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TiO2_Pd prepared by the incipient wet impregnation (IWI) method was successfully used as a photocatalyst for the degradation of an emerging water pollutant, clofibric acid (CA). It exhibits an improved photoactivity in comparison with different commercial titania in the degradation of CA (25 ppm). The irradiation intensity, photocatalyst dose, CA concentration and influence of water quality and of some salts in the reaction medium were systematically examined to understand their effects on the process efficiency. A total pollutant decomposition and a high mineralization yield (78%) were achieved in 50 and 190 min, respectively, in the optimal conditions, which is very promising for practical applications. [ABSTRACT FROM AUTHOR]

Decontamination of dye molecules from polluted water through photocatalyse process is reported to be a performing technology. In this study, sol gel synthesis route was used to prepare ZnO nanoparticles and ZnO modified natural and abundant bentonitic clay. ZnO and ZnO-clay nanocomposites were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, N2 adsorption–desorption, transmission electron microscopy techniques and tested for Acridine orange dye photodegradation using artificial UV irradiation. Experimental data indicates that ZnO-clay was an efficient photocatalyst under UV irradiation and in the presence of H2 O2 oxidant (around 97.8% of Acridine orange removal and 82.7% mineralization were achieved after 90 min). Adsorption experiments were studied and both pseudo-second-order and pseudo-first-order for kinetics models fitted the Acridine orange adsorption data except with pure ZnO catalyst adsorption process is described only by pseudo-second-order model. Photocatalytic degradation data of Acridine orange followed the first-order removal rate with three materials: pure clay, ZnO and ZnO-clay and the apparent rate constant increased with photocatalyst performance. The mechanistic detail of the dye photodegradation was studied via the separation and identification of the products intermediates by liquid chromatography–mass spectrometry method. Obtained results suggested that the N-de-methylation mechanism of Acridine orange (AO) dye took place leading to the generation of mono-, di-, tri-, and tetra-N-de-methylated AO products during the reaction. Synthetic pho)tocatalyst ZnO-clay was reused three times without an apparent decrease in its degradation effi)ciency even after 3 runs (94.7% of AO removal), proving the high stability and reutilisability. As well, ZnO-clay was tested in the treatment of a real textile effluent and obtained results (80.6% of effluent mineralization) confirm its great performance in the environmental decontamination. [ABSTRACT FROM AUTHOR]

We synthesized the compound Hg12Sb6(Br5,186I6,814) by chemical vapour transport method. Its structure was determined by single crystal X-ray diffraction. The optical band gap was determined as 2,1 eV according to UV-vis diffuse reflectance spectroscopy. Furthermore, the photocatalytic experiments have shown the ability of the Hg12Sb6 (Br5,186I6,814) to degrade rhodamine B (RhB) under solar light radiation. The ab initio calculations using the CASTEP code give a gap of 1,7 eV in good agreement with that found experimentally. [ABSTRACT FROM AUTHOR]

Here, we demonstrate that a metallaphotoredox‐catalyzed cross‐electrophile coupling mechanism provides a unified method for the α‐arylation of diverse activated alkyl chlorides, including α‐chloroketones, α‐chloroesters, α‐chloroamides, α‐chlorocarboxylic acids, and benzylic chlorides. This strategy, which is effective for a wide variety of aryl bromide coupling partners, is predicated upon a halogen atom abstraction/nickel radical‐capture mechanism that is generically successful across an extensive range of carbonyl substrates. The construction and use of arylacetic acid products have further enabled two‐step protocols for the delivery of valuable building blocks for medicinal chemistry, such as aryldifluoromethyl and diarylmethane motifs. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of humic acid (HA) in aqueous solution with titanium dioxide (TiO2) as catalyst has been studied. The effect of initial pH of the solution on the photocatalytic degradation has been examined. The photocatalytic process of humic acid has been followed by the determination of UV-VIS spectra and total organic carbon (TOC) of the reaction solution. The results showed that at low pH values, the degradation of HA was very favorable due to the adsorbent nature of the catalyst. The mineralization of the organic matter was observed with a reduction of the TOC of the order of 70 and 80% at pH = 7 and 3 respectively. Parameters such as absorbance ratio and Specific UV Absorbance (SUVA) were also calculated and the results revealed a reduction of the macromolecules of HA into compounds of smaller sizes. Moreover an aromaticity reduction of the treated HA was observed due to the action of hydroxyl radicals. [ABSTRACT FROM AUTHOR]

In this study, different commercially available TiO 2 powders (Degussa P25, pure anatase, and rutile) were submitted to selective dissolution treatments, with H 2 O 2 /NH 4 OH and 10% HF, known to remove rutile and anatase from physical mixtures. The aim was to check whether a particular separation method designed to remove a specific crystalline phase influences the properties of the other phase from the mixture or not. More precisely, we have studied how the HF dissolution method designed to selectively remove the anatase affected the physicochemical and photocatalytic properties of rutile. In a similar way, the changes in the anatase properties were studied, after the H 2 O 2 /NH 4 OH treatment, initially used to remove rutile from the mixture. All the samples were characterized by X-ray diffraction, nitrogen adsorption–desorption, transmission electron microscopy, diffuse reflectance (DR) ultraviolet–visible, and Raman spectroscopy. The photocatalytic activity of these powders was tested in the oxidation of p -chlorophenol from water. The selective treatment methods not only dissolved the target phase but also changed some physicochemical and the photocatalytic performances of the other TiO 2 crystalline phase in a considerable manner. These aspects should be taken into account in the studies regarding the synergistic effects of anatase and rutile, especially in reconstructed TiO 2 photocatalysts. [ABSTRACT FROM AUTHOR]

Compounds with the nominal formula K2[LnTa3O10] (Ln = La, Nd, Pr), crystallising in a cation-deficient Ruddlesden-Popper structure, were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray powder diffraction data and high-resolution transmission electron microscopy. The samples were also analysed to determine their specific areas (Brunauer-Emmett-Teller method) and degree of hydration (thermogravimetric analysis) and were tested as photocatalysts in the photocatalytic production of H2 from water. The activity to produce H2 from pure water decreased in the order Pr > La > Nd. The NiO x impregnation on the surface of the photocatalysts had no notable effect on the photocatalytic activity. [ABSTRACT FROM AUTHOR]

Pollution of water from a wide range of organic pollutants is a serious environmental problem. Conventional water treatment technologies are not very effective for reducing the concentration of these pollutants to a desirable level. The aim of this work was to evaluate the efficiency of two technologies in reducing the pollutant concentration of two wastewater samples. Therefore, cross-linked cyclodextrin (CD) polymers were synthesized and their adsorption capacities were evaluated. An emerging oxidation process using doped TiO 2 was also evaluated. For both technologies, we observed a decrease in the total organic carbon (TOC) content due either to the adsorption of pollutants by CD polymers or to the mineralization of pollutants by photocatalysis. [ABSTRACT FROM AUTHOR]

Catalysis plays a key role in chemical production, energy processing, air purification, water treatment, food processing, and the life sciences. Nanostructured materials with high surface areas and some unique properties have received widespread interest in electrocatalysis and photocatalysis. Recently, the author's research team has designed and studied a variety of novel functional nanomaterials. This review article is derived from the author's 2013 Canadian Catalysis Lectureship Award Lecture and focuses primarily on the electrocatalytic activities of platinum- and palladium-based nanomaterials and the development of TiO2-based nanostructured photocatalysts. Palladium possesses several exceptional properties that may enable promising applications in hydrogen detection, purification, and storage. The significant roles of palladium-based nanomaterials in facilitating the growth of a hydrogen economy are addressed. As platinum-based catalysts are vital to the development of fuel cells and sensors, the design of high-performance platinum-based electrocatalysts is highlighted. Additionally, TiO2 is considered to be one of the most promising photocatalysts due to its nontoxicity, high stability, and cost effectiveness. The modification of TiO2 nanomaterials to achieve visible light response is discussed as well. It is anticipated that the development of advanced functional nanostructured catalysts will further improve the efficiency and reduce the cost of electrochemical and photochemical processes, making them more attractive in addressing the pressing global energy and environmental issues. [ABSTRACT FROM AUTHOR]

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Abstract: TiO2/graphene composite photocatalysts were fabricated and the photocatalytic hydrogen-generating capabilities of the catalysts from H2O and H2S were investigated. The results showed that Ti-O-C bond formed in the TiO2/graphene composites, and as a co-catalyst, graphene attached to semiconductor surfaces can efficiently enhance the hydrogen evolution from H2O and H2S, which can be compared with that of the same semiconductor materials containing platinum under the same conditions. And the TiO2/graphene composite photocatalysts can still remain over 90% photocatalytic activity after photocatalytic hydrogen-generating from H2S and renewed in organic solution. [Copyright &y& Elsevier]

Abstract: This article is aimed at presenting (i) a fundamental research on the efficiency of photocatalysis in water disinfection and (ii) the efficiency of a photocatalytic prototype, developed by Buxair firm, to remove avian influenza virus in air. In water disinfection, two model strains of Escherichia coli (K12 PHL849 and K12 PHL1273) were selected and a comparison of the efficiencies of TiO2 Degussa P-25 versus TiO2 Millennium PC500 were estimated. A more important inactivation of E. coli PHL1273 was obtained on TiO2 Millennium PC500, in line with its better adherence on this solid. An experimental study was performed using a dialysis membrane to investigate the impact of the contact between the microorganisms and the photocatalyst and to determine the role of H2O2 generated in situ. In air disinfection, a total inactivation of virus A/H5N2, close to avian influenza virus A/H5N2, was obtained in a single pass in the Buxair® gas phase dynamic photoreactor using a contaminated air flow rate of 40m3/h. [Copyright &y& Elsevier]

Abstract: TiO2 photocatalytic mineralization of β-naphthol: influence of some inorganic ions, ethanol, and hydrogen peroxide. In this work, the photocatalytic oxidation of β-naphthol in aqueous suspensions of TiO2 was investigated at room temperature, by following the formation of CO2. The disappearance of β-naphthol fits a Langmuir-Hinshelwood kinetic model. The activation energy for the degradation reaction of β-naphthol is estimated at 10.2kJ/mol. The effects of some additives such as ethanol, H2O2, and inorganic ions (Cl−, SO4 2−, HCO3 −, NO3 −, Fe3+, Cu2+, and Cr3+) on the photomineralization of β-naphthol were examined. The inhibition of the anions for this reaction was in the order: NO3 −

Problems arise at water treatment works due to the reaction of natural organic matter with chlorine to produce disinfection by-products (DBP). Trihalomethanes (THMs) are the main DBP regulated in various countries. The UK THM standard is 100 μg L–1 while in the USA it is 80 μg L–1. At certain times of the year the efficiency of conventional treatment processes is compromised due to seasonal increases in the concentration of natural organic matter (NOM). During these periods water treatment works generally increase the coagulant dose but this subsequently increases the volume of potable sludge generated. Advanced oxidation processes have the potential to remove NOM and thereby reduce the DBP formation. Here the adsorption of NOM onto pelletised titanium dioxide (TiO2) and the oxidation of the surface of the pellets by UV light have been shown to reduce the dissolved organic carbon (DOC) concentration of source water by 70%. [ABSTRACT FROM AUTHOR]

Abstract: P-doped TiO2 nanoparticles were prepared by the sol–gel method and characterized by XRD, BET, SEM, XPS and UV–vis spectrum. The results indicated that the doping of phosphorus could efficiently inhibit the grain growth and enhance the surface area of TiO2 nanoparticles. The doped phosphorus was present as the pentavalent-oxidation state, which can replace a part of Ti4+ in the crystal lattice of anatase. Because P5+ can accept photoelectron as the electron trap center, its doping reduces the recombination rate of photogenerated charge carriers. In addition, P-doped TiO2 nanoparticles also show stronger absorption in the visible light range than the pure sample, because of the formation of an impurity energy level within the band gap of TiO2. Correspondingly, P-doped TiO2 nanomaterials show higher ability of NADH photogenenration under visible-light irradiation than pure TiO2. [Copyright &y& Elsevier]

Abstract: Here we show that a solar driven, self-cleaning coating was deposited onto organic fluorocarbon paint using a hybrid system. The system utilizes the corona treatment technique, the inert sol–gel coating and the anatase TiO2 layer. With the corona treatment, an organic surface was activated to allow a uniform TiO2 sol–gel coating. This sol–gel layer has two functions: firstly, it acts as binder to adhere the nano size TiO2 particles; secondly, it acts as barrier to prevent substrate-damage from the photocatalytic reaction. Using this approach, a strong and crack-free TiO2 sol–gel coating was obtained. The very fresh TiO2 sol–gel coating shows almost zero water contact angle even without exposure to sunlight, and this super-hydrophilic property is retained under sunlight irradiation. These properties differentiate our approach from other study [1]. With such photocatalytic and hydrophilic characteristics, dirt residues on the surface were either readily oxidized or simply washed away by rain. To cite this article: R. Cai et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: The ability of polyoxometallates (POM), molecular-anionic metal oxides, to act as photocatalysts in the electron transfer from organic substrates to metal ions will be presented. In the process, illumination at the O → M charge-transfer band (near-visible and UV regions), renders POM strong oxidants able to abstract electrons from a great variety of organic compounds, including organic pollutants. The photochemically reduced POMs can in turn act as soluble cathodes, able to reduce several metal ions to the elemental state. The process can be implemented for (i) the controlled reductive precipitation and recovery of valuable or toxic metals that can also be combined with the degradation of organic pollutants in a one-pot system and (ii) the synthesis of several metal nanoparticles in a simple and efficient way. To cite this article: A. Troupis et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: A wave-guide type photocatalytic rod that is consisting of a glass tube with transparent TiO2 (outside) and an optical wave-guide rod (inside) was designed and examined its performance. A model of polluted water, which contains 100 ppm of toluene or phenol, was taken in a 500 ml of beaker and the performance of this unit was evaluated by the removal rate of pollutants in water under photo-irradiation. Acrylic rod with 6-mm diameter was used as the wave-guide of light. One end of acrylic rod 50 mm had a frosted part or a screw thread for increasing seep out of the light. For the glass tube with transparent TiO2, four kinds with different film thickness were prepared by the dip-coating method. The wave-guide type photocatalytic rods effectively eliminated toluene and phenol and the total amount of intermediates formation was low. To cite this article: N. Negishi et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: The photocatalytic oxidation of phenol in water under a visible light over anatase-type titanium dioxide (Tytanpol A11, Poland), modified by carbon deposited via n-hexane carbonisation, was investigated. The catalysts, which had small (0–0.2 mass%) and high (0.69–0.85 mass%) contents of carbon showed a little lower catalytic photoactivity than pristine TiO2. However, the catalyst with high content of carbon (0.85 mass%) gave almost 14-times lower turbidity in the phenol solution after the photocatalyst sedimentation. These two factors depend on the carbon content and have an influence on the ‘practical efficiency’ of the catalysts. The ‘practical efficiency’ of the catalyst under visible light, calculated from these two factors, was therefore 14-times higher for the catalyst containing 0.85 mass% carbon (whereas for UV radiation, it was found to be lower – 0.2 mass% –; this is the result of a previous work). The surface modification of the catalyst with 0.85% carbon seemed to be stable under visible light. The deposition of carbon on TiO2 by carbonisation of n-hexane was supposed to lead to obtain the catalyst, which could be easily used in a water-treatment system under visible light. To cite this article: A.W. Morawski et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: In order to understand the origin of visible-light photocatalysis by nitrogen-doped titania, titania (anatase) films whose composition can be varied in a controlled way have been grown in situ and subsequently characterized by XPS, UPS, and ex situ AFM. Two very different in situ methods for nitrogen-doping were used, N+ implantation and nitride oxidation, and the chemical identity and depth distributions of the resulting chemical species were established. It is found that N+ implantation results in extensive reduction of the titania, re-oxidation with O2 establishing an essentially oxidized surface. Both methods of preparation result in the nitrogen being located beneath the surface. These results have significant implications for our understanding for the origin of visible light activity of nitrogen-doped catalysts. In particular, they indicate that earlier interpretations may be oversimplified or even incorrect. To cite this article: A. Orlov et al., C.R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: The need to increase the photodegradation rates of toxic materials that may coexist in effluent streams together with less harmful contaminants is discussed. Despite the relatively scarce data on this issue, it is possible to outline several process parameters, such as pH, doping, and type of solvent that may influence photodegradation rates with some specificity. Most of these parameters act through controlling the mass transport of the reactants to the photoactive surfaces. Mass transport control is also the basis for several synthetic approaches for obtaining preferential photodegradation, out of which surface modification by imprinted contaminants, and the ‘adsorb-and-shuttle’ approach, should be considered as methods that may provide high specificity. To cite this article: Yaron Paz et al., C R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: Scientific studies on photocatalysis started about three decades ago. Titanium dioxide (TiO2), which is one of the most basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this short account, we will briefly discuss some fundamental studies on TiO2 photocatalysis, summarize the present commercialization of TiO2-based products, and highlight several points for the future development of TiO2 photocatalysis. To cite this article: A. Fujishima, X. Zhang, C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

Abstract: TiO2 photocatalysis has attracted considerable scientific and practical interest during the last three decades. One major current direction in this research area is the design and preparation of novel TiO2-based photocatalysts possessing high photocatalytic activity to satisfy the requirements for practical applications. For the development of successful strategies to achieve this goal it is, however, of utmost importance to improve the mechanistic understanding of the basic principles of photocatalysis. Therefore, various nanosized TiO2 photocatalysts including pure TiO2, Fe(III)-doped TiO2 and platinized TiO2 have been synthesized in our laboratories and their photocatalytic activity has been studied in detail. Several unexpected results have been obtained during these investigations and two new mechanistic models have consequently been developed for their explanation. On the one hand, it was observed that Fe(III)-doped TiO2 nanoparticles form extended networks in aqueous suspensions with the particles being attached in a way that their atomic planes are aligned parallel to one another. Through the so-called Antenna Mechanism the resulting energetic coupling throughout a long chain of titania nanoparticles will enable an energy and/or exciton transfer from the particle where the initial photon absorption took place to the particle where the electron transfer process finally occurs. On the other hand, the so-called deaggregation concept was introduced to explain a 50% increase of the quantum yield when methanol was photocatalytically oxidized in aqueous suspensions of platinized TiO2 nanoparticles employing pulsed laser excitation instead of continuous illumination. Within each individual laser pulse, the ensemble of nanoparticles absorbs sufficient energy to initiate the deaggregation of the particle network held together by hydrogen bonds thus opening up additional surface area for methanol adsorption and oxidation. To cite this article: C.-yi Wang et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Mesoporous tantalum oxide, Fe3+-doped mesoporous tantalum oxide, and bis(toluene) titanium reduced mesoporous tantalum oxide were used for the first time as Schrauzer-type photocatalysts for the conversion of dinitrogen to ammonia. The materials were characterized by XRD, TEM, XPS, and nitrogen absorption before and after catalytic runs. The results showed low to moderate activities depending on the composition. In contrast to previously studied Ti catalysts, Fe doping and heat pretreatment were not prerequisites for photocatalytic activity, but did improve the turnover rates by up to a factor of two. The optimal Fe loading for the tantalum oxides was found to be 1 wt% and the optimal heating condition at 300 °C for 3 h. Increased surface area and heat treatment were also found to improve activities. Contrary to our expectations, reduction of the mesostructure with bis(toluene) titanium had little effect on the catalytic activity. In spite of the dramatically higher surface areas of the mesoporous tantalum oxides as compared with bulk titanias used previously in this process, the overall catalytic activities were still less than those obtained in the Schrauzer system. This suggests that the increase in diffusion and surface area offered by the mesoporous structure is offset by the smaller crystalline domain sizes in the walls of the structure, leading to poor electron-hole separation and a reduction in catalytic efficiency. Key words: mesoporous, Schrauzer, ammonia, photocatalysis, tantalum oxide. [ABSTRACT FROM AUTHOR]

Nosocomial infections are an important health problem and cause of complications and death in hospitalized patients. This problem should be solved from the preventive angle, avoiding the spread of infections by designing disinfection methods based on the photocatalytic activity of semiconductor materials such as tin oxide (SnO 2 ). The antimicrobial activity of UV light was tested by using inoculation with Candida albicans ATCC10231 on SnO 2 thin films and counting colony forming units (CFU). The interaction of UV light with SnO 2 was analyzed by density functional theory (DFT) and the extension to the Hubbard model (DFT+U) schemes to predict the electron behavior at the subatomic level. After exposure to UV light, C. albicans showed a reduction of 36.5% in viable cells, and when SnO 2 was included, cell viability was reduced by 60.2%. Measurements of the electronic structure obtained by the first-principle calculations under the DFT and DFT+U schemes showed that the O-p orbitals mediate the oxidation process in the bulk semiconductor. By including the surface effects when cleaving the (1 0 0) plane, the three orbitals O-p, Sn-p, and Sn-s are the mediators. SnO 2 films are promising antimicrobial coatings because UV light has a synergic activity with thin films, resulting in faster disinfection.