Synthesis and characterization of V–C60/TiO2 photocatalysts designed for degradation of methylene blue

C₆₀/TiO₂ and V–C₆₀/TiO₂ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol–gel method. Fullerene had absorptive and semiconducting properties, and vanadium could enhance the photogenerated electron transfer. The V–C₆₀/TiO₂ composite shows a good photo-degradation activity. XRD patterns of the composites showed that the C₆₀/TiO₂ composite contained a mixture of anatase and rutile phase forms while the V–C₆₀/TiO₂ composite contained a typical single and clear anatase phase. The surface properties seen by SEM and FE-SEM present a characterization of the texture on C₆₀/TiO₂ and V–C₆₀/TiO₂ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong V peaks for the V–C₆₀/TiO₂ composite. From the photocatalytic results, the excellent activity of the C₆₀/TiO₂ and V–C₆₀/TiO₂ composites for degradation of methylene blue under UV irradiation could be attributed to both the effects between photocatalysis of the supported TiO₂ and charge transfer of the fullerene, and the introduction of vanadium to enhance the photogenerated electrons transfer.     

Electrochemical properties of two-component polymers of palladium and pyrrolidine and piperazine derivatives of C60

Redox-active films have been generated via electrochemical reduction in a solution containing palladium(II) acetate and [C₆₀]fullerene, or derivatives of C₆₀. The C₆₀ derivatives include piperazine (piperazine-C₆₀), pyrrolidine (CH₃-pyr-C₆₀), and a pyrrolidine salt, [(CH₃)₂-pyr-C₆₀]⁺ attached to the fullerene unit. In these films, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. The polymer yields involving the piperazine and pyrrolidine derivatives of C₆₀ are significantly lower than the yield of the C₆₀/Pd film. The CH₃-pyr-C₆₀/Pd and [(CH₃)₂-pyr-C₆₀]⁺/Pd films are electrochemically active in the negative potential region due to the reduction of the fullerene moiety. Reduction of the CH₃-pyr-C₆₀/Pd film is accompanied by the transport of supporting electrolyte cations from the solution into the film. In the first reduction step of the [(CH₃)₂-pyr-C₆₀]⁺/Pd film, both cations and anions of the supporting electrolyte are involved. The piperazine-C₆₀/Pd film exhibits electrochemical activity at both negative and positive potentials. In the negative potential region, reduction of the fullerene cage takes place. Oxidation of the piperazine moiety is responsible for the observed current in the positive potential range. Here, the oxidation process of this polymer is significantly influenced by the presence of metallic palladium particles in the film.     

Visible light responsive titanium dioxide–cyclodextrin–fullerene composite with reduced charge recombination and enhanced photocatalytic activity

Titanium dioxide (TiO₂)–fullerene (C₆₀) composite is prepared from TiO₂ and β-cylcodextrin (CD) encapsulated C₆₀ using the solar light irradiation. The absorption of the composite extends to the visible light region due to the charge transfer from CD and C₆₀ to TiO₂. The composite shows reduced charge recombination compared to that of the bare TiO₂ and TiO₂/CD. The rate constant values for the photodegradation reactions of methylene blue and 4-chlorophenol (4-CP) are significantly higher (∼2–5 times) for the composites with 0.5 and 1.5 wt.% C₆₀ compared to that of the bare TiO₂. Photocatalytic studies in the presence of scavengers reveal that the composites produce higher amount of reactive oxygen species (ROS). The enhanced photocatalytic activity of the composites is attributed to the visible light responsiveness, reduced charge recombination and increased formation of ROS. The photodegradation of 4-CP is significantly faster in the presence of the composite with 1.5 wt.% C₆₀ and is attributed to the synergistic effect of higher adsorption and increased ROS formation. The ROS formation by C₆₀ is possible because of the non-aggregated state of C₆₀ molecules in the composite and is assigned to the method which employs CD molecules to disperse C₆₀ in the composite.     

Preparation and Characterization of Pt/C and Pt/TiO2 Electrocatalysts by Liquid Phase Photodeposition

The preparation of carbon and titanium dioxide supported Pt catalysts through a photochemical and photocatalytic routes were investigated. The catalysts were prepared by irradiation with UV-light (365 nm) at room temperature using H₂PtCl₆ and C₁₀H₁₄O₄Pt (Pt(acac)₂) as platinum precursors. The kinetic studies revealed that H₂PtCl₆ produced metallic platinum faster than Pt(acac)₂ and also showed that the amount of platinum deposited on TiO₂ was higher than on carbon. The samples were characterized by X-ray diffraction, SEM/EDS and cyclic voltammetry. X-ray diffraction permitted to identify the crystallographic (111) and (200) planes from platinum metal on the catalysts synthesized, the intensity of peaks depends of the amount of platinum deposited. SEM/EDS test confirmed what it was found by the kinetics studies. The electrocatalytic activity was compared with a commercial Pt E-Tek catalyst (10 wt%). The electrochemical results showed that Pt/C-AA catalyst synthesized by liquid phase photo-deposition method has stability in acid media and high distribution of the actives sites on the electrode surfaces. It could be considered as a candidate for electro-catalyst for polymer electrolyte fuel cell. The Pt/TiO₂ catalysts did not present electrochemical activity.     

Characterization and relative photonic efficiencies of a new Fe-ACF/TiO2 composite photocatalysts designed for organic dye decomposition

The effect of Fe treatment on the Fe-activated carbon fiber (ACF)/TiO₂ composite catalysts was studied. Then the characterizations of Fe-ACF/TiO₂ composite catalysts were determined by employing BET, SEM, XRD and EDX instruments to analyze the potential factors. The adsorption data showed that the composites had decreased surface compared with the pristine ACF. From the results, it was shown the blocking of the micropores on the surface of ACF by treatment of Fe compound and Ti source. SEM micrographs for the Fe-ACF/TiO₂ composite catalysts indicated that practically all the ferric compounds and titanium dioxide introduced were located onto the ACF surfaces and consequently, there were dispersed into very small crystallites with growth of titanium dioxide. The XRD results showed patterns for the anatase and rutile typed titanium dioxide structure with a Fe mediated compound from the composites. The EDX results showed that the presence of C and O with Ti peaks on the Fe-ACF/TiO₂ composites decreased with an increase Fe concentration incorporated. Finally, organic dye (MB) decomposition showed the synergetic effects of adsorption, photo-degradation and enhancement of photonic activity of Fe component.     

Physical and electrochemical characterization of nanocomposites formed from polythiophene and titaniumdioxide

A simple method for covering titanium dioxide particles with a polythiophene film by chemical preparation was developed. The resulting nanocomposites consisted of a titanium dioxide core with a grain size of 25-250 nm and a polythiophene shell between 1 and 2 nm thickness. The composites were characterized by scanning electron microscopy, thermogravimetry, X-ray photoelectron spectroscopy, cyclovoltammetry, impedance spectroscopy and photocurrent spectroscopy. The content of polythiophene in the composite (determined by thermogravimetry), was between 2% and 5%. Disk-like electrodes were prepared by pressing and then characterized by various electrochemical methods. A reversible redox potential of the polythiophene of +1.0 V (NHE) was determined by cyclic voltammetry. The reduced form of polythiophene behaved as a p-type semiconductor so that the composite with n-type TiO₂ contained the properties of a p/n-junction. In the photocurrent spectra (depending on the applied potential), the characteristic anodic peaks of the TiO₂ at λ=320 nm and cathodic peaks of the polythiophene around λ=500 nm were found. A new cathodic peak observed at 370 nm was explained as a new feature of the pn interface.     

Resistivity and thermal reproducibility of carbon black and metallic powder filled silicone rubber heaters

Flexible heaters were prepared by extruding platinum‐catalyzed silicone rubber composites with conductive carbon black (CB) and metallic fillers. The conductor resistivity of the extruded heaters decreased in order of conductive titanium dioxide (TiO₂) > aluminum powder ≈ zinc powder > copper powder. Thermoelectric switching phenomena were investigated for the silicone rubber/CB/metallic powder systems. The positive temperature coefficient effect was dependent mainly on the CB content rather than on the content of the metallic powders. Resistivity and thermal reproducibility of the extruded heaters were also investigated by periodically applying AC voltage of 110 V. The heaters containing copper and TiO₂ powders exhibited excellent electrical reproducibility. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1122–1128, 2005     

Fullerene lipids: Synthesis of novel nitrogen-bridged [60]fullerene fatty ester derivatives

Reactions of methyl 6-azido-hexanoate, 8-azido-octanoate, and 12-azido-dodecanoate with [60]fullerene (1) gave the corresponding aza-[60]fullerene ester derivatives (2a-2c, 22–35% based on the amount of [60]fullerene reacted). The nitrogen atom is bonded to the [60]fullerene cage to yield a “[5,6]-open” type aza substructure. This was confirmed by the appearance of 30–31 sp ² signals at δ_C 133–147 in the carbon nuclear magnetic resonance spectra. Reaction of methyl 11-azido-7-undecynoate with [60]fullerene furnished a mixture of aza-[60]fullerene (2d, 53%) and aziridine-[60]fullerene (2e, 38%) ester derivatives. Compound 2e was identified as the “[6,6]-closed” type aziridine-[60]fullerene derivative, which displayed 10 sp ² signals in the region δ_C 140–145 and one signal at δ_C 85.05 for the sp ³ carbons of the cage. Refluxing a solution of compound 2d in toluene for 50 h gave about 50% yield of compound 2e, but not vice versa.     

Genotoxic responses to titanium dioxide nanoparticles and fullerene in gpt delta transgenic MEF cells

Background  

Titanium dioxide (TiO₂) nanoparticles and fullerene (C₆₀) are two attractive manufactured nanoparticles with great promise in industrial and medical applications. However, little is known about the genotoxic response of TiO₂ nanoparticles and C₆₀ in mammalian cells. In the present study, we determined the mutation fractions induced by either TiO₂ nanoparticles or C₆₀ in gpt delta transgenic mouse primary embryo fibroblasts (MEF) and identified peroxynitrite anions (ONOO^-) as an essential mediator involved in such process.     

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light

CdSe, CdSe-TiO₂, and CdSe-C₆₀/TiO₂ composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C₆₀/TiO₂ composite contained a typical single and clear anatase phase. SEM of the CdSe-C₆₀/TiO₂ composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C₆₀/TiO₂ composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C₆₀ and CdS-C₆₀/TiO₂ composites.     

Dye sensitized CO<Subscript>2</Subscript> reduction over pure and platinized TiO<Subscript>2</Subscript>

TiO₂ thin and thick films promoted with platinum and organic sensitizers including novel perylene diimide dyes (PDI) were prepared and tested for carbon dioxide reduction with water under visible light. TiO₂ films were prepared by a dip coating sol–gel technique. Pt was incorporated on TiO₂ surface by wet impregnation [Pt(on).TiO₂], or in the TiO₂ film [Pt(in).TiO₂] by adding the precursor in the sol. When tris (2,2′-bipyridyl) ruthenium(II) chloride hexahydrate was used as sensitizer, in addition to visible light activity towards methane production, H₂ evolution was also observed. Perylene diimide derivatives used in this study have shown light harvesting capability similar to the tris (2,2′-bipyridyl) ruthenium(II) chloride hexahydrate.     

Fabrication and characterization of fullerene-Nafion composite membranes

Fullerene-Nafion composite membranes have been fabricated through a new solution casting for the first time. The fullerenes used for the composites included C₆₀ and polyhydroxy fullerene (PHF), C₆₀(OH)_n (n ∼ 12). The dispersion of the fullerene in the composite membrane was much more refined with smaller agglomeration particles, relative to the previously prepared fullerene-Nafion composites in which the fullerene was introduced through doping. The miscibility of the hydrophobic fullerene, C₆₀, in the Nafion matrix was further improved by a new fullerene dispersant, poly[tri(ethylene oxide)benzyl]fullerene, C₆₀[CH₂C₆H₄(OCH₂CH₂O)₃OCH₃]_n (n ∼ 5), synthesized in this work. The solution-cast fullerene composites also demonstrated a significant improvement in the physical stability relative to the fullerene-doped Nafion composites through a better integration of the fullerene into the Nafion matrix. Furthermore, increased loadings of the fullerene in Nafion were made possible through the new solution-casting method, compared to the previous doping method. The water characteristics in the fullerene composites have been examined by TGA and ¹H pulse NMR measurements. The interactions between the fullerene and the Nafion have been studied through ATR FT-IR and molecular dynamics simulations which suggested PHF resides primarily in the hydrophobic domain of Nafion when the loading was low. The voltammetric measurements also have shown that the fullerene composites have the reduced limiting current density, compared to Nafion membranes without fullerenes.     

Development of nanostructured polyaniline–titanium dioxide gas sensors for ammonia recognition

The performance at room temperature of nanostructured polyaniline (PANi)–titanium dioxide (TiO₂) ammonia gas sensors was investigated. The PANi–TiO₂ thin-film sensors were fabricated with a spin-coating method on glass substrates. PANi–TiO₂ (0–50%) sensor films were characterized for their structural, morphological, optical, and various gas-sensing properties. The structural analysis showed the formation of nanocrystalline TiO₂, whereas PANi exhibited an amorphous nature. Morphological analysis of the PANi–TiO₂ nanocomposites film revealed a uniform distribution of TiO₂ nanoparticles in the PANi matrix. The absorption peaks in the Fourier transform infrared spectra and ultraviolet–visible spectra of the PANi–TiO₂ composite film were found to shift to higher wave numbers compared to those observed in pure PANi. The observed shifts were attributed to the interaction between the TiO₂ particles and the PANi molecular chains. The gas-sensing properties showed that the sensors exhibited selectivity to ammonia (NH₃) at room temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Removal of gaseous toluene by using TiO<Subscript>2</Subscript> film doped of Ru-dye/Pt in a pilot scale photoreactor

The photodegradation efficiency (PE) of gaseous toluene was investigated by using titanium dioxide (TiO₂) film doped of ruthenium (Ru)-dye/platinum (Pt) in a 3,600 L pilot reactor. Ru-dye was applied as a sensitizer to enhance PE of toluene in both UV and visible wavelength range since its major peaks are 225 nm, 325 nm, 375 nm, and 525 nm. PE by using Pt/TiO₂ was more enhanced since Pt plays a role as an electron trapper in UV light range. The 3.2 μm thickness of TiO₂ film was optimized for the highest PE. The highest PE was 75%, 85%, and 90% by TiO₂, Pt/TiO₂, and Ru-dye/Pt/TiO₂ film, respectively.     

Synthesis and Photoelectric Property of Poly(3-Octylthiophene)/Titanium Dioxide Hybrid

A series of conducting polymer complexes of poly(3-octylthiophene) and titanium dioxide (POT/TiO₂) in different proportions were synthesized. X-ray diffraction patterns (XRD) indicated that the interplaner spacing of the composite samples is smaller than the pure TiO₂. X-ray photoelectron spectroscopy (XPS) and IR support a chemical interaction between POT and nano-TiO₂ in the complexes. Cyclic voltammetry (CV) showed that the energy gap of the POT/TiO₂ composite was 0.43 eV, which was smallest when the proportion was 1:1. Ultraviolet–visible spectra (UV–vis) and luminescence spectra (FL) showed that optical performance was far superior to both POT and TiO₂.     

The Effect of Coating TiO<Subscript>2</Subscript> on the CO Oxidation of the Pt/γ-Alumina Catalysts

Abstract  

The effect of coating TiO₂ on the CO oxidation of the Pt/γ-alumina catalysts was observed through activity tests and surface characterization spectroscopy by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) experiments. XPS results evidenced the occurrence of different Pt²⁺ species and metallic Pt⁰ at the surface which suggest electron transfer of titanium (cation) to the platinum atom and the reduction of titanium (Ti⁴⁺ → Ti³⁺). FTIR analyses suggested oxygen spillover mechanism at the interface between titanium dioxide and platinum that may explain the catalytic activity of the platinum titania-supported catalysts. The apparent activation energy for the CO oxidation was 52.5 kJ/mol and similar for all catalysts. However, the frequency factor changed significantly, indicating interfacial phenomena caused by CO and oxygen adsorptions over TiO _x species and Al₂O₃ support with similar dispersions.     

Electrochemical synthesis and in situ spectroelectrochemistry of conducting polymer nanocomposites. I. polyaniline/TiO2, polyaniline/ZnO,and polyaniline/TiO2+ZnO

The polyaniline (PAn), polyaniline/titanium dioxide (PAn/TiO₂), polyaniline/zinc oxide (PAn/ZnO), and a novel conducting polymer nanocomposites, polyaniline/titanium dioxide + zinc oxide (PAn/TiO₂+ZnO), were synthesized by in situ electropolymerization and potential cycling on gold electrode. The PAn and nanocomposite films were characterized by cyclic voltammetry, Fourier transform infra‐red (FTIR) spectroscopy, in situ resistivity measurements, in situ UV–Visible, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The differences between cathodic and anodic peaks of three redox couples were obtained for PAn and polymeric nanocomposite films. During cathodic and anodic scans, the shift of potential was observed for polymer nanocomposite films. The characteristic FTIR peaks of PAn were found to shift to lower wavelengthsin polymer nanocomposite films. These observed effects have been attributed to interaction of TiO₂, ZnO, and TiO₂+ZnO particles with PAn molecular chains. Significant differences from in situ resistivity of PAn and nanocomposite films were obtained. The resistance of PAn/TiO₂, PAn/ZnO, and PAn/TiO₂+ZnO films were found to be smaller than the PAn film. The in situ UV–Visible spectra for Pan and polymer nanocomposite films were studied. The results show the intermediate spectroscopic properties between PAn and polymer nanocomposite films. The morphological analyses of PAn and nanocomposite films have been investigated. The nanocomposites SEM and TEM micrographs suggest that the inorganic semiconductor particles were incorporated in organic conducting polymer, which consequently modifies the morphology of the films significantly. POLYM. COMPOS., 35:351–363, 2014. © 2013 Society of Plastics Engineers     

Effect of Cu powder addition on thermoelectric properties of Cu/TiO2−x composites

Spark plasma sintering was used to fabricate Cu/TiO_2−x composites by adding Cu powder to nonstoichiometric titanium dioxide, TiO_2−x. The composition and crystal forms of the composites were examined. The thermoelectric properties of the composites were measured and the effects of composite formation on these properties were discussed. The rule of mixture (ROM) of composite and general effective medium theory (GEM) were used to investigate the composite effects of the Cu/TiO_2−x composites. The results revealed that the electrical resistivities of the composites was much lower than that of TiO_2−x. As the added amount of Cu powder increased, the electrical properties of the composites shifted from semiconductor behavior to metallic behavior. The thermoelectric performances of the composites improved as a result of composition formation. The thermoelectric performance can be improved by adjusting the balance among electrical resistivity, thermal conductivity and the Seebeck coefficient, based on the composite effects.     

Core‐shell method of synthesis,characterizations, and ac conductivity studies of polyaniline/n‐TiO2 composites

Polyaniline/nano‐titanium dioxide composites (PANI/n‐TiO₂) were prepared using α‐dextrose as surfactant and ammonium per sulfate as oxidant. The PANI/n‐TiO₂ composite is characterized by Fourier transform infrared spectra and confirmed the presence of benzenoid and qunoide ring structures and also formation of free ions. The transmission electron microscopy study reveals that the size of TiO₂ is in the order of 7 nm where as the composite size is of the order of 13 nm; further, it is observed that the TiO₂ particles are intercalated to form a core shell of PANI. The X‐ray diffraction (XRD) studies show that the monoclinic structure of the composites. ac Conductivity, permittivity, and tangent loss studies on these samples suggest that these composites may be well suited for gas sensor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The optical properties of PVA/TiO2 composite nanofibers

The electrospun nanofibers emerge several advantages because of extremely high specific surface area and small pore size. This work studies the effect of PVA nanofibers diameter and nano‐sized TiO₂ on optical properties as reflectivity of light and color of a nanostructure assembly consisting polyvinyl alcohol and titanium dioxide (PVA/TiO₂) composite nanofibers prepared by electrospinning technique. The PVA/TiO₂ composite spinning solution was prepared through incorporation of TiO₂ nanoparticles as inorganic optical filler in polyvinyl alcohol (PVA) solution as an organic substrate using the ultrasonication method. The morphological and optical properties of collected composites nanofibers were highlighted using scanning electron microscopy (SEM) and reflective spectrophotometer (RS). The reflectance spectra indicated the less reflectance and lightness of composite with higher nanofiber diameter. Also, the reflectance and lightness of nanofibers decreased with increasing nano‐TiO₂ concentration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013