Journal articles: 'Photolyse UV-C'

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Maré, George R. De, Guy J. Collin, and Hélène Deslauriers. "Évaluation des ruptures de liaison α(C—H) centrale et terminale dans la photolyse du propène gazeux à 184,9 nm." Canadian Journal of Chemistry 73, no. 8 (August 1, 1995): 1267–73. http://dx.doi.org/10.1139/v95-155.

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The minor, α(C—H) photofragmentation processes in the far-UV photolysis of gaseous propene at λ = 184.9 nm are investigated. At this wavelength the β(C—H) and α(C—C) photofragmentation processes are of major importance, accounting for more than 95% of the primary reaction process. The total quantum yield of the three α(C—H) bond cleavage processes is close to 0.03. However [Formula: see text] and the sum of the two [Formula: see text] cleavages is 0.005 ± 0.003. Thus [Formula: see text] whereas statistically one expects 1:2. Thus the energy of the bond that is breaking is important, even though the photon energy is much higher than that required to break it. The geometrical parameters, total energies, and fundamental frequencies of the cis- and trans-propen-1-yl and propen-2-yl radicals have been determined by abinitio methods at various levels of theory (STO-3G, 3-21G, 6-31G, 6-31G*, and 6-31G** basis sets; UHF, ROHF, and GVB methods). cis-Propen-1-yl is predicted to be 0.6–1.0 kJ mol−1 lower in energy than trans-propen-1-yl, except with the minimal STO-3G basis set. The optimizations predict that propen-2-yl is more stable than the cis- and trans-propen-1-yl radicals by 14 ± 3 kJ mol−1. Keywords: propene, unimolecular reactions, photochemistry, α(C—H) cleavage, propenyl radicals.

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Guitonneau, S., S. Momege, A. Schafmeier, P. O. Viac, and P. Meallier. "Étude comparative de la dégradation du bromoxynil et du bromoxynil heptanoate par photolyse UV et par oxydation chimique (H²O²/UV ; O³ ; Cl²)." Revue des sciences de l'eau 8, no. 2 (April 12, 2005): 201–16. http://dx.doi.org/10.7202/705219ar.

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Les dégradations du bromoxynil heptanoate et du bromoxynil ont été étudiées pour différents traitements chimiques (03, Cl2) et photochimiques (H202/W; W254) en milieu aqueux dilué. Les expériences ont été réalisées à pH 7 pour le bromoxynil (CO=5 10-5 mol 1-1) et à pH 4 pour le bromoxynil heptanoate (CO=10-6 mol 1-1) afin de limiter la réaction d'hydrolyse. Les résultats obtenus montrent une bonne dégradation de ces deux pesticides aussi bien par irradiation W que par oxydation chimique au chlore ou à l'ozone. L'ajout de peroxyde d'hydrogène dans le milieu n'augmente pas de façon significative l'efficacité du traitement par rapport à l'irradiation seule. Parmi tous les traitements étudiés, l'ozonation est le procédé le plus efficace. L'analyse par couplage GC-MS des produits de réaction au cours de l'irradiation UV a permis d'identifier quatre photoproduits correspondant à la substitution des atomes de brome soit par un atome d'hydrogène, soit par un groupement OH. Les produits identifés sont A: -3,4 dihydroxy -5 bromobenzonitrile; B: -3,4,5 trihydroxybenzonitrile; C: -3,4 dihydroxybenzonitrile; D: -4 hydroxybenzo- nitrile. Un schéma réactionnel de photodégradation du bromoxynil heptanoate a été proposé dans cette étude.

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Emmerich, Hans-Joachim, Martin Saft, Leonie Schneider, Dennis Kock, Alfred Batschauer, and Lars-Oliver Essen. "A topologically distinct class of photolyases specific for UV lesions within single-stranded DNA." Nucleic Acids Research 48, no. 22 (December 3, 2020): 12845–57. http://dx.doi.org/10.1093/nar/gkaa1147.

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Abstract Photolyases are ubiquitously occurring flavoproteins for catalyzing photo repair of UV-induced DNA damages. All photolyases described so far have a bilobal architecture with a C-terminal domain comprising flavin adenine dinucleotide (FAD) as catalytic cofactor and an N-terminal domain capable of harboring an additional antenna chromophore. Using sequence-similarity network analysis we discovered a novel subgroup of the photolyase/cryptochrome superfamily (PCSf), the NewPHLs. NewPHL occur in bacteria and have an inverted topology with an N-terminal catalytic domain and a C-terminal domain for sealing the FAD binding site from solvent access. By characterizing two NewPHL we show a photochemistry characteristic of other PCSf members as well as light-dependent repair of CPD lesions. Given their common specificity towards single-stranded DNA many bacterial species use NewPHL as a substitute for DASH-type photolyases. Given their simplified architecture and function we suggest that NewPHL are close to the evolutionary origin of the PCSf.

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González-Burciaga, Luis A., Juan C. García-Prieto, Cynthia M. Núñez-Núñez, and José B. Proal-Nájera. "Statistical Analysis of Methotrexate Degradation by UV-C Photolysis and UV-C/TiO2 Photocatalysis." International Journal of Molecular Sciences 24, no. 11 (May 31, 2023): 9595. http://dx.doi.org/10.3390/ijms24119595.

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Methotrexate (MTX) is a folic acid analog and has been used to treat a wide variety of malignant and non-malignant diseases. The wide use of these substances has led to the continuous discharge of the parent compound and its metabolites in wastewater. In conventional wastewater treatment plants, the removal or degradation of drugs is not complete. In order to study the MTX degradation by photolysis and photocatalysis processes, two reactors were used with TiO2 as a catalyst and UV-C lamps as a radiation source. H2O2 addition was also studied (absence and 3 mM/L), and different initial pHs (3.5, 7, and 9.5) were tested to define the best degradation parameters. Results were analyzed by means of ANOVA and the Tukey test. Results show that photolysis in acidic conditions with 3 mM of H2O2 added is the best condition for MTX degradation in these reactors, with a kinetic constant of 0.028 min−1. According to the ANOVA test, all considered factors (process, pH, H2O2 addition, and experimentation time) caused statistically significant differences in the MTX degradation results.

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Bayram, Özgür, Christoph Biesemann, Sven Krappmann, Paul Galland, and Gerhard H. Braus. "More Than a Repair Enzyme:Aspergillus nidulansPhotolyase-like CryA Is a Regulator of Sexual Development." Molecular Biology of the Cell 19, no. 8 (August 2008): 3254–62. http://dx.doi.org/10.1091/mbc.e08-01-0061.

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Cryptochromes are blue-light receptors that have presumably evolved from the DNA photolyase protein family, and the genomes of many organisms contain genes for both types of molecules. Both protein structures resemble each other, which suggests that light control and light protection share a common ancient origin. In the genome of the filamentous fungus Aspergillus nidulans, however, only one cryptochrome/photolyase-encoding gene, termed cryA, was identified. Deletion of the cryA gene triggers sexual differentiation under inappropriate culture conditions and results in up-regulation of transcripts encoding regulators of fruiting body formation. CryA is a protein whose N- and C-terminal synthetic green fluorescent protein fusions localize to the nucleus. CryA represses sexual development under UVA350-370 nmlight both on plates and in submerged culture. Strikingly, CryA exhibits photorepair activity as demonstrated by heterologous complementation of a DNA repair-deficient Escherichia coli strain as well as overexpression in an A. nidulans uvsBΔ genetic background. This is in contrast to the single deletion cryAΔ strain, which does not show increased sensitivity toward UV-induced damage. In A. nidulans, cryA encodes a novel type of cryptochrome/photolyase that exhibits a regulatory function during light-dependent development and DNA repair activity. This represents a paradigm for the evolutionary transition between photolyases and cryptochromes.

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González-Burciaga, L. A., J. C. García-Prieto, C. M. Núñez-Núñez, M. García-Roig, and J. B. Proal-Nájera. "Methotrexate Degradation by UV-C and UV-C/TiO2 Pro-cesses with and without H2O2 Addition on Pilot Reactors." International Journal of Environmental Science and Development 11, no. 10 (2020): 471–76. http://dx.doi.org/10.18178/ijesd.2020.11.10.1292.

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Methotrexate (MTX) is an anti-cancer drug that can be excreted up to 90% after administration due to its low biodegradability. Advanced Oxidation Processes (AOPs) are a feasible alternative for the elimination of MTX in the environment. In this research, AOPs were performed in specialized patented reactors (UBE Photocatalytic systems and BrightWater Titanium Advanced Oxidation Process) under experimental pilot conditions. Photolysis and heterogeneous photocatalysis (UV and UV/TiO2) experiments were performed with and without addition of H2O2 and at different initial pHs. Best degradation percentage was achieved by photolysis when initial pH was 3.5 and added H2O2 was 3 mM, reaching a MTX degradation of 82% after 120 min of reaction. HPLC-MS analysis of the resulting samples showed four possible byproducts of MTX degradation, which presented a higher ecotoxicity than the starting compound.

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González-Burciaga, Luis A., Juan C. García-Prieto, Manuel García-Roig, Ismael Lares-Asef, Cynthia M. Núñez-Núñez, and José B. Proal-Nájera. "Cytostatic Drug 6-Mercaptopurine Degradation on Pilot Scale Reactors by Advanced Oxidation Processes: UV-C/H2O2 and UV-C/TiO2/H2O2 Kinetics." Catalysts 11, no. 5 (April 29, 2021): 567. http://dx.doi.org/10.3390/catal11050567.

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6-Mercaptopurine (6-MP) is a commonly used cytostatic agent, which represents a particular hazard for the environment because of its low biodegradability. In order to degrade 6-MP, four processes were applied: Photolysis (UV-C), photocatalysis (UV-C/TiO2), and their combination with H2O2, by adding 3 mM H2O2/L (UV-C/H2O2 and UV-C/TiO2/H2O2 processes). Each process was performed with variable initial pH (3.5, 7.0, and 9.5). Pilot scale reactors were used, using UV-C lamps as radiation source. Kinetic calculations for the first 20 min of reaction show that H2O2 addition is of great importance: in UV-C experiments, highest k was reached under pH 3.5, k = 0.0094 min−1, while under UV-C/H2O2, k = 0.1071 min−1 was reached under the same initial pH; similar behavior was observed for photocatalysis, as k values of 0.0335 and 0.1387 min−1 were calculated for UV-C/TiO2 and UV-C/TiO2/H2O2 processes, respectively, also under acidic conditions. Degradation percentages here reported for UV-C/H2O2 and UV-C/TiO2/H2O2 processes are above 90% for all tested pH values. Ecotoxicity analysis of samples taken at 60 min in the photolysis and photocatalysis processes, suggests that contaminant degradation by-products present higher toxicity than the original compound.

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Kawasaki, Koji, and Hideo Iwasaki. "Involvement of glycogen metabolism in circadian control of UV resistance in cyanobacteria." PLOS Genetics 16, no. 11 (November 30, 2020): e1009230. http://dx.doi.org/10.1371/journal.pgen.1009230.

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Most organisms harbor circadian clocks as endogenous timing systems in order to adapt to daily environmental changes, such as exposure to ultraviolet (UV) light. It has been hypothesized that the circadian clock evolved to prevent UV-sensitive activities, such as DNA replication and cell division, during the daytime. Indeed, circadian control of UV resistance has been reported in several eukaryotic organisms, from algae to higher organisms, although the underlying mechanisms remain unknown. Here, we demonstrate that the unicellular cyanobacterium Synechococcus elongatus PCC 7942 exhibits a circadian rhythm in resistance to UV-C and UV-B light, which is higher during subjective dawn and lower during subjective dusk. Nullification of the clock gene cluster kaiABC or the DNA-photolyase phr abolished rhythmicity with constitutively lower resistance to UV-C light, and amino acid substitutions of KaiC altered the period lengths of the UV-C resistance rhythm. In order to elucidate the molecular mechanism underlying the circadian regulation of UV-C resistance, transposon insertion mutants that alter UV-C resistance were isolated. Mutations to the master circadian output mediator genes sasA and rpaA and the glycogen degradation enzyme gene glgP abolished circadian rhythms of UV-C resistance with constitutively high UV-C resistance. Combining these results with further experiments using ATP synthesis inhibitor and strains with modified metabolic pathways, we showed that UV-C resistance is weakened by directing more metabolic flux from the glycogen degradation to catabolic pathway such as oxidative pentose phosphate pathway and glycolysis. We suggest glycogen-related metabolism in the dark affects circadian control in UV sensitivity, while the light masks this effect through the photolyase function.

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Xu, Bingjie, Guoyan Zhan, Bin Xu, Haijie Du, Hang Luo, Tianfeng Wang, Changchao Zhan, and Yi Yang. "Degradation of acetaminophen in aqueous solution by UV and UV-activated sludge processes." Water Science and Technology 78, no. 10 (November 23, 2018): 2088–95. http://dx.doi.org/10.2166/wst.2018.483.

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Abstract Acetaminophen (N-acetyl-p-aminophenol, APAP) is one of the most common antipyretic analgesics used to treat common ailments throughout the world. Recently, APAP has been frequently detected in wastewater effluent and groundwater, resulting in potential risks to the environment. Current methods for eliminating APAP are complicated and cost-prohibitive. This study examined APAP degradation by ultraviolet-C (UV-C) and UV-C irradiation combined with activated sludge (UV/AS) to evaluate potential applications in wastewater treatment. The results of this study indicate that UV-C irradiation reached an APAP degradation efficiency of more than 52% and a degradation rate of 0.0012–0.0013 min−1 during 720 min of exposure, while the initial APAP concentration exhibited only a nominal effect on the degradation rate. However, the UV/AS treatment demonstrated an APAP degradation rate that was 9.6 times the rate of the UV-C-only treatment, with a degradation efficiency of 99% over the same UV irradiation period. The results further indicated that APAP photolysis efficiency was more effective when applied to sterilized AS than when applied to unsterilized AS. Finally, excessive dosage of both AS and humic acid inhibited APAP photolysis efficiency.

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Safitri, Vanny Yulia, Adlis Santoni, Diana Vanda Wellia, Khoiriah Khoiriah, and Safni Safni. "Degradation of Paracetamol by Photolysis Using C-N-codoped TiO2." Molekul 12, no. 2 (November 30, 2017): 189. http://dx.doi.org/10.20884/1.jm.2017.12.2.378.

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Paracetamol is generally used as analgesic and antipyretic drugs. Contamination paracetamol in the environment can occur because of waste material disposal from production site and immediate disposal of household that cause water pollution. Paracetamol is degraded by photolysis method under irradiation 10 watt UV-light (λ=365 nm), visible-light (Philips LED 13 watt 1400 lux) and solar-light with and without addition C-N-codoped TiO2catalyst. The solution is analyzed by UV-Vis spectrophotometer at λ 200-400 nm. Optimum weight of C-N-codoped TiO2 catalyst obtained is 20 mg under UV-light photolysis. Paracetamol 4 mg/L is degraded 45.48% after 120 minutes under UV-light irradiation without catalyst, and increases to be 69.31% by using 20 mg catalyst. While degradation percentage of paracetamol is 16.96 % without catalyst, the percentage increases to be 34.29% after using 20 mg catalyst for 120 minutes photolysis under visible-light. Degradation of paracetamol by solar light achieves only 12.27% in absance of catalyst for 120 minutes irradiation, but it increases significantly until 70.39% in presence of 20 mg catalyst.

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Fraikin, G. Ya, N. S. Belenikina, and A. B. Rubin. "Molecular bases of signaling processes regulated by cryptochrome sensory photoreceptors in plants." Биохимия 88, no. 6 (June 15, 2023): 947–61. http://dx.doi.org/10.31857/s0320972523060052.

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The blue-light sensors cryptochromes compose the widespread class of flavoprotein photoreceptors, regulating in plants signaling processes underlying their development, growth, and metabolism. In several algae cryptochromes may act not only as sensory photoreceptors but also as photolyases, catalyzing the repair of UV-induced DNA lesions. Cryptochromes bind FAD as the chromophore in the photolyase homologous region (PHR) domain and contain the cryptochrome C-terminal extension (CCE), which lacks in photolyases. Photosensory process in cryptochrome is initiated by photochemical chromophore conversions, including the formation of FAD redox forms. In a state with the chromophore reduced to neutral radical (FADH•), photoreceptory protein undergoes phosphorylation, conformational changes, and disengagement of the PHR domain and CCE with the subsequent formation of oligomers of cryptochrome molecules. Photooligomerization is a structural basis of functional activity of cryptochromes, which determines the formation of their complexes with variety of signaling proteins, including transcriptional factors and transcription regulators. Interactions in such complexes change the protein signaling activity, leading to gene expression regulation and plant photomorphogenesis. In recent years, multiple papers, reporting novel, more detailed information about molecular mechanisms of above-mentioned processes were published. The present review largely focuses on the analysis of data contained in these publications, particularly regarding structural aspects of cryptochrome transitions into photoactivated states and regulatory signaling processes mediated by cryptochrome photoreceptors in plants.

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Ljubas, Davor, Mirta Čizmić, Katarina Vrbat, Draženka Stipaničev, Siniša Repec, Lidija Ćurković, and Sandra Babić. "Albendazole Degradation Possibilities by UV-Based Advanced Oxidation Processes." International Journal of Photoenergy 2018 (December 20, 2018): 1–6. http://dx.doi.org/10.1155/2018/6181747.

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Pharmaceuticals are present in an aquatic environment usually in low (ng/L) concentrations. Their continuous release can lead to unwanted effects on the nontarget organisms. The main points of their collection and release into the environment are wastewater treatment plants. The wastewater treatment plants should be upgraded by new technologies, like advanced oxidation processes (AOPs), to be able to degrade these new pollutants. In this study, the degradation of albendazole (ALB), a drug against parasitic helminths, was investigated using four UV-based AOPs: UV photolysis, UV photocatalysis (over TiO2 film), UV + O3, and UV + H2O2. The ranking of the degradation process degree of the ALB and its degradation products for studied processes is as follows: UV photolysis < UV photocatalysis with TiO2 < UV + O3 < UV + H2O2. The fastest degradation of ALB and its degradation products was obtained by UV-C + H2O2 process with a degradation efficiency of 99.95%, achieved in 15 minutes.

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Kostina, Svetlana S., and William J. Leigh. "A combined kinetic and computational study of the reactions of transient germylenes with oxiranes and thiiranes in solution." Canadian Journal of Chemistry 93, no. 4 (April 2015): 435–44. http://dx.doi.org/10.1139/cjc-2014-0401.

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The reactions of dimethyl- and diphenylgermylene (GeMe2 and GePh2, respectively) with cyclohexene oxide (CHO) and propylene sulfide (PrS) have been studied in hydrocarbon solvents at 25 °C by laser flash and steady-state photolysis methods using appropriately substituted germacyclopent-3-ene derivatives as germylene precursors. GeMe2 reacts with CHO and PrS with rate constants in the range of 1.2–1.7 × 1010 M−1 s−1 in hexanes at 25 °C to form new transient products that are assigned to the corresponding Lewis acid-base complexes of the germylene with the substrates. The complexation reactions were found to be reversible and are characterized by equilibrium constants of KC = (3.7 ± 0.8) × 103 M−1 and (3 ± 1) × 104 M−1 for complexation of GeMe2 with CHO and PrS, respectively. The complexes decay over approximately 10 μs with the concomitant formation of tetramethyldigermene (Ge2Me4), identifiable by its characteristic UV-vis spectrum centered at λmax = 370 nm. Diphenylgermylene behaves analogously, reacting rapidly and reversibly with the two substrates to form the corresponding Lewis acid-base complexes (λmax ≈ 355 nm) that decay over several tens of microseconds with the concomitant growth of the characteristic UV-vis spectrum of tetraphenyldigermene (Ge2Ph4) (λmax = 440 nm). Steady-state photolysis of the germylene precursors in the presence of CHO afforded germanium-containing oligomers but showed no evidence of oxygen abstraction or the formation of substrate-derived product(s). Similar photolyses in the presence of PrS also afforded germanium-containing oligomers, but as well yielded propene in 20%–30% yield and (in the case of the GePh2 precursor) minor amounts of low molecular weight compounds that appear to be derived from the corresponding germanethione. Density functional theory calculations of the chalcogen abstraction reactions of GeMe2 with oxirane and thiirane in the gas phase have been carried out at the B3LYP/6-311+G(d,p) level of theory and are in good qualitative agreement with the experimental data.

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Marien, Cédric B. D., Marie Le Pivert, Antonin Azaïs, Ignace Christian M’Bra, Patrick Drogui, Ahmad Dirany, and Didier Robert. "Kinetics and mechanism of Paraquat’s degradation: UV-C photolysis vs UV-C photocatalysis with TiO2/SiC foams." Journal of Hazardous Materials 370 (May 2019): 164–71. http://dx.doi.org/10.1016/j.jhazmat.2018.06.009.

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Custer, Thomas, Urszula Szczepaniak, Marcin Gronowski, Nathalie Piétri, Isabelle Couturier-Tamburelli, Jean-Claude Guillemin, Michał Turowski, and Robert Kołos. "Isomerization of cyanopropyne in solid argon." Physical Chemistry Chemical Physics 21, no. 25 (2019): 13668–78. http://dx.doi.org/10.1039/c8cp06739b.

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Cyanopropyne, CH₃–CC–CN, is a simple molecule whose photochemistry we have explored. UV photolysis of this molecule in an Ar matrix was performed and quantum chemical calculations used to better understand photoproduct production.

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Kuźmiński, Kamil, Antoni W. Morawski, and Magdalena Janus. "Photocatalytic decomposition of surfactants on nitrogen modified TiO2." E3S Web of Conferences 59 (2018): 00017. http://dx.doi.org/10.1051/e3sconf/20185900017.

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In these studies advanced oxidation processes such as: photolysis, ozonation and photocatalysis for anionic and cationic surfactants decomposition were used. Nitrogen modified titanium dioxide and commercial TiO2-P25 were used for photocatalytic tests. UV-C lamp and different dose of ozone: 186, 383, 478 and 563 mg/(dm3·h) were used. The optimal system for anionic and cationic surfactants decomposition was connection of ozonation with UV-C irradiation.

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Karci, Akin, Idil Arslan-Alaton, and Miray Bekbolet. "Oxidation of nonylphenol ethoxylates in aqueous solution by UV-C photolysis, H2O2/UV-C, Fenton and photo-Fenton processes: are these processes toxicologically safe?" Water Science and Technology 68, no. 8 (October 1, 2013): 1801–9. http://dx.doi.org/10.2166/wst.2013.422.

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UV-C, H2O2/UV-C, Fenton and photo-Fenton treatment of a nonylphenol polyethoxylate (NP-10) were comparatively studied, primarily focusing on the acute toxicity of degradation products. Formic, acetic and oxalic acids were all identified as the degradation products of NP-10; however, the sole common carboxylic acid was found to be formic acid for the studied treatment processes. The percent relative inhibition towards Vibrio fischeri increased from 9% to 33% and 24% after 120 min-UV-C and H2O2/UV-C treatment, respectively. Complete NP-10 and 70% of its total organic carbon (TOC) content was removed by the photo-Fenton process, which ensured the fastest removal rates and lowest inhibitory effect (8% after 120 min treatment). The acute toxicity pattern being observed during H2O2/UV-C and photo-Fenton treatment positively correlated with temporal evolution of the identified carboxylic acids, whereas unidentified oxidation products were the most likely origin of the acute toxicity in UV-C photolysis.

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Kvaskoff, David, Ullrich Mitschke, Chris Addicott, Justin Finnerty, Pawel Bednarek, and Curt Wentrup. "Interconversion of Nitrenes, Carbenes, and Nitrile Ylides by Ring Expansion, Ring Opening, Ring Contraction, and Ring Closure: 3-Quinolylnitrene, 2-Quinoxalylcarbene, and 3-Quinolylcarbene." Australian Journal of Chemistry 62, no. 3 (2009): 275. http://dx.doi.org/10.1071/ch08523.

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Photolysis of 3-azidoquinoline 6 in an Ar matrix generates 3-quinolylnitrene 7, which is characterized by its electron spin resonance (ESR), UV, and IR spectra in Ar matrices. Nitrene 7 undergoes ring opening to a nitrile ylide 19, also characterized by its UV and IR spectra. A subsequent 1,7-hydrogen shift in the ylide 19 affords 3-(2-isocyanophenyl)ketenimine 20. Matrix photolysis of 1,2,3-triazolo[1,5-c]quinoxaline 26 generates 4-diazomethylquinazoline 27, followed by 4-quinazolylcarbene 28, which is characterized by ESR and IR spectroscopy. Further photolysis of carbene 28 slowly generates ketenimine 20, thus suggesting that ylide 19 is formed initially. Flash vacuum thermolysis (FVT) of both 6 and 26 affords 3-cyanoindole 22 in high yield, thereby indicating that carbene 28 and nitrene 7 enter the same energy surface. Matrix photolysis of 3-quinolyldiazomethane 30 generates 3-quinolylcarbene 31, which on photolysis at >500 nm reacts with N2 to regenerate diazo compound 30. Photolysis of 30 in the presence of CO generates a ketene (34). 3-Quinolylcarbene 31 cyclizes on photolysis at >500 nm to 5-aza-2,3-benzobicyclo[4.1.0]hepta-2,4,7-triene 32. Both 31 and 32 are characterized by their IR and UV spectra. FVT of 30 yields a mixture of 2- and 3-cyanoindenes via a carbene–carbene–nitrene rearrangement 31 → 2-quinolylcarbene 39 → 1-naphthylnitrene 43. The reaction mechanisms are supported by density functional theory calculations of the energies and spectra of all relevant ground and transition state structures at the B3LYP/6–31G* level.

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Ukpebor, J. E., and E. E. Ukpebor. "Comparison on the Effect of different Light Sources on the Fate of 1,2,3,6-tetrahydro-N-(trichloromethylthio) phthalimide Using LCMS." Nigerian Journal of Environmental Sciences and Technology 1, no. 1 (March 2017): 28–33. http://dx.doi.org/10.36263/nijest.2017.01.0020.

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The photodegradation of 1,2,3,6-tetrahydro-N-(trichloromethylthio) phthalimide [captan -(CPT)] on apple surfaces by different UV radiation (UV-C -254 nm and full UV spectra – 250 – 750 nm) was investigated. Results obtained demonstrate the UV – light irradiance on apple surfaces has the capability of markedly reducing the concentration of surface sorbed levels of CPT (which is frequently detected on fruit surfaces) through direct and possibly indirect photochemical degradation. The loss of CPT was found to be significant for the experimental conditions described here, with >80% loss of initial concentrations of the test chemical under UV-B & C light within 30 minutes of light exposure. In general, CPT decayed more quickly under the UV A-B compared to UV –C. The rate of degradation (kCPT) was found to be 2.0 x 10-3 and 3.1 x 10-3 min -1 for the Xenon “750 W/m2” and UV-C lamps respectively with corresponding half-lives of 346.5 min and 22.57 min. Photolysis of CPT is usually as a result of the homolytic dissociation of a C-Cl bond.

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Starling, Maria Clara V. M., Patterson P. Souza, Annaïg Le Person, Camila C. Amorim, and Justine Criquet. "Intensification of UV-C treatment to remove emerging contaminants by UV-C/H2O2 and UV-C/S2O82−: Susceptibility to photolysis and investigation of acute toxicity." Chemical Engineering Journal 376 (November 2019): 120856. http://dx.doi.org/10.1016/j.cej.2019.01.135.

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Dingwall, Paul, Andreas Greb, Lorène N. S. Crespin, Ricardo Labes, Biagia Musio, Jian-Siang Poh, Patrick Pasau, David C. Blakemore, and Steven V. Ley. "C–H functionalisation of aldehydes using light generated, non-stabilised diazo compounds in flow." Chemical Communications 54, no. 83 (2018): 11685–88. http://dx.doi.org/10.1039/c8cc06202a.

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Here we explore further the use of oxadiazolines, non-stabilised diazo precursors which are bench stable, in direct, non-catalytic, aldehyde C–H functionalisation reactions under UV photolysis in flow and free from additives.

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Verhaar, Robin, David W. C. Dekkers, Iris M. De Cuyper, Mark H. Ginsberg, Dirk de Korte, and Arthur J. Verhoeven. "UV-C irradiation disrupts platelet surface disulfide bonds and activates the platelet integrin αIIbβ3." Blood 112, no. 13 (December 15, 2008): 4935–39. http://dx.doi.org/10.1182/blood-2008-04-151043.

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Abstract UV-C irradiation has been shown to be effective for pathogen reduction in platelet concentrates, but preliminary work indicated that UV-C irradiation of platelets can induce platelet aggregation. In this study, the mechanism underlying this phenomenon was investigated. Irradiation of platelets with UV-C light (1500 J/m2) caused platelet aggregation, which was dependent on integrin αIIbβ3 activation (GPIIb/IIIa). This activation occurred despite treatment with several signal transduction inhibitors known to block platelet activation. UV-C also induced activation of recombinant αIIbβ3 in Chinese hamster ovary (CHO) cells, an environment in which physiologic agonists fail to activate. Activation of αIIbβ3 requires talin binding to the β3 tail, yet αIIbβ3-Δ724 (lacking the talin binding site) was activated by UV-C irradiation, excluding a requirement for talin binding. The UV-C effect appears to be general in that β1 and β2 integrins are also activated by UV-C. To explain these findings, we investigated the possibility of UV-C–induced photolysis of disulfide bonds, in analogy with the activating effect of reducing agents on integrins. Indeed, UV-C induced a marked increase in free thiol groups in platelet surface proteins including αIIbβ3. Thus, UV-C appears to activate αIIbβ3 not by affecting intracellular signal transduction, but by reduction of disulfide bonds regulating integrin conformation.

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Safni, Umiati Loekman, Fitra Febrianti, Maizatisna, and Tadao Sakai. "DEGRADASI ZAT WARNA SUDAN I SECARA SONOLISIS DAN FOTOLISIS DENGAN PENAMBAHAN TiO2-ANATASE." Jurnal Riset Kimia 1, no. 2 (February 12, 2015): 163. http://dx.doi.org/10.25077/jrk.v1i2.67.

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ABSTRACT Degradation of Sudan I dye had been done with sonolysis and photolysis by adding anatase-TiO2. Sonolysis method were performed using an ultrasound with frequency of 45 kHz. Photolysis method were performed using an irradiation of UV light with λ = 359 nm. Degradation of 4 mg/L Sudan I with addition of 0.1000 g anatase-TiO2 at pH = 7.0, temperature 25 ± 1°C, percentage of degradation 64.04% within 180 minutes sonolysis. Degradation of 4 mg/L Sudan I using photolysis with addition of 0.1000 g anatase-TiO2 at pH = 7.0 and percentage of degradation 100% within 180 minutes photolysis. Degradation of 4 mg/L Sudan I using sonolysis and photolysis simultaneously with addition of 0.1000 g anatase-TiO2 at pH = 7.0 and percentage of degradation 94.04% within 180 minutes treatment. Keywords : degradation, sonolysis, photolysis, Sudan I, anatase-TiO2.

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Rivas, Javier, Olga Gimeno, Teresa Borralho, and Maria Carbajo. "UV-C photolysis of endocrine disruptors. The influence of inorganic peroxides." Journal of Hazardous Materials 174, no. 1-3 (February 2010): 393–97. http://dx.doi.org/10.1016/j.jhazmat.2009.09.065.

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Choi, Sung Won, Hafiz Muhammad Shahbaz, Jeong Un Kim, Da-Hyun Kim, Sohee Yoon, Se Ho Jeong, Jiyong Park, and Dong-Un Lee. "Photolysis and TiO2 Photocatalytic Treatment under UVC/VUV Irradiation for Simultaneous Degradation of Pesticides and Microorganisms." Applied Sciences 10, no. 13 (June 29, 2020): 4493. http://dx.doi.org/10.3390/app10134493.

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Efficiencies of various treatments for UVC photolysis (ultraviolet light-C at 254 nm), VUV photolysis (vacuum ultraviolet light at 254 nm and 185 nm), UVC-assisted titanium dioxide photocatalysis (UVC-TiO2), and VUV-assisted titanium dioxide photocatalysis (VUV-TiO2) were investigated for the degradation of pesticides including pyraclostrobin, boscalid, fludioxonil, and azoxystrobin and inactivation of microorganisms Escherichia coli K12 as a surrogate for E. coli O157:H7 and Saccharomyces cerevisiae in aqueous solutions and on the surface of fresh cut carrots. The degradation efficiencies of VUV were higher than for UVC on pesticides in aqueous solutions. However, there was no significant difference between degradation efficiencies for UVC and UVC-TiO2 treatments, and between VUV and VUV-TiO2 treatments. UVC, VUV, UVC-TiO2, and VUV-TiO2 showed similar inactivation effects against E. coli K12 and S. cerevisiae in aqueous solutions. The combined use of UVC and VUV treatments (combined UV) and combined use of UVC-TiO2 and VUV-TiO2 treatments (combined UV-TiO2) showed higher efficiencies (72–94% removal) for the removal of residual pesticides on fresh cut carrots than bubble water washing (53–73% removal). However, there was no significant difference in removal efficiency between combined UV and combined UV-TiO2 treatments. For E. coli K12 and S. cerevisiae on fresh cut carrots, the combined UV-TiO2 treatment (1.5 log and 1.6 log reduction, respectively) showed slightly higher inactivation effects than combined UV (1.3 log and 1.2 log reduction, respectively). Photolysis and TiO2 photocatalytic treatments under UV irradiation, including VUV as a light source, showed potential for the simultaneous degradation of pesticides and microorganisms as a non-chemical and residue-free technique for surface disinfection of fresh produce.

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Safni, Safni, Eno Okta Patricia, Trisna Ollinovela, and Yulizar Yusuf. "Degradation of Phenol Using Sonolysis and Photolysis by TiO2/RHAC Catalyst and Analysis with Spectrophotometer UV-VIS and HPLC." al-Kimiya 10, no. 1 (June 30, 2023): 50–56. http://dx.doi.org/10.15575/ak.v10i1.24775.

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This study focuses on the degradation of phenol in aqueous solutions using photolysis and sonolysis methods. It investigates the impact of catalyst mass, types of light (UV-A, UV-C, and visible light), types of catalyst (RHAC, TiO2, and TiO2/RHAC), and processing time on phenol degradation. The phenol solutions are analyzed before and after degradation using Spectrophotometer UV-Vis and HPLC. The research aims to understand the factors influencing phenol degradation and provide a basis for further studies to enhance the efficiency of phenol removal. Results show significant improvements in degradation percentages of phenol by using TiO2/RHAC as the catalyst. Sonolysis achieves a degradation of 20.82% with a catalyst, which increases to 50.57% with the catalyst. Photolysis achieves a degradation of 29.06%, which rises to 91.99% with the catalyst. The highest degradation percentage is achieved using UV-A light for 5 hours with a catalyst mass of 30 mg of TiO2/RHAC catalyst. HPLC analysis confirms a decreased phenol concentration and the presence of intermediate compounds. The TiO2/RHAC catalyst demonstrates the promising potential for efficient phenol degradation in aqueous solutions.

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Lomakin, Sergey, Yurii Mikheev, Sergey Usachev, Svetlana Rogovina, Lubov Zhorina, Evgeniya Perepelitsina, Irina Levina, et al. "Evaluation and Modeling of Polylactide Photodegradation under Ultraviolet Irradiation: Bio-Based Polyester Photolysis Mechanism." Polymers 16, no. 7 (April 4, 2024): 985. http://dx.doi.org/10.3390/polym16070985.

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In our study, we investigated the accelerated aging process of PLA under 253.7 nm UV-C irradiation with the use of the GPC, NMR, FTIR, and DSC methods and formal kinetic analysis. The results of GPC and DSC indicated a significant degree of destructive changes in the PLA macromolecules, while spectroscopic methods NMR and FTIR showed maintenance of the PLA main structural elements even after a long time of UV exposure. In addition to that, the GPC method displayed the formation of a high molecular weight fraction starting from 24 h of irradiation, and an increase in its content after 144 h of irradiation. It has been shown for the first time that a distinctive feature of prolonged UV exposure is the occurrence of intra- and intermolecular radical recombination reactions, leading to the formation of a high molecular weight fraction of PLA decomposition products. This causes the observed slowdown of the photolysis process. It was concluded that photolysis of PLA is a complex physicochemical process, the mechanism of which depends on morphological changes in the solid phase of the polymer under UV radiation.

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Chen, Tsu-feng, Ruey-an Doong, and Wen-gang Lei. "Photocatalytic degradation of parathion in aqueous TiO2 dispersion: the effect of hydrogen peroxide and light intensity." Water Science and Technology 37, no. 8 (April 1, 1998): 187–94. http://dx.doi.org/10.2166/wst.1998.0324.

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The photodegradation of parathion in the direct photolysis, UV/TiO2, UV/H2O2 and UV/TiO2/H2O2 systems was investigated at 25°C. The effect of light intensity was also examined to clarify the relationship between the photo flux and decomposition rate of parathion. Results of the study demonstrated that no obvious degradation of parathion in dark reaction occurred within 24 hours. However, the addition of TiO2 and/or H2O2 promotes the degradation efficiency of parathion. Adding H2O2 was more effective in the photocatalytic oxidation of parathion than TiO2. Also, hydrogen peroxide was found as an intermediate with the maximum concentration of 55 μM in UV/TiO2 system during the photodegradation of parathion. A higher intensity of lamp could increase the degradation rate of parathion. However, the quantum efficiency for degradation of parathion decreased from 0.053 to 0.006 when light intensity increased from 100 W to 450W. Photodecomposition followed a pseudo-first-order reaction. The rate constants of parathion ranged from 0.003 min−1 for direct photolysis to 0.023 min−1 for UV/TiO2/H2O2 system. This study indicated that photocatalytic degradation is a highly promising technology for detoxifying parathion.

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Safni, Maizatisna, Zulfarman, and T. Sakai. "DEGRADASI ZAT WARNA NAPHTOL BLUE BLACK SECARA SONOLISIS DAN FOTOLISIS DENGAN PENAMBAHAN TIO2-ANATASE." Jurnal Riset Kimia 1, no. 1 (February 11, 2015): 43. http://dx.doi.org/10.25077/jrk.v1i1.66.

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ABSTRACTDegradation of naphtol blue black dye had been done by sonolysis and photolysis with adding anatase-TiO2. Sonolysis method were performed using an ultrasound with frequency 45 kHz, and photolysis using an irradiation of UV light l= 359 nm. The optimum condition for degradation of 6 mg/L naphtol blue black by sonolysis with addition of 0.1000 g anatase-TiO2 were found at pH = 3.0 and temperature 30 ± 1°C. Percentage of degradation at pH and temperature optimum was 65.20% within 120 minutes treatment. Degradation of 6 mg/L naphtol blue black by photolysis with addition of 0.1000 g anatase-TiO2 was optimum at pH=3.0 and percentage of degradation was 68.72% within 120 minutes irradiation without stirring. The combine of sonolysis and photolysis method simultaneously for degradation of naphtol blue black dye by adding anatase-TiO2, achieved 92.51% degradation after 60 minutes treatment. Keywords : sonolysis, photolysis, naphtol blue black

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Gilboa, Yael, Yuval Alfiya, Sara Sabach, Eran Friedler, and Yael Dubowski. "H2S Removal from Groundwater by Chemical Free Advanced Oxidation Process Using UV-C/VUV Radiation." Molecules 26, no. 13 (June 30, 2021): 4016. http://dx.doi.org/10.3390/molecules26134016.

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Sulfide species may be present in groundwater due to natural processes or due to anthropogenic activity. H2S contamination poses odor nuisance and may also lead to adverse health effects. Advanced oxidation processes (AOPs) are considered promising treatments for hydrogen-sulfide removal from water, but conventional AOPs usually require continuous chemical dosing, as well as post-treatment, when solid catalysts are applied. Vacuum-UV (VUV) radiation can generate ·OH in situ via water photolysis, initiating chemical-free AOP. The present study investigated the applicability of VUV-based AOP for removal of H2S both in synthetic solutions and in real groundwater, comparing combined UV-C/VUV and UV-C only radiation in a continuous-flow reactor. In deionized water, H2S degradation was much faster under the combined radiation, dominated by indirect photolysis, and indicated the formation of sulfite intermediates that convert to sulfate at high radiation doses. Sulfide was efficiently removed from natural groundwater by the two examined lamps, with no clear preference between them. However, in anoxic conditions, common in sulfide-containing groundwater, a small advantage for the combined lamp was observed. These results demonstrate the potential of utilizing VUV-based AOP for treating H2S contamination in groundwater as a chemical-free treatment, which can be especially attractive to remote small treatment facilities.

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Yu, Haixia, Wenji Yu, Liu Yang, Chongrong Fang, and Manping Xu. "Surface discoloration analysis and lignin degradation fragments identification of UV-irradiated moso bamboo (Phyllostachys pubescens Mazel)." BioResources 10, no. 1 (January 23, 2015): 1617–26. http://dx.doi.org/10.15376/biores.10.1.1617-1626.

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Color changes caused by artificial UV radiation of Moso bamboo (Phyllostachys pubescens Mazel) were recorded as a function of exposure time to obtain the maximum absorption trend by the Kubelka-Munk (K-M) spectra. Lignin photolysis into smaller molecules was evaluated using spectrophotometry and gas chromatography-mass spectrometry (GC-MS) analysis. Results showed that the K-M absorption peak increased in the yellow and red regions (360 to 500 nm) when compared with the untreated sample, which was in accordance with the yellow-red shift by visual observation. The maximum absorption of the K-M spectra from UVB phototreated bamboo was in the UV region. GC-MS analysis showed that benzene carbonyls, organic acid, and esters were the major types of photolysized molecules of bamboo lignin, which were derived from the C-C bonds adjacent to the α-carbonyl. UV irradiation (295 to 400 nm) resulted in the breakdown of carbonyl and unsaturated C-C groups conjugated to aromatic ring at the Cα ., which partly contributed to the quick discoloration at the initial 100 h of UV irradiation.

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Zhu, Yanping, Yuxuan Cao, Shihu Shu, Pengjin Zhu, Dongfang Wang, He Xu, and Dongqing Cai. "Comparison of Medium-Pressure UV/Peracetic Acid to Remove Three Typical Refractory Contaminants of Textile Wastewater." Processes 11, no. 4 (April 12, 2023): 1183. http://dx.doi.org/10.3390/pr11041183.

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In this work, the performance of medium-pressure UV/peracetic acid (MPUV/PAA/H2O2) was explored on removing reactive black 5 (RB5), aniline (ANL), and polyvinyl alcohol (PVA), three typical refractory contaminants in printing and dyeing wastewater, compared with MPUV/H2O2. MPUV/PAA/H2O2 showed 75.0, 44.9, and 57.7% removals of RB5, ANL, and PVA, respectively, within 5 min. The removal of RB5 increased from 68.98 to 91.2%, with pH increasing from 6 to 9, while the removals of ANL and PVA were much less pH-dependent. Quenching experiment results indicated that UV photolysis and radical (i.e., •OH and R-C•) oxidation contributed to RB5 removal, while PAA showed high activity in the oxidation of ANL. For PVA, •OH oxidation and UV photolysis were likely the main mechanisms. The coexisting natural organic matter had a negative effect on the degradation of RB5 and PVA. In addition, MPUV/PAA/H2O2 could effectively degrade those pollutants without increasing the toxicity. This work provides a theoretical reference for the utilization of MPUV/PAA/H2O2 in removing structurally diverse refractory contaminants from printing and dyeing wastewater.

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Sério, João, Ana Paula Marques, Rosa Huertas, João Goulão Crespo, and Vanessa Jorge Pereira. "Occurrence and Treatment of Antibiotic-Resistant Bacteria Present in Surface Water." Membranes 13, no. 4 (April 11, 2023): 425. http://dx.doi.org/10.3390/membranes13040425.

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According to the World Health Organization, antibiotic resistance is one of the main threats to global health. The excessive use of several antibiotics has led to the widespread distribution of antibiotic-resistant bacteria and antibiotic resistance genes in various environment matrices, including surface water. In this study, total coliforms, Escherichia coli and enterococci, as well as total coliforms and Escherichia coli resistant to ciprofloxacin, levofloxacin, ampicillin, streptomycin, and imipenem, were monitored in several surface water sampling events. A hybrid reactor was used to test the efficiency of membrane filtration, direct photolysis (using UV-C light emitting diodes that emit light at 265 nm and UV-C low pressure mercury lamps that emit light at 254 nm), and the combination of both processes to ensure the retention and inactivation of total coliforms and Escherichia coli as well as antibiotic-resistant bacteria (total coliforms and Escherichia coli) present in river water at occurrence levels. The membranes used (unmodified silicon carbide membranes and the same membrane modified with a photocatalytic layer) effectively retained the target bacteria. Direct photolysis using low-pressure mercury lamps and light-emitting diode panels (emitting at 265 nm) achieved extremely high levels of inactivation of the target bacteria. The combined treatment (unmodified and modified photocatalytic surfaces in combination with UV-C and UV-A light sources) successfully retained the bacteria and treated the feed after 1 h of treatment. The hybrid treatment proposed is a promising approach to use as point-of-use treatment by isolated populations or when conventional systems and electricity fail due to natural disasters or war. Furthermore, the effective treatment obtained when the combined system was used with UV-A light sources indicates that the process may be a promising approach to guarantee water disinfection using natural sunlight.

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Castells, Enric, Jean Molinier, Stephanie Drevensek, Pascal Genschik, Fredy Barneche, and Chris Bowler. "det1-1-induced UV-C hyposensitivity through UVR3 and PHR1 photolyase gene over-expression." Plant Journal 63, no. 3 (May 6, 2010): 392–404. http://dx.doi.org/10.1111/j.1365-313x.2010.04249.x.

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Liu, Ronghua, and Thomas T. Tidwell. "A stabilized and persistent tetraketene: 1,4-bis(1′,4′-dioxo-3′-trimethylsilyl-2′-buta-1′,3′-dienyl)benzene." Canadian Journal of Chemistry 73, no. 11 (November 1, 1995): 1818–22. http://dx.doi.org/10.1139/v95-224.

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Reaction of 1,4-bis(trimethylsilylethynyl)benzene with CCl3COCl and Zn gave 1,4-bis(4′,4′-dichloro-2′-trimethylsilyl-3′-oxo-1′-cyclobutenyl)benzene (7), which reacted with concentrated H2SO4 at 87 °C to give 1,4-bis(2′-trimethylsilyl-3′,4′-dioxo-1′-cyclobutenyl)benzene (8). Photolysis of 8 in CDCl3 with 350 nm light gave the bisketene 9, which on further photolysis formed the title tetraketene 10, as identified by its spectral properties. Upon heating of 10 the successive closure of the two bisketene moieties, first to give the mono(cyclobutenedione) 9 and then to reform 8 in a slower step, was observed by NMR and UV spectroscopy. Reaction of 10 with MeOH gave the tetraester 11, which was assigned the erythro configuration at each of the succinate moieties. Keywords: ketenes, photolysis, cyclobutenediones, esterification, silicon.

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Tong, Alfred Y. C., Rhiannon Braund, Eng W. Tan, Louis A. Tremblay, Tristan Stringer, Katherine Trought, and Barrie M. Peake. "UV-induced photodegradation of oseltamivir (Tamiflu) in water." Environmental Chemistry 8, no. 2 (2011): 182. http://dx.doi.org/10.1071/en10095.

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Environmental contextOseltamivir (Tamiflu) is widely used to prevent and treat influenza but conventional wastewater processes involving sedimentation and biotic oxidation do not appear to significantly remove it from sewage, leading to its discharge into the environment. A range of advanced oxidation processes (AOPs) involving photolysis of aqueous solutions of oseltamivir with UV alone, UV/H2O2 and UV/H2O2/FeII is demonstrated to lead to photodegradation of oseltamivir to products with no ecotoxicity observed. These AOPs may therefore offer potentially environmentally friendly sewage water treatment options. AbstractAqueous solutions of the antiviral drug oseltamivir phosphate (OSP, Tamiflu, (3R,4R,5S)-ethyl 4-acetamido-5-amino-3-(pentan-3-yloxy)cyclohex-1-enecarboxylate) were degraded using advanced oxidation processes (AOPs) involving photodegradation with UV alone, UV/H2O2 and UV/H2O2/FeII (photo-Fenton reaction). The photodecay of the parent OSP in all three cases followed first-order kinetics with respective rate constants of 0.21, 1.56 and 1.75 min–1 at 20°C in pH 7 phosphate-buffered Milli-Q water. The rate of UV/H2O2 photolysis in the presence of 2-methylpropan-2-ol was significantly slower with an approximate first-order rate constant of 0.13 min–1 suggesting the involvement of •OH in the degradation process. NMR spectroscopy, mass spectrometry and high-performance liquid chromatography (HPLC) with UV diode array detection were used to identify the crude photoproduct as the hydroxylated OSP derivative (3S,4R,5S)-ethyl 4-acetamido-5-amino-2-hydroxy-3-(pentan-3-yloxy)cyclohexanecarboxylate that occurs by an unknown mechanism. OSP and this crude photoproduct demonstrated no effect on the survival of Quinquelaophonte sp. over 96 h.

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Wiersma, Sandra D., Alessandra Candian, Joost M. Bakker, Jonathan Martens, Giel Berden, Jos Oomens, Wybren Jan Buma, and Annemieke Petrignani. "Photolysis-induced scrambling of PAHs as a mechanism for deuterium storage." Astronomy & Astrophysics 635 (February 28, 2020): A9. http://dx.doi.org/10.1051/0004-6361/201936982.

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Aims. We investigate the possible role of polycyclic aromatic hydrocarbons (PAHs) as a sink for deuterium in the interstellar medium (ISM) and study UV photolysis as a potential underlying chemical process in the variations of the deuterium fractionation in the ISM. Methods. The UV photo-induced fragmentation of various isotopologs of deuterium-enriched, protonated anthracene and phenanthrene ions (both C14H10 isomers) was recorded in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer. Infrared multiple photon dissociation spectroscopy using the Free-Electron Laser for Infrared eXperiments was applied to provide IR spectra. Infrared spectra calculated using density functional theory were compared to the experimental data to identify the isomers present in the experiment. Transition-state energies and reaction rates were also calculated and related to the experimentally observed fragmentation product abundances. Results. The photofragmentation mass spectra for both UV and IRMPD photolysis only show the loss of atomic hydrogen from [D − C14H10]+, whereas [H − C14D10]+ shows a strong preference for the elimination of deuterium. Transition state calculations reveal facile 1,2-H and -D shift reactions, with associated energy barriers lower than the energy supplied by the photo-excitation process. Together with confirmation of the ground-state structures via the IR spectra, we determined that the photolytic processes of the two different PAHs are largely governed by scrambling where the H and the D atoms relocate between different peripheral C atoms. The ∼0.1 eV difference in zero-point energy between C–H and C–D bonds ultimately leads to faster H scrambling than D scrambling, and increased H atom loss compared to D atom loss. Conclusions. We conclude that scrambling is common in PAH cations under UV radiation. Upon photoexcitation of deuterium-enriched PAHs, the scrambling results in a higher probability for the aliphatic D atom to migrate to a strongly bound aromatic site, protecting it from elimination. We speculate that this could lead to increased deuteration as a PAH moves towards more exposed interstellar environments. Also, large, compact PAHs with an aliphatic C–HD group on solo sites might be responsible for the majority of aliphatic C–D stretching bands seen in astronomical spectra. An accurate photochemical model of PAHs that considers deuterium scrambling is needed to study this further.

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Kerst, Corinna, Martin Byloos, and William J. Leigh. "Far-UV laser flash photolysis in solution. A time-resolved spectroscopic study of the chemistry of 1,1-dimethyl-1,3-(1-sila)-butadiene." Canadian Journal of Chemistry 75, no. 7 (July 1, 1997): 975–82. http://dx.doi.org/10.1139/v97-117.

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Laser flash photolysis (193 nm) of 1,1-dimethyl-(1-sila)cyclobut-2-ene in hexane solution leads to the formation of a transient species [Formula: see text] assigned to 1,1-dimethyl-1,3-(1-sila)butadiene on the basis of its UV absorption spectrum (λmax = 312 nm), and reactivity toward methanol (kMeOH = (3.6 ± 0.1) × 109 M−1 s−1; kH/kD = 1.3 ± 0.1), ethanol (kEtOH = (2.41 ± 0.06) × 109 M−1 s−1), tert-butanol (kBuOH = (1.8 ± 0.1) × 109 M−1 s−1; kH/kD = 1.5 ± 0.1), and oxygen [Formula: see text]. Experiments using isooctane and acetonitrile as solvent are also described. In acetonitrile, the lifetime of the silene is shortened considerably compared to hydrocarbon solvents, presumably due to quenching by adventitious water. In isooctane, under conditions of low excitation intensity, the siladiene decays with clean pseudo-first-order kinetics and a maximum lifetime of ~ 5 μs at 23 °C. The decay rate constant varies only slightly with temperature over the 20–60 °C range, leading to Arrhenius activation parameters of Ea = 0.5 ± 0.2 kcal/mol and log A = 5.7 ± 0.2. While steady state irradiation experiments suggest that in the absence of silene traps the predominant fate of the silabutadiene is thermal ring closure to regenerate the precursor, it is concluded that the rate constants and activation parameters for decay of the siladiene measured by flash photolysis represent a composite of those due to thermal electrocyclic ring closure (with Ea > ~3 kcal/mol) and reaction with adventitious quenchers (probably water, with Ea < 0). The measured Arrhenius parameters for reaction of the siladiene with methanol in isooctane (Ea = −2.6 ± 0.3 kcal/mol and log A = 7.6 ± 0.3) are consistent with this proposal. The potential and limitations of the use of 193-nm laser excitation for flash photolysis studies in solution are discussed. Keywords: far-UV, silene, flash photolysis, kinetics, electrocyclic.

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Berhanu, T. A., J. Savarino, J. Erbland, W. C. Vicars, S. Preunkert, J. F. Martins, and M. S. Johnson. "Isotopic effects of nitrate photochemistry in snow: a field study at Dome C, Antarctica." Atmospheric Chemistry and Physics Discussions 14, no. 23 (December 23, 2014): 33045–88. http://dx.doi.org/10.5194/acpd-14-33045-2014.

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Abstract. Stable isotope ratios of nitrate preserved in deep ice cores are expected to provide unique and valuable information regarding paleo-atmospheric processes. However, due to the post-depositional loss of nitrate in snow, this information may be erased or significantly modified by physical or photochemical processes before preservation in ice. We have investigated the role of solar UV photolysis in the post-depositional modification of nitrate mass and stable isotope ratios at Dome C, Antarctica during the austral summer of 2011/12. Two 30 cm snow pits were filled with homogenized drifted snow from the vicinity of the base. One of these pits was covered with a plexiglass plate that transmits solar UV radiation, while the other was covered with a different plexiglass plate having a low UV transmittance. Samples were then collected from each pit at a 2–5 cm depth resolution and a 10 day frequency. At the end of the season, a comparable nitrate mass loss was observed in both pits for the top-level samples (0–7 cm). At deeper levels (7–30 cm), a significant nitrate mass loss (ca. 30%) was observed in the UV-exposed pit relative to the control field. From the nitrate stable isotope ratios and concentration losses measured in the snow nitrate exposed to solar UV, we have derived average apparent isotopic fractionations (15&varepsilon;,18&varepsilon; and 17E) of −67.8 ± 12‰, 12.5 ± 6.7‰ and 2.2 ± 1.4‰ for δ15N, δ18O, and Δ17O, respectively. These values are fairly stable throughout the season and are in close agreement with the apparent fractionations measured in natural snow at Dome C. Meanwhile, for the control samples in which solar UV was blocked, an apparent average 15&varepsilon; value of −12.0 ± 1.7‰ was derived. The difference in the apparent 15&varepsilon; values obtained for the two experimental fields strongly suggests that solar UV photolysis plays a dominant role in driving observed nitrate mass loss and resulting isotopic fractionation. We have also observed an insensitivity of 15&varepsilon; with depth in the snowpack under the given experimental setup. This is due to the uniform attenuation of incoming solar UV by snow, as 15&varepsilon; is strongly dependent on the shape of the incoming light flux. Together with earlier work, the results presented here represent a strong body of evidence that solar UV photolysis is the most relevant post-depositional process modifying the mass and stable isotope ratios of snow nitrate at low accumulation sites where most deep ice cores are drilled. Nevertheless, modeling the loss of nitrate in snow is still required before a robust interpretation of ice core records can be provided.

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Berhanu, T. A., J. Savarino, J. Erbland, W. C. Vicars, S. Preunkert, J. F. Martins, and M. S. Johnson. "Isotopic effects of nitrate photochemistry in snow: a field study at Dome C, Antarctica." Atmospheric Chemistry and Physics 15, no. 19 (October 9, 2015): 11243–56. http://dx.doi.org/10.5194/acp-15-11243-2015.

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Abstract. Stable isotope ratios of nitrate preserved in deep ice cores are expected to provide unique and valuable information regarding paleoatmospheric processes. However, due to the post-depositional loss of nitrate in snow, this information may be erased or significantly modified by physical or photochemical processes before preservation in ice. We investigated the role of solar UV photolysis in the post-depositional modification of nitrate mass and stable isotope ratios at Dome C, Antarctica, during the austral summer of 2011/2012. Two 30 cm snow pits were filled with homogenized drifted snow from the vicinity of the base. One of these pits was covered with a plexiglass plate that transmits solar UV radiation, while the other was covered with a different plexiglass plate having a low UV transmittance. Samples were then collected from each pit at a 2–5 cm depth resolution and a 10-day frequency. At the end of the season, a comparable nitrate mass loss was observed in both pits for the top-level samples (0–7 cm) attributed to mixing with the surrounding snow. After excluding samples impacted by the mixing process, we derived an average apparent nitrogen isotopic fractionation (15&varepsilon;app) of −67.8 ± 12 ‰ for the snow nitrate exposed to solar UV using the nitrate stable isotope ratios and concentration measurements. For the control samples in which solar UV was blocked, an apparent average 15&varepsilon;app value of −12.0 ± 1.7 ‰ was derived. This difference strongly suggests that solar UV photolysis plays a dominant role in driving the isotopic fractionation of nitrate in snow. We have estimated a purely photolytic nitrogen isotopic fractionation (15&varepsilon;photo) of −55.8 ± 12.0 ‰ from the difference in the derived apparent isotopic fractionations of the two experimental fields, as both pits were exposed to similar physical processes except exposure to solar UV. This value is in close agreement with the 15&varepsilon;photo value of −47.9 ± 6.8 ‰ derived in a laboratory experiment simulated for Dome C conditions (Berhanu et al., 2014). We have also observed an insensitivity of 15&varepsilon; with depth in the snowpack under the given experimental setup. This is due to the uniform attenuation of incoming solar UV by snow, as 15&varepsilon; is strongly dependent on the spectral distribution of the incoming light flux. Together with earlier work, the results presented here represent a strong body of evidence that solar UV photolysis is the most relevant post-depositional process modifying the stable isotope ratios of snow nitrate at low-accumulation sites, where many deep ice cores are drilled. Nevertheless, modeling the loss of nitrate in snow is still required before a robust interpretation of ice core records can be provided.

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Hitomi, Kenichi, Luciano DiTacchio, Andrew S. Arvai, Junpei Yamamoto, Sang-Tae Kim, Takeshi Todo, John A. Tainer, Shigenori Iwai, Satchidananda Panda, and Elizabeth D. Getzoff. "Functional motifs in the (6-4) photolyase crystal structure make a comparative framework for DNA repair photolyases and clock cryptochromes." Proceedings of the National Academy of Sciences 106, no. 17 (April 9, 2009): 6962–67. http://dx.doi.org/10.1073/pnas.0809180106.

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Homologous flavoproteins from the photolyase (PHR)/cryptochrome (CRY) family use the FAD cofactor in PHRs to catalyze DNA repair and in CRYs to tune the circadian clock and control development. To help address how PHR/CRY members achieve these diverse functions, we determined the crystallographic structure of Arabidopsis thaliana (6-4) PHR (UVR3), which is strikingly (>65%) similar in sequence to human circadian clock CRYs. The structure reveals a substrate-binding cavity specific for the UV-induced DNA lesion, (6-4) photoproduct, and cofactor binding sites different from those of bacterial PHRs and consistent with distinct mechanisms for activities and regulation. Mutational analyses were combined with this prototypic structure for the (6-4) PHR/clock CRY cluster to identify structural and functional motifs: phosphate-binding and Pro-Lys-Leu protrusion motifs constricting access to the substrate-binding cavity above FAD, sulfur loop near the external end of the Trp electron-transfer pathway, and previously undefined C-terminal helix. Our results provide a detailed, unified framework for investigations of (6-4) PHRs and the mammalian CRYs. Conservation of key residues and motifs controlling FAD access and activities suggests that regulation of FAD redox properties and radical stability is essential not only for (6-4) photoproduct DNA repair, but also for circadian clock-regulating CRY functions. The structural and functional results reported here elucidate archetypal relationships within this flavoprotein family and suggest how PHRs and CRYs use local residue and cofactor tuning, rather than larger structural modifications, to achieve their diverse functions encompassing DNA repair, plant growth and development, and circadian clock regulation.

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Karci, Akin, Idil Arslan-Alaton, Tugba Olmez-Hanci, and Miray Bekbolet. "Degradation and detoxification of industrially important phenol derivatives in water by direct UV-C photolysis and H2O2/UV-C process: A comparative study." Chemical Engineering Journal 224 (May 2013): 4–9. http://dx.doi.org/10.1016/j.cej.2012.11.049.

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Amelia, Fitrah, Safni, and Hamzar Suyani. "DEGRADASI SENYAWA IMIDAKLOPRID SECARA ADVANCED OXIDATION PROCESSES DENGAN PENAMBAHAN TIO2-ANATASE." Jurnal Riset Kimia 8, no. 2 (March 30, 2015): 108. http://dx.doi.org/10.25077/jrk.v8i2.225.

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Imidacloprid is active compounds in Confidor 200 SL with have toxical character. Degradation of Imidacloprid in Advanced Oxidation Processes (AOPs) method by using TiO2 catalyst can reduce toxic level. Advanced Oxidation Processes (AOPs) method which is used is Sonolysis, Photolysis, and Ozonolisis. The result of sonolysis, Photolysis, and Ozonolysis measured by spectrophotometer UV-Vis with λ 400-600 nm, and than optimum degradation waste after addition of catalys measured by HPLC. The result of degradation of Imidacloprid 6 mg/L using sonolysis without addition catalys is more smallest from addition catalys which degradated in 60 minute, temperature 25±1 °C. At the same time with Photolysis methode for addition catalys we get the degradation is more biggest from addition catalys. Degradation percentage of imidacloprid without addition of TiO2-anatase reach is small from with addition of TiO2. Measure using HPLC for each methode we get more than one peak in chromatogram. It means there are other coumpounds in imidacloprid solution.

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Kelbysheva, Elena S., Mariam G. Ezernitskaya, Rinat R. Aysin, Tatyana V. Strelkova, Alexey N. Rodionov, and Lyudmila N. Telegina. "Optical and Electrochemical Properties of a Photosensitive Pyromellitic Diimide Derivative of Cymantrene." Molecules 28, no. 20 (October 15, 2023): 7098. http://dx.doi.org/10.3390/molecules28207098.

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Photochemical properties of symmetrical pyromellitic diimide containing two cymantrenyl fragments at two nitrogen atoms were studied with IR, NMR, UV-vis, ESI-MS, and cyclic voltammetry. It was found that new unstable chelates are formed during photolysis. At the same time, the CO ligand dissociates from two Mn(CO)3 fragments during photoexcitation, which dramatically changes the electronic and redox properties of the molecule compared to the cymantrene derivative containing one imide fragment. Photolysis leads to a color change from light yellow to green. DFT calculations confirmed the possibility of the formation of complexes due to the loss of one or two CO ligands from manganese atoms. The results obtained with variation of photolysis conditions demonstrated the hemilabile character of the Mn-O=C(imide) bond. On addition of external ligands, the color and electrochemical properties changed, which is promising for the use of this complex as a sensor for small molecules.

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Han, Chao, Guangxin Wang, Chu Cheng, Chaoyang Shi, Yichao Yang, and Mingjin Zou. "A kinetic and mechanism study of silver-thiosulfate complex photolysis by UV-C irradiation." Hydrometallurgy 191 (January 2020): 105212. http://dx.doi.org/10.1016/j.hydromet.2019.105212.

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Goldstein, Sara, David Behar, and Joseph Rabani. "Nature of the Oxidizing Species Formed upon UV Photolysis of C-TiO2 Aqueous Suspensions." Journal of Physical Chemistry C 113, no. 28 (June 22, 2009): 12489–94. http://dx.doi.org/10.1021/jp9019969.

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Nam, Sook-Hyun, Ju-Won Lee, Eun-Ju Kim, Jae-Wuk Koo, and Tae-Mun Hwang. "Evaluation of Portable Rhodamine B Analyzer for Monitoring OH Radical Scavenging Demand in Ultraviolet Advanced Oxidation Processes." Sustainability 13, no. 23 (November 30, 2021): 13279. http://dx.doi.org/10.3390/su132313279.

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A portable OH radical scavenging demand analyzer that can be installed and operated on site was developed to measure water quality indicators that influence the generation of OH radicals from UV/hydrogen peroxide reactions to determine the UV dose and the hydrogen peroxide injection concentration. Rhodamine B (RhB) was used as an indicator for the continuous measurement of the OH radical scavenging demand of four samples with different water quality parameters using the rapid, easy, and real-time UV-Vis spectrophotometer method. The results demonstrated that the estimated rate constant for the RhB color decay rate resulting from direct UV photolysis was low enough to verify its suitability as a probe compound. The mean values of the OH radical scavenging demand for target water samples at different organic concentrations were 20,659 s−1 for plant N, 42,346 s−1 for plant C, 32,232 s−1 for plant Y, and 81,669 s−1 for plant B. Variations in the monitoring results for the target water treatment plants suggest that on-site OH radical scavenging demands should be considered to determine the UV dose and the hydrogen peroxide injection concentration for the UV advanced oxidation process.

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Joseph, Collin G., Yun Hin Taufiq-Yap, and Vigneswar Krishnan. "Ultrasonic Assisted Photolytic Degradation of Reactive Black 5 (RB5) Simulated Wastewater." ASEAN Journal of Chemical Engineering 17, no. 2 (July 7, 2018): 37. http://dx.doi.org/10.22146/ajche.49554.

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The present study is based on a hybrid advanced oxidation process (AOP) of sono-photolysis system, of which sonication (35 kHz) and photolysis UV-C (254nm) were applied simultaneously to effectively degrade a selected recalcitrant dye-based pollutant, Reactive Black 5 (RB5). The influence of the solution pH and concentration were manipulated throughout this study to investigate the sonophotodegradation kinetics and synergistic effects on the RB5 degradation. Increasing the solution concentration resulted in lowered degradation rate due to the inner filter effect by the dye molecules and reduced the generation of hydroxyl radicals. The results confirmed that the sonophotolysis rate was better at basic medium (67.7%) in comparison to acidic medium (46.9%) due to the ionization of RB5. Synergistic effects were analyzed based on the first order kinetic rate model. It was found that the synergistic effect was observed for all the experiments conducted which resulted from an increase in the (•OH) radicals due to the photolysis of H2O2 formed by the sonolysis process. This hybrid system, sonophotolysis system, was able to degrade RB5 into intermediates with a total reaction time of 1h.

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Bulak, M., D. M. Paardekooper, G. Fedoseev, and H. Linnartz. "Photolysis of acetonitrile in a water-rich ice as a source of complex organic molecules: CH3CN and H2O:CH3CN ices." Astronomy & Astrophysics 647 (March 2021): A82. http://dx.doi.org/10.1051/0004-6361/202039695.

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Context. Many C-, O-, and H-containing complex organic molecules (COMs) have been observed in the interstellar medium (ISM) and their formation has been investigated in laboratory experiments. An increasing number of recent detections of large N-bearing COMs motivates our experimental investigation of their chemical origin. Aims. We investigate the potential role of acetonitrile (CH3CN) as a parent molecule to N-bearing COMs, motivated by its omnipresence in the ISM and structural similarity to another well-known precursor species, CH3OH. The aim of the present work is to characterize the chemical complexity that can result from vacuum UV photolysis of a pure CH3CN ice and a more realistic mixture of H2O:CH3CN. Methods. The CH3CN ice and H2O:CH3CN ice mixtures were UV irradiated at 20 K. Laser desorption post ionization time-of-flight mass spectrometry was used to detect the newly formed COMs in situ. We examined the role of water in the chemistry of interstellar ices through an analysis of two different ratios of H2O:CH3CN (1:1 and 20:1). Results. We find that CH3CN is an excellent precursor to the formation of larger nitrogen-containing COMs, including CH3CH2CN, NCCN/CNCN, and NCCH2CH2CN. During the UV photolysis of H2O:CH3CN ice, the water derivatives play a key role in the formation of molecules with functional groups of: imines, amines, amides, large nitriles, carboxylic acids, and alcohols. We discuss possible formation pathways for molecules recently detected in the ISM.

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Ramos, Paweł, and Mateusz Broncel. "Influence of Storage Conditions on the Stability of Gum Arabic and Tragacanth." Molecules 27, no. 5 (February 23, 2022): 1510. http://dx.doi.org/10.3390/molecules27051510.

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Storage conditions should be chosen so that they do not affect the action and stability of the active pharmaceutical substance (API), and excipients used in pharmacy. UV irradiation, increased temperature, and relative humidity can decompose storage substances by photolysis, thermolysis, and hydrolysis process, respectively. The effect of physical factors may be the decomposition of pharmaceutical substances or their inappropriate action, including pharmacological effects. Polymers of natural origin are increasingly used in the pharmaceutical industry. With this in mind, we evaluated the effect of storage conditions on the stability of gum arabic (GA) and tragacanth (GT). The influence of higher temperature, UV irradiation, and relative humidity on GA and GT was tested. Thermogravimetry (TG, c-DTA), colorimetric analysis, UV-Vis spectrophotometry, and optical microscopy were used as research methods. The TGA and c-DTA examination indicated that decomposition of GA starts at a higher temperature compared to GT. This indicate that gum arabic is more resistant to higher temperatures compared to tragacanth. However, the conducted analysis showed that gum arabic is more sensitive to the tested storage conditions. Among the tested physical conditions, both polymers were most sensitive to conditions of increased relative humidity in the environment.

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Journal articles on the topic 'Photolyse UV-C'

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