Action Of UV Light Research Articles

UV protection and insecticidal activity of microencapsulated Vip3Ag4 protein in Bacillus megaterium

In this study, secretable Vip3Ag4 protein was encapsulated in Bacillus megaterium and used for quantitative bioassays, in order to determine the UV photoprotective capacity of the cell, for preventing inactivation of the insecticidal activity of the protein. The non-encapsulated and purified protein was exposed to the UV light showing a LC50 of 518 ng/cm2 against Spodoptera littoralis larvae, whereas the exposed encapsulated protein exhibited 479 ng/cm2. In addition to the capability to accumulate Vip3 proteins for the development of novel insecticidal formulates, the B. megaterium cell has demonstrated to provide moderate protection against the deleterious action of UV light.

Composites Based on Polyvinyl Alcohol and WO3: Preparation and Photochromic Characteristics

A comparative analysis of the photochromic properties of composites based on polyvinyl alcohol and WO3 nanoparticles stabilized with polyvinylpyrrolidone with different molecular weights has been performed. The composites possess reversible photochromicity. The results of electron absorption spectroscopy, thermal analysis, and mechanical tests showed that under the action of UV light, crosslinking of the polymer can occur depending on the molecular weight of the stabilizer and the polymer matrix.

Dielectric and photoelectric properties of Sm2O3 regulated by ZnO

With the trend of electronic information technology towards miniaturization, integration and intelligence, higher requirements are put forward for the performance of dielectric ceramic materials. In this paper, a series of doped samples Sm2O3-xZnO (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) were successfully prepared by the traditional solid state reaction method, and the complex dielectric properties of the ceramic samples were investigated as a function of temperature (100 K–400 K) and frequency (102–106 Hz) separately. A new phase Zn6.76Sm2.58O10.6 was found in all samples, and all samples were complex. At a higher temperature, 350 K, with the increase of ZnO doping content, the maximum dielectric constant is 434.7, the dielectric loss is as low as 0.0098, and the dielectric performance is significantly increased compared with room temperature. UV–Vis DRS test showed that the absorbance of the sample increased with the increase of ZnO content, and the side reaction showed that the dielectric constant and dielectric loss of the sample were improved under the action of UV light. These provide an experimental basis for the application of samarium based dielectric ceramics.

Self-Sanitizing Polycaprolactone Electrospun Nanofiber Membrane with Ag Nanoparticles.

The objective of this research was to develop an environment-friendly and scalable method for the production of self-sanitizing electrospun nanofibers. This was achieved by immobilizing silver nanoparticles (Ag NPs) onto plasma-treated surfaces of biodegradable polycaprolactone (PCL) nanofibers. The plasma deposited polymer layer containing carboxyl groups played a critical role in providing a uniform distribution of Ag NPs on the nanofiber surface. Ag ions were absorbed by electrostatic interaction and then reduced under the action of UV-light. The concentration and release of Ag ions were analyzed using the EDXS/XPS and ICP AES methods, respectively. Although high levels of Ag ions were detected after 3 h of immersion in water, the material retained a sufficient amount of silver nanoparticles on the surface (~2.3 vs. 3.5 at.% as determined by XPS), and the release rate subsequently decreased over the next 69 h. The antipathogenic properties of PCL-Ag were tested against gram-negative and gram-positive bacteria, fungi, and biofilm formation. The results showed that the PCL-Ag nanofibers exhibit significant antimicrobial activity against a wide range of microorganisms, including those that cause human infections. The incorporation of Ag NPs into PCL nanofibers resulted in a self-sanitizing material that can be used in variety of applications, including wound dressings, water treatment, and air filtration. The development of a simple, scalable, and environmentally friendly method for the fabrication of these nanofibers is essential to ensure their widespread use in various industries. The ability to control the concentration and release rate of Ag ions in the PCL nanofibers will be critical to optimize their efficacy while minimizing their potential toxicity to human cells and the environment.

Synergy of UV light and heat in peptide degradation

Degradation of peptides and proteins by UV light involves formation of hydroperoxide intermediates. We hypothesised that accumulation of these hydroperoxides would enhance subsequent further damage upon heating, resulting in UV and heat acting synergistically. The enhanced peptide/protein degradation is particularly relevant for dead biological tissues such as human hair, which are often subjected to alternating UV (i.e., sunlight exposure) and heat (e.g., flat ironing) treatments. The light-heat synergism hypothesis was tested using short protected peptides as protein mimics. By quantifying oxidative peptide degradation, we confirmed synergistic action of UV light and subsequent heat treatment. A combination of analytical techniques including mass spectrometry and isotope exchange experiments was used to detect and quantify hydroperoxide intermediates formed upon UV exposure. Their role in peptide degradation was further confirmed by treatment with NaBH4 which destroyed hydroperoxides and increased thermal stability. Expanding these model results to a real system, we have demonstrated that thermal degradation of human hair is enhanced by the preceding treatment with solar-simulated light.

Study on the Effect of Ultraviolet Absorber UV-531 on the Performance of SBS-Modified Asphalt.

Asphalt pavements at high altitudes are susceptible to aging and disease under prolonged action of UV light. To improve their anti-ultraviolet aging performance, UV-531/SBS-modified asphalts with UV-531 dopings of 0.4%, 0.7%, and 1.0% were prepared by the high-speed shear method, and the effect of UV-531 on the conventional performance of SBS-modified asphalt before aging was studied by needle penetration, softening point and 5 °C ductility tests. The high- and low-temperature rheological properties of UV-531/SBS-modified asphalt before and after aging were also analyzed by high temperature dynamic shear rheology test and low-temperature glass transition temperature test. Finally, the effect of UV-531 on the anti-aging performance of SBS-modified asphalt was evaluated by three methods, including rutting factor ratio, viscosity aging index, and infrared spectroscopy. The results show that with the increase of UV-531 doping, the needle penetration and 5 °C ductility show an increasing trend, but the effect on the softening point is small. The high temperature stability of SBS-modified asphalt is not much affected by the addition of UV-531, and the low-temperature stability is improved, and when 0.7% UV absorber is added, SBS-modified asphalt shows better low-temperature performance. The results of all three evaluation methods show that the addition of UV-531 significantly improved the anti-UV aging performance of SBS-modified asphalt, with the amount of 0.7% providing the asphalt with the best anti-UV aging performance. The results of the study can provide an important reference for improving the anti-ultraviolet aging performance of SBS-modified asphalt.

Preparation and characterization of thermal‐ and light‐triggered self‐healing azobenzene polymer

AbstractBoth temperature‐ and light‐triggered self‐healing azobenzene polymer was successfully synthesized via radical copolymerization of 4‐(furan‐maleimide ethyl) methyl methacrylate (MMA‐FMI), 4′‐(oxyhexyl methacrylate)‐4‐(oxyfuran‐2‐carbomethoxy) azobenzene (MMA‐FAzo) and 6‐(4′‐methoxy‐4‐oxyazobenzene)‐hexyl methacrylate at 50°C. The structure of the polymer was characterized by proton nuclear magnetic resonance (1H‐NMR) spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography. Interestingly, furan and maleimide thermally reversible groups were introduced into the polymer. After the furan rings on the MMA‐FMI were removed at high temperatures, the exposed maleimide groups were further added with the furan rings on the MMA‐FAzo to form a crosslinked network. The crosslinked polymer film was still soluble in the anisole after heating, which could further illustrate the thermal reversibility of the polymer film and realized the recyclability and reworkability of the side‐chain azobenzene polymer. 1H‐NMR could prove that the crosslinked polymer was completely decrosslinked and the polymer was thermoreversible. Ultraviolet–visible (UV–Vis) absorption spectra showed rapid photoisomerization of the polymer, and surface‐relief grating formed on the crosslinked PAzo film was also investigated using illumination from a linearly polarized Kr+ laser beam. The surface modulation depth and grating spacing were about 149 nm, and 1.7 μm, respectively. What is more, the polarized light microscopy showed that the crosslinked polymer film could be self‐repaired under the combined action of UV light and heating.

H2O2/UV catalytic degradation of furacilin by Fe-Ni oxyhydroxides synthesized via coprecipitation

The article considers the structural and photocatalytic properties of nickel–iron double oxyhydroxide synthesized by co-precipitation. X-ray phase analysis of the powder and scanning electron microscopy showed that the NiOOH-FeOOH nanostructures have a crystalline structure and a scaly-layered structure.UV spectroscopy confirmed the photocatalytic activity of nanostructures in the degradation of furacilin under the action of UV light. The process of photocatalytic decomposition of furacilin in the presence of a synthesized photocatalyst is considered. The statistical model was developed using central composite rotatable design method. The calculated values of the degree of degradation of furacilin are confirmed by experimental results. The optimal process parameters were also determined, namely the concentration of the photocatalyst, hydrogen peroxide and processing time.

Эффекты комбинированного действия гипертермии и УФ-света на клетки дрожжей: фактор времени и последовательность воздействия

In modern methods of cancer therapy, combinations of influencing factors having various nature are widely used to achieve the highest therapeutic effect: ionizing radiation, chemotherapy drugs, hyperthermia, non-ionizing radiation, etc. The greatest cells damaging effect is achieved when the treatments are applied simultaneously. An increase in the interval between the treatments leads to final effect decrease. However, how the degree of the effect depends on the time gap has not been studied in detail. The paper presents the results of a study of this dependence with a different sequence of applied treatments. Combination of UV radiation and hyperthermia were examined. The choice of treatments is due to attention to the Vavilov-Cherenkov radiation, which arises when accompanies high-energy ionizing radiation used in oncotherapy and most of which is a continuous UV spectrum. And if we consider the Vavilov-Cherenkov radiation responsible for UV-like damages, which has its effect on the final result of the action of high-energy ionizing radiation, then it becomes clear that it is necessary to understand the behavior of UV light when it is used in combination with other damaging factors. Thus, the aim of the work is to study the effect of a sequence of applied treatments and the time gap between them on the magnitude of the final effect of the sequential action of UV light and hyperthermia on yeast cells. The dependence obtained in the work is of a multidirectional nature, changing from synergism to additivity, turning into antagonism with time gap rising. It is shown that the effect practically does not depend on the sequence of the treatments application, but significantly depends on the time gap between them. Such patterns were obtained for the first time. But it is indicates that when using in practice the combined action of ionizing radiation or UV light with hyperthermia, it should be remembered that the final effect can differ from expected.

TiO2 MOCVD coating for photocatalytic degradation of ciprofloxacin using 365 nm UV LEDs - kinetics and mechanisms

This work presents a solution for the photocatalytic degradation of the antibiotic ciprofloxacin (CIP) in water, without using P25 TiO2 powder and thus getting rid of expensive separation steps. It consists in using a TiO2 coating that is directly deposited on the optical window of a photocatalytic micro-reactor and 365 nm UV LEDs as radiation source. P25 TiO2 powder was also studied as reference. HPLC-MS was used to determine the transformation products and the pathways reactions. CIP was slowly degraded by the photolysis reaction at 365 nm: (75 % removal after 8 h of UV irradiation). However, no significant decrease of the total organic carbon (TOC) was noticed, thus showing the presence of transformation products not degraded by the action of UV-light alone. For a low catalyst amount (i.e 0.12 g of TiO2, whatever the form, powder or coating, per liter of contaminated water,), excellent CIP degradation by photocatalysis was observed. Complete CIP degradation after 1 h of irradiation was required using P25 and 8 h using TiO2 coating. Different preferential reaction pathways were identified for both TiO2 catalysts. The Langmuir-Hinshelwood model showed a very good representation of the kinetics, unlike its simplified pseudo-first order model. Photocatalysis experiments did not show a complete mineralization (60–70 % of TOC removal), but most of the aromatic transformation products were degraded. The last transformation products were identified as small aliphatic acids. There is therefore a real interest in using MOCVD coating of TiO2 for sustainable wastewater treatment to avoid expensive catalyst separation. A study with a spiked real effluent from a wastewater treatment plant was performed and a satisfactory degradation was obtained. Slower kinetics were found due to the presence of additional organic products and scavenger compounds such as HCO3−.

ИК-спектроскопия в исследовании процессов УФ-модификации иммобилизованного трипсина

Исследован механизм воздействия УФ-излучения на трипсин, иммобилизованный на матрице среднемолекулярного (200 кДа) и высокомолекулярного (350 кДа) хитозанов. Установлено, что ферментативная активность молекул иммобилизованного трипсина под воздействием УФ-излучения практически не подвержена изменению. Выдвинуто предположение о фотопротекторном эффекте матрицы хитозана. Выявлено, что при дозе 6040 Дж/м2 происходят изменения в структуре белкового комплекса, связаные с варьированием количества неупорядоченных структур и β-слоев в молекуле фермента, –СОО– колебаниями аминокислот, проявляющиеся в снижении активности препарата.

Comparative characteristics of sterically hindered phenols and nitroxide radicals as stabilizers of polyethylene photodegradation

Introduction. Polymeric materials (PM) are increasingly used in various industries and agriculture. Under the action of UV light, PM are destroyed. UV stabilizers are used to protect PM from photodegradation. Their action is based on the absorption of the photoactive sunlight component or on the deactivation of excited molecules that have already absorbed a light quantum, as well as on the inhibition of dark light-induced reactions. The work objective is to provide a comparative analysis of compounds of the sterically hindered phenols (SHP) series and nitroxide radicals (NR) as the PM photodegradation inhibitors. Materials and Methods . Reagents of the “purum” grade, LDPE premium grade 15803-020 polyethylene film were used for the investigations. The stabilizer was applied to the film by dipping. Carbonyl groups in polyethylene were determined by IR spectroscopy. IR spectra were recorded on Varian-640 instrument. Research Results. 2,4,6-tri-tert-amylphenol (1), 2-methyl-4,6-di-tert-butylphenol (2), 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl (3), 3-carboxamido-2,2,5,5-tetramethylpyrrolin-1-oxyl (4) were tested as stabilizers for photo-oxidative degradation of polyethylene. It is known that the accumulation of carbonyl and hydroxyl groups is recorded in PM samples under irradiation in the process of photodegradation through the IR spectroscopy. The absorption band of the carbonyl group at 1720 cm - 1 appears in the IR spectra of oxidized polyethylene. The IR spectra analysis shows that the content of carbonyl groups in the check samples is significantly higher than in the samples treated by stabilizer solutions. Discussion and Conclusions . The experiments show that ni-troxide radicals of 3-carboxamido-2,2,5,5-tetramethylpyrrolin-1-oxyl series and 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl are the best photostabilizers of polyethylene. Moreover, there is no significant difference between the radicals of the 2,2,6,6-tetramethylpiperidine and 2,2,5,5-tetramethylpyrroline series. Sterically hindered phenols, under photodegradation, have a far smaller stabilizing effect, falling short of nitroxide radicals.

Discovering the effect of alum on UV photo-degradation of gelatin binder via FTIR, XPS and DFT calculation

In the field of cultural heritage, a growing interest is focused on the UV photo-degradation of organic binders induced by mineral pigments. But the effect of alum on the UV photo-degradation of gelatin binder remains unclear, which are two of the most common materials in traditional Chinese painting and calligraphy. This paper investigated alterations in composition, the secondary structure and morphology of gelatin under the individual or compound action of UV light and alum. Results showed that alum can obviously accelerate the alterations in the secondary structure and morphology of gelatin. The results of FTIR, XPS and DFT calculation confirmed that alum can directly or indirectly provide active hydrogen atom and O2· radicals, so the initiation and propagation process of gelatin photodegradation were promoted. The paper discovered the mechanism of the degradation of protein binders in Chinese traditional cultural heritage, and provided important theoretical basis for find suitable treatments for conservation or targeted materials for protection.

Glyphosate photodegradation: stoichiometry, kinetic and catalytic effects

Photodegradation of glyphosate (PMG) in aqueous solution by the action of UV-light and the catalytic effect of copper and copper-alga Ulva lactuca is described. The photodegradation kinetic reaction of PMG can be explained using a first-order kinetic model, with a mean rate constant of k = (0.04 ± 0.01) h-1 and a mean half-life (τ) = (17 ± 4) h. The quantum yield (φ) obtained for the photochemical decomposition of PMG was (4.8 ± 0.1) 10-4 mol Einstein-1. The resulting photodegradation by-products obtained were acetate, aminomethylphosphonic acid (AMPA), phosphate, sarcosine and to a lesser extent nitrate. The rate of PMG degradation is increased by the presence of copper and Cu-alga Ulva lactuca in the reaction media. The present work represents a new understanding on the photodegradation of the herbicide glyphosate and the results obtained may contribute to the development of new remediation technologies.

Graphene may help to solve the Casimir conundrum in indium tin oxide systems

We reconsider the long-explored problem that the magnitude of the measured Casimir force between an Au sphere and an indium tin oxide (ITO) film decreases significantly with no respective changes in the ITO dielectric permittivity required by the Lifshitz theory. Two plausible resolutions of this conundrum are discussed: the phase transition of an ITO film from metallic to dielectric state and the modification of a film surface under the action of UV light. To exclude the latter option, we propose an improvement in the experimental scheme by adding a graphene sheet on top of an ITO film. The formalism is developed allowing precise calculation of the Casimir force between an Au sphere and a graphene sheet on top of ITO film deposited on a quartz substrate. In doing so Au, ITO, and quartz are described by the frequency-dependent dielectric permittivities and real graphene sheet with nonzero mass-gap parameter and chemical potential by the polarization tensor at nonzero temperature. Numerical computations performed both before and after the phase transition resulting from the UV treatment show that the presence of graphene leads to only a minor decrease in the drop of the Casimir force which remains quite measurable. At the same time, in the presence of graphene the guess that an observed drop originates from the modification of an ITO surface by the UV light breaks down. Similar results are obtained for the configuration of two parallel plates consisting of a graphene sheet, an ITO film and a quartz substrate. The proposed experiments involving additional graphene sheets may help in resolution of the problems arising in application of the Lifshitz theory to real materials.

Effect of Photo-and Thermoactivation of CdSe Cores on the Luminescent Properties of CdSe@CdS Colloidal Quantum Dots

The effect of photo-and thermoactivation of the CdSe cores of colloidal quantum dots (CQDs) on the luminescent properties of the CdSe@CdS CQDs formed on them has been studied. It has been established that an optimum combination of the action of UV light and heat on the CdSe cores has a favorable effect on the luminescent characteristics of the CdSe@CdS CQDs formed on them, noticeably increasing the quantum yield of luminescence, narrowing the spectral emission band, and enhancing their stability.

Ignition induced the short-term action of UV light as possible evidence of chain branching in the reacting CH3Cl + Cl2 mixture

Ignition takes place in a mixture of chloromethane and chlorine at atmospheric pressure and room temperature 0.1 s after the irradiation of the mixture with a UV light pulse from a mercury quartz lamp. Temperature fields are presented, which demonstrate the development of the ignition process in the dark period. Calculations show that, after the initiation is stopped, the concentration of chlorine atoms decreases to a critical value within a time of the order of 0.02 s. The observed ignition can be explained by chains branching caused by the decay of the excited CCl 3 * radical that have accumulated energy upon the successive substitution of chlorine atoms for hydrogen in the chloromethane molecule.

Powerful combination of analytical and chemometric methods for the photodegradation of 5-Fluorouracil

The photodegradation of the antineoplastic drug 5-fluorouracil (5-FU) under the action of UV light was studied using UV–vis spectroscopy and High Performance Liquid Chromatography coupled to Diode Array Detector and High Resolution Mass Spectrometry (HPLC-DAD-HRMS). To analyze, integrate and interpret the degradation kinetics, the Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) chemometric method has been applied. The high complexity of the photodegradation process of this drug involving up to seven different photoproducts showed the advantages of the proposed approach which provides simultaneously mechanistic and structural information explaining the 5-FU photodegradability. Moreover, this study provides a new tool to be used for elucidating the photodegradation kinetics at real time.

Spectrally resolved infrared microscopy and chemometric tools to reveal the interaction between blue light (470 nm) and methicillin-resistant Staphylococcus aureus

Blue light inactivates methicillin-resistant Staphylococcus aureus (MRSA), a Gram-positive antibiotic resistant bacterium that leads to fatal infections; however, the mechanism of bacterial death remains unclear. In this paper, to uncover the mechanism underlying the bactericidal effect of blue light, a combination of Fourier transform infrared (FTIR) spectroscopy and chemometric tools is employed to detect the photoreactivity of MRSA and its distinctive pathway toward apoptosis after treatment. The mechanism of action of UV light and vancomycin against MRSA is also investigated to support the findings. Principal component analysis followed by linear discriminant analysis (PCA- LDA) is employed to reveal clustering of five groups of MRSA samples, namely untreated (control I), untreated and incubated at ambient air (control II), irradiated with 470nm blue light, irradiated with 253.5 UV light, and vancomycin-treated MRSA. Loadings plot from PCA-LDA analysis reveals important functional groups in proteins (1683, 1656, 1596, 1542cm−1), lipids (1743, 1409cm−1), and nucleic acids region of the spectrum (1060, 1087cm−1) that are responsible for the classification of blue light irradiated spectra and control spectra. Cluster vector plots and scores plot reveals that UV light-irradiated spectra are the most biochemically similar to blue light- irradiated spectra; however, some wavenumbers experience a shift. The shifts between blue light and UV light irradiated loadings plot at νasym PO2− band (from 1228 to 1238cm−1), DNA backbone (from 970 to 966cm−1) and base pairing vibration of DNA (from 1717 to 1712cm−1) suggest distinctive changes in DNA conformation in response to irradiation. Our findings indicate that irradiation of MRSA with 470nm light induces A-DNA cleavage and that B-DNA is more resistant to damage by blue light. Blue light and UV light treatment of MRSA are complementary and distinct from the known antimicrobial effect of vancomycin. Moreover, it is known that UV-induced cleavage of DNA predominantly targets B-DNA, which is in agreement with the FTIR findings. Overall the results suggest that the combination of light and vancomycin could be a more robust approach in treating MRSA infections

UV-LED photocatalytic oxidation of carbon monoxide over TiO2 supported with noble metal nanoparticles

The TiO2 catalysts supported with 0.01–4wt% Pt, Pd, or Au were prepared via chemical reduction of inorganic precursors with NaBH4 or their photoreduction in water-ethanol solution under UV irradiation. The samples were characterized by the means of X-ray fluorescence, N2 adsorption, TEM, XPS and UV-Vis spectroscopy and investigated in the processes of dark catalytic and UV-LED photocatalytic oxidation of carbon monoxide at room temperature. UV-LED irradiation of all the synthesized catalysts resulted in an increase in CO oxidation rate compared to the oxidation without UV. Two parallel pathways including thermal catalytic oxidation on metal particles and photocatalytic oxidation by the action of UV light were proposed for the M/TiO2 catalysts.The domed dependence of photocatalytic oxidation rate on the metal content was observed for all the metal deposited catalysts and had a maximum at 1wt% for Pt and 0.05wt% for Pd and Au. The activity of the 1wt% Pt/TiO2 catalyst was 7 and 11 times higher than that of the 0.05wt% Pd- and Au-loaded samples, respectively. For the 1wt% Pt/TiO2 sample, the deposition method via chemical reduction with NaBH4 resulted in a much higher activity than the photoreduction method. The effects of the metal nature, its content and the preparation method on CO photocatalytic oxidation rate are discussed in the terms of metal particle size and charge state based on the data from TEM and XPS analyses.