Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2015"
TL;DR: In this article, a BiOBr (p-type)-Bi2WO6 (n-type) heterojunction semiconductor was synthesized by the hydrothermal method.
Abstract: Photocatalysis is a growing area of study for a clean and renewable energy source, particularly the degradation of organics in wastewater and polluted air. Researchers have studied the combination of various semiconductors to create photocatalysts with improved activities, but little has been reported in selecting semiconductors based on their extrinsic type—namely n-type or p-type. In this study, a BiOBr (p-type)-Bi2WO6 (n-type) heterojunction semiconductor was synthesized by the hydrothermal method. The new materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and diffuse-reflection spectroscopy (DRS). Their photocatalytic activities were examined by measuring the degradation rate of Rhodamine B with photocatalysts synthesized using various atomic ratios of BiOBr and Bi2WO6 (1:4, 1:1, and 4:1). These new composites’ ability to effectively degrade dye pollutants shed light on the benefits of using heterojunction photocatalysts, and also on the importance of considering the semiconductor type when forming composite photocatalysts.
143 citations
TL;DR: A brief, historical overview of 10 apparently different, although in some cases, closely related, popular reaction mechanisms and their associated rate equations is given and in which the rate expression for each mechanism is derived from basic principles as mentioned in this paper.
Abstract: A brief, historical overview of 10 apparently different, although in some cases, upon inspection, closely related, popular proposed reaction mechanisms and their associated rate equations, is given and in which the rate expression for each mechanism is derived from basic principles, Appendix A . In Appendix B , each of the 5 main mechanisms are tested using datasets, comprising initial reaction rate vs. organic pollutant concentration, [P] and incident irradiance, ρ , data, reported previously for TiO 2 , where P is phenol, 4-chlorophenol and formic acid. The best of those tested, in terms of overall fit, simplicity, usefulness and versatility is the disrupted adsorption kinetic model proposed by Ollis. The usual basic assumptions made in constructing these mechanisms are reported and the main underlying concerns explored.
108 citations
TL;DR: In this article, the effect of addition of six successive transition metal elements of fourth period, namely chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) was studied.
Abstract: The purpose of this work is to design and develop a series of stable and effective TiO 2 photocatalysts prepared by a modified precipitation method. In order to improve the photo response of the TiO 2 to the visible region, the effect of addition of six successive transition metal elements of fourth period, namely chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) was studied. Two different types of dyes, methyl orange (MO, azo dye) and methylene blue (MB, thiazine dye group), were used to investigate the influence of structure of dyes on the photocatalytic degradation rates. The results showed that loading titania with 0.3 wt.% of different transition metal elements was found to have significant influences on the crystallographic structure, physical properties and optical absorption properties of titania based catalysts, as well as catalytic activity during dye degradation reactions. The optical reflection edge was obviously shifted to the visible light range with the transition metal additives. The band gap energies of the doped TiO 2 samples were considerably narrower than that of plain TiO 2 . The different activity levels of the catalysts for both dyes clearly show that the photocatalytic activity of samples strongly depended on the metal dopant used. Among all the catalysts, Cu/TiO 2 sample exhibited the highest photocatalytic activity under visible light for both of the dyes owing to the low band gap energy and delayed electron-hole recombination.
106 citations
TL;DR: In this article, a TiO 2 photocatalyst synthesized using a sol-gel procedure was modified through photodeposition and tested for its efficiency in hydrogen production by heterogeneous photocatalysis in the presence of different alcohols as sacrificial agents.
Abstract: In this work, a TiO 2 photocatalyst synthesized using a sol–gel procedure (SG750) was Pt modified through photodeposition (SG750-2.1 wt%Pt) and tested for its efficiency in hydrogen production by heterogeneous photocatalysis in the presence of different alcohols as sacrificial agents. The tested alcohols were: methanol, ethanol, ethyleneglycol and glycerol. Production was continuously followed for 3.5 h. The concentration of each alcohol that resulted in the highest production was optimized and some of the degradation intermediates were identified and quantified in both gaseous and the remaining liquid phase at the end of the process. Optimum concentrations were found to be around 17.13 M for methanol and 7.34 M for ethanol, ethyleneglycol and glycerol. In terms of sacrificial agent used, hydrogen production was as follows: methanol > ethanol > ethyleneglycol > glycerol. The stability of the photoactivity of the catalyst was demonstrated through reuse cycles with 0.011 M of sacrificial agent and was also compared with that of commercial photocatalysts, in this case Aeroxide TiO 2 P25 and Hombikat UV-100, with the same photodeposited Pt%.
100 citations
TL;DR: In this article, the interaction of carbon dots (C-dots) prepared from orange juice with silver nanoparticles (AgNPs) using fluorescence spectroscopy was investigated.
Abstract: In this paper, we investigated the interaction of carbon dots (C-dots) prepared from orange juice with silver nanoparticles (AgNPs) using fluorescence spectroscopy. It was found that AgNPs efficiently quench the fluorescence of C-dots as a result of fluorescence resonance energy transfer (FRET). Thus, a novel FRET system between C-dots (as the donor) and AgNPs (as the acceptor) was introduced. Moreover, it was found that cysteine even at nanomolar levels could recover the fluorescence of C-dots due to the competitive adsorption of this compound onto AgNPs. This was exploited to design a simple and selective method for the determination of cysteine in the concentration range from 6.0 to 300 nM, with a detection limit of 4.0 nM. Cysteine was determined by this method in human plasma and urine samples with satisfactory results.
90 citations
TL;DR: In this article, the effects of operating parameters, such as H 2 O 2 dosage, pH value, dye concentration and temperature, on the decolorization of C.I. Reactive Blue 181 (RB181), anthraquinone dye, was investigated.
Abstract: In this study, the decolorization of C.I. Reactive Blue 181 (RB181), anthraquinone dye, by UV/H 2 O 2 processes was investigated. The effects of operating parameters, such as H 2 O 2 dosage, pH value, dye concentration and temperature were examined. The optimum conditions were determined as [H 2 O 2 ] = 500 mg/L, [RB181] = 500 mg/L and pH 3 for 20 min reaction time. The decolorization was achieved by the UV/H 2 O 2 process because of the production of some oxidizing agents as a result of UV irradiation. The decolorization kinetic of RB181 followed pseudo-first-order reaction kinetic. Thermodynamic analysis showed negative values of Δ H indicating exothermic under natural conditions.
84 citations
TL;DR: In this article, a composite was obtained in mild hydrothermal conditions using fly ash, TiO 2 and a cationic surfactant (HTAB), which was used as an adsorption substrate and as photocatalyst for the simultaneous removal of two commercial dyes (Bemacid Red, BR; Bemacid Blue, BB).
Abstract: A novel composite was obtained in mild hydrothermal conditions using fly ash, TiO 2 and a cationic surfactant (HTAB). The components were involved in extensive re-structuring processes, evidenced by XRD, FT-IR, SEM, AFM, BET and surface energy measurements. The composite was used as adsorption substrate and as photocatalyst for the simultaneous removal of two commercial dyes (Bemacid Red, BR; Bemacid Blue, BB). The experimental tests were run at the natural pH of the suspension, which was alkaline (pH 10.6). In the experimental conditions electrostatic interactions due are less extensive, and the data can be directly linked to the substrate’s morphology and dyes molecular structure and size. It was found that adsorption efficiency is strongly influenced by the micro-pores on the substrate and the kinetics mainly depends on the dyes flexibility. For the azo dye (BR), photocatalysis was found to run independent from adsorption while for the anthraquinone dye (BB) the process proves to be more complex. Under UV irradiation, the removal efficiencies reached after 240 min were of 93% for BR and of 77% for BB.
79 citations
TL;DR: In this paper, the photocatalytic NO removal abilities of a number of common TiO 2 materials, surface-saturated with photogenerated HNO 3, with their behaviours observed during the typical 5-h-long ISO standard test were compared.
Abstract: Although the NO removal-based air-purification ISO method ISO 22197-1:2007 is well established, its preconditioning requirements mean that only the initial activity of the photocatalyst under test is measured owing to the often-reported, gradual alteration of the surface kinetics for NO oxidation by air through the accumulation of surface HNO 3 . Herein, we compare the photocatalytic NO removal abilities of a number of different, common TiO 2 materials, surface-saturated with photogenerated HNO 3 , with their behaviours observed during the typical 5 h-long ISO standard test. It is found that all the TiO 2 materials studied eventually become largely NO to NO 2 converters after sufficient exposure to NO under irradiation (>5 h) due to the accumulation of surface HNO 3 . The UV exposure time, t *, necessary to reach this HNO 3 saturated condition is different for each different catalyst. As a consequence, an alternative preconditioning process for the ISO method is proposed which can be used to provide a more realistic measure of the photocatalytic activity of the underlying material and provide a measure of the NO x removing capacity of the photocatalytic material under test.
75 citations
TL;DR: In this paper, the photocatalytic efficiency of Fe-doped TiO 2 (Fe-TiO 2 ) nanocomposite thin films for organic contaminant degradation was evaluated.
Abstract: This study characterized and evaluated photocatalytic efficiency of Fe-doped TiO 2 (Fe–TiO 2 ) nanocomposite thin films coated on side-glowing optical fibers (SOFs) for organic contaminant degradation. For the first time Fe–TiO 2 thin films with mixed anatase and rutile phases were successfully grown on SOFs using polymer assisted hydrothermal deposition (PAHD) method. The photocatalyst films were characterized using transmission and scanning electron microscopes, energy-dispersive X-ray, X-ray diffraction, and X-ray photoelectron spectroscopes. The photocatalytic efficiencies of the catalysts coated SOFs were studied by the degradation of Rhodamine B as a representative organic contaminant. The results showed that 5% Fe–TiO 2 thin films (Fe:TiO 2 molar ratio), mixture of anatase and rutile phases, achieved the highest photocatalytic activity under the irradiation of ultraviolet (UV) and visible light. The coupled adsorption and photocatalytic oxidation of Rhodamine B by the SOFs coated with photocatalyst nanocomposite thin films followed the Langmuir–Hinshelwood kinetic model, and the apparent first-order rate constants achieved 0.50 h −1 and 0.33 h −1 under UV and visible light irradiation, respectively. Photocatalytic degradation efficiency was affected by pH and initial organic concentration. Reactivation and regeneration of the used catalysts, and long-term photoactivity testing of catalysts coated SOFs demonstrated the durability of synthesized photocatalysts for water treatment.
72 citations
TL;DR: In this paper, the interaction between chlorophyll (Chl) and Ag NPs, over a wide range of nanoparticle concentrations (from 0.μM to 200.0μM), was evaluated by monitoring the ChlF.
Abstract: Silver nanoparticles (Ag NPs) are among the most widely produced and used nanomaterial due to their antimicrobial and antibacterial properties, allowing a wide range of commercial applications. Thereby, the increasing use of Ag NPs should inevitably lead to the release and accumulation of these NPs into the environment, resulting in adverse effects on plants, animals and humans. Chlorophyll fluorescence (ChlF) has been proposed as a non-destructive and accurate tool for detecting the impacts of environmental stress on plants. Little is known about the photophysical behavior of plants when exposed to a metallic NPs-containing environment. The present study evaluated the interaction between chlorophyll (Chl) and Ag NPs, over a wide range of nanoparticle concentrations (from 0 μM to 200.0 μM), by monitoring the ChlF. The results reveal that the ChlF is quenched in the presence of Ag NPs, as a result of the static and dynamic quenching processes. The present results suggest that ChlF has a great potential to be used in the future as an analytical tool for monitoring the interaction of plants and NPs as well as investigating the effects of NPs on plants.
66 citations
TL;DR: In this article, the photocatalytic performance of the obtained products were evaluated by analyzing the degradation of methyl orange (MO) solution under UV irradiation and showed that the catalysts of the Ag/ZnO/graphene nanocomposites with different graphene content showed better photocatalysis.
Abstract: Ag/ZnO/graphene (Ag/ZnO/G) nanocomposites were successfully synthesized by a facile low-temperature microwave-assisted solution method. The morphology and phase structure of the prepared samples were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The photocatalytic performance of the obtained products were evaluated by analyzing the degradation of methyl orange (MO) solution under UV irradiation. The Ag/ZnO/graphene nanocomposites showed higher photocatalytic efficiency than ZnO or Ag/ZnO. Photocatalytic activity of Ag/ZnO/graphene nanocomposites with different graphene content was studied. Firstly the photocatalytic efficiency of the Ag/ZnO/graphene nanocomposites increased with the increase of graphene oxide (GO) content from 0 to 1%, then the photocatalytic efficiency decreased while the percent of GO addition reached 2%. The photostability testing of the Ag/ZnO/graphene nanocomposites with 1% GO content showed that the catalyst has excellent photocatalytic activity and photostability for the degradation of MO. It is believed that this facile, rapid microwave-assisted strategy is scalable and can be applied to synthesize other metal/semiconductor oxide/graphene nanocomposites for different applications in different fields.
TL;DR: In this paper, the effect of sensitization on photocatalytic properties of TiO2 thin films was studied by measurements of X-ray diffraction (XRD), infrared spectroscopy (IR) and absorption diffuse reflectance.
Abstract: We studied the effect of sensitization on photocatalytic properties of TiO2 thin films. We synthesized tetracarboxy-phthalocyanines of Cu (PcTcCu) and Zn (PcTcZn) for using Achar method; TiO2 thin films were deposited by doctor blade method, after that, thin films were sensitized through chemisorption method. Properties of TiO2 and sensitized-TiO2 thin films were studied by measurements of X-ray diffraction (XRD), infrared spectroscopy (IR) and absorption diffuse reflectance. The XRD patterns indicated that sensitization did not affect the crystalline phases radio of the TiO2 films; furthermore, the optical analysis showed that after sensitization process TiO2 photophysical properties improved greatly in visible regions. Photocatalytic degradation of methylene blue was studied under visible irradiation in aqueous solution and, the pseudo-first order model was used to obtain kinetic information of the photocatalytic degradation. Results indicated that photocatalytic activities of PcTcZn–TiO2 and PcTcCu–TiO2 were 2.8 times and 3.6 times better than TiO2 thin films, these results also indicated that magnetic properties of metal complex in the phthalocyanines determines the efficiency of sensitizer in photocatalytic process. Finally the efficiency in photocatalytic process improved greatly when methylene blue photo-degradation were assisted with slight amount of H2O2.
TL;DR: In this article, the synthesis of ZnO with nano-corncobs morphology was reported, which was used as catalysts for degradation of methyl orange under simulated sun-light.
Abstract: This paper reports the synthesis of ZnO with nano-corncobs morphology; this method consists of two stages of reaction: the first is the formation of ZnO precursor at 70 °C by a mixture formed from a Nital solution (ethanol + nitric acid) and zinc acetate; the second stage occurs at 180 °C, where the combustion process occurs to obtain the ZnO nanoparticles. XRD data showed the presence of hexagonal single-phase ZnO with the wurtzite crystal structure. FE-SEM images indicated that the synthesized ZnO presents nano-corncobs morphology. The analysis of photoluminescence spectra shows the presence of oxygen vacancies in the synthesized ZnO, which are related to the ratio of polar and non-polar planes. The commercial and synthesized ZnO were used as catalysts for degradation of methyl orange under simulated sun-light. Results showed that synthesized ZnO is more catalytically active for photodegradation under simulated sun-light than commercial ZnO. Photocatalytic activity tests showed that best activity was obtained with uncalcined ZnO powders and this enhanced activity was attributed to the synergistic effect found between the material polar plane and oxygen vacancies. Additionally, electrochemical experiments shown that synthesized ZnO by Nital solution are free of photocorrosion.
TL;DR: In this article, the effects of morphology change of SrTiO3 particles on the behavior of photogenerated charge carriers are studied by time-resolved absorption (TA) spectroscopy from the visible to mid-IR region.
Abstract: The effects of the morphology-change of SrTiO3 particles on the behavior of photogenerated charge carriers are studied by time-resolved absorption (TA) spectroscopy from the visible to mid-IR region. In the case of as-purchased defect-rich commercial SrTiO3 particles, most of the charge carriers are deeply trapped, showing a transient absorption peak at 11,000 cm−1. Scanning electron microscopy reveals that the irregular-shaped primary particles are heavily aggregated and that the photocatalytic activity for the water splitting reaction is negligibly small. However, when this powder is flux-treated by SrCl2, fine cubic SrTiO3 crystals exposing well-defined surfaces are formed and the photocatalytic activity is greatly improved. TA measurements show that the spectral shape is changed dramatically: the number of deeply trapped electrons is reduced, and that of shallowly trapped electrons producing the absorption band at 2500 cm−1 is increased. The change in electron trap depth, observed upon flux treatment, is due to the decrease in the number of defects. We also found that further flux treatment in an Al2O3 crucible (i) induces Al doping into SrTiO3, (ii) enhances the photocatalytic activity, (iii) changes the spectral shape, and (iv) prolongs the lifetime of shallowly trapped electrons. The increase in photocatalytic activity is presumably due to the change in lifetime.
TL;DR: A novel fluorescent probe based on a selenide switch for the detection of HOCl in lysosomes has been designed and synthesized on a 1,8-naphthalimide scaffold and exhibited a high selectivity for HOCl over various reactive oxygen species (ROS) with a fast response and a large fluorescence enhancement in aqueous media.
Abstract: The development of fluorescent probes for hypochlorous acid (HOCl) has received intense attention because of the biological significance of HOCl. In this work, a novel fluorescent probe based on a selenide switch for the detection of HOCl in lysosomes has been designed and synthesized on a 1,8-naphthalimide scaffold. The probe exhibited a high selectivity for HOCl over various reactive oxygen species (ROS) with a fast response and a large fluorescence enhancement in aqueous media. Confocal microscopy imaging of living cells indicated that the probe was able to accumulate in lysosomes and was successfully applied to imaging exogenous HOCl in living cells. Attempts of using Lyso-NI-Se to image HOCl in stimulated RAW264.7 cells failed, probably due to the absence of endogenous HOCl in lysosomes or the undesirable detection limit.
TL;DR: In this paper, the roles of reactive species, OH, 1O2, e−cb and h+vb were studied by adding the specific scavengers and the results indicate that OH plays a critical role in UV TiO2 photocatalysis of CYN.
Abstract: Cylindrospermopsin (CYN), a problematic potent cyanotoxin, is produced during harmful algal blooms and its presence in fresh water lakes and rivers is a threat to human health. UV TiO2 photocatalysis leads to the rapid degradation of CYN following pseudo-first-order kinetics. The pseudo-first-order rate constants (k) are strongly dependent on the reaction conditions, including the initial CYN and TiO2 concentrations, light intensity and solution pH. The observed faster degradation under acidic conditions may be due to the enhanced electrostatic attraction between the positive TiO2 surface and the anionic sulfate group in CYN. The degradation is proportional to the light intensity under our experimental conditions. The roles of reactive species, OH, 1O2, e−cb and h+vb were studied by adding the specific scavengers and the results indicate that OH plays a critical role in UV TiO2 photocatalysis of CYN. Detailed product studies using liquid chromatography mass spectrometry (LC/MS) indicate OH mediated degradation pathways predominantly occur via oxidation of the uracil ring in CYN, leading to hydroxylation and ring opened products. ELISA results demonstrate that TiO2 photocatalysis leads to a significant decrease in the biological activity of CYN as a function of treatment time. Our results indicate TiO2 photocatalysis may be applicable for the degradation of CYN and uracil based compounds.
TL;DR: In this paper, the photoactivity of the synthesized hematite particles was tested towards the degradation of phenol under photo-Fenton conditions, obtaining optimal results in the pH range 3-4.
Abstract: Hematite particles with controlled size and shape (cubic, spherical and ovoidal, with size range from hundreds nm to μm) were produced by modulating the conditions of synthesis and were characterized by different techniques (XRD spectroscopy, scanning electron microscopy, BET analysis, dynamic light scattering, UV–vis spectroscopy). The photoactivity of the synthesized hematite particles was tested towards the degradation of phenol under photo–Fenton conditions, obtaining optimal results in the pH range 3–4. Although the smaller particles have a larger contact interface between the solid and the solution, no obvious relationship was found between size and photoactivity. A possible explanation is that the smallest particles tested showed an important radiation scattering, which would interfere with radiation absorption and, therefore, with photoactivity. In contrast, the most photoactive samples were those showing the highest concentrations of leached iron. This issue would imply that photoactivity may be related to partial dissolution of hematite with formation of Fe(II) and of photo-active Fe(III) species, which activate the classic photo–Fenton process. Anyway, leached Fe was limited to the μg L −1 range that is safely far from the mg L −1 limits for wastewater.
TL;DR: In this article, the antibacterial activity of the material was measured in the dark and under UV and white light irradiation; this is the first time that an Ag 3 PO 4 -based material was tested under these conditions.
Abstract: Fish bones were converted into materials consisting of silver phosphate (Ag 3 PO 4 ), β-calcium phosphate (β-Ca 3 (PO 4 ) 2 , β-TCP) and hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp), as well as of metallic silver (Ag 0 ), with a simple treatment in solution and calcination (650 or 1000 °C). The antibacterial activity of the material was measured in the dark and under UV and white light irradiation; this is the first time that an Ag 3 PO 4 -based material was tested under these conditions. Results showed light-enhanced antibacterial properties toward Gram-positive and Gram-negative strains (Methicillin-resistant Staphylococcus aureus – MRSA, Escherichia coli , Pseudomonas aeruginosa ), with inactivation rates of up to 99.999% under UV light, and 99% for E. coli under white light (artificial indoor lighting). The photocatalytic activity was also tested, and the degradation of methylene blue dye was observed under both UV and white light. Even if the MB degradation was to a smaller extent under white light, it was approximately twice that of the commercial photocatalyst P25. This work demonstrates the valorisation of a food industry by-product such as fish bones to form a potentially valuable material, with important applications in self sterilizing surfaces and environmental remediation.
TL;DR: In this article, a simple and mild one-step chemical method was developed to produce novel and highly efficient α-Fe2O3/polypyrrole (PPy) photocatalysts.
Abstract: We developed a simple and mild one-step chemical method to produce novel and highly efficient α-Fe2O3/polypyrrole (PPy) photocatalysts. The formation of α-Fe2O3/PPy nanocomposites proceeds via a simultaneous gelation and polymerization process. The XRD results revealed that all the diffraction peaks can be perfectly indexed to the rhombohedral structure of α-Fe2O3 and the polymerization of Py did not change the crystalline phase of α-Fe2O3. TEM images show that Fe2O3 nanoparticles are quite uniform in shape and size and their particle sizes are decreased from 20 to 5 nm by increasing Py content from 5 to 25%. The lattice fringes (3.7 A) are distinctly visible and revealed structurally uniform crystals of α-Fe2O3 without dislocation. Compared to pure Fe2O3, the newly developed nanocatalyst demonstrated a remarkable activity toward the photocatalytic degradation of methylene blue (MB) under UV irradiation, at ambient temperature. Complete degradation of MB was achieved after only 20 min in the presence of the optimum photocatalyst containing 10% Py. The effective photocatalytic performance is associated with the mesoporous structure and crystalline nature of the prepared nanocomposites. Additionally, such enhanced photocatalytic behavior was rationalized in terms of a synergetic effect for light absorption between α-Fe2O3 and PPy that eventually led to better charge separation and suppression of charge recombination. The photocatalyst could be removed from the reaction mixture and its recyclability remains effective after five cyclic runs. Proposed mechanism for the degradation of MB with the α-Fe2O3/PPy nanocatalyst under UV irradiation is also presented and thoroughly discussed.
TL;DR: In this article, a general kinetic model for the photothermal oxidation of polypropylene has been derived from the basic auto-oxidation mechanistic scheme in which the main sources of radicals are the thermolysis and photolysis of the most unstable species, i.e. hydroperoxides.
Abstract: A general kinetic model for the photothermal oxidation of polypropylene has been derived from the basic auto-oxidation mechanistic scheme in which the main sources of radicals are the thermolysis and photolysis of the most unstable species, i.e hydroperoxides. Thermolysis is a uni- or bi-molecular reaction whose rate constant obeys an Arrhenius law. In contrast, photolysis is exclusively a unimolecular reaction and its rate constant is independent of temperature. According to the quantum theory, this latter is proportional to the energy absorbed by photosensitive species and thus, accounts for the impact of UV-light intensity and wavelength on the global oxidation kinetics. The validity of this model has been checked on iPP films homogeneously oxidized in air over a wide range of temperatures and UV-light sources. It gives access to the concentration changes of: (i) primary (hydroperoxides) and secondary (carbonyls) oxidation products, (ii) double bonds, (iii) chain scissions and crosslinking nodes, but also to the subsequent changes in molecular masses. These calculations are in full agreement with the photolysis results reported by Carlsson and Wiles in the 70s [1–3]. However, the model seems to be only valid for UV-light energies equivalent to about 10 suns as upper boundary, presumably because of multiphotonic excitations or chromophores photosensitization (i.e. termolecular photo-physical reactions), both enhanced at high irradiances.
TL;DR: In this article, the effect of chemical structures of 2,2′-bipyridinium salts (BP2+) as the electron carrier molecules on the visible-light induced conversion of CO2 to formic acid with the system consisting of water-soluble zinc tetraphanelporphyrin tetrasulfonate (ZnTPPS) and formate dehydrogenase (FDH) in the presence of triethanolamine (TEOA) as an electron donor molecule was investigated.
Abstract: Effect of chemical structures of some 2,2′-bipyridinium salts (BP2+) as the electron carrier molecules on the visible-light induced conversion of CO2 to formic acid with the system consisting of water-soluble zinc tetraphneylporphyrin tetrasulfonate (ZnTPPS) and formate dehydrogenase (FDH) in the presence of triethanolamine (TEOA) as an electron donor molecule was investigated. Irradiation of a CO2 saturated solution containing TEOA, ZnTPPS, BP2+ and FDH with visible light resulted in production of formic acid. By using 1,1′-ethylene-2,2′-bipyridinium dibromide (DB2+) as an electron carrier molecule, the effective formic acid production was observed compared with the other 2,2′-bipyridinium salt derivatives.
TL;DR: In this paper, the use of Fe(III)-EDDS complexing agent as an alternative to conventional acidic pH photo-Fenton for the treatment of the pesticide imidacloprid in natural water was evaluated.
Abstract: This study evaluates the use of the Fe(III)-EDDS complexing agent as an alternative to conventional acidic pH photo-Fenton for the treatment of the pesticide imidacloprid in natural water. The main objective is to estimate whether Fe(III)-EDDS is a viable alternative when treating waters containing high concentrations of contaminants. To this end, the mode of action of Fe(III)-EDDS is examined in the presence of carbonates, at different aeration conditions and at different temperatures. The role of HO2 center dot/O-2(center dot-) radical species and some aspects of the Fe(III)-EDDS complexation mechanism are discussed. Degradation kinetics and toxicities of generated intermediates are compared between Fe(III)-EDDS and conventional photo-Fenton treatment. An overview of the benefits and limitations of the process is presented. (C) 2015 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the efficiency of W-doped TiO2 in the photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA) was investigated.
Abstract: This work was aimed at studying the efficiency of W-doped TiO2 in the photocatalytic degradation of 4-chloro-2-methylphenoxyacetic acid (MCPA). Different wt.% of W-doped TiO2 was synthesized via the sol–gel method and characterized. The characterizations included powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), N2 sorption, Raman spectroscopy, fluorescence spectrometry, and electron spin resonance spectroscopy (ESR). Result from the BJH pore size distribution shows the materials are mesoporous with BET surface area ranging from 86.08–91.71 m2/g. All materials showed polycrystalline anatase phase with decreasing crystal size as the percentage dopant increases. The best photocatalytic activity was obtained with 0.1 wt.% W-doped TiO2 (0.1 WT) at a natural pH of 5, which may have resulted from its relatively reduced band gap; crystal size; and lesser amount of oxygen vacancy. 0.1 WT had an optimum catalyst concentration of 600 mg/L under artificial light irradiation at a rate constant and half-life of 4.31 × 10−3 s−1 and 160 s, respectively. The intermediates/products as analyzed by the LC-MS were 2-hydroxybuta-1, 3-diene-1, 4-diyl-bis (oxy) dimethanol and 2-(4-hydroxy-2-methylphenoxy) acetic acid which are relatively safer than MCPA.
TL;DR: The results suggest that iron-mediated advanced oxidation processes (AOPs) have a high potential for the removal of endosulfan and its by-product from contaminated water.
Abstract: This study investigated iron-mediated oxidative processes for the photochemical degradation of endosulfan, a chlorinated insecticide and central nervous system disruptor. At UV fluence of 360 mJ/cm 2 , 52.4% and 32.0% removal of 2.45 μM initial endosulfan was observed by UV/Fe 3+ and UV/Fe 2+ processes, respectively, at an initial concentration of 17.8 μM iron. The degradation of endosulfan by UV/Fe 3+ or UV/Fe 2+ was dramatically enhanced by adding peroxide (i.e., H 2 O 2 , S 2 O 8 2− or HSO 5 − ). Among the UV/peroxide/Fe processes, the highest degradation efficiency of 99.0% at UV fluence of 360 mJ/cm 2 was observed by UV/HSO 5 − /Fe 2+ with 2.45 μM [endosulfan] 0 , 17.8 μM [Fe 2+ ] 0 , and 49.0 μM [HSO 5 − ] 0 . The observed degradation rate constant of endosulfan was promoted either by increasing [Fe 2+ ] 0 and/or [peroxide] 0 or by decreasing [endosulfan] 0 , while the initial degradation rate of endosulfan increased with increasing [Fe 2+ ] 0 , [peroxide] 0 , or [endosulfan] 0 . At UV fluence of 6000 mJ/cm 2 , 45.0% mineralization as represented by the decrease in total organic carbon content was observed by UV/HSO 5 − /Fe 2+ at 9.80 μM [endosulfan] 0 , 980 μM [HSO 5 − ] 0 , and 17.8 μM [Fe 2+ ] 0 . The major by-product of endosulfan was observed in all cases to be endosulfan ether which was further degraded with an extended reaction time. The results suggest that iron-mediated advanced oxidation processes (AOPs) have a high potential for the removal of endosulfan and its by-product from contaminated water.
TL;DR: In this article, a photochromism based on reversible proton transfer between metastable-state photoacids and acidochromic dyes is studied, which reversibly produces a large proton concentration under moderate irradiation, protonates the acidochrome dyes and induce color change.
Abstract: Photochromism based on reversible proton transfer between metastable-state photoacids and acidochromic dyes is studied. Metastable-state photoacids reversibly produce a large proton concentration under moderate irradiation, protonate the acidochromic dyes and induce color change. This mechanism is different from that of conventional photochromic materials based on photoinduced structural change. The color change and the stimulating wavelength can be controlled by choosing different acidochromic dyes and photoacids. Reversible changes of various colors under sunshine or visible lights of different wavelengths were demonstrated in both solutions and polymer matrix.
TL;DR: In this paper, a fast-responsive fluorescent sensor for Ag+ was successfully developed by taking advantage of the aggregation-induced emission (AIE) property of tetraphenylethylene motif with a detection limit of 874 × 10−7 M.
Abstract: A new fast-responsive “turn on” fluorescent sensor for Ag+ was successfully developed by taking advantage of the aggregation-induced emission (AIE) property of tetraphenylethylene motif with a detection limit of 874 × 10−7 M The sensor exhibits highly selective and sensitive recognition toward Ag+ ions over the other 12 metal ions due to the high electrophilic and thiophilic character of Ag+ ions The 1H NMR titration and dynamic light scattering (DLS) spectra conclude that the binding of the sensor with Ag+ ions forms fluorescent nanoaggregates in aqueous media due to its AIE enhancement A stoichiometric ratio (1:2) of the sensor and Ag+ was determined by a Job’s plot
TL;DR: In this article, the difference in the photocatalytic oxidation mechanism in WO3 and BiVO4 photocatalysis was investigated by a fluorescence probe method under 470nm LED irradiation using coumarin and coumarlin-3-carboxylic acid as fluorescence probes.
Abstract: WO3 and BiVO4 attract widely research interests for their ability to oxidize water and generate O2 by visible light. In order to clarify the photocatalytic oxidation mechanism, OH radical ( OH) generation in the photocatalytic reactions was investigated by a fluorescence probe method under 470 nm LED irradiation using coumarin and coumarin-3-carboxylic acid as fluorescence probes. The generation yield of OH for WO3 was found to be comparable to that for anatase TiO2, while that for BiVO4 was much smaller. On Cu2+ deposition, the OH generation rate was increased for BiVO4, but not for WO3. On the addition of H2O2, the yield of OH was increased for all the photocatalysts used. On the basis of the results the difference in the oxidation mechanism in WO3 and BiVO4 photocatalysis was discussed.
TL;DR: The spectral sensitivity of bipy-containing fluoroionophores, such as AVBs, to zinc(II) can be exploited to prepare fluorescent indicators for this ion, and AVB moieties are incorporated in fluorescent heteroditopic ligands, so that the variation of zinc( II) concentration over a relatively large range can be correlated to fluorescence changes in either intensity or color.
Abstract: This article reviews the zinc(II)-dependent photophysical properties of arylvinylbipyridines (AVBs), a class of fluoroionophores in which 2,2'-bipyridyl and an aryl moiety are electronically conjugated. Zinc(II) binding of an AVB may lead to an emission bathochromic shift of the fluoroionophore without diminishing its fluorescence quantum yield. This observation can be explained using the excited state model of electron donor-π bridge-electron acceptor "push-pull" fluorophores, in which the bipy moiety acts as an electron acceptor, and zinc(II)-coordination strengthens its electron affinity. The spectral sensitivity of bipy-containing fluoroionophores, such as AVBs, to zinc(II) can be exploited to prepare fluorescent indicators for this ion. In several cases, AVB moieties are incorporated in fluorescent heteroditopic ligands, so that the variation of zinc(II) concentration over a relatively large range can be correlated to fluorescence changes in either intensity or color. AVB fluoroionophores are also used to introduce an intramolecular Forster resonance energy transfer (FRET) strategy for creating zinc(II) indicators with high photostability and a narrow emission band, two desired characteristics of dyes used in fluorescence microscopy.
TL;DR: In this article, the InVO4/TiO2 heterojunction system has been prepared by means of a practical impregnation method in alcoholic media and the obtained photocatalysts were characterized by several techniques, such as X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and electron microscopy (SEM/TEM).
Abstract: The InVO4/TiO2 heterojunction system has been prepared by means of a practical impregnation method in alcoholic media. The obtained photocatalysts were characterized by several techniques, such as X-ray powder diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS) and electron microscopy (SEM/TEM). Also, nitrogen adsorption–desorption isotherms were employed in order to determine the surface area (BET) and pore-size distribution (BJH) of the samples. We have observed that the addition of InVO4 did not provide changes in the structural and textural properties of TiO2 but substantially improved its photocatalytic properties. The best photocatalytic performance for the degradation of phenol was achieved for TiO2 with 0.5 wt.% loading of InVO4. From these results it can be inferred that the effective separation of the charge carriers produced an improvement in the photocatalytic performances of the InVO4/TiO2 heterojunction photocatalysts. In the same way, a possible mechanism is discussed in order to explain the enhanced photoactivity under UV–vis irradiation.
TL;DR: The synthesis and photophysicochemical properties of mono and tetra-pyridyloxy substituted indium(III) phthalocyanines (InPcs) are presented in this paper.
Abstract: The synthesis and photophysicochemical properties of mono- and tetra-pyridyloxy substituted indium(III) phthalocyanines (InPcs) are presented in this study. General trends are described for quantum yields of fluorescence, triplet, singlet oxygen and photodegradation as well as lifetimes of fluorescence and triplet state of these compounds. The complexes exhibited high singlet oxygen quantum yields ( Ф Δ ) ranging from 0.44 to 0.66 in DMF, and from 0.44 to 0.69 in DMSO and Ф Δ = 0.31 for the quartenized tetra substituted InPc which is soluble in water. The triplet quantum yields ( Ф T ) ranged from 0.77 to 0.95 in DMF and from 0.77 to 0.94) in DMSO. The tetra substituted photosensitizers do not differ in their inactivation of bacteria with over 8 log reduction of viable bacteria when compared with the mono substituted photosensitizer which could only manage a 1 log reduction.