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Progress in Medicinal Chemistry 1990
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Food Chemistry Jul 2014Fructose has shown significant reactivity during ultraviolet light (UV, 254nm) processing of fruit juices that can adversely affect product quality. The present study...
Fructose has shown significant reactivity during ultraviolet light (UV, 254nm) processing of fruit juices that can adversely affect product quality. The present study demonstrates that this reactivity of fructose is due to the oxidative nature of products formed from UV induced photolysis of fructose. This was accomplished using fluorescein, a fluorescent dye that loses fluorescence intensity upon reaction with oxidative species. Fructose caused a concentration dependent decay of fluorescence from fluorescein only in presence of UV, indicating oxidative nature of photolysis products of fructose. The transient oxidative species including free radicals and not one of the final photolysis products, furan, were responsible for fluorescence decay. Addition of an antioxidant and removal of oxygen from solution lowered the rate of fluorescence decay, suggesting strategies that can be employed to lower the deleterious effects of fructose on products. The understanding developed can be used to optimise UV processing of juices.
Topics: Fructose; Oxidation-Reduction; Oxygen; Photolysis; Ultraviolet Rays
PubMed: 24518343
DOI: 10.1016/j.foodchem.2014.01.008 -
Chemical Reviews Jan 2013
Review
Topics: Molecular Structure; Organic Chemicals; Photolysis
PubMed: 23256727
DOI: 10.1021/cr300177k -
Journal of Photochemistry and... Dec 2019In the present study, we assessed the oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide (HO) photolysis with a 405-nm laser...
Oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide photolysis with high-power laser irradiation for the treatment of periodontitis.
In the present study, we assessed the oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide (HO) photolysis with a 405-nm laser device at an output power of ≥100 mW in hamsters. Twenty-four cheek pouches from 12 male Syrian hamsters received 7-min treatment with pure water (PW), 3% HO, laser irradiation of PW at 100 mW, laser irradiation of 3% HO at 100 mW, laser irradiation of PW at 200 mW, or laser irradiation of 3% HO at 200 mW (n = 4 each). The diameter of the irradiation area was set at 3 mm; accordingly, the calculated irradiances (optical power densities) of the 100- and 200-mW laser lights were approximately 1400 and 2800 mW/cm, respectively. In addition, 12 cheek pouches from six animals received laser irradiation of 3% HO at 100 mW for 1, 3, or 5 min (n = 4 each). Each treatment was repeated three times at 1-h intervals. Macroscopic and histological changes were evaluated 24 h after the last treatment. In addition, in vitro bactericidal activity of the treatment against periodontal pathogens was evaluated. We found that 405-nm laser irradiation of 3% HO caused moderate to severe oral mucosal irritation when performed at powers of 100 and 200 mW for ≥3 min, while the same treatment performed at 100 mW for 1 min resulted in mild irritation. Moreover, 1-min HO photolysis at 100 mW caused a >4-log decrease in viable bacterial counts. These findings suggest that 1-min HO photolysis, which can effectively kill periodontal pathogens, may be acceptable when a 405-nm laser device is used at 100 mW. However, use of the laser at a lower power would be preferable for the prevention of unnecessary oral mucosal irritation.
Topics: 3T3-L1 Cells; Animals; Anti-Infective Agents; Cell Survival; Cricetinae; Electron Spin Resonance Spectroscopy; Hydrogen Peroxide; Lasers; Male; Mice; Mouth Mucosa; Periodontitis; Photolysis; Porphyromonas gingivalis; Reactive Oxygen Species; Streptococcus mutans
PubMed: 31726378
DOI: 10.1016/j.jphotobiol.2019.111633 -
Environmental Science & Technology Aug 2019Heterogeneous oxidation of SO is one of the promising mechanisms to account for high loading of sulfate during severe haze periods in China. Our earlier work reported on...
Heterogeneous Oxidation of SO in Sulfate Production during Nitrate Photolysis at 300 nm: Effect of pH, Relative Humidity, Irradiation Intensity, and the Presence of Organic Compounds.
Heterogeneous oxidation of SO is one of the promising mechanisms to account for high loading of sulfate during severe haze periods in China. Our earlier work reported on the SO oxidation by OH and NO produced during 250 nm nitrate photolysis (. , , 86-91). Here, we extend that work to examine sulfate production during nitrate photolysis at 300 nm irradiation, which can additionally generate NO or HNO, N(III). Flow cell/in situ Raman experiments showed that the reactive uptake coefficient of SO, γ, can be expressed as γ = 1.64 × , where is the nitrate photolysis rate in the range of (1.0-8.0) × 10 M s. Our kinetic model with the predicts that N(III) is the main contributor to the SO oxidation, followed by NO contribution. Furthermore, the addition of OH scavengers (e.g., glyoxal or oxalic acid) does not suppress the sulfate production because of the reduced N(III)-consuming reactions and the high particle pH sustained by their presence. Our calculations illustrate that under characteristic haze conditions, the nitrate photolysis mechanism can produce sulfate at ∼1 μg m h at pH 4-6 and = 10 M s. The present study highlights the importance of in-particle nitrate photolysis in heterogeneous oxidation of SO by reactive nitrogen (NO/HNO and NO) under atmospherically relevant actinic irradiation. However, the nitrate photolysis rate constant needs to be better constrained for ambient aerosols.
Topics: China; Humidity; Hydrogen-Ion Concentration; Photolysis; Sulfates
PubMed: 31241323
DOI: 10.1021/acs.est.9b01623 -
Chemosphere Mar 2015
Topics: Air Pollutants; Fluorocarbons; Photolysis
PubMed: 24746526
DOI: 10.1016/j.chemosphere.2014.03.066 -
Environmental Science & Technology Dec 2019Indoor photolysis of nitrous acid (HONO) generates hydroxyl radicals (OH), and since OH is fast reacting, it may be confined within the HONO-photolyzing indoor volume of...
Indoor photolysis of nitrous acid (HONO) generates hydroxyl radicals (OH), and since OH is fast reacting, it may be confined within the HONO-photolyzing indoor volume of light. This study investigated the HONO-photolysis-induced formation of indoor OH, the transformation of OH to hydroperoxy radicals (HO), and resulting spatial distributions of those radicals and their oxidation products. To do so, a computational fluid dynamics (CFD) model framework was established to simulate HONO photolysis in a room and subsequent reactions associated with OH and HO under a typical range of indoor lighting and ventilation conditions. The results showed that OH and HO were essentially confined in the volume of HONO-photolyzing light, but oxidation products were relatively well distributed throughout the room. As the light volume increased, more total in-room OH was produced, thereby increasing oxidation product concentrations. Spatial distributions of OH and HO varied by the type of artificial light (e.g., fluorescent versus incandescent), due to differences in photon flux as a function of light source and the distance from the source. The HO generation rate and air change rate made notable impacts on product concentrations.
Topics: Air Pollution, Indoor; Hydrodynamics; Hydroxyl Radical; Nitrous Acid; Photolysis
PubMed: 31693359
DOI: 10.1021/acs.est.9b06315 -
Molecules (Basel, Switzerland) Jun 2018The mechanisms of the photolysis reactions are studied theoretically at the M06-2X/6-311G(d) level of theory, using the four types of group 14 molecules that have the...
The mechanisms of the photolysis reactions are studied theoretically at the M06-2X/6-311G(d) level of theory, using the four types of group 14 molecules that have the general structure, Ph₃M⁻M'Ph₂Me (M and M' = Si and Ge), as model systems. This study provides the first theoretical evidence for the mechanisms of these photorearrangements of compounds that contain a M⁻M' single bond. The model investigations indicate that the preferred reaction route for the photolysis reactions is, as follows: reactant → Franck-Condon (FC) region → minimum (triplet) → transition state (triplet) → triplet/singlet intersystem crossing → photoproducts (both di-radicals and singlets). The theoretical findings demonstrate that the formation of radicals results from reactions of the triplet states of these reactants. This could be because both the atomic radius and the chemical properties of silicon and germanium are quite similar to each other and compared to other group 14 elements, their photolytic mechanisms are nearly the same. The results for the photolytic mechanisms that are studied in this work are consistent with the available experimental observations and allow for a number of predictions for other group 14 dimetallane analogues to be made.
Topics: Metals; Models, Theoretical; Molecular Structure; Photolysis
PubMed: 29867070
DOI: 10.3390/molecules23061351 -
Journal of Agricultural and Food... Oct 2009There is little information about pesticide photostability on plants, especially when considering the effects of the formulation. We evaluated the photostability of a...
There is little information about pesticide photostability on plants, especially when considering the effects of the formulation. We evaluated the photostability of a herbicide, mesotrione, on wax films. These surfaces are good systems to mimic the outer layer of the leaf. Within the range of recommended agricultural rates, pure mesotrione half-life on cuticular wax films was between 100 and 160 min. Formulated, the phototransformation rate was multiplied by a factor of 4.8. We assume that the acceleration is mainly due to the surfactants, agents that allow a better spreading of the active ingredient at the leaf surface. Since mesotrione photolysis is a fast process on wax films, we can assume that this process would be significant in the field after treatment.
Topics: Cyclohexanones; Drug Stability; Herbicides; Kinetics; Photolysis
PubMed: 20560626
DOI: 10.1021/jf901996d -
Water Research Jul 2016Treatment of real effluents from industries using AOPs stands to be an imperative task of crucial importance yet quite huge a challenge largely given the nature of...
Treatment of real effluents from industries using AOPs stands to be an imperative task of crucial importance yet quite huge a challenge largely given the nature of complexity of these wastewaters. The present work sought to develop a versatile system aimed at the treatment of real wastewater using a bubbling annular reactor, which enables us to test the efficiency of photolysis; photocatalysis, photoelectrocatalysis and direct ozonation using oxygen or ozone as gas flow. A TiO2 nanotubes electrode was used as photocatalyst in photocatalytic and photoelectrocatalytic measurements with and without coupling with ozonation under pH 3.0 and pH 8.0 leading to 50% of color removal after 60 min reaction. However, the results indicated 90% of color removal upon the bubbling of ozone after 15 min of treatment. A synergistic effect was observed in all experiments using the AOPs in the presence of ozone under both pH values. Interestingly though, 85% of decolorization was obtained through direct ozonation without any change in the effluent following 10 min of treatment. The results were discussed in terms of electric energy per order and were compared to those reported previously. For real textile wastewater, ozonation appears to be a promising candidate for full-scale effluent decolorization.
Topics: Color; Ozone; Photolysis; Textile Industry; Textiles; Wastewater
PubMed: 27076061
DOI: 10.1016/j.watres.2016.04.004