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Photochemical & Photobiological Sciences

Sohini Basu Roy, Chandraday Prodhan, Keya Chaudhuri, Kajal Krishna Rajak
Here, we report the design and synthesis of the fluorescent probe APBHN, which was derived from 2-(1H-benzo[d]imidazol-2-yl)benzenamine and is capable of detecting intracellular Zn and Cu ions in the micromolar range. Single-crystal X-ray analysis revealed that the structure of the ligand comprises a fused cyclic system with a pendent naphthol moiety. With the addition of Zn and Cu ions the inherent fluorescence behaviour of the ligand APBHN is perturbed via a chemodosimetric change that involves a 1,5 proton shift followed by C-N bond cleavage...
May 24, 2017: Photochemical & Photobiological Sciences
Jonathan P Hopwood, Jacob W Ciszek
Thin-films of three dihydroindolizine molecular switches were monitored via polarization modulation infrared reflection absorption spectroscopy to quantify solid state and surface-based inhibition of switching as a function of irradiation time. In the solid state, the molecular switches diverged dramatically with flexible alkyl substituents resulting in switching rates up to three times that of switches containing rigid analogs. For thin-films, decreasing film thickness from 30 nm to approximately 4 molecules thick resulted in an increase in inhibition...
May 23, 2017: Photochemical & Photobiological Sciences
Lixin Zang, Huimin Zhao, Xueyu Ji, Wenwu Cao, Zhiguo Zhang, Peisong Meng
Conventional photodynamic therapy (PDT) uses red light for deeper penetration. A natural compound, aloe emodin (AE) with anticancer and photosensitising capabilities, excited by blue light, is proposed to treat superficial diseases. The photophysical properties and singlet oxygen quantum yield (ΦΔ) of AE, as well as the cytotoxic effects of AE on human cells, were investigated. The absorption and emission spectra of AE were analyzed. The ΦΔ of AE was measured by a relative method. In order to study the relationship between ΦΔ and the oxygen concentration, the dependence of ΦΔ on the oxygen concentration was investigated...
May 22, 2017: Photochemical & Photobiological Sciences
Szymon Wojtyła, Wojciech Macyk, Tomasz Baran
Bare and photosensitized copper iodides were tested in photocatalysed degradation of an organic dye (Acid Red 1) and inactivation of fungi (Saccharomyces cerevisiae). CuI, with the band gap energy slightly lower than that of TiO2, appeared to be highly efficient in these processes. Sensitization of copper iodide was achieved by surface modification with [Cu(SCN)2(phen)2]. The photosensitization mechanism encompasses a metal to metal charge transfer, Cu(I) → Cu(II). The applied photosensitizer binds to CuI through thiocyanate ligands resulting in the formation of an active Cu(II)/Cu(I) hybrid photocatalyst ([Cu(II)(SCN)2(phen)2]@Cu(I)I)...
May 17, 2017: Photochemical & Photobiological Sciences
Lucimara P Ferreira, Gustavo G Parra, Débora C K Codognato, André M Amado, Roberto S da Silva
The cytotoxicity of nitrofurantoin (NFT) in the dark and after light exposure (UVA irradiation, λ = 385 nm) was evaluated in murine melanoma B16F10 cells. NFT induces both cell proliferation and inhibition of cell viability. The dominance of one or the other effect depends on the drug concentration, incubation time (tinc) and irradiation dose. The uptake of NFT in these cells, as well as its photocytotoxicity, reaches saturation after 24 hours of incubation. The mechanism of cell death in the dark is associated with the enzymatic release of nitric oxide (NO)...
May 17, 2017: Photochemical & Photobiological Sciences
E Kukcinaviciute, A Sasnauskiene, D Dabkeviciene, V Kirveliene, V Jonusiene
The primary or acquired cancer chemoresistance is a major problem in the treatment of cancer patients. It could be overcome by non-overlapping treatment regimens such as photodynamic therapy (PDT). PDT is based on the oxidation of cellular components which occurs when a light-excited photosensitizer generates reactive oxygen species (ROS). In this study the effect of mTHPC mediated PDT (mTHPC-PDT) on 5-FU resistant colorectal cancer (CRC) cells HCT116 was investigated. The results show that mTHPC-PDT overcomes 5-FU resistance and is effective against chemoresistant colorectal carcinoma cells...
May 16, 2017: Photochemical & Photobiological Sciences
Dushanthi S Dissanayake, Gregory T McCandless, Mihaela C Stefan, Michael C Biewer
Spiropyrans are notable among different classes of photochromic compounds due to their large structural and electronic transformation upon isomerization. In order to parlay the electronic differences associated with the two isomeric forms into a materials based switch, the spiropyran ultimately requires a covalent attachment through a conjugated pathway. In this work a synthetic method was developed to incorporate spiropyran (SP) into thiophene based materials. A series of compounds with a systematic variation of substituents were synthesized (SP-T, SP-T-Br, SP-T-T, SP-T-T-T and SP-T-T-T-T-SP) and their photochromism in both polar (methanol) and non-polar (toluene) solvents were studied...
May 16, 2017: Photochemical & Photobiological Sciences
Romina R Heymann, Matthew D Thum, Apryl L Hardee, Daniel E Falvey
Photolysis of anthraquinone or flavin photosensitizers in the presence of calcium EDTA complexes results in decomposition of the EDTA complex, releasing free Ca(2+). In the case of the flavin sensitizers, it is shown that millimolar concentrations of Ca(2+) can be released using visible light (>440 nm) and with quantum yields as high as 0.31. The utility of this system is further demonstrated by in situ photogelation of an alginate solution.
May 12, 2017: Photochemical & Photobiological Sciences
Rui Zhang, Gang Li, Yue Zhang
In this study, we decorated CdS on the surface of MIL-125(Ti) using a photochemical method to prepare the CdS-MIL-125(Ti) nanocomposites. The obtained samples were characterized by a series of techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, electrochemical measurements and UV-Vis diffuse reflectance spectra (DRS). The results show that the CdS nanoparticles were highly dispersed on surface of MIL-125(Ti). The combination will promote the separation of electron-hole pairs and increase the dispersity of CdS...
May 12, 2017: Photochemical & Photobiological Sciences
Ji He, Yang Liu, Jianrong Gao, Liang Han
Three D-D-π-A triphenylamine-coumarin sensitizers were designed and synthesized with a triphenylamine and coumarin double donor and a cyanoacrylic acid acceptor. Thiophene, bithiophene and phenylthiophene were used as π-bridges, respectively, and the effects of different π-bridges on the photophysical properties and photovoltaic performance were investigated. With the incorporation of an additional thiophene unit, the bithiophene π-bridge contributes to better light absorption and hence superior JSC compared with the thiophene π-bridge...
May 12, 2017: Photochemical & Photobiological Sciences
A Patrón-Soberano, B P Núñez-Luna, S Casas-Flores, A De Las Peñas, R B Domínguez-Espíndola, V Rodríguez-González
One-dimensional titanate nanotubes (H2Ti2O5·H2O) functionalized with silver nanoparticles (AgNPs) exhibited unique properties for the effective inactivation of the Gram-negative Escherichia coli within 45 minutes under irradiation using a 65 W halogen lamp. The pathway of the photo-assisted catalytic inactivation was examined by SEM and TEM using a reproducible biological protocol for sample preparations. The membrane integrity of the bacteria was damaged due to the oxidative stress caused by the reactive oxygen species, the bacteriostatic effect of the highly-dispersed-surface AgNPs (∼5 nm) and the sharp nanotube penetration that induced the cell death...
May 11, 2017: Photochemical & Photobiological Sciences
Priyadarshi Roy Chowdhury, Krishna G Bhattacharyya
Optically responsive, luminescent Ni/Co/Ti layered double hydroxide (LDH), synthesized by a single step hydrothermal route, exhibits highly efficient photodegradation of cationic and anionic dyes, Rhodamine B (∼99.8%) and Acid Red G (∼99.6%) respectively, better than that of commercial catalysts like NiO, CoO and TiO2. The LDH has been characterized by using XRD, XPS, PL, TRES, EIS, TEM, SEM-EDX, AFM, UV-visible DRS, N2-sorption desorption, ξ-potential, FT-IR and TG techniques. The characterized results indicate that the LDH possesses hexagonal morphology, a high surface area, a narrow band gap, defect states and oxygen vacancies within its layered framework...
May 10, 2017: Photochemical & Photobiological Sciences
Masaaki Yusa, Toshi Nagata
Under the irradiation of red light (690 nm), quinones were converted to hydroquinones by thiols in the presence of metallophthalocyanines. The reaction proceeded via the charge separation between the triplet state of phthalocyanine and the quinone. The product determining step was protonation of the quinone anion radical, as indicated by the fact that the reaction was accelerated by the use of more acidic thiols or addition of an acid.
May 9, 2017: Photochemical & Photobiological Sciences
Trevor M Safko, Shenlong Jiang, Lei Zhang, Qun Zhang, Richard G Weiss
Photoinduced intermolecular proton-transfer processes from N,N-dimethyl-3-arylpropan-1-ammonium chloride salts (ArCl, with aryl as 1-pyrenyl, 9-anthryl, and 2-naphtyl) to a solvent molecule have been investigated by steady-state and dynamic spectroscopic methods. The intermolecular proton-transfers are coupled either to the formation of an exciplex or to a solvent-separated ion pair in what we have termed a 'proton-coupled charge-transfer reaction'. A range of solvents has been observed to mediate both the ground-state conformations of the ArCl and the extent of electron transfer...
May 9, 2017: Photochemical & Photobiological Sciences
Pameli Datta, Peter A Philipsen, Peter Olsen, Morten K Bogh, Peter Johansen, Anne V Schmedes, Niels Morling, Hans C Wulf
The 25-hydroxy vitamin D (25(OH)D) production caused by UVB exposure is usually underestimated as the concurrent degradation of 25(OH)D is not considered. Therefore, the decrease in 25(OH)D was investigated during a 7-week period in winter when ambient UVB is negligible. Twenty-two healthy Danish individuals (113 samples) participated and had a mean and steady maximal 25(OH)D start level of 132 nmol l(-1) (range of 68-216 nmol l(-1)) due to long-term UVB treatment prior to this study. In this group with high 25(OH)D start levels, the decrease in 25(OH)D was best described by an exponential model...
May 9, 2017: Photochemical & Photobiological Sciences
Luis F Suárez Salas, Jose L Flores Rojas, Augusto J Pereira Filho, Hugo A Karam
Ultraviolet (UV) solar irradiance measurements performed in the central Andes, Huancayo, Peru (12.0°S, 75.3°W, 3313 m asl) at 1 min intervals between January 2003 and December 2006 were used to analyse daily, monthly, and annual cycles of UV solar irradiance. The measurements were performed using a GUV-511 multi-channel filter radiometer at four wavelengths: 305, 320, 340, and 380 nm. UV irradiance data under clear sky and all sky conditions were separated using a procedure based on calculation of normalized irradiance...
May 4, 2017: Photochemical & Photobiological Sciences
Alex R Jones
Biologically active derivatives of vitamin B12 are organometallic cobalt-corrinoid complexes crucial for the healthy function of humans, animals and microbes. Their role as cofactors to numerous, thermally-driven metabolic enzymes is well described, and varies depending on the nature of the upper axial ligand. This ligand also significantly influences the photophysics and photochemistry of B12. In this Perspective I will discuss the various aspects of B12 photochemistry, from its dynamic spin chemistry to the considerable potential it has for biotechnology applications...
May 2, 2017: Photochemical & Photobiological Sciences
L N Corîci, S Shova, V Badea, D Aparaschivei, O Costisor, L Cseh
The network of chemical reactions of 2,6-bis(5-bromo-2-hydroxybenzylidene)cyclohexanone (BHBC) when subjected to light and different pH values has been investigated. The pH dependent species involved in the chemical network have been identified and characterized by NMR and UV-VIS spectroscopy. Direct pH jumps were carried out by adding a strong acid to equilibrated solutions of trans-chalcone (Ct) forming the flavylium cation which was stable only under extremely acidic conditions (pH < 0.5). The single crystal X-ray study and NMR analysis has confirmed the structure of the new flavylium cation...
April 26, 2017: Photochemical & Photobiological Sciences
Andreia Romeiro, Diana Freitas, M Emília Azenha, Moisés Canle, Hugh D Burrows
We report a comparative study on the photodegradation of the widely used benzodiazepine psychoactive drug alprazolam (8-chloro-1-methyl-6-phenyl-4H-[1,2,4]triazolo[4,3-a][1,4]benzodiazepine, ALP) using direct photolysis, and titanium dioxide photocatalyzed reaction. Titanium dioxide photocatalysts were prepared as nanoparticles by acidic sol-gel methods, calcined at two different temperatures, and their behavior compared with P25 (Degussa type) TiO2. Efficient photodegradation was observed in the photocatalytic process, with over 90% degradation after 90 minutes under optimized conditions...
April 26, 2017: Photochemical & Photobiological Sciences
Shota Fujino, Minoru Yamaji, Hideki Okamoto, Toshiki Mutai, Isao Yoshikawa, Hirohiko Houjou, Fumito Tani
We studied the photoproducts of 1-(n-phenanthryl)-2-(m-phenanthryl)ethenes (nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorption measurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing nEm by photocyclization of stilbene derivatives...
April 25, 2017: Photochemical & Photobiological Sciences
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