Short-wave Ultraviolet Radiation Research Articles

Electroconductive and photoelectric properties of Pt/(100) β-Ga2O3 Schottky barrier diode based on Czochralski grown crystal

Pt/(100) β-Ga2O3 Schottky barrier diodes were fabricated using a plate cleaved from the crystal grown by Czochralski method. Their electroconductive and photoelectric characteristics were studied. The following values were obtained: the Schottky barrier height (1.69/1.62/1.74 eV), ideality coefficient (1.09/1.14), saturation current density (9.91 × 10–15 A/cm2), diode series resistance (7.98 kΩ), and net donor concentration [(1.8–2.4) × 1018 cm–3]. The diodes demonstrate a high rectification ratio of 1010 at an applied voltage of ± 1 V and a relatively low experimental value of the leakage current density ∼10–11 A/cm2. These structures are solar-blind and also capable of operating in self-powered mode. The diodes are highly sensitive to short-wave ultraviolet radiation with a wavelength λ ≤ 265 nm. The maximum values of responsivity (20.4 A/W), external quantum efficiency (1.2 × 104%), and detectivity (9.6 × 1015 Hz0.5 × cm × W–1) of diodes were registered under exposure to irradiation at λ = 210 nm and at applied voltage of −1 V. The responsivity and external quantum efficiency values in the self-powered operation mode were 12.3 A/W and 7.2 × 103%, respectively. The diodes showed low rise and decay times in self-powered operation mode for photodiode based on Ga2O3: 14 and 30 ms, respectively.

High-speed performance self-powered short wave ultraviolet radiation detectors based on κ(ε)-Ga2O3

High-speed solar-blind short wavelength ultraviolet radiation detectors based on κ(ε)-Ga2O3 layers with Pt contacts were demonstrated and their properties were studied in detail. The κ(ε)-Ga2O3 layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates. The spectral dependencies of the photoelectric properties of structures were analyzed in the wavelength interval 200–370 nm. The maximum photo to dark current ratio, responsivity, detectivity and external quantum efficiency of structures were determined as: 180.86 arb. un., 3.57 A/W, 1.78 × 1012 Hz0.5∙cm∙W−1 and 2193.6%, respectively, at a wavelength of 200 nm and an applied voltage of 1 V. The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)−Ga2O3 interface under ultraviolet exposure. The detectors demonstrated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga2O3 interface. The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%, respectively. The rise and decay times in self-powered mode did not exceed 100 ms.

An led device for short-wave ultraviolet irradiation

An led device for short-wave ultraviolet irradiation

Elementary Steps in Steady State Kinetic Model Approximation for the Homo-Heterogeneous Photocatalysis of Carbamazepine

Elucidating physicochemical processes in the degradation of pollutants may optimize their removal from water sources. Although the photodegradation of carbamazepine (CBZ) in Advanced Oxidation Processes (AOPs) has been widely studied, there is no detailed report on the elementary steps of the kinetics. This study proposes a set of elementary steps for the AOP of CBZ, combining short-wave ultraviolet radiation (UVC), a homogeneous reagent (H2O2), and a heterogeneous catalyst (TiO2), which includes the excitation of both reagents/catalysts by UVC photons, the adsorption of CBZ by the excited TiO2, or its oxidation by hydroxyl radicals. Assuming the steady-state approximation on the intermediate products (excited TiO2, CBZ-excited TiO2 complex, and hydroxyl radicals) leads to rate laws for the degradation of CBZ, in which UVC radiation, TiO2, and H2O2 are pseudo-first-order at all concentrations or intensities and have no direct influence on CBZ pseudo-order, whereas CBZ shifts from pseudo-first-order at low concentrations to pseudo-zero-order at high concentrations. Several experiments to test the mechanism were conducted by varying CBZ, H2O2, and TiO2 concentrations and UVC radiation intensities. The measured results indeed fit the suggested mechanism for the first three, but the irradiation intensity appears to shift the CBZ influence from pseudo-second- to pseudo-first-order with increased intensities. Part of the elementary steps were changed to fit the results.

Ultrasound stimulated production of exopolysaccharide with anti-UV radiation activity by increasing cell permeability of Paenibacillus polymyxa

Exopolysaccharide (EPS) produced by Paenibacillus polymyxa PYQ1 may be a promising agent used in the cosmetic field for skin care because of its protective benefits against short-wave ultraviolet (UVC, 100–280 nm) radiation, which induces cytotoxicity in HaCaT cells. We attempted to use low-intensity ultrasound to enhance its fermentation, and the yield of EPS increased by 24 % under the optimum ultrasonic treatment (90 W, 45 s in 9 h). Results of further experiments show that low-intensity ultrasound will kill a few bacterial cells. Therefore, the remaining bacterial cells have more space and more nutrients, growing faster and producing EPS more efficiently. The recoverable physical damage caused by ultrasound increased the cell permeability, and for the first time, we found that low-intensity ultrasound up-regulated the expression of membrane transporters involved with the transport of sucrose and polysaccharides. Owing to these changes, the utilization of carbon sources was accelerated, and the transport of EPS was promoted to the outside of bacterial cells such that the production of EPS was enhanced.

Auxiliaries Ce3+/Sb3+ of Sm3+ in borosilicate glass phosphors: Optimal utilization of energetic UV photons

Sm3+-doped borosilicate (NKBSB) glass phosphors have been certified to be excited by short-wave ultraviolet (UVC), long-wave ultraviolet (UVA), violet and blue radiation. Further, the introduction of Ce3+ and Sb3+ into the Sm3+-doped NKBSB glass system significantly extends the excitable region to the whole ultraviolet (UV) radiation region, and optimally enhances the ability of Sm3+ to capture energetic UV photons. Due to the intersections of energy bands, the maximum sensitization coefficient is up to 18.9 under the cooperative sensitization of auxiliaries Ce3+ and Sb3+ on Sm3+. More interestingly, the distinguished fluorescence emissions of Ce3+-Sb3+-Sm3+ tri-doped NKBSB glasses towards entire UV excitation are identified from the images and videos. The exceptional sensitization performance and outstanding excitation extension offer insights in designing UV pumping optical devices of light color adjustment and light conversion.

Effect of Chitosan/Thyme Oil Coating and UV-C on the Softening and Ripening of Postharvest Blueberry Fruits.

This study investigated the possible mechanism of softening and senescence of blueberry after harvest using chitosan/thyme oil coating combined with UV-C (short wave ultraviolet irradiation) treatment. On the 56th day of storage, the CBP, cellulose, and hemicellulose contents in the chitosan/thyme oil coating +UV-C-treated group were 1.41, 1.65, and 1.20 times higher than those in the control group. Compared with the control group, the activities of polygalacturonase (PG), pectin methylesterase (PME), β-glucosidase (β-Gal), and cellulose (Cx) were significantly reduced (p < 0.05) after chitosan/thyme oil coating +UV-C, and their maximum values decreased by 5.41 μg/h g, 5.40 U/g, 12.41 U/g, and 3.85 μg/h g, respectively. Moreover, chitosan/thyme oil coating combined with UV-C treatment inhibited the gene expression of PG, PME, Cx, and β-Gal and then regulated the decrease in PG, PME, Cx, and β-Gal activities, inhibited the degradation of cell wall polysaccharides, and delayed the softening and senescence of postharvest blueberries. The results showed that chitosan/thyme oil coating, UV-C, and chitosan/thyme oil coating + UV-C could significantly inhibit postharvest softening of blueberry; chitosan/thyme oil coating +UV-C had the best effect.

Investigation of UV light treatment (254 nm) on the reduction of aflatoxin M1 in skim milk and degradation products after treatment

This study investigates the reduction of aflatoxin M1 (AFM1) in skim milk by using ultraviolet light at 254 nm and the effects of influencing factors on the efficacy including treatment time (min), depth of samples (mm), contamination level (μg L−1), stirring, temperature, and fat content in milk. The colour and pH of milk samples were measured to evaluate the influence of the treatment on these values. It was found that short-wave ultraviolet radiation (UVC) reduced up to 50% of AFM1 in milk after 20 min of treatment regardless of the initial AFM1 contamination level. Treatment time, depth of samples, and stirring were all found to significantly (P < 0.05) enhance the reduction of AFM1. The milk colour was affected but there was no influence on the pH of milk samples at any duration of UV exposure. It is concluded that UVC light treatment has the potential to reduce AFM1 in milk.

Insights on the effectiveness of pneumatic and ultrasonic atomization in combination with UVC light for processing of fruit juices.

This study evaluated the effectiveness of spraying juices, during shortwave ultraviolet irradiation (UVC) treatments as an alternative to promote more contact area, by means of ultrasonic atomization (UA) and pneumatic atomization (PA). Four juices with dissimilar physical characteristics were processed to assess the effect of suspended solids and turbidity. Antioxidant activity, anthocyanins, ascorbic acid, and inactivation of Saccharomyces cerevisiae inoculated in the juices were evaluated. Five decimal reduction cycles were reached after two passes of orange or grapefruit juice through the UVC + UA arrangement. On the other hand, five decimal reduction cycles were achieved after three passes in the UVC + PA arrangement. Losses of 11% and 14% of ascorbic acid were observed in orange and grapefruit juice, respectively, while anthocyanin content presented losses of 50% and antioxidant activity decreased by 40% for pomegranate and blueberry juice, correspondingly.

Possibilities of syndrome-oriented medical rehabilitation in diseases of the respiratory organs in the resort of the Southern coast of Crimea

Aim. To evaluate the possibilities of physiotherapeutic syndrome-oriented medical rehabilitation (MR) for lung diseases (LD) in the climatic resort of the Southern Coast of Crimea (SCC). Materials and methods. In a single-center retrospective observational study, an analysis was made of the rehabilitation effects of physiotherapeutic interventions in a contingent of 100 patients with LD. Examination and treatment of patients was carried out in accordance with the standard of health resort care for patients with LD. Additionally, psychological studies and therapeutic effects were carried out by transcranial electrical stimulation, dynamic electrical nerve stimulation, mud therapy with Saki therapeutic mud, aromatherapy with sage oil and breathing training with a breathing simulator “New Breath”. The assessment of the values of 23 domains of “International Classification of Functioning, Disability and Health” (ICF) was carried out according to the methodology developed in the “ARI n.a. I.M.Sechenov”. The values of domains at the beginning and at the end of the MR course were evaluated, as well as the dynamics of domains (equal to the result of subtracting the values of the domain at the end of the course from the value at the beginning of the course). Mathematical analysis of the obtaineddata was carried out using the methods of multivariate statistics. Results. A statistically significant (at p &lt; 0.05) positive dynamics of a number of domains was established, indicating the success of a comprehensive course of MR, including domains b2401, b410, b420, b450, b455, b4552, b4601 and an integrated assessment of the functional state (IAFS). The 18 equations of the positive effect of course doses of physiotherapeutic procedures (alternating magnetic field, DENS, ultrasound therapy, halotherapy, inhalation therapy, aromatherapy, pelopathy, short-wave ultraviolet irradiation and massage) on the effectiveness of MR for 12 domains and for IAFS were obtained. Conclusion. The use of ICF domains as rehabilitation syndromes is substantiated. The complex of physiotherapeutic influences used in the treatment of patients with LD in the SCC climatic resort has significant potential for successful syndrome-oriented MR.

Clinical and laboratory assessment of the antimicrobial effect of water ozonated with short-wave ultraviolet radiation on the microbiota of periodontal pockets in the complex treatment of periodontitis

The study is devoted to the study of the effect of water ozonated with the help of short-wave ultraviolet radiation, used in the removal of dental plaque and hydromassage of the gums, on the microbiota of periodontal pockets.Examination and treatment of 102 patients aged 35–55 years with a diagnosis of chronic generalized periodontitis of moderate severity was carried out. The results of microbiological studies indicate the high efficiency of the removal of dental plaque using water ozonated with short-wave ultraviolet radiation and hydromassage of the gums in the complex treatment of chronic generalized periodontitis of moderate severity. The study of the microbiota of periodontal pockets after the use of ozonized water showed a significant decrease in the frequency of detection of representatives of anaerobic periodontopathogens, with an increase in the sowing of species of stabilizing microbiota.

Aging of 3D Printed Polymers under Sterilizing UV-C Radiation.

In the context of the COVID-19 pandemic, shortwave ultraviolet radiation with wavelengths between 200 nm and 280 nm (UV-C) is seeing increased usage in the sterilization of medical equipment, appliances, and spaces due to its antimicrobial effect. During the first weeks of the pandemic, healthcare facilities experienced a shortage of personal protective equipment. This led to hospital technicians, private companies, and even members of the public to resort to 3D printing in order to produce fast, on-demand resources. This paper analyzes the effect of accelerated aging through prolonged exposure to UV-C on mechanical properties of parts 3D printed by material extrusion (MEX) from common polymers, such as polylactic acid (PLA) and polyethylene terephthalate-glycol (PETG). Samples 3D printed from these materials went through a 24-h UV-C exposure aging cycle and were then tested versus a control group for changes in mechanical properties. Both tensile and compressive strength were determined, as well as changes in material creep properties. Prolonged UV-C exposure reduced the mechanical properties of PLA by 6–8% and of PETG by over 30%. These findings are of practical importance for those interested in producing functional MEX parts intended to be sterilized using UV-C. Scanning electron microscopy (SEM) was performed in order to assess any changes in material structure.

Human milk: processing and conservation – a review

Human milk has a balance of nutrients and bioactive compounds, and it must be the exclusive food source during the first six months of the infant's life. In cases where the woman is unable to breastfeed, due to hypogalactia or pre-existing disease, the use of donated human milk, available in human milk banks, is recommended. Currently, in the human milk banks the processing applied for greater conservation is Holder pasteurization. Therefore, the objective of this work is to perform a search in the literature about new possible treatments to be applied to human milk, and its influence on its physical-chemical composition; and in this sense, the studied processes were: Holder pasteurization, lyophilization, spray-drying, high hydrostatic pressure, high temperature and short time, and short wave ultraviolet irradiation. For that, a search was performed in databases, and 126 articles were selected to carry out this review according to the keywords used. It was observed that the studied treatments can be applied for the processing and conservation of human milk, once it was applied in matrices with similar composition.

The effect of ultraviolet diode radiation on the growth rate of Alternaria colonies

Phytopathogenic micromycetes induce dangerous crop diseases. Traditionally, fungicides have been used to prevent these diseases. In recent years, environmentally friendly non-chemical methods for combating fungal infections have been developed. In particular, ultraviolet (UV) treatment of various wavelengths, intensities and origins has been shown to be effective. In this work, we have analysed the effect of diode low-intensity shortwave UV radiation (UV-C) on the growth and potential viability of the mycelium of Alternaria radicina and A. alternata, the pathogens of important crops. It was shown that irradiation by UV-C diode inhibited growth of Alternaria species at the early stages of development. This effect was high in the first 3 d after UV exposure; however, after 5 d after irradiation, the growth of pathogenic fungi fully restored, suggesting that UV can be only used for partial removal of Alternaria. It was found that A. alternata is less sensitive to diode UV irradiation. The obtained results indicate that the Alternaria micromycetes, particularly, A. alternata, containing high melanin levels, are resistant to low-intensity UV-C diode irradiation.

Short Wave Ultraviolet Light (UV-C) Effectiveness in the Inactivation of Bacterial Spores Inoculated in Turbid Suspensions and in Cloudy Apple Juice

Liquid foods might present interferences in their optical properties that can reduce the effectiveness of short-wave ultraviolet radiation (UV-C) treatments used for sterilization purposes. The effect of turbidity as UV-C interference factor against the inactivation of bacterial spores was analysed by using phosphate-buffered saline solutions (PBS) of different turbidity values (2000, 2500, and 3000 NTU) which were adjusted with the addition of apple fibre. These suspensions were inoculated with spores of Bacillus subtilis and Alicyclobacillus acidoterrestris. While higher UV-C doses increased the inactivation rates of spores, these were reduced when turbidity values increased; a dose of 28.7 J/mL allowed inactivation rates of B. subtilis spores of 3.96 Log in a 2000-NTU suspension compared with 2.81 Log achieved in the 3000-NTU one. Spores of B. subtilis were more UV-C-resistant than A. acidoterrestris. Cloudy apple juice inoculated with A. acidoterrestris spores was processed by UV-C at different doses in a single pass and with recirculation of the matrix through the reactor. Inactivation increased significantly with recirculation, surpassing 5 Log after 125 J/mL compared with 0.13 Log inactivation after a single-pass treatment at the same UV-C dose. UV-C treatments with recirculation affected the optical properties (absorption coefficient at 254 nm and turbidity) of juice and increased browning as UV-C doses became higher.

Combined effects of ultra-high pressure homogenization and short-wave ultraviolet radiation on the properties of cloudy apple juice

This work addresses the physicochemical, enzymatic and sensory changes in cloudy apple juice treated by ultra-high pressure homogenization (UHPH) and short-wave ultraviolet radiation (UV–C) applied at 20 °C. Those technologies were applied in single and combined treatments at different UHPH pressures (200–300 MPa) and UV-C doses (14.3–27.8 J/mL). UV-C treatments could not effectively inactivate enzymes, but treatments at 300-MPa UHPH reduced pectin methylesterase activity to a 24.6%, and polyphenol oxidase activity was not detected. Those samples presented a higher antioxidant capacity (283% measured by FRAP, and 286.4% by DPPH) than in non-treated juice, and after a combination with 28.7 J/mL of UV-C the polyphenols content augmented to 277.6%. Sensory evaluation revealed that UHPH at 300 MPa and UV-C at 21.5 J/mL significantly changed perceptible odour and overall flavour of cloudy apple juice, while treatments at 200 MPa didn't produce any significant changes in the different parameters. The results obtained in this study give a promising perspective of what a combination of both technologies can bring about in terms of obtaining stabilized fruit juices with improved antioxidant activity and polyphenol availability.

Optimizational orange emitting behavior of Li2Na1-xBP2O8:xPr solid solutions under an short-wave ultraviolet irradiation

Li2Na1-xBP2O8:xPr3+ (x = 0–0.04 mol) solid solutions were synthesized by a high temperature sintering process. The crystalline phase, microstructure, chemical state of constituent element, and luminescence were performed. Excited by the short-wave ultraviolet light originating from 4f2 → 4f15d1 of Pr3+, an orange emitting behavior (3P0 → 3F3 of Pr3+, 673 nm) was proposed. The relationship between the doping Pr3+ concentration and the orange emitting behavior was analyzed. Concentration quenching occurs due to electric dipole – dipole interaction. All work revealed that the title solid solution is a selected material for solid state illumination and lighting.

Relationship between the COVID-19 Outbreak and Temperature, Humidity, and Solar Radiation Across China

Novel coronavirus (COVID-19)-infected pneumonia appeared in Wuhan City, Hubei Province, China in early December 2019. Since then, COVID-19 cases have appeared in many provinces in China. While the incidence of many infectious diseases, including that of coronavirus, shows seasonal patterns, our understanding of this phenomenon is still incomplete. We used fifth-generation re-analysis data (ERA-5) released by the European Center for Long-Term Weather Forecast (ECMWF), counted the cumulatively confirmed cases in each province from January and February 2020, and analyzed the data after the outbreak of COVID-19 from early December in China. The relationship between the number of cases and the monthly average temperature, specific humidity, and downward short-wave ultraviolet (UV) radiation in each province of China, showed that COVID-19 cases were concentrated in the provinces with temperatures in range of 0–10 °C. The downward short-wave UV radiation in these areas was below 1.5 MJ·m-2·d, while the specific humidity range was between 2–6 g/kg. These meteorological and environmental factors may be the most suitable environments for potential transmission of the virus. A further understanding of the environmental factors that are prevalent in the development of COVID-19 will help predict the potential risks of the global spread of this disease, and provide support for the prevention and surveillance of countries around the world.

Natural aeolian dust particles have no substantial effect on atmospheric polycyclic aromatic hydrocarbons (PAHs): A laboratory study based on naphthalene

Natural aeolian dust (AD) particles are potential carriers of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. The heterogeneous interaction between them may lead to worsened air quality and enhanced cytotoxicity and carcinogenicity of ambient particulates in downwind areas, and this topic requires in-depth exploration. In this study, AD samples were collected from four Asian dust sources, and their physical properties and compositions were determined, showing great regional differences. The physical and chemical interactions of different AD particles with naphthalene (Nap; model PAH) were observed in aqueous systems. The results showed that AD particles from the Loess Plateau had weak adsorption to Nap, which was fitted by the Langmuir isotherm. There was no obvious adsorption to Nap found for the other three AD samples. This difference seemed to depend mainly on the specific surface area and/or the total pore volume. In addition, the Nap in the aqueous solution did not undergo chemical reactions under dark conditions and longwave ultraviolet (UV) radiation but degraded under shortwave UV radiation, and 2-formylcinnamaldehyde and 1,4-naphthoquinone were the first-generated products. The degradation of Nap in the aqueous solution was probably initiated by photoionization, and the reaction rate constant (between 1.44 × 10−4 min−1 and 8.55 × 10−4 min−1) was much lower than that of Nap with hydroxyl radicals. Instead of inducing or promoting the chemical change in Nap, the AD particles slowed photodegradation due to the extinction of radiation. Therefore, it is inferred that natural AD particles have no substantial effect on the transportation and transformation of PAHs in the atmosphere.

Mechanisms of Generation of Relief High-Frequency Holographic Structures on Dichromated Gelatin Exposed to Shortwave UV Radiation

The application of two types of alternative action on gelatin in the layers of dichromated gelatin (DCG) was considered: structuring with the use of selective light tanning by the radiation of a He–Cd laser ( $$\lambda=440$$ nm) and destruction performed by exposure of layers to short-wave ultraviolet radiation ( $$\lambda<270$$ nm). The crucial role of UV exposure of samples in generating high-frequency relief-phase gratings with diffraction efficiency higher than 50 $$\%$$ on DCG layers thinner than 2 $$\mu$$ m is shown. It is noted that the application of traditional treatment methods of DCG layers leads to smoothened relief due to action of surface tension forces at high spatial frequencies. In addition, significant broadening of the domain of registered spatial frequencies (up to 1500 mm $${}^{-1}$$ ) for recording relief holographic gratings is achieved by applying the modified technique of gelatin treatment based on reduced time of water procedures and by using the isopropanol baths for quick layer dehydration.