Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2006"
TL;DR: Azobenzene (azo) chromophores have been incorporated into a wide variety of materials and molecular architectures, including polymers, dendrimers, and molecular glasses as mentioned in this paper.
Abstract: Azobenzene (azo) chromophores have been incorporated into a wide variety of materials and molecular architectures, including polymers, dendrimers, and molecular glasses. Azobenzene exhibits a uniquely clean and efficient photochemistry, with facile geometric isomerization about the azo bond, converting the molecule from trans to cis . This review discusses the extensive number of investigations of azobenzene photo-switching and photo-modulation. In particular, azos can be used to alter material behaviour with light, switching both molecular and macroscopic properties. A large number of photobiological studies have shown that interfacing the azo chromophore with enzymes and biopolymers is feasible and useful. The all-optical surface patterning unique to azobenzenes is also reviewed. Lastly, azobenzene photomechanical effects are discussed.
490 citations
TL;DR: In this article, the photocatalytic activity of Fe 3+ -doped anatase nanosized TiO 2 photocatalyst was investigated for the degradation of active yellow XRG dye.
Abstract: Fe 3+ -doped anatase nanosized TiO 2 photocatalysts have been prepared by combining sol–gel method with hydrothermal treatment. The samples were characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET)-specific surface area ( S BET ), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From results of UV–vis diffuse reflectance spectroscopy, Fe 3+ -doped TiO 2 extends its absorption to longer than 500 nm, which leads to an obvious photocatalatic activity under visible irradiation. From XRD, EPR, AAS and XPS, it was found that Fe exist in trivalent ionic state substituting Ti 4+ in TiO 2 lattice and its concentration decreases from the surface to the center of doped TiO 2 . The photocatalytic activity of prepared samples was investigated for the photocatalytic degradation of active yellow XRG dye. The photocatalytic activity of TiO 2 doped with appropriate content of Fe 3+ exceeded those of non-doped TiO 2 and P25 both under UV and visible light irradiation.
438 citations
TL;DR: In this article, the principle of dye-sensitized solar cells (DSCs) in terms of a new physics-based equivalent circuit model was discussed, and the highest efficiency scores of 10.4% and 10.8% (aperture illumination area 1.004 cm2 and 0.2227 cm2, respectively) were confirmed by a public test center.
Abstract: The present paper discusses the principle of dye-sensitized solar cells (DSCs) in terms of a new physics-based equivalent circuit model. This model is proposed following analysis by electrochemical impedance spectroscopy of the voltage dependence of the internal resistance elements of DSCs. The influence of these elements upon cell performance in areas such as short circuit current density (JSC), open circuit voltage (VOC) and fill factor (FF) was examined based on the equivalent circuit. It was demonstrated that the haze factor of TiO2 electrodes is a useful index when fabricating light-confined TiO2 electrodes to improve JSC, and that blocking the TiO2 surface with molecules is an effective way of reducing interfacial charge recombination at the TiO2 surface and of improving shunt resistance and VOC. FF was also improved by reduction of the internal series resistance, which is composed of the following three elements: the redox reaction resistance at the platinum counter electrode, the resistance of carrier transport by ions in the electrolyte, and resistance due to the sheet resistance of the transparent conducting oxide. Finally, the highest efficiency scores of 10.4% and 10.8% (aperture illumination area 1.004 cm2 and 0.2227 cm2, respectively) were confirmed by a public test center.
388 citations
TL;DR: In this article, the effect of the deposition parameters on the cell was studied, in particular differences between ion-by-ion and cluster deposition mechanisms, and cell efficiencies up to 2.8% under solar conditions were obtained.
Abstract: CdSe is homogeneously deposited into nanoporous TiO 2 films and used in liquid junction photoelectrochemical solar cells. The effect of the deposition parameters on the cell are studied, in particular differences between ion-by-ion and cluster deposition mechanisms. CdSe deposition on a Cd-rich CdS film that was deposited first into the TiO 2 film, or selenization of the Cd-rich CdS layer with selenosulphate solution improves the cell parameters. Photocurrent spectral response measurements indicate photocurrent losses due to poor collection efficiencies, as shown by the strong spectral dependence on illumination intensity. Cell efficiencies up to 2.8% under solar conditions have been obtained.
363 citations
TL;DR: In this article, tetracycline solutions were irradiated in aqueous suspensions of TiO 2 with three different light sources: a UV lamp, a solarium device and a UV-A lamp.
Abstract: To compare tetracycline abatement efficiency, tetracycline solutions were irradiated in aqueous suspensions of TiO 2 with three different light sources: a UV lamp, a solarium device and a UV-A lamp. Negligible degradation was observed when irradiations were performed in absence of TiO 2 . In contrast, rapid tetracycline degradation was observed in the presence of 0.5 g l −1 of TiO 2 . Close to 50% of its initial concentration was eliminated after 10, 20 and 120 min when the irradiation source used was a UV lamp, a solarium device and a UV-A lamp, respectively. Significant mineralization was also obtained when the UV lamp and solarium were used for photocatalysis. The antibacterial activity of selected microorganisms was drastically inhibited when exposed to tetracycline solutions treated by the photocatalyst over short irradiation periods.
289 citations
TL;DR: In this paper, the interaction between methylene blue (MB) and bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorbance spectroscopy.
Abstract: The interaction between methylene blue (MB) and bovine serum albumin (BSA) was investigated by fluorescence and UV–vis absorbance spectroscopy. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by MB is mainly a result of the formation of MB–BSA complex and electrostatic interactions play an important role to stabilize the complex. The Stern–Volmer quenching constant K SV and corresponding thermodynamic parameters Δ H , Δ G , and Δ S were calculated. The distance r between donor (BSA) and acceptor (MB) was obtained according to fluorescence resonance energy transfer (FRET). The effect of MB on the conformation of BSA has been analyzed by means of UV–vis absorbance spectra and synchronous fluorescence spectroscopy.
267 citations
TL;DR: Anatase type N-F-codoped TiO 2 powder was successfully prepared by a sol-gel-solvothermal method using tetrabutyl titanate as precursor as discussed by the authors.
Abstract: Anatase type N–F-codoped TiO 2 powder was successfully prepared by a sol–gel-solvothermal method using tetrabutyl titanate as precursor. The effect of acidity and solvents on crystallinity, morphology, and size of the prepared N–F–TiO 2 powder particles was investigated. The prepared catalysts were characterized by X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG–DTA), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflection spectroscopy (UV–vis–DRS). The photo-catalytic activity of N–F–TiO 2 powder was measured by using the reaction of photocatalytic degradation of p -chlorophenol. It was shown that the surface of N–F–TiO 2 powder was strongly acidic, and it was confirmed that the N–F-codoped TiO 2 powder showed strong visible-light absorption and high photocatalytic activity for p -chlorophenol and Rhodamine B under visible light irradiation (400–500 nm). The catalyst showed very high visible-light activity toward photocatalytic degradation of p -chlorophenol. Under the irradiation of 150 W tungsten halogen light for 12 h, the conversion could be as high as 17.8%, which was 1.75, 1.25 and 1.5 times higher than that of commercial P25 TiO 2 , N–TiO 2 , and F–TiO 2 powder in a suspension system, respectively. The high visible-light photocatalytic activity of the N–F-codoped TiO 2 may result from the generation of additional band of N 2p in the forbidden band, and the synergetic effect of nitrogen and fluorine doped.
215 citations
TL;DR: In this article, a novel electrodeposited CdS nanoparticle-modified highly-ordered TiO2 nanotube-array photoelectrode and its application to photo-electrochemical cells is reported.
Abstract: A novel electrodeposited CdS nanoparticle-modified highly-ordered TiO2 nanotube-array photoelectrode and its application to photoelectrochemical cells is reported. Results show formation of a thin, nanoparticulate CdS layer, comprised of sphere-like 10–20 nm diameter nanoparticles, on the anodic synthesized TiO2 nanotube-array (inner diameter of 70 nm, wall thickness 25 nm and ca. 400 nm length) electrode. The resulting CdS–TiO2 photoelectrode has an as-fabricated bandgap of 2.53, and 2.41 eV bandgap after sintering at 350 °C in N2 ambient. Photoelectrochemical properties are described in detail.
208 citations
TL;DR: In this paper, the photocatalytic degradation of an anionic azo-dye, i.e., Orange II in aerated aqueous suspension under UV-vis and visible (λ ǫ > 400 nm) illumination was investigated.
Abstract: TiO 2 , CdS and coupled CdS/TiO 2 powders with CdS percentage varied from 5 to 50% (w/w) have been prepared by a sol–gel method. These pure and composite semiconductors were tested for the photocatalytic degradation of an anionic azo-dye, i.e. Orange II in aerated aqueous suspension under UV–vis and visible ( λ > 400 nm) illumination. The photocatalytic efficiency of the CdS/TiO 2 couples is found to strongly depend on the proportion of CdS. Under UV–vis light, CdS/TiO 2 couples containing a low proportion of CdS are found to be as efficient as pure TiO 2 which shows the best photocatalytic activity. Under visible illumination, these formers exhibit faster degradation rate than both isolated components of the composite photocatalyst. The results obtained under both illumination conditions are compared and discussed in order to elucidate the respective role of Acid Orange II and CdS in the photosensitization mechanism of TiO 2 .
201 citations
TL;DR: In this paper, the authors examined the visible light water-photoelectrolysis and photoelectrochemical properties of highly ordered titania nanotube arrays as a function of nanotubes crystallinity, length (up to 6.4mm), and pore size.
Abstract: We examine the visible light water-photoelectrolysis and photoelectrochemical properties of highly ordered titania nanotube arrays as a function of nanotube crystallinity, length (up to 6.4 μm), and pore size. Most noteworthy of our results, under visible light AM 1.5 illumination (100 mW/cm2) the titania nanotube array photoanodes (1 cm2 area), pore size 110 nm, wall thickness 20 nm, and length 6 μm, generate hydrogen by water photoelectrolysis at a rate of 175 μL/h, with a photoconversion efficiency of 0.6%. The energy–time normalized hydrogen evolution rate is 1.75 mL/h W. The oxygen bubbles evolving from the nanotube array photoanode do not remain on the sample, hence the output remains stable with time irrespective of the duration of hydrogen production.
200 citations
TL;DR: In this article, a review of the findings of a range of studies aimed at describing the influence of the N-doping of TiO2 thin films and particles on possible visible light induced photoactivity is presented.
Abstract: A brief review of the findings of a range of studies aimed at describing the influence of the N-doping of TiO2 thin films and particles on possible visible light induced photoactivity is presented. By way of a new approach to the direct growth of N-doped TiO2 thin films, the physical and photochemical effects of the addition of ammonia during atmospheric chemical vapour deposition (CVD) growth of TiO2 are described. It is found that the addition of ammonia to the CVD reactive gas mixture causes a dramatic change in film morphology and a reduction in growth rates. In addition, it is found that although we have clear evidence for the incorporation of ?O-substitutional N atoms within the growing film, there is no evidence of any appreciable photocatalytic activity of the doped TiO2 films when irradiated with visible light. In fact the degradation in film morphology results in a decrease in conventional uv-induced photoactivity as compared to that for an undoped film. These findings are discussed in terms of the findings of other studies of N-doped TiO2 films that have been reported.
TL;DR: In this article, the microstructure of ZnO films was modified through the formation and pyrolysis of layered hydroxide zinc acetate (LHZA) grown in a methanolic solution of zincacetate dihydrate.
Abstract: To improve dye-loading in photoanodes, microstructure of ZnO films was modified through the formation and pyrolysis of layered hydroxide zinc acetate (LHZA) grown in a methanolic solution of zinc acetate dihydrate Appropriate annealing treatments for the films led to the formation of mesoporous microstructure with an average pore diameter of 12 nm It was demonstrated that loading of N-719 in the ZnO films was successful without influence of protons in solutions, as evidenced by a large dye amount of 14 × 10 –7 mol/cm 2 , and hence a high short-circuit photocurrent density of 126 mA/cm 2 Sandwich-type dye-sensitized solar cells using the present ZnO/N-719 photoanode exhibited a conversion efficiency as high as 41% (AM-15, 100 mW/cm 2 )
TL;DR: In this paper, an overview of the recent work related to the fabrication of 3D micro-structures and photonic devices by means of the two-photon polymerization (2PP) technology is introduced.
Abstract: This article presents an overview of the recent work related to the fabrication of three-dimensional (3D) micro-structures and photonic devices by means of the two-photon polymerisation (2PP) technology. The principle of the 2PP technique and the method for micro-fabrication are introduced in this article. The solidified size of a micro-structure formed during the photo-polymerisation process can be controlled by adjusting optical fabrication parameters; the minimum size can be as small as 150 nm. The influence of photo-initiators and material properties of a resin are discussed. Recent progress related to the development of initiators and resins for 2PP is briefly introduced. Chemical processes, preparation procedures and post-processing of the common resins (including commercialised and customer-made ones) are summarised in tables. Micro-structures such as photonic crystal woodpile structures fabricated by using various resins are reviewed. The performance indicators of common resins for photonic crystal application are emphasised.
TL;DR: In this article, the photocatalytic surface sites on SO 4 2− /TiO 2 were investigated by pyridine adsorption and in situ Fourier transform infrared (FT-IR) spectroscopy.
Abstract: Photocatalytic surface sites on SO 4 2− /TiO 2 were investigated by pyridine adsorption and in situ Fourier transform infrared (FT-IR) spectroscopy. Results revealed that the sulfate-modification not only increased the number of strong Lewis acidic sites, but also induced a large amount of strong Bronsted acidic sites on the surface of TiO 2 . Pyridine molecules were chemically captured on Bronsted and Lewis acidic sites on the SO 4 2− /TiO 2 surface. These pyridine molecules were progressively decomposed to final products of CO 2 and H 2 O under actual photocatalytic conditions. The high photocatalytic performance of SO 4 2− /TiO 2 can be explained by the improved surface acidities that favor the adsorption of both oxygen and pyridine molecules. Moreover, the Lewis acidic sites could react with H 2 O and was then converted to Bronsted acidic sites, leading to the activation of the water. This conversion promoted the formation of hydroxyl groups on the catalyst surface, which could also contribute to the high photocatalytic reactivity of SO 4 2− /TiO 2 .
TL;DR: In this paper, the photocatalytic activity of mesoporous anatase TiO2 nanofibers was evaluated using a simple hydrothermal post-treatment of titanate nanotubes.
Abstract: Mesoporous anatase TiO2 nanofibers were prepared by a simple hydrothermal post-treatment of titanate nanotubes. The as-prepared samples were characterized with transmission electron microscopy (TEM), thermogravimetry (TG), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and N2 adsorption–desorption measurement. The photocatalytic activity of the mesoporous TiO2 nanofibers was evaluated by photocatalytic oxidation of acetone in air. The effects of hydrothermal post-treatment time on the structures and photocatalytic activity of the mesoporous TiO2 nanofibers were discussed. The results showed that the photocatalytic activity of the TiO2 nanofibers prepared by this method exceeded that of Degussa P25 when the hydrothermal post-treatment time was kept at 200 °C for 3–24 h. This could be attributed to the fact that the former had smaller crystallite size, larger specific surface area, and higher pore volume.
TL;DR: In this paper, the degradation of three commercially available textile azo dyes, Solophenyl Green BLE 155% (SG), Erionyl Red B (ER), and Chromotrope 2R (C2R), has been studied by using photochemical and photocatalytic processes under UV irradiation.
Abstract: The degradation of three commercially available textile azo dyes, Solophenyl Green BLE 155% (SG), Erionyl Red B (ER) and Chromotrope 2R (C2R), has been studied by using photochemical and photocatalytic processes under UV irradiation. The adequacy of each process depends on the concentration of dye. At low dye concentration, the neat photochemical degradation is very efficient. The photocatalytic process, using either slurry of Degussa P-25 TiO 2 or a biphasic mixture of TiO 2 and activated carbon (AC), more effectively bleaches heavier colored solutions. The heterogeneous photocatalytic regime was characterized in terms of catalyst load, TiO 2 to AC mass ratio, initial dye concentration and oxygen partial pressure. Catalyst recovery and reuse was also analyzed. Based on the Langmuir–Hinshelwood approach, reaction rates and adsorption equilibrium constants were calculated. A positive effect on the photocatalytic degradation was observed by the addition of AC to TiO 2 catalyst, which was quantified in terms of a synergy factor ( R ). The efficiencies of different photo-induced degradation processes were compared based on the experimentally determined apparent rate constants, mineralization degrees and initial quantum yields.
TL;DR: In this article, the authors used FT-IR spectroscopy to monitor the SA test and the appearance of CO2 in a self-cleaning selfcleaning film, and found that the CO2 generated was >90% that expected throughout the photomineralisation process for the sol-gel titania film.
Abstract: The destruction of stearic acid (SA), the SA test, is a popular approach used to evaluate the activities of photocatalytic films The destruction of SA via semiconductor photocatalysis is monitored simultaneously, using FT-IR spectroscopy, via the disappearance of SA and the appearance of CO2 Sol–gel and P25 films of titania are used as the semiconductor photocatalytic self-cleaning films A conversion factor is used of 97 × 1015 molecules of SA cm−2 ≡ 1 cm−1 integrated areas of the peaks in the FT-IR of SA over the range 2700–3000 cm−1, which is three times that reported previously by others As the SA disappeared the concomitant amount of CO2 generated was >90% that expected throughout the photomineralisation process for the sol–gel titania film In contrast, the slightly more active, and scattering, P25 titania films generated CO2 levels that dipped as low as 69% during the course of the photoreaction, but eventually recovered to ≅100% that expected based on the amount of SA present The importance of these results with respect to SA test and the evaluation of new and existing self-cleaning films are discussed briefly
TL;DR: In this article, the bacterial inactivation of Escherichia coli on Ag-cotton textiles was investigated under different experimental conditions with novel Ag-nanoparticles fixed on cotton textiles.
Abstract: The bacterial inactivation of Escherichia coli on Ag–cotton textiles were investigated under different experimental conditions with novel Ag-nanoparticles fixed on cotton textiles. The evaluation of the bactericide performance of the Ag–cotton was compared with the one observed for Ag–TiO2–cotton loaded textiles. The procedure used allowed us to prepare highly dispersed Ag-cluster species, 2–4 nm in size, as observed by transmission electron microscopy (TEM). By depth profile analysis, the X-ray photoelectron spectroscopy (XPS) revealed that the Ag profile in the 15 topmost layers remained almost constant before and after E. coli inactivation. The cotton loading was fairly low and of the order of 0.10 wt.% Ag/wt. of cotton. By infrared spectroscopy no modification of the Ag–cotton could be detected before or after E. coli inactivation due to the small absorption coefficient of Ag and the very low metal loading of Ag on the cotton. The E. coli was completely abated on Ag–cotton textiles immediately after the contact took place, due to the strong bacteriostatic effect of the dispersed silver clusters on the cotton surface.
TL;DR: In this article, the application of Fenton and photo-Fenton type processes, UV/Fe 2+ /H 2 O 2 and UV/ Fe 0 /H2 O 2, for dye wastewater treatment was investigated.
Abstract: Application of Fenton and photo-Fenton type processes, UV/Fe 2+ /H 2 O 2 and UV/Fe 0 /H 2 O 2 , for dye wastewater treatment was investigated. In the first stage of the study, Fenton type processes were optimized regarding the iron catalyst concentration and the iron catalyst/H 2 O 2 ratio. In the next step, Fe 2+ /H 2 O 2 and Fe 0 /H 2 O 2 at optimal process parameters were combined with UV radiation in order to enhance dye degradation. The destruction of model organic pollutant, azo dye C.I. Acid Orange 7 (AO7), was monitored on the basis of decolorization and mineralization extents, determined by UV–vis and TOC analyses, respectively. All studied processes have shown high efficiency in the bleaching of the studied dye model solution with complete decolorization achieved in all cases. Mineralization extents depended on the type and the dosage of added iron catalysts for Fenton type reaction. The highest mineralization extent was achieved by UV/Fe 0 /H 2 O 2 , 90.09% of TOC removal. A quantum yield of AO7 organic dye, Φ = 6.5 × 10 −3 mol Einstein −1 , was determined on the basis of decolorization of AO7 by direct photolysis.
TL;DR: In this article, nanometric particles of CdS (a narrow band gap semiconducting material) were used to impregnate TiO2 in order to optimize its photocatalytic properties.
Abstract: Titanium dioxide is broadly used as a catalyst for photochemical reactions. In this work, nanometric particles of CdS (a narrow band gap semiconducting material) were used to impregnate TiO2 in order to optimize its photocatalytic properties. CdS/TiO2 semiconductor composites were obtained in 1, 3, 5 and 20 mol% proportion and characterized by differential thermogravimetric analysis (DTG), X-ray diffraction (XRD), laser-induced fluorescence (LIF) and resonance Raman spectroscopy. The results identified the CdS in hexagonal geometry and the TiO2 in anatase form. Resonance Raman spectroscopy data revealed a lattice softening of the TiO2-anatase phase due to electronic interaction between TiO2 and CdS in the CdS/TiO2 catalyst. The effect of modifying the proportion of CdS in the catalyst electronic properties and efficiency was also studied. The photocatalytic activity of the CdS/TiO2 was investigated using artificial UV light for degradation of the textile azo-dye Drimaren red. The photocatalytic analysis revealed better efficiency for the CdS/TiO2 5% composite as compared with other CdS/TiO2 proportions and with TiO2 alone.
TL;DR: In this paper, the photocatalytic removal of atrazine from water was investigated using immobilised TiO2 films in a stirred tank reactor designed to maximise mass transfer.
Abstract: The photocatalytic removal of atrazine from water was investigated using immobilised TiO2 films in a stirred tank reactor designed to maximise mass transfer. The degradation of atrazine was demonstrated with a number of breakdown products identified including the stable end product cyanuric acid. The process was monitored using high performance liquid chromatography (HPLC), total organic carbon analysis (TOC) and liquid chromatography-mass spectrometry (LC-MS). A decrease in the TOC was observed and attributed to the oxidative degradation of atrazine side chains. Intermediates identified included 2-chloro-4-acetamido-6-isopropylamino-1,3,5-tiiazine, 2-chloro-4-ethylamino-6-(1methyl-1-ethanol)amino-1,3,5-triazine, 2-chloro-4-ethylamino-6-(2-propanol)amino-1,3,5-triazine, 2-hydroxyatrazine, desethylatrazine, deisopropylatrazine, 2-hydroxydesethyl atrazine and cyanuric acid. Operational parameters such as catalyst loading, oxygen concentration, initial pollutant concentration and UV source were investigated. Atrazine removal followed first order kinetics and the rate was dependent upon catalyst loading up to an optimum loading (above which a decrease in the degradation rate was observed). No difference in the rate was observed when either air and 02 sparging was used. The rate was directly proportional to initial concentration in the rangestudied. The use of UVB irradiation did not appear to increase the rate of degradation in comparison with UVA irradiation. However, the maximum apparent quantum yield for the photocatalytic degradation was higher under UVB (0.59%) compared to UVA (0.34%).
TL;DR: In this paper, the interaction between 3,3-bis(4-hydroxy-1-naphthyl)-phthalide (NPP) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy.
Abstract: The interaction between 3,3-bis(4-hydroxy-1-naphthyl)-phthalide (NPP) and bovine serum albumin (BSA) have been studied by fluorescence spectroscopy. The binding of NPP quenches the BSA fluorescence. By the fluorescence quenching results, it was found that the binding constant K = 5.30 × 10 4 L mol −1 , and number of binding sites n = 0.9267. In addition, according to the synchronous fluorescence spectra of BSA, the results showed that the fluorescence spectra of BSA mainly originate from the tryptophan residues. Finally, the distance between the acceptor NPP and BSA was estimated to be 1.94 nm using Foster's equation on the basis of fluorescence energy transfer. The interaction between NPP and BSA has been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer.
TL;DR: In this paper, the effect of reaction solvents on the phase composition, specific surface area and photocatalytic activity of titania photocatalyst was also characterized for the oxidative destruction of nitrogen monoxide under irradiation of visible light.
Abstract: Nitrogen doped or nitrogen/sulfur co-doped titania photocatalyst TiO 2− x A y (A = N, S) which can be excited by visible light were prepared by mixing aqueous TiCl 3 solutions with various nitrogen sources such as hydroxylamine (NH 2 OH), hexamethylenetetramine (HMT, C 6 H 12 N 4 ), urea ((NH 2 ) 2 CO) and thiourea ((NH 2 ) 2 CS) followed by hydrothermal treatment at 190 °C. The titania powders prepared using hydroxylamine consisted of rutile crystals with non-homogeneous size distribution. The nitrogen doped titania powders prepared using hexamethylenetetramine consisted of mainly mono-size spherical brookite crystals, whereas those using urea and thiourea consisted of belt-like rutile particles. The TiO 2− x A y (A = N, S) powders showed excellent visible-light absorption and photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light. The effect of reaction solvents on the phase composition, specific surface area and photocatalytic activity was also characterized.
TL;DR: This laser kinetics features of the electron decay of TiO2 in the presence of the Escherichia coli (E coli) phosphatidyl-ethanolcholine (PE) and lipo-polysaccharides (LPS) cell wall components were reported in this paper.
Abstract: This laser kinetics features of the electron decay of TiO2 in the presence of the Escherichia coli (E coli) phosphatidyl-ethanolcholine (PE) and lipo-polysaccharides (LPS) cell wall components were are reported in this study The interaction of the biomolecules with the photogenerated charge carriers was determined and the reaction rates were measured The effect of the variation of ionic strength of the colloidal TiO2 on the electron decay was determined in the presence of PE and E coli The ionic strength seems to affect the equilibrium absorption of the biomolecules on TiO2 The e− decay was measured for TiO2 samples having different sizes, charge and isoelectric points (IEP) by laser spectroscopy for different types of TiO2 TiO2 Degussa P-25 mediated the E coli abatement most effectively compares to other TiO2 samples The structural features of different TiO2 samples were related to the degradation of E coli and also related to the fast kinetics results
TL;DR: In this paper, the authors performed structural and surface characterisation of catalysts in order to establish a correlation between the oxoanion stability during calcination and the further photocatalytic behavior of TiO2.
Abstract: Photocatalytic oxidation of phenol was performed over acid pre-treated TiO2 prepared by a sol–gel method. Several oxoacids were used in the acid pre-treatment (nitric, sulfuric and phosphoric acids). Wide structural and surface characterisation of catalysts was carried out in order to establish a correlation between the oxoanion stability during calcination and the further photocatalytic behaviour of TiO2. Pre-treatment with sulfuric and phosphoric acids clearly stabilises TiO2 catalyst against sintering, maintaining anatase phase and relatively high surface area values with respect to untreated TiO2. On the other hand, nitric pre-treatment seems to favour sintering process. Acid treatment leads to an excess of adsorbed protons (Bronsted acid sites) incorporated to the TiO2 surface. During calcination, the elimination of these hydroxyl groups would be the responsible for the generation of a highly defective material that readily losses the oxygen ions from their surface. Different stability of adsorbed oxoanions would stabilise the anatase crystal phase as well these oxygen vacancies formed during calcination, preventing at the same time the sintering process. The occurrence of oxygen vacancies could favour the appearance of small rutile phase dispersed onto the surface of an anatase matrix performing the photoinduced electronic process. Best photocatalytic behaviour is found for pre-sulfated TiO2 samples calcined at such high temperature for which sulfates have been eliminated.
TL;DR: In this paper, a short review highlights the fabrication of metal oxide-based nanomaterials via nanosecond pulsed laser ablation of metallic target materials in water and aqueous surfactant solutions.
Abstract: Numerous experiments for nanomaterial fabrication using pulsed laser ablation in liquid have been reported. Most studies have focused on the formation of noble-metal nanoparticles and their surface plasma-resonant optical properties. This short review highlights the fabrication of metal oxide-based nanomaterials such as oxide and hydroxide nanoparticles, as well as layered nanocomposites, via nanosecond pulsed laser ablation of metallic target materials in water and aqueous surfactant solutions. These crystallized oxide-based nanomaterials are formed through the ejection of ablated species with extremely high density and high kinetic energy followed by oxidation in the liquid. © 2006 Elsevier B.V. All rights reserved.
TL;DR: The nanorods/nanoparticles TiO 2 with mesoporous structure were synthesized by hydrothermal method at 150°C for 20h and the prepared material had average pore diameter about 7-12nm as mentioned in this paper.
Abstract: Nanorods/nanoparticles TiO 2 with mesoporous structure were synthesized by hydrothermal method at 150 °C for 20 h. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. The nanorods had diameter about 10–20 nm and the lengths of 100–200 nm, the nanoparticles had diameter about 5–10 nm. The prepared material had average pore diameter about 7–12 nm. The BET surface area and pore volume of the sample are about 203 m 2 /g and 0.655 cm 3 /g, respectively. The nanorods/nanoparticles TiO 2 with mesoporous structure showed higher photocatalytic activity (I 3 − concentration) than the nanorods TiO 2 , nanofibers TiO 2 , mesoporous TiO 2 , and commercial TiO 2 (ST-01, P-25, JRC-01, and JRC-03). The solar energy conversion efficiency ( η ) of the cell using nanorods/nanoparticles TiO 2 with mesoporous structure was about 7.12% with J sc of 13.97 mA/cm 2 , V oc of 0.73 V, and f f of 0.70; while η of the cell using P-25 reached 5.82% with J sc of 12.74 mA/cm 2 , V oc of 0.704 V, and f f of 0.649.
TL;DR: In this article, nitrogen-doped TiO2 films were grown by atomic layer deposition (ALD) using TiCl 4, N H 3 and water as precursors, and the films were characterized by XRD, XPS, SEM and UV-vis spectrometry.
Abstract: Titanium dioxide (TiO2) is recognized as the most efficient photocatalytic material, but due to its large band gap energy it can only be excited by UV irradiation. Doping TiO2 with nitrogen is a promising modification method for the utilization of visible light in photocatalysis. In this work, nitrogen-doped TiO2 films were grown by atomic layer deposition (ALD) using TiCl 4 ,N H 3 and water as precursors. All growth experiments were done at 500 ◦ C. The films were characterized by XRD, XPS, SEM and UV–vis spectrometry. The influence of nitrogen doping on the photocatalytic activity of the films in the UV and visible light was evaluated by the degradation of a thin layer of stearic acid and by linear sweep voltammetry. Light-induced superhydrophilicity of the films was also studied. It was found that the films could be excited by visible light, but they also suffered from increased recombination. © 2005 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the photocatalytic degradation of formic acid (FA) and benzoic acid was investigated in TiO2 and ZnO water suspensions under different experimental conditions, and the effect of different initial amounts of substrates and the dependence of the reaction rate on the initial pH of the TiO 2 suspensions was interpreted under the light of a pseudosteady state Langmuir-Hinshelwood rate form and of the electrostatic interactions occurring at the water-semiconductor interface.
Abstract: The photocatalytic degradation of formic acid (FA) and benzoic acid (BA), chosen as model organic molecules with acidic properties, was investigated in TiO2 and ZnO water suspensions under different experimental conditions. Hydrogen peroxide evolution, formed through a reductive pathway started by conduction band electrons, was also simultaneously monitored during the degradation runs. The effect of different initial amounts of substrates and the dependence of the reaction rate on the initial pH of the TiO2 suspensions was interpreted under the light of a pseudo-steady state Langmuir–Hinshelwood rate form and of the electrostatic interactions occurring at the water–semiconductor interface. ZnO appeared a more effective photocatalyst than TiO2 for BA, but not for FA degradation. A much higher amount of hydrogen peroxide was detected in ZnO irradiated suspensions, both in the presence and in the absence of the substrates, mainly because of its lower photocatalytic decomposition rate on such oxide. The rate of hydrogen peroxide evolution during the photocatalytic oxidation of BA on TiO2 could be related to the rate of the oxidation process, while H2O2 could not be detected during the photocatalytic degradation of FA on this oxide, mainly because of the reduced shielding ability of this substrate.
TL;DR: In this paper, the authors used a combined plug-flow model to study the photodegradability of some VOCs in an annular reactor and showed that the apparent rate constant (k*) is equal to kK representing the Langmuir-Hinshelwood rate constants.
Abstract: The photodegradation of some VOCs in an annular reactor is chemical step controlled. The limitation due to mass transfer is negligible. The use of a combined plug-flow model shows that the apparent rate constant (k*) is equal to kK representing the Langmuir–Hinshelwood rate constants. So the design of an annular reactor using the L–H model can be considered. The photodegradability of the tested VOCs is strongly dependent on the product kK. Trichloroethylene is the best degraded while toluene is the worst. The study of the mineralization rate, defined as the ultimate degradation phase of the compounds, shows that this last is firstly dependent on the contact time and not on the nature of the VOC. Moreover increasing the inlet VOC concentration leads to a decrease in the mineralization rate.