High Intensity Ultraviolet Light Research Articles

The Electronic Impact of Light-Induced Degradation in CsPbBr3 Perovskite Nanocrystals at Gold Interfaces.

The understanding of the interfacial properties in perovskite devices under irradiation is crucial for their engineering. In this study we show how the electronic structure of the interface between CsPbBr3 perovskite nanocrystals (PNCs) and Au is affected by irradiation of X-rays, near-infrared (NIR), and ultraviolet (UV) light. The effects of X-ray and light exposure could be differentiated by employing low-dose X-ray photoelectron spectroscopy (XPS). Apart from the common degradation product of metallic lead (Pb0), a new intermediate component (Pbint) was identified in the Pb 4f XPS spectra after exposure to high intensity X-rays or UV light. The Pbint component is determined to be monolayer metallic Pb on-top of the Au substrate from underpotential deposition (UPD) of Pb induced from the breaking of the perovskite structure allowing for migration of Pb2+.

UV photocatalytic activity of titanium dioxide (TiO2) surface contaminated with bacterial biofilm: Implications for photo-restoration of osteoconductivity

Ultraviolet (UV) light-mediated activation of titanium dioxide (TiO2) cleans the surface microenvironment through photocatalysis, but it is unknown whether this occurs when TiO2 surfaces is contaminated with bacterial biofilms. We therefore formed bacterial biofilms on TiO2 surfaces through culture with oral microorganisms from rats, which were subsequently exposed to high-intensity broadband UV light for 12 min. Osteoblast attachment, proliferation, and phenotypes were significantly compromised on biofilm-contaminated TiO2 surfaces, but UV treatment restored these biological activities to native baselines of TiO2 surfaces. The strength of bone-implant integration was 18.3 N for original implants, 1.5 N for biofilm-contaminated implants, and 30.5 N for biofilm-contaminated/UV-treated implants in a rat femur model after two weeks of healing. Histologically, there was limited, fragmented bone formation around biofilm-contaminated implants separated by thick fibrous tissue, while biofilm-contaminated/UV-treated implants induced robust bone formation with extensive direct bone-implant contact. Lipopolysaccharide (LPS) deposited on biofilm-contaminated TiO2 surfaces which was decomposed and removed by UV treatment. Notably, biofilm-contaminated TiO2 surfaces became superhydrophilic after UV treatment despite the persistence of carbon and nitrogen compounds, and UV treatment significantly restored the surface morphology of the innate titanium on the biofilm-contaminated TiO2 surfaces. In summary, bacterial biofilm severely compromised titanium osteoconductivity, but treatment of contaminated titanium with UV light significantly restored osteoconductivity through substantially decreased accumulation of carbon, nitrogen, and LPS; the re-emergence of micro-topography; and the induction of superhydrophilicity, paving the way for photoenergy-mediated debridement of TiO2 surface for clinical benefit.

Photoresponsive wood composite for photoluminescence and ultraviolet absorption

Transparent wood has received much attention for construction applications due to its good mechanical properties, optical properties, and ideal thermal insulation. Since ultraviolet light is one of the most significant environmental stress agents for human skin, ultraviolet absorbing transparent wood composite will be highly desirable. Herein, ultraviolet absorbing photoluminescence wood composite was obtained by immersing wood templates into photoresponsive polymer. The injected substances were well polymerized in wood cell lumen, resulting in good dimensional stability, mechanical properties, and thermal stability. In addition, the sample displayed a good photoluminescence process, during which it could intercept and absorb high-intensity ultraviolet light. The unique properties of the ultraviolet absorbing photoluminescence wood composite could potentially be applied in building, furniture, windows, sensor, and security materials.

Photosensitive Formulation for Additive Manufacturing-3D Printing

UV curing is a photochemical process in which high-intensity ultraviolet light is used to instantly cure or ��dry�� coatings, inks, adhesives and thin film technology. It has been around as a coating for wood, paper and as a clear coating via photolithography process on printed circuit boards PCBs or integrated circuit boards ICBs for years. It is fast becoming one of the most popular techniques in the paint and coatings industry. Most of the formulation use multifunctional acrylate monomers or oligomers or a mixture of them that crosslink under exposure to UV/EB radiations in a free radical process. We briefly present the advantages of EB vs. UV. A new type of formulation based on multifuctional monomer of dicyclopentadiene epoxy derivative with additional diluent as co-reactive solvent will be described and evaluated. This formulation differs from the acrylate one by the use of a cationic photoinitiator. The final product presents all the advantages of epoxy resins viz. better adherence, mechanical and thermal properties, compared to acrylate systems. Formulation has been optimized thanks to the differential scanning photocalorimetry DPC. This type of formulation is developed for additive digital manufacturing - 3D Printing (building layer by layer).

Multiple Phototransduction Inputs Integrate to Mediate UV Light-evoked Avoidance/Attraction Behavior in Drosophila.

Short-wavelength light guides many behaviors that are crucial for an insect's survival. In Drosophila melanogaster, short-wavelength light induces both attraction and avoidance behaviors. How light cues evoke two opposite valences of behavioral responses remains unclear. Here, we comprehensively examine the effects of (1) light intensity, (2) timing of light (duration of exposure, circadian time of day), and (3) phototransduction mechanisms processing light information that determine avoidance versus attraction behavior assayed at high spatiotemporal resolution in Drosophila. External opsin-based photoreceptors signal for attraction behavior in response to low-intensity ultraviolet (UV) light. In contrast, the cell-autonomous neuronal photoreceptors, CRYPTOCHROME (CRY) and RHODOPSIN 7 (RH7), signal avoidance responses to high-intensity UV light. In addition to binary attraction versus avoidance behavioral responses to UV light, flies show distinct clock-dependent spatial preference within a light environment coded by different light input channels.

The Effect of High-Intensity Ultraviolet Light to Elicit Microalgal Cell Lysis and Enhance Lipid Extraction.

Currently, the energy required to produce biofuel from algae is 1.38 times the energy available from the fuel. Current methods do not deliver scalable, commercially viable cell wall disruption, which creates a bottleneck on downstream processing. This is primarily due to the methods depositing energy within the water as opposed to within the algae. This study investigates ultraviolet B (UVB) as a disruption method for the green algae Chlamydomonas reinhardtii, Dunaliella salina and Micractinium inermum to enhance solvent lipid extraction. After 232 seconds of UVB exposure at 1.5 W/cm2, cultures of C. reinhardtii (culture density 0.7 mg/mL) showed 90% disruption, measured using cell counting, correlating to an energy consumption of 5.6 MJ/L algae. Small-scale laboratory tests on C. reinhardtii showed bead beating achieving 45.3 mg/L fatty acid methyl esters (FAME) and UV irradiation achieving 79.9 mg/L (lipids solvent extracted and converted to FAME for measurement). The alga M. inermum required a larger dosage of UVB due to its thicker cell wall, achieving a FAME yield of 226 mg/L, compared with 208 mg/L for bead beating. This indicates that UV disruption had a higher efficiency when used for solvent lipid extraction. This study serves as a proof of concept for UV irradiation as a method for algal cell disruption.

Impact of Cleaning Procedures on Adhesion of Living Cells to Three Abutment Materials.

To test the adhesion properties of live gingival fibroblasts to three different implant abutment materials after five different cleaning procedures. Highly polished discs of lithium disilicate (LS), zirconium dioxide (Zr), and titanium alloy (Ti) were fabricated. The specimens were cleaned by one of five different methods: steam (S), argon plasma (AP), ultrasound and disinfection (UD), ultrasound and sterilization in an autoclave (UA), or photofunctionalization with high-intensity ultraviolet light (PF). Cell detachment force (adhesion) was measured by single-cell force spectroscopy, which is a method to quantify cell adhesion at the single cell level. Data were statistically analyzed using parametric tests (analysis of variance [ANOVA], t tests). Cell detachment forces in the low nN regime were recorded in all experiments. Significant differences in cell adhesion on the different materials were found as a function of the cleaning method (P ≤ .0001). For LS abutments, no significant differences between the cleaning methods could be found (P > .05). For Zr specimens, the AP method showed the highest cell detachment forces, followed by UD, PF, S, and UA (S/UD, S/UA, S/PF, AP/UD, and UD/PF were not significantly different from each other). For Ti abutments, UD showed the highest cell detachment forces, followed by S, AP, and UA/PF (S/UD, S/UA, S/PF, AP/U, and UA/PF were not significantly different from each other). All cleaning methods provided comparable cell detachment forces for LS abutments. AP/PF or ultrasonic cleaning were the most suitable methods for strong cell adhesion on Zr. UD provided the best cell adhesion for Ti.

Impact of UV irradiation on multiwall carbon nanotubes in nanocomposites: Formation of entangled surface layer and mechanisms of release resistance

Multiwall carbon nanotubes (MWCNTs) are nanofillers used in consumer and structural polymeric products to enhance a variety of properties. Under weathering, the polymer matrix will degrade and the nanofillers may be released from the products potentially impacting ecological or human health. In this study, we investigated the degradation of a 0.72% (by mass) MWCNT/amine-cured epoxy nanocomposite irradiated with high intensity ultraviolet (UV) light at various doses, the effects of UV exposure on the surface accumulation and potential release of MWCNTs, and possible mechanisms for the release resistance of the MWCNT surface layer formed on nanocomposites by UV irradiation. Irradiated samples were characterized for chemical degradation, mass loss, surface morphological changes, and MWCNT release using a variety of analytical techniques. Under 295 nm–400 nm UV radiation up to a dose of 4865 MJ/m2, the nanocomposite matrix underwent photodegradation, resulting in formation of a dense, entangled MWCNT network structure on the surface. However, no MWCNT release was detected, even at very high UV doses, suggesting that the MWCNT surface layer formed from UV irradiation of polymer nanocomposites resist release. Four possible release resistance mechanisms of the UV-induced MWCNT surface layer are presented and discussed.

High-performance, in-plane switching liquid crystal device utilizing an optically isotropic liquid crystal blend of nanostructured liquid crystal droplets in a polymer matrix

A light scatter-free, transparent, thermally stable, optically isotropic liquid crystal mixture was achieved among three different mixtures of liquid crystal E7: Norland Optical Adhesive 65 with concentrations 30:70, 40:60, and 50:50wt%. The 50:50wt% mixture exhibited the best performed optically isotropic state when exposed to ultraviolet light of intensity 150mW/cm2 for droplet formation. The high intensity ultraviolet light curing process induces nano-sized liquid crystal droplets in the polymer matrix of average droplet size 218nm, characterized by scanning electron microscope. The analyzed result shows an excellent contrast ratio (CR) equal to 1574 at the normal direction and a high CR at a wide viewing angle. The magnitude of Kerr constant in these nano-sized PDLC was ~7.36×10−10mV−2, which was more than ~330 times that of a conventional Kerr material such as nitrobenzene. Unprecedented fast rising and falling times of approximately 385µs and 1.1ms, respectively, were achieved for the device. This high-performance material also eliminated the long-term hurdle of hysteresis to make it a promising candidate for next-generation display and photonic technologies.

Atomic layer deposition TiO2/Al2O3 nanolayer of dyed polyamide/aramid blend fabric for high intensity UV light protection

Ultraviolet (UV) irradiation can cause a severe damage to textiles, such as color fading, polymer degradation, and mechanical strength decrease. The aim of this study was to deposit inorganic UV blocking agents onto polyamide/aramid dyed fabric using atomic layer deposition (ALD) technique to produce functional fabrics that are resistant to high intensity UV light. Scanning electron microscopy (coupled to energy‐dispersive spectroscopy), X‐ray photoelectron spectroscopy, and thermogravimetry studies demonstrated that TiO2, Al2O3, and TiO2/Al2O3 nanolayer could be successfully deposited onto the fiber surface. The dyed fabrics with different ALD coatings showed excellent high intensity UV resistance and were also more resistant to high intensity UV‐induced mechanical strength damage. These results suggested that the ALD technology could be effective technique to improve the properties of dyed fabrics. POLYM. ENG. SCI., 55:1296–1302, 2015. © 2015 Society of Plastics Engineers

Effect of light wavelength on motility and magnetic sensibility of the magnetotactic multicellular prokaryote ‘Candidatus Magnetoglobus multicellularis’

'Candidatus Magnetoglobus multicellularis' is a magnetotactic microorganism composed of several bacterial cells. Presently, it is the best known multicellular magnetotactic prokaryote (MMP). Recently, it has been observed that MMPs present a negative photoresponse to high intensity ultraviolet and violet-blue light. In this work, we studied the movement of 'Candidatus Magnetoglobus multicellularis' under low intensity light of different wavelengths, measuring the average velocity and the time to reorient its trajectory when the external magnetic field changes its direction (U-turn time). Our results show that the mean average velocity is higher for red light (628nm) and lower for green light (517nm) as compared to yellow (596nm) and blue (469nm) light, and the U-turn time decreased for green light illumination. The light wavelength velocity dependence can be understood as variation in flagella rotation speed, being increased by the red light and decreased by the green light relative to yellow and blue light. It is suggested that the dependence of the U-turn time on light wavelength can be considered a form of light-dependent magnetotaxis, because this time represents the magnetic sensibility of the magnetotactic microorganisms. The cellular and molecular mechanisms for this light-dependent velocity and magnetotaxis are unknown and deserve further studies to understand the biochemical interactions and the ecological roles of the different mechanisms of taxis in MMPs.

Ambient-protecting organic light transducer grown on pentacene-channel of photo-gating complementary inverter

Usually, organic thin-film transistors (TFTs) including pentacene TFTs have a bottom gate device architecture with an open back channel surface, thus requiring an ambient protecting layer on the organic devices. If the requested protecting layer has another function by chance, even more unique applications may be developed on the organic device. For such bi-functional applications, we have investigated a hydrophobic 6,13-pentacenequinone (PQ) crystalline layer on pentacene TFT for two reasons. Firstly, crystalline pentacenequinone–crystalline pentacene is quite similar to SiO2–Si structure. Because the PQ is a molecular form of already-oxidized pentacene, diffusion of water and oxygen molecules into channel pentacene may not be easy when the PQ layer is well grown on pentacene making a good PQ–pentacene interface. Moreover, the PQ protects the pentacene from high intensity ultraviolet (UV) light, since it transduces the UV into green light. After we had fabricated pentacene-based complementary photo-gating inverter devices, our inverters with the crystalline-grown PQ on pentacene channel demonstrated strong ambient-endurance preserving good inverter characteristics for 60 days under quite humid ambient air, and they also demonstrated dynamic photo-gating at a low voltage of 5 V without any UV-induced degradation.

Shear Properties of a Glass-Fibre/Vinylester Composite Cured with High Intensity Ultraviolet Light for use in Automated Manufacturing Processes

This work presents preliminary results on the potential for rapid curing of a glass-fibre/vinylester composite with high-intensity ultraviolet (UV) light. Two 10-ply laminates were manufactured by hand lay-up with a resin formulated with a photo-initiator (Derakane 411-350 vinylester and Ciba Specialty Chemicals Irgacure 819 photo initiator). For the first laminate, all 10 plies were laid-up at once, then cured in approximately 4 minutes using a high intensity 200 Watt mercury short arc UV light. For the second laminate, each ply was laid and then exposed for less than 1 second to the same UV light. Testing of the resin-sensitive interlaminar shear strength showed no difference in properties between the two laminates. Furthermore, the shear strength was comparable to the properties of laminates cured via traditional heat curing methods with a typical 24-hour room temperature cure followed by a thermal post-cure. The study shows that a ply-by-ply approach to lay-up and partial cure, which is the likely procedure for automated ply-by-ply placement process, such as automated fibre placement, does not affect laminate performance.

Fiber-optic bio-sniffer (biochemical gas sensor) for high-selective monitoring of ethanol vapor using 335 nm UV-LED

A fiber-optic bio-sniffer (biochemical gas sensor) for continuous monitoring of gaseous alcohol with high sensitivity and high-selectivity was fabricated and tested. The bio-sniffer uses alcohol dehydrogenase (ADH) for recognition of ethanol. Usually, enzyme loses activity in the gas phase. The bio-sniffer solved this problem by applying a flow-cell to refresh and wet the enzyme immobilized membrane by circulating phosphate buffer (PB). The bio-sniffer measures ethanol vapor by measuring fluorescence of nicotinamide adenine dinucleotide (NADH), which is produced by enzymatic reaction at the flow-cell. In order to construct a simplified system suitable for on-site applications, a high-intensity ultraviolet light emitting diode (UV-LED) was utilized as an excitation source. Assessment of the bio-sniffer was performed using a standard gas generator. First, the operating condition of the bio-sniffer was optimized by investigating fluorescent spectrum and the dependence of fluorescent characteristics on flow-rate of PB. As a result, the bio-sniffer was confirmed to be useful for continuous gas monitoring and the calibration range was 0.30–300 ppm. High-selectivity due to specific activity of enzyme was also confirmed. Thus, the ADH bio-sniffer was expected to be useful for breath analysis or medical screening applications.

Resin hardness and interlaminar shear strength of a glass-fibre/vinylester composite cured with high intensity ultraviolet (UV) light

Resin hardness and interlaminar shear strength of a glass-fibre/vinylester composite cured with high intensity ultraviolet (UV) light

Photolysis of cyclopiazonic acid to fluorescent products

Cyclopiazonic acid (CPA) is a mycotoxin produced by some of the same species of fungi that produce the more widely known aflatoxins. As a consequence it has been found previously that CPA and the aflatoxins may co-occur in commodities under certain conditions. CPA, which is a substituted indole, has a chromophore with absorptions in the ultraviolet (UV) region (223 nm, 278 nm). Quantification of CPA is commonly accomplished by liquid chromatographic separation followed by detection of one of the UV absorbances. CPA has not previously been described as fluorescent, and it likely is not. However, herein we report that, following exposure to high intensity UV light in a photochemical reactor, fluorescent products of CPA are produced. In methanol or aqueous acetonitrile these products have an excitation maximum of 372 nm and an emission maximum of 462 nm. Upon exposure to UV light for extended periods a decrease in the absorbance of CPA at 223 nm and 278 nm and a concomitant increase in fluorescence was observed. CPA and aflatoxin B1 were separated by reverse-phase liquid chromatography and the eluant was subjected to post-column photolysis, which allowed the fluorescence detection of both toxins. The ability to photolyse CPA and detect this toxin by fluorescence may open up new avenues for determination of this mycotoxin alone or together with the aflatoxins.

Radiation-induced damage in calcium fluoride ionic crystals exposed to high-intensity ultraviolet and vacuum ultraviolet light

An experimental setup for studying optical materials under the action of plasma-emitted intense (up to 105 W/cm2) ultraviolet and vacuum ultraviolet radiation is described, and methods for estimating the radiation damage are developed. The damage produced in calcium fluoride ionic crystals at ∼300 K by low (103 rad) and moderate (106 rad) absorbed doses is experimentally estimated.

High-intensity Low-pressure Electrodeless Mercury-Argon Lamp for UV Disinfection of Wastewater

Recently, ultraviolet (UV) radiation has been applied as a disinfection method for wastewater treatment plants. A high-intensity and high-power UV light source is required in the field of bacilli sterilization. The electrodeless UV lamp turns on by delivering RF-frequency power from the power supply through the matching circuit into the induction coil around the lamp. The electric current passing through the induction coil generates a magnetic field. The gas sealed inside the lamp is excited and ionized by the magnetic field, and so discharge of the gas occurs and light is emitted. Thus the discharge produces UV emission. Using RF frequency power circuit technology and optimizing UV lamp shape, we have made it possible to input power of 500W to a 500mm-length luminescent lamp. Moreover, an over 30% rate of UV radiating efficiency has been obtained. It realizes a high-intensity and high-power ultraviolet light source. Optimization of water current path in the sewage effluent disinfection has realized a colon bacillus removal ratio of 99.9%.

Laser damage probability studies of fused silica modified by MeV ion implantation

Energetic ions in the MeV regime have pronounced effects on the stress-state and geometry of fused silica. In particular, Polman and co-workers have shown that 4 MeV xenon ions cause substantial changes in thin films and microspheres of fused silica. For example, 2 μm wide trenches in thin films can be partially closed and microspheres substantially distorted. In our study, we investigate implantation into bulk silica and the subsequent response to high intensity ultra violet light. Specifically, we compare the damage threshold of fused silica to intense ultra violet light at 355 nm before and after room temperature ion bombardment and find little change despite clear alteration of the stress-state in the glass. We have also performed molecular dynamics simulations in order to understand the underlying effects that lead to obscuration of optics under laser and ion irradiation.

An optical fiber sensor based on cladding photoluminescence for high power microwave plasma ultraviolet lamps used in water treatment

Low-pressure mercury lamps are commonly used for germicidal applications such as water and wastewater sterilisation. The germicidal effect is due to the emission of light at 254 nm, which leads to the destruction of most waterborne bacteria. The Microwave plasma ultraviolet lamp (MPUVL) is a new technology for generating a high intensity ultraviolet (UV) light. A Fluorescent optical fiber based sensor is presented which is used for monitoring the output of a high power microwave UV light source and its control. This sensor is a fiber which has had its cladding removed and been coated with a phosphor doped polymer.