Photocatalyst

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Photocatalyst

  • tio2 photocatalyst


  • Selected Abstracts


    Heterointegration of Pt/Si/Ag Nanowire Photodiodes and Their Photocatalytic Properties

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Yongquan Qu
    Abstract Photocatalyst mediated photoelectrochemical processes can make use of the photogenerated electrons and holes onsite for photocatalytic redox reactions, and enable the harness and conversion of solar energy into chemical energy, in analogy to natural photosynthesis. However, the photocatalysts available to date are limited by either poor efficiency in the visible light range or insufficient photoelectrochemical stability. Here, it is shown that a Pt/Si/Ag nanowire heterostructure can be rationally synthesized to integrate a nanoscale metal-semiconductor Schottky diode encased in a protective insulating shell with two exposed metal catalysts. The synthesis of Pt/Si/Ag nanowire diodes involves a scalable process including the formation of silicon nanowire array through wet chemical etching, electrodeposition of platinum and photoreduction of silver. The Pt/Si/Ag diodes exhibit highly efficient photocatalytic activity for a wide range of applications including environmental remediation and solar fuel production in the visible range. In this article, photodegradation of indigo carmine and 4-nitrophenol are used to evaluate the photoactivity of Pt/Si/Ag diodes. The Pt/Si/Ag diodes also show high activity for photoconversion of formic acid into carbon dioxide and hydrogen. [source]


    Heterointegration of Pt/Si/Ag Nanowire Photodiodes and Their Photocatalytic Properties

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Yongquan Qu
    Abstract Photocatalyst mediated photoelectrochemical processes can make use of the photogenerated electrons and holes onsite for photocatalytic redox reactions, and enable the harness and conversion of solar energy into chemical energy, in analogy to natural photosynthesis. However, the photocatalysts available to date are limited by either poor efficiency in the visible light range or insufficient photoelectrochemical stability. Here, it is shown that a Pt/Si/Ag nanowire heterostructure can be rationally synthesized to integrate a nanoscale metal-semiconductor Schottky diode encased in a protective insulating shell with two exposed metal catalysts. The synthesis of Pt/Si/Ag nanowire diodes involves a scalable process including the formation of silicon nanowire array through wet chemical etching, electrodeposition of platinum and photoreduction of silver. The Pt/Si/Ag diodes exhibit highly efficient photocatalytic activity for a wide range of applications including environmental remediation and solar fuel production in the visible range. In this article, photodegradation of indigo carmine and 4-nitrophenol are used to evaluate the photoactivity of Pt/Si/Ag diodes. The Pt/Si/Ag diodes also show high activity for photoconversion of formic acid into carbon dioxide and hydrogen. [source]


    Graphite Oxide as a Photocatalyst for Hydrogen Production from Water

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
    Te-Fu Yeh
    Abstract A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4,4.3,eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42,nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20,vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination. [source]


    ChemInform Abstract: Efficient Nonsacrifical Water Splitting Through Two-Step Photoexcitation by Visible Light Using a Modified Oxynitride as a Hydrogen Evolution Photocatalyst.

    CHEMINFORM, Issue 27 2010
    Kazuhiko Maeda
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: Self-Assembled 3-D Architectures of BiOBr as a Visible Light-Driven Photocatalyst.

    CHEMINFORM, Issue 30 2008
    Jun Zhang
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Hydrothermal Synthesis of Fine NaTaO3 Powder as a Highly Efficient Photocatalyst for Overall Water Splitting.

    CHEMINFORM, Issue 21 2007
    Yungi Lee
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    Ag/AgBr/TiO2 Visible Light Photocatalyst for Destruction of Azodyes and Bacteria.

    CHEMINFORM, Issue 29 2006
    Chun Hu
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    Ag+ -Inserted NbO2F as a Novel Photocatalyst.

    CHEMINFORM, Issue 43 2005
    Takashi Murase
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Microemulsion-Mediated Solvothermal Synthesis of Nanosized CdS-Sensitized TiO2 Crystalline Photocatalyst.

    CHEMINFORM, Issue 38 2003
    Jimmy C. Yu
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Graphite Oxide as a Photocatalyst for Hydrogen Production from Water

    ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
    Te-Fu Yeh
    Abstract A graphite oxide (GO) semiconductor photocatalyst with an apparent bandgap of 2.4,4.3,eV is synthesized by a modified Hummers' procedure. The as-synthesized GO photocatalyst has an interlayer spacing of 0.42,nm because of its moderate oxidation level. Under irradiation with UV or visible light, this GO photocatalyst steadily catalyzes H2 generation from a 20,vol % aqueous methanol solution and pure water. As the GO sheets extensively disperse in water, a cocatalyst is not required for H2 generation over the GO photocatalyst. During photocatalytic reaction, the GO loses some oxygen functional groups, leading to bandgap reduction and increased conductivity. This structural variation does not affect the stable H2 generation over the GO. The encouraging results presented in this study demonstrate the potential of graphitic materials as a medium for water splitting under solar illumination. [source]


    Pool boiling on a superhydrophilic surface

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2003
    Y. Takata
    Abstract Titanium Dioxide, TiO2, is a photocatalyst with a unique characteristic. A surface coated with TiO2 exhibits an extremely high affinity for water when exposed to UV light and the contact angle decreases nearly to zero. Inversely, the contact angle increases when the surface is shielded from UV. This superhydrophilic nature gives a self-cleaning effect to the coated surface and has already been applied to some construction materials, car coatings and so on. We applied this property to the enhancement of boiling heat transfer. An experiment involving the pool boiling of pure water has been performed to make clear the effect of high wettability on heat transfer characteristics. The heat transfer surface is a vertical copper cylinder of 17 mm in diameter and the measurement has been done at saturated temperature and in a steady state. Both TiO2 -coated and non-coated surfaces were used for comparison. In the case of the TiO2 -coated surface, it is exposed to UV light for a few hours before experiment and it is found that the maximum heat flux (CHF) is about two times larger than that of the uncoated surface. The temperature at minimum heat flux (MHF) for the superhydrophilic surface is higher by 100 K than that for the normal one. The superhydrophilic surface can be an ideal heat transfer surface. Copyright 2002 John Wiley & Sons, Ltd. [source]


    Photocatalytic reduction of carbonates and formation of some energy rich systems in the presence of Toluidine Blue

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2001
    Sarita Jain
    Abstract Aqueous sodium and potassium carbonates have been photoreduced in the presence of Toluidine Blue solution (which is also the photocatalyst). The photocatalytic formation of formic acid and formaldehyde was measured spectrophotometrically using Nash reagent. The effect of variation of various parameters like pH, amount of photocatalyst (Toluidine Blue concentration), concentration of Na2CO3 and K2CO3, light intensity, etc., on the yield of photoproducts was also investigated. A tentative mechanism for this reduction has been proposed. Copyright 2001 John Wiley & Sons, Ltd. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 8 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Cover Picture: (Adv. Synth.

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010
    Catal.
    The cover picture, provided by David W.,C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)32+ readily accepts a photon from a visible light source to populate the *Ru(bpy)32+ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the ,-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched ,-alkyl aldehyde. [source]


    Photooxidation of Benzyl Alcohols with Immobilized Flavins

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
    Harald Schmaderer
    Abstract Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800,h,1 and turnover numbers (TON) of up to 68 were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the heterogeneous photocatalyst stops the reaction conversion immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26,h,1, TON of 280 and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts. [source]


    Sterilization system for air purifier by combining ultraviolet light emitting diodes with TiO2

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2009
    Xiaohui Huang
    Abstract BACKGROUND: Ultraviolet light emitting diodes (UV LEDs) were used as a light source in TiO2 photocatalysis because of their many advantages, such as, long life, safety, low pollution, etc. In this experiment, a light source panel was successfully fabricated with UV LEDs, the light intensities of which were relatively uniform. RESULTS: The sterilization process comprised two steps. First, an aerosol was blocked by high efficient particulate air (HEPA) filter paper coated with TiO2 photocatalyst. Second, Staphylococcus aureus in the aerosol decreased gradually in the photocatalysis process of UV LED/TiO2. After 52 h irradiation all the S. aureus were killed. CONCLUSION: The UV LED light source panel had a larger surface for irradiation than a mercury lamp. Thus, its sterilization efficiency was much better than that of traditional methods. The feasibility of UV LED/TiO2 for photocatalysis was proved. Copyright 2009 Society of Chemical Industry [source]


    Photocatalytic degradation of gaseous trichloroethene using immobilized ZnO/SnO2 coupled oxide in a flow-through photocatalytic reactor

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2005
    Taicheng An
    Abstract The photocatalytic degradation of gaseous trichloroethene (TCE) was investigated on immobilized ZnO/SnO2 coupled oxide in a flow-through photocatalytic reactor. It was found that gaseous photocatalysis is an efficient method for volatile organic compounds' abatement and air purification. Degradation of ,100% was found for TCE at the concentrations examined, up to 400 ppmv, in a flow-through dry synthetic gas stream. In our tested conditions, the flow rate had little influence on the photocatalytic degradation efficiencies of TCE, while the relative humidity had a significant influence on the photocatalytic degradation of TCE. The photocatalytic degradation efficiencies of TCE increased slowly below 20% relative humidity and then decreased as the relative humidity increased further. The deactivation of used immobilized photocatalyst was not observed within the 200 h testing period in the present experiment, although the surface of the photocatalyst changed greatly during the use of the photocatalyst. Copyright 2004 Society of Chemical Industry [source]


    Kinetic behaviour of the adsorption and photocatalytic degradation of salicylic acid in aqueous TiO2 microsphere suspension

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004
    XZ Li
    Abstract A new photocatalyst, named TiO2 microspheres, prepared by a sol-spraying-calcination method, can freely suspend with air bubbling in its aqueous suspension and easily settle down from a water phase under gravity. The experimental results demonstrated that TiO2 microspheres had better adsorption capacity than conventional TiO2 powders, due to large surface area, large pore volume, and also a porous structure. The photocatalytic activity of TiO2 microspheres in aqueous suspension was evaluated using salicylic acid (SA) as a model substrate. It was found that the Langmuir,Hinshelwood model in its integral form described the kinetics of SA photocatalytic degradation in the TiO2 microsphere suspensions better than its simplified form as a first-order reaction model, since the significant substrate adsorption on the catalysts was not negligible. The kinetics of SA photocatalytic degradation with different initial concentrations and pH was further investigated. The experiments demonstrated that the change of pH could significantly affect the adsorption of SA in the TiO2 microsphere suspensions. The effects of substrate adsorption rate and photoreaction rate on the overall performance of photocatalytic degradation is also discussed on the basis of experimental data. Copyright 2004 Society of Chemical Industry [source]


    Oxidative degradation of 4-nitrophenol in UV-illuminated titania suspension

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001
    Jimmy Lea
    Abstract An internally-irradiated annular photoreactor has been used to investigate the oxidative degradation of aqueous 4-nitrophenol with titania as the photocatalyst. Reaction runs were performed over a 3-h period and in practically all cases, complete degradation was possible within about 2,h. The kinetics was determined as a function of nitrophenol concentration, oxygen partial pressure, catalyst loading, pH, temperature and light intensity. The reaction was characterised by a relatively low activation energy of 7.83,kJ,mol,1 although transport intrusions were negligible. Rate decreased almost exponentially with pH while a quadratic (maximum) behaviour with respect to both oxygen pressure and nitrophenol concentration is symptomatic of self-inhibition possibly due to the formation of intermediates which competitively adsorb on similar sites to the reactants. Increased catalyst dosage also improved the reaction rate although the possible effects of light scattering and solution opacity caused a drop at loadings higher than about 1.20,g,dm,3. Rate, however, has a linear dependency on light intensity, suggesting that hole,electron recombination processes were negligible at the conditions investigated. 2001 Society of Chemical Industry [source]


    High-performance liquid chromatographic/tandem mass spectrometric identification of the phototransformation products of tebuconazole on titanium dioxide

    JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2002
    Paola Calza
    Abstract Tebuconazole is a widely used fungicide. The formation of by-products on irradiated titanium dioxide as a photocatalyst was evaluated. Several species derived from tebuconazole degradation were identified and characterized by HPLC/MSn. A pattern of reactions accounting for the observed intermediates is proposed. Different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds), leading to a wide range of intermediate compounds. All these molecules are more hydrophylic than tebuconazole. The main steps involved are (1) the hydroxylation of the molecule with the formation of three species having [M + H]+ 324; the hydroxylation occurs on the C-1 carbon and on the aromatic ring in the two ortho -positions; (2) the cleavage of a C,C bond with the release of the tert -butyl moiety and the formation of a species having m/z 250; analogously to step 1, also on this species a further hydroxylation reaction occurs; (3) through the loss of the triazole moiety with the formation of a structure with m/z 257. Copyright 2002 John Wiley & Sons, Ltd. [source]


    A novel CD4-conjugated ultraviolet light-activated photocatalyst inactivates HIV-1 and SIV efficiently,

    JOURNAL OF MEDICAL VIROLOGY, Issue 8 2008
    Koushi Yamaguchi
    Abstract In this study, we found that the electric potential derived from the redox reaction of ultraviolet (UV)-illuminated CD4-conjugated titanium dioxide (TiO2) inactivated a wide range of high-titered primary HIV-1 isolates, regardless of virus co-receptor usage or genetic clade. In vitro incubation of HIV-1 isolates with CD4-conjugated TiO2 (CD4-TiO2) followed by UV illumination led to inhibition of viral infectivity in both H9 cells and peripheral blood mononuclear cells as well as to the complete inactivation of plasma virions from HIV-1-infected individuals. Treatment with a newly established extra-corporeal circulation system with the photocatalyst in rhesus macaques completely inactivated plasma virus in the system and effectively reduced the infectious plasma viral load. Furthermore, plasma viremia and infectious viral loads were controlled following a second therapeutic photocatalyst treatment during primary SIVmac239 infection of macaques. Our findings suggest that this therapeutic immunophysical strategy may help control human immunodeficiency viral infection in vivo. J. Med. Virol. 80:1322,1331, 2008. 2008 Wiley-Liss, Inc. [source]