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Главная страница Новости науки Journal of Photochemistry and Photobiology A: Chemistry
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ScienceDirect Publication: Journal of Photochemistry and Photobiology A: Chemistry
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ScienceDirect Publication: Journal of Photochemistry and Photobiology A: Chemistry
  • Hydrogen-bonded self-assembly, spectral properties and structure of supramolecular complexes of thiamonomethine cyanines with cucurbit[5,7]urils
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): Marina V. Fomina, Alexander S. Nikiforov, Vitaly G. Avakyan, Artem I. Vedernikov, Nikolai A. Kurchavov, Lyudmila G. Kuz’mina, Yuri A. Strelenko, Judith A.K. Howard, Sergey P. Gromov

    The complex formation of thiamonomethine cyanine dyes bearing two N-ammoniohexyl or two N-ethyl substituents with cucurbit[5,7]urils (CB[5,7]) in aqueous solutions was studied by electronic and 1H NMR spectroscopy, including spectrophotometric, fluorescence, and 1H NMR titration methods. It was found that CB[5] forms external complexes with the dyes, while CB[7] forms internal (inclusion) complexes of 1:1 and 1(dye):2(CB[5,7]) composition. The complexation with CB[5,7] changes the absorption spectra of cyanine dyes and induces a considerable fluorescence enhancement. The stability constants of the complexes were determined (logK 1:1 varies in the range from 3.53 to more than 6, and logK 1:2 varies in the range from 3.5 to 4.32). The dye with ammoniohexyl substituents forms more stable complexes owing to hydrogen bond formation between the NH3 + groups and the carbonyl groups of the CB[5,7] portals. The structure of supramolecular complexes was confirmed by quantum chemical calculations.

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  • Mechanistic investigation of visible light responsive Ag/ZnO micro/nanoflowers for enhanced photocatalytic performance and antibacterial activity
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): Sze-Mun Lam, Jian-Ai Quek, Jin-Chung Sin

    Visible light responsive Ag-doped flower-like ZnO (Ag/ZnO) micro/nanostructure photocatalysts with different loadings of Ag were successfully fabricated through surfactant-free co-precipitation and photodeposition routes. The as-prepared samples have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic tests demonstrated that the Ag/ZnO micro/nanoflowers enhanced visible light responsive photoactivity towards the degradation of Fast Green dye and inactivation of Escherichia coli. Particularly, the 5wt% Ag/ZnO samples showed excellent photoactivity in comparison with those of pure ZnO and commercial TiO2. The PL spectra showed that the Ag incorporation could effectively stimulate the separation efficiency of photogenerated charge carrier in Ag/ZnO. The trapping experiments indicated that superoxide anion (O2 ) radicals and hole (h+) were the major reactive oxygen species for the Ag/ZnO photocatalytic system. Much effort was also focused on the visible light photocatalytic antibacterial activity using Escherichia coli by observing the antibacterial response, minimum inhibitory concentration (MIC) and membrane integrity assay. The results showed that the Ag/ZnO can be used as photocatalysts and antibacterial agents for potential practical applications in the wastewater treatment.

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  • A novel fluorescent and colorimetric probe for cascade selective detection of Fe(III) and pyrophosphate based on a click generated cyclic steroid–rhodamine conjugate
    Publication date: 1 April 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 356

    Author(s): Zhen Zhang, Chengquan Deng, Yuan Zou, Lei Chen

    A novel fluorescent and colorimetric probe containing deoxycholic acid and rhodamine moieties was developed by click chemistry, and its cascade selective detection of ferric ion (Fe3+) and pyrophosphate (PPi) was investigated in details by spectral measurements. The probe displayed turn-on orange fluorescence and colorless to pink color change upon binding with Fe3+ by reversibly forming the metal complex and opening the spirolactam ring of rhodamine. Through a tandem ligand exchange, PPi with higher affinity for Fe3+ removed the metal from the complex and restored the spectral signal of the probe. The experimental results suggested that this novel molecule could serve as an efficient and economical dual signal chemosensing system for cascade bi-target analysis of Fe3+ and PPi with high selectivity, low detection limits and fast response time. Notably, this bi-functional probe also showed excellent performances in monitoring Fe3+ and PPi on silica gel plates, in water samples and living cells.

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  • Substitution effect in 2-spiropropane-1,3-diyl derivatives: A DFT and CASSCF study
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): Maryam Souri, Tayebeh Kazemi

    In this study, the electronic structure of 2-spiropropane-1,3-diyl and its derivatives have been investigated. Different DFT methods, including: B3LYP, BLYP, M06-2X, PBE0 and PBEPBE, have been applied to investigate the substitution effect on the geometry and stability of considered triplet diradicals. Complete active space approach has been applied to survey the effect of ground state charge multiplicity on the stability of considered diradicals. The role of through- space interactions in stabilization of singlet CH3 substituted diradical, comparing with triplet sate, has been verified. On the other hand, it has been demonstrated that, the through- bond interactions in 2-spiropropane-1,3-diyl and Cl, F, OH substituted species cause the triplet state to be more stable than singlets. The charge distributions on the studied singlet and triplet diradicals confirm the importance of the through- bond and through- space interactions, too. Different substituted diradicals have higher diradical character, comparing with the parent molecule, 2-spiropropane-1,3-diyl. Substitution of Cl group, in molecule 4, maximize the diradical character of this molecule. The NLO properties of considered diradicals have been investigated and it has been stablished that the singlet species show higher values of average second-order hyperpolarizability than triplets. The maximum NLO property is belonged to the Cl substituted 2-spiropropane-1,3-diyl singlet diradical.

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  • Fe3+-doped TiO2 nanopowders for photocatalytic mineralization of oxalic acid under solar light irradiation
    Publication date: 1 April 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 356

    Author(s): Elena Craciun, Luminita Predoana, Irina Atkinson, Ioana Jitaru, Elena Maria Anghel, Veronica Bratan, Catalina Gifu, Crina Anastasescu, Adriana Rusu, Valentin Raditoiu, Eugenia Vasile, Mihai Anastasescu, Ioan Balint, Maria Zaharescu

    Iron (III) doped TiO2 nanopowders were synthesized by solgel method starting from the concentrated alcoholic solutions of tetraethyl (TET) and tetraisopropyl (TIP) orthotitanate precursors. TET precursor leads to gel formation while TIP precursor conducted to powder generation. The optimized thermal treatments, derived from TG/DTA analysis, allowed the transformation of precursor powders and gels into crystalline powders with anatase structure, as determined by X-ray diffraction (XRD). Corroboration of XRD, FT-IR and Raman investigations lead to the conclusion that Fe3+ was introduced substitutionally into TiO2 matrix. TEM analysis revealed similar morphology for all prepared samples, consisting of nanometric particles. UV–vis spectroscopy evidenced that Fe3+ dispersed into TiO2 matrix shifts the optical bandgap to the visible range. The photocatalytic mineralization of oxalic acid over Iron (III) doped TiO2 nanopowders under simulated solar irradiation was studied to assess the application potential of these materials in depollution field. CO2 production was identified as main product of photocatalytic reaction. The CO2 output was proportional to the surface area of the photocatalysts. In mean time, the lower was the optical band-gap of tested materials the higher was the photocatalytic activity for mineralization of oxalic acid. Introduction of Fe3+ into TiO2 lattice leads to creation of optically active redox sites, able to absorb the visible component of solar light. A reaction mechanism was advanced based on experimental facts. The role of substitutional Fe3+ in mechanism of oxalic acid photomineralization was examined in relationship with generation of e and h+ charges and O2 and OH radicals. The optimized preparation method, requiring lower amounts of reagents and milder synthesis conditions, lead to homogeneous Fe3+/TiO2 materials with promising potential for depollution applications.

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  • Substituent effect of side chains on the photochemical behavior of a new generation 1,4-dihydropyridine: Lercanidipine
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): Sebastián Cumsille, Javier Morales, Catalina Sandoval-Altamirano, Germán Günther, Andrés Vega, Nancy Pizarro

    Lercanidipine (LERCA) is a third generation antihypertensive drug belonging to the 1,4-dihydropyridine’s family, which has been reported to induce photoallergic and/or phototoxic effects in patients with long term treatment. The electronic nature of substituents on the 4-aryl moiety bonded to the 1,4-dihydropyridine ring has been described to strongly affect the photophysical and photochemical behavior of this family of compounds, which displays a typical absorption band around 360nm. LERCA undergoes photodegradation after excitation, with a first order kinetic, in significant competition to the radiative path. The photodegradation quantum yields for LERCA are higher than for its homologue nimodipine (NIMO), thus indicating that the substituents on the 1,4-dihydropyridinic ring also affect their photophysical and photochemical properties. The media where the photodegradation takes place impacts on the product profile, in a homogeneous one the photoproducts obtained appear to be more polar than those obtained for a micro-heterogeneous one (micelles or bilayers mimicking biological media).

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  • Synthesis of AMoO4 (A = Ca, Sr, Ba) photocatalysts and their potential application for hydrogen evolution and the degradation of tetracycline in water
    Publication date: 1 April 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 356

    Author(s): Ali M. Huerta-Flores, I. Juárez-Ramírez, Leticia M. Torres-Martínez, J. Edgar Carrera-Crespo, T. Gómez-Bustamante, O. Sarabia-Ramos

    Alkaline earth metal molybdates AMoO4 (A = Ca, Sr, Ba) were synthesized by the traditional solid-state reaction. The structural, morphological, textural and optical properties of metal molybdates were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmet-Teller (BET) method, diffuse reflectance UV–vis spectroscopy (UV–vis DRS), and photoluminescence spectroscopy (PL). Electrochemical characterization through OCP and EIS measurements was performed to elucidate the photoresponse and electrical properties of metal molybdates. Energy band diagrams obtained by theoretical calculations and experimental data revealed that the synthesized molybdates present convenient band positions to be used in photocatalytic processes. For this reason, these compounds were tested as catalysts in photoinduced processes such as hydrogen production and tetracycline degradation. Accordingly to results, the studied molybdates were able to produce hydrogen (∼240 μmol g−1 h−1) under UV light irradiation and also these materials provoked the degradation of tetracycline (85% in pure water and 97% with the addition of H2O2). In conclusion, CaMoO4, SrMoO4, and BaMoO4 are suitable photocatalysts for water splitting and degradation of organic compounds.

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  • Novel PAMAM dendrimers with porphyrin core as potential photosensitizers for PDT applications
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): M. Paula Militello, Raquel E. Hernández-Ramírez, Irina V. Lijanova, Carlos M. Previtali, Sonia G. Bertolotti, Ernesto M. Arbeloa

    The photophysical properties of meso-substituted tetraphenyl porphyrins with PAMAM branches, and one peripherally-modified derivative with thiazole groups were studied in DMF solution. The singlet states of the compounds were characterized by means of absorption and fluorescence spectroscopies. The triplet state decay kinetics and the triplet–triplet absorption spectra were determined by laser flash photolysis. Triplet state spectra showed intense absorbance with a maximum at around 450nm and other bands in the regions of 300–400 and 500–800nm, for all compounds. The triplet quantum yields (ΦT) and the singlet oxygen quantum yields (ΦΔ) were estimated to be ca. 0.50 and 0.45, respectively. From the present results, it is inferred that the triplet states of these molecules allow an efficient energy transfer to molecular oxygen, which makes them potentially suitable for photodynamic therapy.

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  • FeOx,SiO2,TiO2/Ti composites prepared using plasma electrolytic oxidation as photo-Fenton-like catalysts for phenol degradation
    Publication date: 1 April 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 356

    Author(s): M.S. Vasilyeva, V.S. Rudnev, A.A. Zvereva, A.Yu. Ustinov, O.D. Arefieva, V.G. Kuryavyi, G.A. Zverev

    FeOx,SiO2,TiO2/Ti composites were formed through combination of the methods of plasma electrolytic oxidation and impregnation. The coatings have been studied by the methods of X-ray diffraction analysis, electron microscopy, and X-ray photoelectron and IR spectroscopy. The photocatalytic activity of oxide coatings has been investigated in the phenol degradation reaction. It was shown that the Fe-containing oxide coatings were highly active in the phenol decomposition under the following conditions: 1. the presence of hydrogen peroxide; 2. ultraviolet irradiation; 3. the presence of iron hydroxide on the surface of coatings. The results suggest that the catalysts studied are similar to photo-Fenton-like catalysts in their mechanism of action. Their activity is determined by the formation of iron-peroxide complexes fixed on the coating surface and thereafter of active radicals under the UV irradiation. The kinetics of phenol decomposition and the effect of the solution pH on the phenol decomposition degree has been studied.

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  • 1, 10-Phenanthroline based ESIPT sensor for cascade recognition of Cu2+ and CN− ions
    Publication date: 15 February 2018
    Source:Journal of Photochemistry and Photobiology A: Chemistry, Volume 353

    Author(s): Navneet Kaur, Gaganpreet Kaur, Priya Alreja

    The optical methods, using organic molecular sensors, for the detection of cations and anions, offer several advantages in being selective and sensitive, in addition to simple in application and in-situ monitoring. Herein, the chemosensing properties of 1,10-phenanthroline based ESIPT sensor 1 have been exploited in CH3CN for several cations. The fluorescence emission intensity of 1 was completely quenched with Cu2+ ions and this in-situ generated 1-Cu2+ complex was further used for cascade recognition of CN ions. The alternate additions of Cu2+ and CN ions generated “on-off-on” fluorescence cycles, enabling 1 to be used as reversible and reconfigurable Set/Rest memorized device at the molecular level.

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