Ultraviolet Light Intensity Research Articles

The organic coating unit, an all-in-one system for reproducible generation of secondary organic matter aerosol

We report on a novel automated oxidation flow reactor to generate a wide variety of organic aerosol samples. The instrument is equipped with a humidifier, a dosing system for volatile organic precursors and an oxidation flow reactor (OFR) for generation of secondary organic matter (SOM). The instrument, known as organic coating unit (OCU), can produce homogeneously nucleated SOM particles or, used in combination with a standard combustion generator (e.g., a diffusion flame soot generator or any other seed particle), particles coated with a controlled amount of SOM. The physical and chemical properties of the generated particles can be controlled in a simple manner by selecting through a touch-screen target values for parameters, such as organic gaseous precursor concentration, humidity, and UV (ultraviolet) light intensity. Parameters and measured quantities are automatically stored in text files for easy export and analysis. Furthermore, we provide stable operation conditions and characterize the physicochemical properties of the generated aerosols with an array of methods, including transmission electron microscopy (TEM), thermal-optical analysis and liquid chromatography coupled with mass spectrometry (LC-MS). This all-in-one instrument is robust, compact, portable, and user-friendly, making it ideal for laboratory or field-based aerosol studies.

Ultraviolet‐Sensitive OLED with Tunable Wavelength and Intensity by Integrated ZnO Nanowires Schottky Junction

AbstractOrganic light‐emitting diode (OLED) displays are one of the dominant flat panel display technologies. Here, a novel ultraviolet (UV)‐sensitive OLED (USO) is reported, which emits visible light with adjustable wavelength and brightness according to the intensity of the incident UV light. The USO employs zinc oxide nanowires (ZnO NWs) with Schottky junctions to control current and engages exciplex‐emitting OLED to emit light according to the incident UV light. As the UV light intensity increases from 0.09 to 8.15 mW cm−2, USO emits light with a peak wavelength that ranges from 595 to 525 nm, a color coordinate from (0.458, 0.485) to (0.339, 0.555), and a light intensity that is anywhere from 97 to 6915 cd m−2. The USO has a fast photoresponse characteristic due to the effect of the Schottky barrier introduced by the close contact of the ZnO NWs and gold electrodes. The luminescence color of the USO changes from dark orange to harsh green because of the exciplexes’ different formation ratios under differing UV intensities. As a result of the USO taking advantage of the Schottky barrier and exciplex, the realization of many innovative applications in optoelectronic devices is possible.

Microwave-ultraviolet co-catalysis of chlorite-oxygen mixture for highly cost-efficient simultaneous removal of NO and Hg0

Developing novel advanced oxidation process (AOP) to simultaneously remove various air pollutants has received considerable attention in past years. This paper develops a novel cost-efficient AOP method of microwave (MW) induced ultraviolet (UV) co-catalyzing trace NaClO2-O2 to simultaneously remove NO and Hg0, the obtained removal efficiencies are 91.4% and 99%, respectively, under a molar ratio of NaClO2 to NO/Hg0 of 1.3:1. The effects of some key parameters including NaClO2 dosage, reaction temperature, input MW power, UV light intensity, concentrations of O2, NO and SO2, and gas flow on the removal of NO and Hg0 were studied. ESR and radical quenching tests demonstrated that superoxide radical (•O2–), hydroxyl radical (•OH), oxychloride radical (ClO•), chlorine dioxide (ClO2) and ozone (O3) were the major reactive species. With the assistance of Na2SO3 absorber, the produced NO2 was efficiently absorbed and controlled to below 5 mg/m3. IC and AFS analyses revealed the distribution of removal products: (i) 51% of NO3– and 85% of Hg2+ were preserved in the MW-UVEL reactor; (ii) the other NO3– and Hg2+ as well as the NO2– generated via the redox reaction between NO2 and SO32- were totally absorbed by the Na2SO3 solution. Mechanism analyses elucidated that the NO removal process was attributed to the radical-induced oxidation reaction, and the contribution order was •O2– > •OH > ClO•/ClO2 > O3; however, the Hg0 removal process was mainly determined by the produced NO2/NO3–, and UV light coupled with other active species contributed less 40%.

Combined effects of high relative humidity and ultraviolet irradiation: Enhancing the production of gaseous NO2 from the photolysis of NH4NO3

Free radicals and nitrogen-containing species produced by nitrate photolysis can affect various atmospheric chemical processes, and thereby the photochemical behavior of atmospheric nitrate aerosols has been attracting much attention. However, the photolysis mechanism of NH4NO3 and its products under different atmospheric conditions remain unclear. In this study, the effects of relative humidity (RH), pH, NH3, ultraviolet (UV) light intensity and halogen ions (Cl−, Br− and I−) on the photolysis of particulate NH4NO3 have been investigated through a flow tube reactor. The results show that RH can significantly enhance the production of gaseous NO2 from the photolysis of NH4NO3 when RH is higher than its deliquescence RH, but almost no NO2 is generated under dry conditions. Under high RH and UV light, the main product of NH4NO3 photolysis is NO2, rather than NO and HONO, and another main species HNO3 which mainly comes from the hydrolysis of product NO2 in the gas path was detected. Almost no NO2 and HNO3 are produced under high RH without UV light or low RH with UV light, showing the combined effect of high RH and UV irradiation on the photolysis of NH4NO3. In addition, under high RH, the lower the pH and the stronger the light intensity, the higher the NO2 production. Furthermore, surprising yields of NO and HONO are detected in the presence of halogen ions, especially in the presence of I−, indicating the important role of halogen ion in the nitrate photolysis. These results provide new insights into the photolysis of atmospheric nitrate aerosols, and may contribute to elucidating the formation and migration of atmospheric nitrate aerosols and the potential mechanisms of the occurrence and evolution of atmospheric pollution and ozone pollution.

Patterned assembly of silicon nanoparticles via femtosecond laser bubble printing for high-performance photodetector applications

With the ever-growing development for nanomaterials, the integration of nanomaterials into electronic devices and sensors requires flexible and efficient selective patterning deposition of the nanomaterials. However, existing patterning techniques of these nanomaterials is limited in practical applications due to the use of templates and tedious preparation process. Here, a facile femtosecond laser bubble printing (FsLBP) technique without mask and tedious preparation process that integrates patterning, assembly, and deposition of nanomaterials is presented. Benefiting from the advantages of this processing technology, arbitrarily patterned assembled silicon (Si) nanoparticles were successfully prepared. In addition, the effect of viscosity and surface tension of the solution in the process of FsLDW on the deposited Si nanoparticles is explored. Owing to the rough and porous structure of the assembled microwires, the microwires have a high-efficiency light trapping ability with an average reflectivity of 2% for visible light and the photodetector based on porous Si microwires exhibits a responsivity of 231 A/W under the irradiation of 365 nm ultraviolet (UV) light. Finally, a device for real-time monitoring of ultraviolet light intensity was obtained, which demonstrate the potential application of the ultrafast laser fabrication method in patterned assembly of nanomaterials.

Direct Visualization of UV-Light on Polymer Composite Films Consisting of Light Emitting Organic Micro Rods and Polydimethylsiloxane.

We experimentally demonstrate the direct visualization of ultraviolet (UV) light using flexible polymer composite films consisting of crystalline organic tris-(8-hydroxyquinoline) aluminum (Alq3) micro-rods and polydimethylsiloxane (PDMS). The representative organic mono-molecule Alq3, which is a core material of organic light-emitting diodes, was used to detect light in the invisible UV region and visualize photoluminescence (PL). Alq3 shows absorption in the UV region and light-emitting characteristics in the green region, making it an optimal material for UV visualization because of its large Stokes transition. Crystalline Alq3 micro-rods were fabricated in a deionized water solution through a sequential process of reprecipitation and self-assembly. Highly bright photoluminescence was observed on the highly crystalline Alq3 micro-rods under UV light excitation, indicating that the crystalline structures of Alq3 molecules affect the visible emission decay of excitons. The Alq3 micro-rods were manufactured as flexible polymer composite films using a PDMS solution to observe UV photodetector characteristics according to UV intensity, and it was confirmed that the intensity of the fine UV light reaching the earth’s surface can be visualized by making use of this UV photodetector.

Vol4 num4-21 Molds manufactured with 3D printing for UV curing using Light-RTM

Ultraviolet (UV) curing is a competitive process both in terms of cycle time and energy consumption. However, it is limited to open mold processes where the material can be irradiated directly with UV light. There is a variant of RTM, Light-RTM, in which the flexible semi-mold can be manufactured with transparent/translucent materials and in small thicknesses. In the present work the feasibility of performing the semi-mold by stereolithography (SLA) has been studied. The photocurable resin selected for SLA was the high temperature resin from FormLabs. First, the UV light transmission has been characterized according to the thickness of the semi-mold wall, in which the mold thickness has been determined in 3 mm. The ageing process has also been analysed, characterising the variation of the transmitted spectrum as a function of the irradiation time for a 3 mm thick plate, where a loss of light transmission of approximately 13 % has been observed for 15 minutes of exposure time. Finally, a semi-mold has been manufactured for the manufacture by Light-RTM of a 150 mm × 40 mm × 2 mm flat plate. During the process, there were no problems of vacuum loss and the intensity of UV light that passes through the semi-mold allows curing the photocurable matrix of the composite material.

Line-shape broadening of an autoionizing state in helium at high XUV intensity

We study the interaction of intense extreme ultraviolet (XUV) light with the 2s2p doubly excited state in helium. In addition to previously understood energy-level and phase shifts, high XUV intensities may lead to other absorption-line-shape distortions. Here, we report on experimental transient-absorption spectroscopy results on the 2s2p line-width modification in helium in intense stochastic XUV fields. A few-level-model simulation is realized to investigate the origins of this effect. We find that the line-shape broadening is connected to the strong coupling of the ground state to the 2s2p doubly excited state which is embedded in the ionization continuum. As the broadening takes place for intensities lower than for other strong-coupling processes, e.g. observed asymmetry changes of the absorption profile, this signature can be identified already in an intermediate intensity regime. These findings are in general relevant for resonant inner-shell transitions in nonlinear experiments with XUV and x-ray photon energies at high intensity.

Development and analysis of a high refractive index liquid phase Si3N4 slurry for mask stereolithography

Ceramic mask stereolithography additive manufacturing technology has the abilities of fast and accurate printing complex and personalized ceramic parts. However, since the ultraviolet light is strongly blocked by the ceramic particles in the slurry during exposure, the slurry with high refractive index ceramic particles has low cure depth, and serious light scattering. This investigation developed a curable silicon nitride slurry with a high refractive index liquid phase, which significantly reduced the refractive index difference between the liquid phase and the silicon nitride ceramic particles. The high refractive index acrylate monomer and solvent were chosen to increase the cure depth while ensuring the curing accuracy. Compared with the slurry whose liquid phase was pure HDDA, the addition of OPPEA and ACMO in the liquid phase showed a better refractive index increasing effect and the strongest cure depth and dimensional accuracy improvement. POE was verified as a suitable non-reactive high refractive solvent. The composition of 20 wt% OPPEA, 10 wt% ACMO, 40 wt% HDDA, and 30 wt% POE were optimized as the high refractive index liquid phase for 40 vol% solid phase silicon nitride slurry. A finite element analysis model of silicon nitride slurry was established, and the distribution of ultraviolet light intensity in silicon nitride slurry with high refractive index liquid phase was numerically simulated.

Comparative Study on Sensing Properties of Fiber-Coupled Microbottle Resonators With Polymer Materials

Optical whispering gallery mode (WGM) microbottle resonators based on a variety of polymer materials (benzocyclobutene (BCB), UV88 (Relentless, China) and Loctite3525 (HenKel, Germany)) were fabricated and investigated experimentally. The polymer materials were spin-coated onto the fiber and cured by ultraviolet (UV) light followed by heating to form a microbottle structure of different shapes and diameters. The WGMs were excited by tapered fiber, and the spectral characteristics of all realized microbottle cavities were evaluated, such as quality factor (Q > 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> ), free spectral range and polarization mode (TE and TM). The temperature and refractive index (RI) sensing performance are analyzed and Q-factor changes during the sensing process. In addition, a newly application of UV light intensity sensing for the polymer microbottle resonators was also demonstrated firstly. According to the experimental results that the microbottle resonator of BCB displays good UV light intensity sensitivity (0.0011 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nm</i> /( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )) and figure of merit (FOM) (0.0122/( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mw/cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> )). This sensor is a simple structure, low-cost material, robust performance, and possesses attractive application prospects in sensing and optical devices.

A self-powered β-Ga2O3/CsCu2I3 heterojunction photodiode responding to deep ultraviolet irradiation

In this paper, a lead-free halide perovskite CsCu2I3 film with high stability was prepared by the anti-solvent assisted crystallization method. Then, we coupled it with Ga2O3 to prepare a corresponding heterojunction deep ultraviolet (UV) photodetector. After testing, we concluded that the photodetector is sensitive to 254 nm UV light. The photodetector has good reproducibility, and has an ultra-high photo-to-dark current ratio (PDCR) of more than 105. In addition, under a bias of 10 V and an illuminated intensity of 200 μW/cm2, the responsivity (R) and specific detectivity (D*) reached 20 mA/W and 107 cm Hz1/2 W−1 (Jones), and the external quantum efficiency (EQE) is 10%. Meanwhile, the prepared photodetector could operate at zero bias, i.e., self-powered operation, along with a photocurrent of about 1 nA under illumination with UV light intensity of 200 μW/cm2.

Investigation of carbon dioxide photoreduction process in a laboratory-scale photoreactor by computational fluid dynamic and reaction kinetic modeling

The production of solar fuels via the photoreduction of carbon dioxide to methane by titanium oxide is a promising process to control greenhouse gas emissions and provide alternative renewable fuels. Although several reaction mechanisms have been proposed, the detailed steps are still ambiguous, and the limiting factors are not well defined. To improve our understanding of the mechanisms of carbon dioxide photoreduction, a multi-physics model was developed using COMSOL. The novelty of this work is the computational fluid dynamic model combined with the novel carbon dioxide photoreduction intrinsic reaction kinetic model, which was built based on three-steps, namely gas adsorption, surface reactions and desorption, while the ultraviolet light intensity distribution was simulated by the Gaussian distribution model and Beer-Lambert model. The carbon dioxide photoreduction process conducted in a laboratory-scale reactor under different carbon dioxide and water moisture partial pressures was then modeled based on the intrinsic kinetic model. It was found that the simulation results for methane, carbon monoxide and hydrogen yield match the experiments in the concentration range of 10−4 mol·m−3 at the low carbon dioxide and water moisture partial pressure. Finally, the factors of adsorption site concentration, adsorption equilibrium constant, ultraviolet light intensity and temperature were evaluated.

Dynamic full-color tunability of high-performance smart windows utilizing absorption-emission effect

The commercialization of vanadium dioxide (VO2) as energy-saving products currently suffers from non-adjustable visible transmittance, resulting in inferior solar regulation efficiency (ΔTsol<15%), low luminous transmittance (Tlum<60%), and monotonous “brown-yellowish” appearance. Here, a concept of exploiting all solar spectra for modifying its inherent color as well as synchronously enhancing ΔTsol has been accomplished on an ultraviolet (UV)-responsive photochromism/VO2 composite film. This structure by itself exhibits low Tlum even in a mild UV environment. We further introduce a fluorescence layer on top of photochromic layer to form a three-layer fluorescence/photochromism/VO2 structure (FPV), which could realize the conversion from UV to visible lights there to block most of the UV light and enhance the Tlum. Such FPV films that are optically manipulated display highly transparent before coloration and, further, can dynamically change to other colors according to different intensities of UV light. Moreover, the FPV films result in an increased solar energy regulation ability up to 20.1%, while maintaining 72.6% visible luminous transmittance. These results break shackles of inherent color and exceed the theoretical limit for traditional thermochromic VO2-smart windows, making them easily acceptable for users.

Photothermal steam reforming: A novel method for tar elimination in biomass gasification

Tar elimination is the bottleneck which hinders the industrial application of gasification due to the risks of corrosion and blockage in downstream components. Tar production decreases the energy efficiency of gasification systems. The steam reforming is attractive for tar treatment, but the high reaction temperature limits its applications. Photothermal catalysis has the potential to decompose organic pollutants, and it is expected to improve tar removal and reduce the reaction temperature. So, the photothermal steam reforming of toluene was performed to evaluate the toluene conversion. The effects of the toluene concentration, the temperature, the steam to carbon ratio, and the ultraviolet light intensity were investigated. The results showed that, compared with the thermal steam reforming, the photothermal steam reforming could significantly improve the conversion of toluene and promote the formation of gaseous products, especially H2. At 600 °C, the conversion of toluene in the photothermal steam reforming was 90.1%, which was 16.3% higher than that in the thermal steam reforming. Moreover, the mechanisms of the photothermal steam reforming were revealed. The introduction of the ultraviolet irradiation could strongly promote the toluene decomposition and alter the reaction pathways. The carbon deposition and agglomeration of the catalyst were inhibited in photothermal steam reforming. Meanwhile, the toluene removal performance and the energy consumption were compared in photothermal and thermal steam reforming. The potential applications of photothermal catalytic tar removal were also described. These findings proposed a novel approach for low-cost but high-efficiency biomass tar removal, thus promoting the clean utilization of biomass energy.

Evaluation of the influence of UV radiation and sodium hypochlorite on the shelf life of strawberries

It is common to combine methods to increase the shelf life of a raw material or product. In this study, we sought to understand the relationship between ultraviolet (UV) radiation and sodium hypochlorite (NaOCl) in attenuating the proliferation of fungus and its deteriorating effect on strawberries. The UV light intensities of 125, 250 and 400 Watts (W) and sodium hypochlorite were tested in concentrations 0.5, 1.0 and 1.5 ppm. The strawberries were sprayed with sodium hypochlorite solutions and then kept for 1 minute in UV light chambers, to then be stored in transparent sealed plastic containers. The strawberry samples with the longest life were those that were sprayed with 0.5 and 1.0 ppm sodium hypochlorite solution combined with exposure to 125 W UV light. These samples had a shelf-life extension of about five days compared to strawberries without any kind of treatment. Thus, it is possible to state that this combination is efficient in cleaning the fruit without causing damage.

Intense quasi-monochromatic resonant harmonic generation in the multiphoton ionization regime

Resonant high-order harmonics, which result in quasi-monochromatic extreme ultraviolet light with coherent intensity enhancement involving autoionizing resonances, have been demonstrated from laser-ablated plumes in the tunnel-ionization regime. Here, we demonstrate resonant harmonics in the previously unexplored multiphoton-ionization regime. We demonstrate an intense resonant harmonic from gallium with an intensity enhancement ratio of 714 relative to the neighboring harmonics, achieved without the need for extreme ultraviolet filtering methods, thus preventing a typical photon flux loss of more than 70%. Three-dimensional time-dependent Schrödinger equation calculations reveal that this increase in the enhancement ratio is due to the low electron wave packet spreading in the multiphoton-ionization regime. These results reveal a method for increasing the intensity and monochromaticity of intense multimicrojoule femtosecond extreme ultraviolet light and will also facilitate understanding of the involvement of autoionizing resonances in generating resonant harmonics in the multiphoton-ionization regime.

Antifungal activity of Zataria multiflora Boiss. essential oils and changes in volatile compound composition under abiotic stress conditions

There is an increasing need for natural compounds for pest control and food preservation in agriculture, food and dairy industries. To satisfy this need, essential oils (EOs) from aromatic plants can serve as flavors, food preservatives and ecofriendly pesticides. This study investigated the potential of different EOs from field-collected leaves of fourteen Zataria multiflora Boiss. populations representing three different chemotypes (carvacrol, thymol and linalool) to inhibit a broad spectrum of fungal pathogens important in food industry and agriculture and the relationship between total leaf elements concentration and EOs compounds. Furthermore, a greenhouse experiment was performed to elucidate the effects of heat stress (33 °C vs. 20 °C), drought stress (50 % reduced irrigation), and ultraviolet light intensity (3, 6 and 9 W m−2 UV-A radiation) on the relative content of specific volatile compounds. The results indicated that low concentrations of carvacrol and thymol, but not of linalool chemotype EOs inhibit significantly the growth of pre- and postharvest pathogens Colletotrichum lindemuthianum, Fusarium sambucinum, Fusarium culmorum, Alternaria dauci and Botrytis cinerea (thymol/carvacrol EOs: 0.8−1 μL, linalool EOs: 4 μL). The analyses revealed further significant correlations between the concentrations of mineral elements in Z. multiflora leaves and relative amounts of EO compounds and antifungal activity. Abiotic stresses, particularly heat and the interaction of drought and heat, induced changes in plants of the linalool chemotype resulting in higher relative amounts of carvacrol (22.7 % and 32.9 % vs. 1.5 %), while drought stress alone did not influence the relative amount of the main volatile compounds of Z. multiflora (carvacrol 1.7 %). Furthermore, the relative amount of linalool was slightly reduced in the linalool chemotype, when plants were subjected to high intensities of UV-A radiation (33.9 % vs. 44.6 %), whilst the relative amount of carvacrol was slightly increased (20.1 % vs. 9%). Moreover, the main volatile compounds of plants from the carvacrol chemotype did not change in response to abiotic stresses. Understanding the effect of environmental conditions on aromatic plant populations and chemotype development helps agriculture and food industry fully exploiting the potential of aromatic plants as a source of natural sustainable fungicides or insecticides.

Preparation of cholesteric polymer networks with broadband reflection memory effect

ABSTRACT In this study, polymer network is prepared by broadband reflective cholesteric liquid crystal (CLC) film with washing out method. By the method of photoinduced molecular diffusion, the CLC film is prepared by adding different concentrations of ultraviolet (UV) absorption dyes into the LC system and irradiated with a series of UV light intensities for different times. The selective reflection property and broadband reflection memory effect of the polymer network are proved, and the response mechanism is given. By refilling the polymer network with different LCs, reflective bands with different central wavelengths and bandwidths can be obtained. It is confirmed that different fillers can recurrence the initial reflection bandwidth of CLCs in different degrees. These results may provide a new idea for total reflection CLC films.

Health &amp; Environmental Impact of Ultraviolet Radiation Exposure used in Currency Sanitizer

Many of the ultraviolet (UV) sources used emit high intensities of UV light, capable of producing painful eye and skin burns. This paper provides information about the hazards associated with UV exposure and the safety precautions to take when working with these sources. Ultraviolet (UV) disinfection technology has existed for many years, but chemicals are still very prominent in disinfection applications today. UV disinfection does, however, provide many benefits over chemical options. It cannot be overdosed, and does not produce by-products, toxins, or volatile organic compound (VOC) emissions. It does not require the storage of hazardous materials and will not affect smell or taste in water and food disinfection applications. In addition, UV light is known to kill more waterborne microbes than chlorination. UV-C currency sanitizer is a fluid less device which can be used to perform the disinfection of various bacteria and viruses, it is based on UV-C light technology. It provides a portable ultraviolet disinfecting device for currency notes which comprises an acrylic case. The light is arranged in the top and bottom and inner layer coated with aluminum foil to increase the utilization of light rays.

Image feature analysis for magnetic particle inspection of forging defects

Magnetic particle inspection is typically used to detect the magnetic leakage caused by defects. This method is mainly used to detect the surface and subsurface defects of ferromagnetic materials. The conventional detection method involves inspectors performing visual inspection under high-power ultraviolet light. However, the intense ultraviolet light can easily damage the eyes of the inspectors. Furthermore, the aforementioned process is not only time consuming but also susceptible to human errors. Therefore, this study developed an automated optical inspection system to perform magnetic particle inspection. Analysis of several image features revealed that a contour compactness between four and five can be used to distinguish defective and non-defective features effectively. The defect identification ability obtained with several input combinations of image features for neural networks was analyzed. The results revealed that a high identification ability can be achieved for defective features when the input combination of area, mean width, and compactness is used.