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Главная страница Новости науки Journal of Photochemistry and Photobiology A: Chemistry
Новости науки
ScienceDirect Publication: Journal of Photochemistry and Photobiology A: Chemistry
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  • Upconversion Tm3+:CeO2/palygorskite as direct Z-scheme heterostructure for photocatalytic degradation of bisphenol A

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): Zhendong Wang, Xiazhang Li, Heming Qian, Shixiang Zuo, Xiangyu Yan, Qun Chen, Chao Yao

    Abstract

    Novel Tm3+:CeO2/palygorskite (Pal) nanocomposites were prepared by a hydrothermal-deposition method. X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectrum(UV–vis), photoluminescence spectroscopy(PL)and Mott-Schottky analysis were employed to characterize the products. Results indicated that Pal skeleton possessed abundant adsorption sites and shortened band gap after modified by hydrochloric acid. Tm3+ doping enhanced the utilization of solar light due to its upconversion from visible to ultraviolet light. Meanwhile, the adsorption edge of the Tm3+:CeO2 was extended to visible region with the formation of intimated Tm3+:CeO2/Pal heterojunctions. The product behaved strongest upconversion luminescence when the doping fraction of Tm3+ was optimized to be 0.02, and the photocatalytic degradation of bisphenol A (BPA) reached 86% when the mass content of Tm3+:CeO2 as compared to Pal was optimized to 10 wt%. The direct Z-scheme system was constructed between Pal and Tm3+:CeO2 leading to the improved charge-separation efficiency and maintenance of high redox potential.

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  • Photoelectrochemical properties of Ba2TiO4 prepared by nitrate route. Application to electro-photocatalysis of phenobarbital mineralization by solar light

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): A. Sahmi, R. Laib, S. Omeiri, K. Bensadok, M. Trari

    Abstract

    Ba2TiO4 elaborated from nitrates decomposition crystallizes in a monoclinic perovskite structure with a crystallite size of 66 ± 2 nm and is applied for the environmental protection. The oxide is characterized by scanning electron microscopy, diffuse reflectance and photo-electrochemistry; an indirect transition at 3.34 eV is determined. The electrical conductivity follows an exponential law: σo exp (-0.40 eV/kT) and the conduction occurs by small polarons hopping through mixed valences Ti4+/3+ with a semi conductor behavior. The intensity potential J(E) characteristic in Na2SO4 (10−2 M, pH ∼ 6) exhibits a small hysteresis similar to a chemical diode. The capacitance measurement recorded at pH ∼ 6 indicates and n-type behavior, due to oxygen vacancies and gives a flat band potential of 0.74 VSCE. As application, the phenobarbital is successfully oxidized by electrocatalysis on Ba2TiO4 with a conversion rate of 55% under an electric current of 120 mA. An enhancement up to 66% has been obtained by electro-photocatalysis under solar illumination. The phenobarbital elimination follows a first order kinetic with a rate constant of 3.22 × 10-3 mn-1 and a reaction mechanism is suggested.

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  • Electron transfer from photoexcited naphthalene-1,4:5,8-bis(dicarboximide) radical anion to Mn(bpy)(CO)3X and Re(bpy)(CO)3X CO2 reduction catalysts linked via a saturated methylene bridge

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): Jose F. Martinez, Nathan T. La Porte, Michael R. Wasielewski

    Abstract

    Supramolecular systems that connect a naphthalene-1,4:5,8-bis(dicarboximide) (NDI) radical anion donor to Mn(bpy)(CO)3Br or Re(bpy)(CO)3Cl CO2 reduction catalysts via a methylene bridge have been synthesized and studied by femtosecond transient visible, near-infrared and mid-infrared spectroscopy. The use of the methylene bridge to link NDI to the complexes does not affect the reduction potentials of the metal complexes. Selective photoexcitation of NDI•− to 2*NDI•− results in ultrafast reduction of the bipyridine (bpy) ligands on both the Mn and Re complexes to form Mn(I)(bpy•−)(CO)3X and Re(I)(bpy•−)(CO)3X in near unity quantum yield, respectively. The initial formation of Mn(I)(bpy•−)(CO)3X is unexpected based on previous electrochemical data that indicates the Mn(I) center is reduced at a more positive potential than the bpy ligand. Moreover, the rate of forward electron transfer in the Mn complex was found to be faster than in the Re complex, while the rate of the back electron transfer in the Re complex was faster than in the Mn complex.

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  • Three-dimensional of graphene oxide Ba2VPbSe6 framework composite attach on cellulose based counter electrode for dye-sensitized solar cell

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): Won-Chun Oh, Kwang Youn Cho, Chong-Hun Jung, Yonrapach Areerob

    Abstract

    In this work, the three-dimensional of graphene oxide/Ba2VPbSe6 composites with cellulose (GB@C) have been successfully synthesized via a simple hydrothermal method and used as the counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The three-dimensional GB@C framework showed multiple benefits, such as high surface area, electrocatalytic ability, stability, and high-speed electron conduction, which can improve the conversion efficiency of DSSCs. The special properties and performances of various amounts of graphene oxide (10–30 wt%) as counter electrodes are presented. The highest photoelectric conversion efficiency (PCE) reached 9.47% with 20 wt% GB@C, which was higher than the pristine Pt CEs at the same conditions. Thus, we introduce a novel GB@C framework an alternative for CEs to improve the performance of DSSC cells.

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  • Modulating the photocatalytic activity of TiO2 (P25) with lanthanum and graphene oxide

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): Letícya Laís Coelho, Dachamir Hotza, Arthur Senra Estrella, Suelen Maria de Amorim, Gianluca Li Puma, Regina de Fatima Peralta Muniz Moreira

    Abstract

    The modulation and tuning of the photocatalytic activity of commercial titanium dioxide (TiO2) P25 nanoparticles is demonstrated through the incorporation of lanthanum (La) and/or graphene oxide (GO). These composite materials, which could have applications in commercial products, were prepared by a two-step hydrothermal method from the corresponding precursors. The effect of La (0.05–2 mol%) and GO (5 m%) content on the crystal structure, morphology and photocatalytic activity of TiO2 was investigated by XRS, SEM, EDS, TEM, UV–vis DRS, point of zero charge, photoluminescence and the decolorization of methylene blue. Lanthanum modified the recombination rate of the photogenerated electron-hole charges on TiO2 by inducing an increase in the structural defects, which resulted in a significant suppression, up to 90%, of the photocatalytic activity in the UVA light region. In contrast, the addition of GO enhanced the photocatalytic activity of TiO2. Materials with tuned intermediate photoactivity within the entire range from high to very low were prepared by dosing appropriate amounts of La and GO species. The strategy of combining La and GO represents a useful and simple method for tuning or for suppressing the photocatalytic activity of TiO2 under UVA light irradiation in materials and consumer products using TiO2.

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  • Optoelectrical characterization of different fabricated donor substituted benzothiazole based sensitizers for efficient DSSCs

    Publication date: 1 March 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 372

    Author(s): Nadavala Siva Kumar, Ahmed A. Ibrahim, Abhishek Dhar, Rohit L. Vekariya

    Abstract

    In the present work, we have synthesized three novel organic sensitizers, based on various donor groups which are in conjugation with similar bridge and acceptor moieties. We have studied the effect of donor groups with common bridge and anchoring group sensitizers on optical, electrochemical, dye sensitized solar cell’s performance and electron transfer interface properties as well. We have also represented systematically analysis of influence of donor groups in structural geometry, energy distribution and energy-transfer from HOMO to LUMO by density functional theory. The B2 sensitizer contains highly conjugated, strong electron withdrawing group and electron transfer form donor group to anchoring group happens much more rapid in it compared to other two sensitizers. However, B2 sensitizer has exhibited 6.23% efficiency under 1 sun light illumination. The influence of donor groups on device performance was clearly shown on IPCE spectrum as well. The studied effect of chenodeoxycholic acid (CDCA) in a sensitizer’s solution as a co-absorbent on the DSSCs performance and exhibited highest efficiency (6.68%). We found that co-absorbent can be hinder the sensitizer aggregation and rise electron injection yield and thus short circuit current (Jsc). The device interface kinetics was studied by electrochemical impedance spectroscopy and calculated electron lifetime, interface charge transfer resistance and recombination resistance by fitted equivalent circuit. Moreover, we have checked high performance device stability up to 700 h, under continuous 1 sun light illumination.

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  • Effect of dissolved natural organic matter on the photocatalytic micropollutant removal performance of TiO2 nanotube array

    Publication date: 15 February 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 371

    Author(s): Yin Ye, Harry Bruning, Wanrong Liu, Huub Rijnaarts, Doekle Yntema

    Abstract

    The TiO2 nanotube array (TNA) is a promising photocatalyst for removal of micropollutants from water, but better understanding on its applicability in complex water matrices is still desired. Therefore this study investigates the effect of dissolved natural organic matter (NOMs) on 4-chloro-2-methylphenoxyacetic acid (MCPA, a typical micropollutant found in many water bodies) removal performance of TNA. The present study shows that although in bulk liquid phase NOMs would undergo photosensitization that can contribute to MCPA removal, the overall effect of NOMs on MCPA removal is detrimental due to the interaction between NOMs and the TNA surface: the total removal of MCPA decreased from 94.3% to 62.0% and 61.8%, in the presence of only 5 mg/L SWR-NOM and UMR-NOM respectively. Acidic pH was found to be able to mitigate the detrimental effect of NOMs (the total removal of MCPA was only decreased from 94.5% to 83.3% and 88.8% under acidic pH, in the presence of 15 mg/L SWR-NOM and UMR-NOM respectively), and the photosensitization effect of NOMs was strengthened; while under alkaline pH conditions the detrimental effect of NOMs completely vanished (the total removal of MCPA increased from 45.7% to 55.7% and 60.5% in the presence of 15 mg/L SWR-NOM and UMR-NOM respectively). Two commonly present co-existing anions, i.e. phosphate and bicarbonate, also mitigate the detrimental effect of NOMs. With 15 mg/L SWR-NOM: the presence of 100 mg/L bicarbonate increased the total removal of MCPA from 49.1% to 65.1%; the presence of 100 mg/L phosphate increased the total removal of MCPA from 49.1% to 62.5%. With 15 mg/L SWR-NOM, the presence of 100 mg/L bicarbonate increased the total removal of MCPA from 45.2% to 56.1%; the presence of 100 mg/L phosphate increased the total removal of MCPA from 45.2% to 62.9%. The photocurrent measurement support that the presence of such anions greatly suppresses the h + scavenging effect of NOMs; while other anions, i.e. chloride, nitrate, sulfate, showed no notable effect.

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  • Concurrent ground and excited state proton transfer of (E)-2-((napthalen-2-ylimino)-methyl)phenol: Modulation in micellar media

    Publication date: 15 February 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 371

    Author(s): Anusree Ray, Saumitra Sengupta, Nitin Chattopadhyay

    Abstract

    The phenomena of ground and excited state proton transfer (GSPT and ESPT) of the synthesized Schiff base, (E)-2-((napthalen-2-ylimino)-methyl)phenol (NMP) have been unraveled in aqueous medium using various spectroscopic techniques. Changes in the absorption and emission spectra of an aqueous solution of the probe upon addition of an external base are ascribed to the proton transfer in both the ground and the excited states. Existence of equilibria between the neutral and the deprotonated species in the two electronic states is established from the observation of the isosbestic and isoemissive points in the absorption and emission spectra. Acid dissociation constants in the ground state (pKa) and photoexcited state (pKa*) of NMP in aqueous medium have been derived from the steady-state experiments using Weller’s method. The time resolved experiments clearly indicate the reversibility of the proton transfer reaction in the photo-excited state. The pKa* value determined from the kinetic measurements corroborates that obtained from the steady state methods. The higher value of pKa* than pKa is rationalized from the higher electron density on oxygen in the photoexcited state relative to the ground state, as obtained from the Mulliken charge densities through quantum chemical calculations. Extending our studies to the micellar environments, it is established that the deprotonation process is favored in cationic micelles while the same is disfavored in anionic or non-ionic micelles. This has been rationalized in terms of the surface charge characteristics of the individual micelles.

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  • Photo-catalytic degradation of triclosan with UV/iodide/ZnO process: Performance, kinetic, degradation pathway, energy consumption and toxicology

    Publication date: 15 February 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 371

    Author(s): Hossein Azarpira, Mohsen Sadani, Mehrnoosh Abtahi, Najmeh Vaezi, Soheila Rezaei, Zahra Atafar, Seyed Mohsen Mohseni, Maryam Sarkhosh, Mansour Ghaderpoori, Hassan Keramati, Rokhsane Hosseini Pouya, Abbas Akbari, Vahid fanai

    Abstract

    This study develops UV/Iodide/ZnO (UIZ) photo reactor to employs it for degradation, dechlorination and mineralization of triclosan (TCS) content of wastewaters. Degradation efficiency of the UV-only, UV/ZnO, UV/Iodide and UIZ processes were determined as 12.3%, 37.3%, 50.43% and 89.83% respectively, at 20 min reaction time, 10 mg L−1 TCS concentration and pH of 7. Findings indicated that the TCS completely degraded within 20 min treatment time. According to Weight ratio evaluations, the 1.26:2:10 ration is the optimal Weight ratio of Iodide /ZnO/TCS in the UIZ process. Analyzing effluents of the UIZ reactor by liquid chromatography/mass spectroscopy after 5, 10, 15 and 20 min reaction time revealed that TCS decomposes to ring-shaped compounds in less than 10 min and all TCS and its metabolites convert to linear compounds within 15 min reaction time. Investigating kinetic of the process through a pseudo first-order model using 1 to 10 mg L−1 TCS over 1 to 15 min reaction time demonstrated that the observed rate constant (kobs) decreases from 0.3405 to 0.0687 min−1 and the observed TCS degradation rate (robs) increases from 3.405 to 13.74 mg L−1 min−1 with increasing the TCS concentration. Furthermore, electrical energy consumption (EEO) of the UIZ process was calculated with kinetic model 2.48 to 12.29 and with merit-figure model 2.87 (2.87–8.95) to 14.88 (14.88–33.02) kW h m−3 from 1 to 10 mg L−1, respectively. In addition, the effect of co-existing water anions on degradation of 10 mg L−1 TCS was explored during 20 min processing. While 100% degradation was achieved in the absence of any anion, adding nitrate, as the most effective anion, decreased the TCS degradation to 72.88%. The highest dechlorination was observed at Iodide/ZnO weight ratio 1.26:1 and pH 9. Mineralization of TCS by UIZ process was achieved 38.6% after 15 min reaction time. In presence of the effluents extracted after 10 min TCS degradation (even after long incubation periods), no growth inhibition was observed using Analysis of the effluent dilution effect and toxicity assessment on Escherichia coli. Finally, feeding effluents of the UIZ photoreactor to cyclic rotating-bed biological reactor (CRBR) helped to reduce COD nearly completely after 1.5 h aeration, respectively. Therefore, the proposed UIZ/CRBR process is a promising technology for efficient treatment of the wastewaters containing TCS.



  • Fluorene – Triazine conjugated porous organic polymer framework for superamplified sensing of nitroaromatic explosives

    Publication date: 15 February 2019

    Source: Journal of Photochemistry and Photobiology A: Chemistry, Volume 371

    Author(s): Saumya Krishnan, Chettiyam Veettil Suneesh

    Abstract

    A porous organic polymer with fluorene and triazine units (PTF), was synthesised through a simple cost effective method. The material was well characterised by FT-IR, solid state 13C NMR and X-ray photoelectron spectroscopic studies. Absorption spectrum indicated the electronic coupling between the two units in the polymer backbone. Experiments proved high thermal and chemical stability, and porous nature of the material. Luminescence of PTF was quenched, on the addition of ppb level concentration of nitroaromatic compounds. This was attributed to the photo induced electron transfer from the electron rich polymer backbone to the electron deficient nitro aromatic compounds. The observed superamplification effect in the fluorescence quenching was studied extensively by a series of ground state absorption, steady state and time resolved fluorescence experiments. Finally, the superamplified quenching was successfully assigned to static quenching by quenching sphere of action model. High value of static quenching constant of the order of 3.9 ×103 M−1, for picric acid combined with detection limit as low as 89 ppb envisages PTF as an effective chemosensor for nitroaromatic explosives.

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    Detection of nitroaromatics via superamplified fluorescence quenching using a porous organic polymer.

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