol–gel synthesis of nano-crystalline WO3 and its photocatalytic Cr(VI) reduction under visible light

A polymerizable sol–gel approach has been employed to synthesize bulk and nano-crystalline WO₃. A W-containing sol–gel resin is formed and subjected to thermally induced free radical polymerization followed by calcination at 450, 650 and 850 °C. TGA analysis was performed to reveal the calcination temperature required for WO₃ formation. The synthesized oxides have been characterized with XRD, SEM, XPS, TEM and diffuse reflectance spectroscopy to probe the crystallinity, surface morphology and electronic structures. BET surface area measurements were carried out for the synthesized materials to follow the effect of calcination temperature on surface area. The calcination temperature was found to be crucial in tuning the crystallinity and non-stoichiometry of the materials. The synthesized catalysts were explored for the efficiency of Cr(VI) photoreduction in aqueous medium under visible light and the results are correlated with the structural and electronic properties of the materials.     

Synergistic effect of montmorillonite–clay and gamma irradiation on the characterizations of waste polyamide copolymer and reclaimed rubber powder nanocomposites

A study on the mechanical properties and thermal evolution of waste polyamide copolymer/waste rubber powder and montmorillonite–clay (WPA/RRP/MMT) nanocomposites exposed to gamma-rays (0–200 kGy) has been carried out. TGA and DSC were used to investigate the influence of the exposure dose and the incorporation of montmorillonite–clay on the thermal parameters of the prepared composites. It was observed that both parameters were highly affected by the incorporated clay and dose. The structural and morphological studies were done by means of EDX and SEM to investigate the structural change imputed by the clay incorporation and irradiation. The chemical absorption behavior of MMT nanocomposites in HCl and NaOH media was investigated. The results show that irradiation markedly magnified the thermal stability and the tensile strength of the nanocomposite.     

Studying the preparation of Ag-loaded Bi12SiO20–Bi2O2SiO3 heterostructure photocatalyst of loose structure with high visible light photocatalytic performance

Journal of Materials Science: Materials in Electronics - The hard agglomeration of bismuth silicate prepared by sol–gel method is the main reason to hinder its modification, photocatalytic...