UV Radiation In Presence Research Articles

Insights into the photoinduced degradation of terbuthylazine from aqueous solution: The synergic effects generated from hydrogen-bond interactions

In this work, we examined the stability of terbuthylazine (TBA) as well as the mechanisms related to its photoinduced degradation considering two conditions: i) when exposed (solely) to UV radiation and ii) when exposed to UV radiation in presence of H2O2. Ground state properties (such as bond lengths, hydrogen-bond interactions, and relative energetics) as well as excited state parameters (vertical excitation energies and generalized oscillator strengths, GOS) were determined through the use of standard and well documented density functional theory based electronic structure methods and, subsequently, explored for accomplishing the purpose of the work; results were obtained considering both the gas-phase and a (water) solvent environment. In terms of ground state, the presence of the additional hydrogen-bond interaction when the H2O2 molecule is nearing the N atom located in the opposite side to the Cl atom in TBA suggested the system to be more stable (for instance, 9.93 kJ/mol at the CAM-B3LYP/aug-cc-pVTZ level of theory in water) than its counterpart with the H2O2 molecule neighboring the N and Cl atoms. The excitation energies determined considering solvation were found to be in fairly good agreement when compared to the corresponding obtained in the gas-phase. Interestingly and more important, a different situation is observed in terms of GOS when solvation is considered. In this case, two excited states (versus no state in the gas-phase) were found to have considerably large GOS and, thus, are expected to be accessible at the UV region. Therefore, the interactions between TBA, H2O2, and water molecules (from the solvent environment) play an important role in regards to the excited states to be accessed. By coexisting with the UV photolysis of the H2O2 molecules in aqueous solution, the synergic effects from the TBA-H2O2-H2O interactions may add to the enhancement in the yield of the photoinduced degradation of TBA.

Photocatalytic degradation of methylene blue with copper(II) oxide synthesized by thermal decomposition of Flubendazole complexes

Novel copper(II) complexes of an anti-parasitic Flubendazole drug (FLU), [Cu(FLU)2X2]·zH2O (X = Cl− (1), C2H3O2− (3), and ClO4− (4), z = 1–4) and [Cu(NO3)(FLU)2(OH2)]∙NO3∙2H2O (2) were synthesized and characterized using elemental analysis, TG, IR, EPR, magnetic and conductance measurements. Geometry optimization and natural bond orbital analysis were performed at DFT/B3LYP/6-31G* level of theory. Electronic transitions were calculated by TD-DFT. Tenorite (CuO) nanoparticles with promising catalytic properties were prepared in air via the controlled thermal decomposition of 1–4. The polymorph and morphology of the prepared nano-tenorite particles were investigated by powder XRD and field emission scanning electron microscope. The catalytic degradation of methylene-blue (MB) dye exposed to the UV radiation in presence of CuO nanoparticles as a catalyst was studied at room temperature in water.

“Protective” Effects of Titanium Dioxide Nano-particles on Daphnia magna Exposed to UV Radiation

Aims: Titanium dioxide nano-particles (nano-TiO2) have been used in sunscreen creams to protect skin againstultra violet (UV) radiation; other applications are polarized glasses, wall paints, etc., however, the ecological risks when nano-TiO2 residues reach aquatic ecosystems is not well documented; therefore, the objective of this study is to give some insight on the attenuating effects of nano-TiO2 against UV radiation on Daphnia magna and the toxicity of nano-TiO2 on this organism. Study Design: Exposing Daphnis to UV radiation in presence and absence of nano-TiO2. Place and Duration of Study: Biotechnology Institute, CNR, Canada and Toxicology laboratory, Faculty of Marine Sciences, University of Sinaloa Mexico; between April and July 2012. Methodology: Daphnis (adults and neonates) were exposed to UV light for varying periods in the absence and presence of nano-TiO2. After 48 h incubation, mortalities were recorded for each experiment. Similar experiments were performed using bulk TiO2 instead of nano-TiO2, to know if protective effect is related to particles size. Finally, to Original Research Article British Journal of Applied Science & Technology, 4(12): 1858-1868, 2014 1859 know if protective effect is outer (blocking UV radiation) or interior (by cellular processes), Daphnis were pre-treated with nano-TiO2, then exposed to UV radiation, and mortalities recorded. Results: The mortalities were significantly lower in presence than in absence of nanoTiO2. Alsomortalities were significantly higher in bulk TiO2 than in nano-TiO2, indicating that nano-TiO2has a protective effect against UV radiation on Daphnis. Also, results indicate that protective effect is exterior, by blocking of UV rather than cellular repair mechanisms (cellular processes). However, at 100mg/L nanoTiO2 concentration, 15% mortality was observed. Conclusion: Nano-TiO2 is a nanomaterial blocking UV radiation; however if residues reach aquatic ecosystems, could be a risk (toxic) for aquatic organisms, because the highest concentration used in this work caused mortalities in Daphnia magna.

Factors influencing photo curing kinetics of novel UV-cured siloxane-modified acrylic coatings: Oxygen inhibition and composition

An experimental study was carried out for the development and characterization of innovative photopolymerizable siloxane-modified acrylic formulations for possible use as protective coatings of stone substrates. The kinetics of the radical photopolymerization mechanism induced by UV radiations in presence of a suitable photoinitiator was studied by a calorimetric analysis by varying the atmosphere (oxygen or nitrogen) and the composition of the mixtures, in particular of the UV photoinitiator.The reactivity, expressed in terms of both heat developed and rate of reaction, was generally found to decrease when the photopolymerization was carried out in air, due the inhibiting action of the oxygen towards the free radical polymerization. The addition of a proper thiol to the acrylic modified resin was found to reduce the adverse effect of oxygen on the kinetic reaction and on the degree of conversion. This result allowed to reduce the content of the photoinitiator and to increase the content of the siloxane in the acrylic based mixtures. The effect of the change of the composition of the formulations on the kinetic behaviour of the acrylic based resins was also analysed by calorimetric analysis. Calorimetric experimental data were fitted to a simple kinetic model for radical photopolymerization reactions. Finally, a proper relationship between the glass transition temperature and the total extent of reaction was applied to the experimental data. A good agreement between the experimental data and both the theoretical models was generally found.

Photocatalytic degradation of PVC–ZnO composite film under tropical sunlight and artificial UV radiation: A comparative study

Disposal of waste plastics imposes serious problems to the environmentalists, since plastics are non-biodegradable and emit carcinogenic gases when incinerated. In a country like India, where solar energy is abundantly available, semiconductor photo catalysis may be a clean and economic technology to combat such a problem. In the present work we addressed to the problem of degrading polyvinyl chloride (PVC) by photo catalysis by exposing a PVC–ZnO composite film to solar radiation as well as to artificial UV radiation in presence of water and air. Degradation in the two processes has been compared. The surface morphology as well as the FTIR spectroscopy of the irradiated film has been critically examined. The degradation was measured by weight loss data and was found to follow a pseudo-first order rate equation. The various parameters studied were loading of the semiconductor and intensity of UV radiation. A possible mechanism has been suggested and the corresponding rate equation has been modeled. The model has been validated by the experimental data.

Study of Curing Kinetics and Thermal Degradation of UV Curable Epoxy Acrylate Resin

Blends of epoxy acrylate resins (acid values 3, 6.5 & 10 mg KOH/gm Solid) with monofunctional monomers (ethoxylated phenol monoacrylate) were prepared by physical mixing, having weight ratio 50:50. These blends were cured by using UV radiations in presence of photo initiator (Darocure 1173). The thermal degradation kinetics of these resin blends were studied, using thermo gravimetric analysis in nitrogen atmosphere at a heating rate of 10°C/min. by applying Coats-Red fern equation. According to the analysis, all the coating films degrade in two steps. In the first step of degradation kinetics, R2M follows 1.75 order (n=1.75) and all other coating films follow second order (n=2) kinetics. In second step, R2M & R3M follow half order (n=0.5) kinetics and R1M follow first order (n=1) degradation kinetics. Order of the reaction is obtained on the basis of best fit analysis, and all the parameters were confirmed by regression analysis. From the reaction order, value of activation energy (E) and pre exponential factor (Z) were calculated by the slop and intercept of the plot between X and Y, respectively.

Version 2 total ozone mapping spectrometer ultraviolet algorithm: problems and enhancements

Satellite instruments provide global maps of surface UV irradiance by combining backscattered radiance measurements with radiative transfer models. The accuracy of the models is limited by uncertainties in input parameters representing the atmosphere and the Earth's surface. To reduce these uncertainties, we have made enhancements to the currently operational TOMS surface UV irradiance algorithm (Version 1) by including the effects of diurnal variations of cloudiness, an improved treatment of snow/ice, and a preliminary aerosol correction. We compare results of the version 1 TOMS UV algorithm and the proposed version. We evaluate different approaches for improved treatment for average cloud attenuation within a satellite pixel, with and without snow/ ice on the ground. In addition to treating cloud transmission based only on the measurements at the local time of the TOMS observations, the results from other satellites and weather assimilation models can be used to estimate atmospheric UV irradiance transmission throughout the day. A new method is proposed to obtain a more realistic treatment of the effects from snow-covered terrain. The method is based on an empirical relation between UV reflectivity and measured snow depth. The new method reduces the bias between the TOMS UV estimations and ground-based UV measurements for snow periods. We also briefly discuss the complex problem of estimating surface UV radiation in presence of UV-absorbing aerosols. The improved (Version 2) algorithm can be applied to reprocess the existing TOMS UV irradiance and exposure estimates (since November 1978) and to future satellite sensors (e.g., GOME-2, OMI on EOS/Aura, and Triana/EPIC).