UV LED Source Research Articles

Development of an image-based fluorometer with smartphone control for paper analytical devices.

This work describes the construction and evaluation of a fluorometer for use in paper analytical devices, using a smartphone to operate the instrument and to perform real-time image-based detection. In this approach, a circular PAD containing twenty analytical plates is rotated at 18° increments under a UV LED source, providing a sequential irradiation of plates and the detection of the luminescence with a lab-made application, capable of automatically identifying the analytical zones and collecting the RGB intensities from the selected pixels. As a proof of concept, the fluorometer performance was evaluated for the determination of quinine in beverages and riboflavin (B2 vitamin) in supplements. Quinine, which is less photoreactive, provided steady-state signals, while riboflavin, which rapidly degrades under UV photons, presented transient responses for RGB detection. For both analytes, linear calibration ranges (R2 > 0.99) were observed from 2.0 mg L-1 to 10.0 mg L-1 with limits of detection estimated at approximately 1.0 mg L-1. Nevertheless, it was demonstrated that successive additions of standard solutions to a single analytical plate of PAD could enhance the signal-to-noise ratios for less concentrated samples, acting as a pre-concentration step. In addition, suitable deviations for the signals (ca. 4.0%) and the absence of systematic errors for most samples (9 out of 11), when compared with a reference method at 95% confidence level, indicates that the proposed strategy is precise and accurate enough to be used as analytical tool for fluorescence detection in PAD.

Single-shot phase retrieval system using a deep UV LED source with visible light converter fluorescent glass

Single-shot phase retrieval system using a deep UV LED source with visible light converter fluorescent glass

Photooxidation of tetrahydrobiopterin as the basis of vitiligo phototherapy

The kinetics of photooxidation of tetrahydrobiopterin was investigated, the quantum yields of the formation of dihydropterin dimers were calculated when using a xenon lamp, a tunable UV laser and a UV LED as UV radiation sources. A comparative analysis of the effectiveness of these sources for the photooxidation process of tetrahydrobiopterin allowed us to conclude that the most effective for the purposes of vitiligo phototherapy are, apparently, UV LED sources with emission maxima in the region of 325 nm. Keywords: vitiligo, tetrahydrobiopterin, melanin, oxidative stress, H2O2, UVB vitiligo phototherapy.

Фотоокисление тетрагидробиоптерина как основа фототерапии витилиго

The kinetics of photooxidation of tetrahydrobiopterin was investigated, the quantum yields of the formation of dihydropterin dimers were calculated when using a xenon lamp, a tunable UV laser and a UV LED as UV radiation sources. A comparative analysis of the effectiveness of these sources for the photooxidation process of tetrahydrobiopterin allowed us to conclude that the most effective for the purposes of vitiligo phototherapy are, apparently, UV LED sources with emission maxima in the region of 325 nm.

Low-Cost Germicidal UV LED as Candidate Light Source for Portable and Field Spectrometer

Ultraviolet Light Emitting Diode (UV LED) is becoming popular, especially during the Covid-19 pandemic. UV LED has a specific wavelength with relatively narrow bandwidth, especially the one that has a shorter wavelength. On the other hand, UV LED has advantages in its low power consumption, compact size, and longer lifetime. This work shows that a wider bandwidth can be elicited by combining multiple UV LED sources. We have measured several low-cost UV LED, which is used as a germicidal lamp using a portable spectrometer that can detect a wavelength from 200 nm to 850 nm. The combined UV LED spectrum light ranges from 254 nm UVC to 400 nm UVA. The light spectrum produced by the LED shows a form of the Gaussian distribution model. Some LEDs have a peak wavelength at UVC around 270nm, and LEDs have a peak wavelength around 400nm at UVA. We can conclude that the low-cost UV LED can be used as a light source for portable or field spectrometers for specific wavelength.

Methodology development for the control of NOx emissions in Aerospace Industry

A large number of studies conducted in Russia and abroad have been devoted to the development of low NOx emission gas turbine engines for aircraft and power stations. However, the continual improvement of the environmental requirements of ICAO (International Civil Aviation Organization) forces new research to be carried out to meet the future goals of reduced emissions produced by gas turbine combustors (GTE), a better understanding of the process of formation of various pollutants is required. Both empirical and theoretical approaches will be studied in this present research work to provide the exhaust concentrations of NOx emissions. In recent years different methods are already developed for this problem, one of them is associated with a theoretical approach. It is well known that correct theoretical models are economical (help’s to avoid experimental work) and can be useful for deep examination of NOx emissions generated in the combustion chamber process. The main objective of this study is to predict NOx emissions in GTE based on the mathematical simulations and chemical kinetics approach.To validate the simulation results, dispersion type optical system was developed in the laboratory. This system includes UV LED source (λ=245-280nm), single-pass absorption cell with length (L=500 mm) and spectrometer DFS-452 (spectral dispersion up to Δλ = 0.2nm/mm) equipped photo detector MORS-1 with a detection range Δλ=50nm. It allowed us to measure concentrations of some matters which absorbed light in the UVC range.

"Green" UV-LED gel nail polishes from bio-based materials.

Gel nail polishes represent an advanced class of nail polishes, with the ability to cure under ultraviolet (UV) radiation, and consequently demonstrate improved properties and greater durability compared to conventional nail polishes. Most gel nail polishes available today are based on petrochemical resources, making them unsustainable. Bio-based materials are excellent renewable resources, with high potential for meeting final-product performance, cost, and environmental needs. In addition, bio-based materials can be modified to make them amenable to being cured by advanced Light Emitting Diode (LED) resources that consume low energy and are safer for human exposure compared to conventional UV-mercury lamps. Consumer preference for use of products made from bio-based sources has been clearly growing. On the other hand, according to the U.S. Department of Energy (DOE) technology roadmap, a considerable amount of basic chemical building blocks should be derived from plant-based renewable materials in near future. However, to the best of our knowledge, bio-based nail products have not been sufficiently explored. Therefore, to keep pace with environmental regulations and consumer preference, there is an unmet opportunity to develop novel, sustainable nail gel polishes with considerable bio-renewable content. In this study, two sustainable UV-LED curable gel nail polish prototypes-one high-solids zero-volatile organic content (VOC) and the other waterborne, both with considerable bio-renewable content, were designed. Both formulations were cured under both UV-mercury and UV-LED radiation sources in order to evaluate their curing efficiency under a UV-LED source. Also, their performance was compared with a commercial petro-based benchmark. The high-solids formulation demonstrated promising performance, exceeding that of the benchmark in opacity, chemical properties, gloss, and pendulum hardness, while the waterborne formulation met most of the desirable requirements with some significant technical benefits, including low odour and higher renewable raw material content. These novel gel nail polishes are greener alternatives to the current products in the market with high potential for promising consumer acceptance.

Synthesis of silver nanoparticles by radiolysis, photolysis and chemical reduction of AgNO3 in Hibiscus sabdariffa infusion (karkadé)

Silver nanoparticles of different average diameters were synthesized by γ-radiolysis, UV-photolysis and chemical reduction of AgNO3 solutions in Hibiscus sabdariffa infusion commonly known as “karkade”. The UV-photolysis was performed either by using a conventional Hg low pressure lamp emitting at 254 nm and also by using a new compact UV-LED source emitting at 360 nm. The kinetics rate constant of silver nanoparticles synthesis produced by γ-radiolysis and UV photolysis were determined and the average diameter of the resulting nanoparticles was estimated.

Light-assisted synthesis and functionalization of silver nanoparticles with thiol derivative thioxanthones: new insights into the engineering of metal/chromophore nanoassemblies

In this study, silver nanoparticles (Ag NPs) were generated, functionalized, and stabilized using a one-step photochemical approach that does not require more than few minutes with a low power near UV LED source. A series of thiol-functionalized thioxanthone (TX) derivatives were prepared and used for the photoinduced synthesis of Ag NPs and their surface functionalization and stabilization. Upon illumination, Ag+ ions are reduced by free radicals generated through an oxidoreductive process occurring between excited TX groups and N-methyldiethanolamine. This process generates monodispersed silver nanoparticles with an average diameter about 2–7 nm depending on the TX derivative used. Due to the strong interaction between Ag atoms and thiol groups of the ligands, AgNPs are capped in situ by TX derivatives and exhibit remarkable stability in solution. Subsequent studies carried out on silver NPs/TX nanoassemblies (designed as AgNPs@S-TX) demonstrated their potentials in free radical photopolymerization of acrylate monomers.

The effect of pH on the photonic efficiency of the destruction of methyl orange under controlled periodic illumination with UV-LED sources

• Combined effects of pH and duty cycle on photooxidation of methyl orange. • Two distinct photonic efficiency regimes with respect to duty cycle. • Predominance of oxidative species in separate regimes. • Effect of duty cycle on photonic efficiency is greater than pH, with greatest impact at low duty cycle. The nature of photon interaction and reaction pH can have significant impacts on semiconductor photocatalysis. This paper describes the effect of pH on the photonic efficiency of photocatalytic reactions in the aqueous phase using TiO 2 catalysts. The reactor was irradiated using periodic illumination with UV-LEDs through control of the illumination duty cycle ( γ ) through a series of light and dark times ( T on / T off ). Photonic efficiencies for methyl orange degradation were found to be comparable at high γ irrespective of pH. At lower γ , pH effects on photonic efficiency were very distinct across acidic, neutral and alkaline pH indicating an effect of complementary parameters. The results suggest photonic efficiency is greatest as illumination time, T on approaches interfacial electron-transfer characteristic time which is within the range of this study or charge-carrier lifetimes upon extrapolation and also when electrostatic attraction between surface-trapped holes, { Ti IV OH } ads + and substrate molecules is strongest.

光盘油墨涂层固化的UV LED光源系统研究

光盘油墨涂层固化的UV LED光源系统研究

Photo- and thermo-chemical vapor generation of mercury

Photochemical vapor generation of both inorganic and methylmercury species can be achieved with equal efficiency when a sample reaction medium containing 2–10% formic acid is irradiated by low power (0.3 mW) deep UV LED sources with output in the range 245–260 nm. Whereas pseudo first order kinetics is evident for reduction of methylmercury, inorganic mercury does not conform to either first or second order models and the overall reaction rate is proportional to the concentration of formic acid but independent of that of mercury. Noteworthy, is that at room temperature, no reduction of either mercury species is achieved when radiation from 360 nm LEDs is used. A thermal reduction system operating at nominally 85 °C can also be used to reduce both mercury species in a 2% formic acid medium with the initial stages of the reaction being dominated by a first order kinetic process that is approximately 7-fold slower for methylmercury. Despite this disparity in reaction rates, direct speciation is not possible. Using a 10 cm quartz tube cell for cold vapor AAS measurement, a limit of detection of 0.68 ng absolute was achieved for mercury using a 9 min irradiation time with the deep UV LED sources. Precision of replicate measurement was 2.4% RSD for a sampled volume of 480 μl of a 200 ng ml−1 solution of Hg2+ (96 ng absolute) in 2% formic acid. The efficacy of the low power deep UV LED photoreactor was demonstrated by quantitation of total mercury in certified reference materials PACS-2 (marine sediment) and DOLT-4 (fish liver tissue) using the method of additions to compensate for matrix interferences.

Cascade transformations involving thiocarbonyls: photoassisted access to bicyclic thiiranes and oxapentalenes

Phenyl(thio)glyoxal, generated via the Norrish type II fragmentation of phenacyl sulfide, undergoes known [4+2] cycloaddition with dienes and the photoactive product is further converted via the interrupted Paternò–Büchi reaction channel into a dihydrofuran derivative possessing the oxapentalene core. The reaction can be carried out in one step as the chromophores are nearly identical and the extended cascade is initiated with the same UV LED source.

High resolution surface scanning of Thick-GEM for single photo-electron detection

An optical system for high resolution scanning of TGEM UV photon detection systems is introduced. The structure exploits the combination of a single Au-coated TGEM under study, and an asymmetric MWPC (Close Cathode Chamber) as post-amplification stage. A pulsed UV LED source with emission down to 240nm has been focused to a spot of 0.07mm on the TGEM surface, and single photo-electron charge spectra has been recorded over selected two dimensional regions. This way, the TGEM gain (order of 10–100) and TGEM photo-electron detection efficiency is clearly separated, unlike in case of continuous illumination. The surface structure connected to the TGEM photon detection is well observable, including inefficiencies in the holes and at the symmetry points between holes. The detection efficiency as well as the gas gain are fluctuating from hole to hole. The gain is constant in the hexagon around any hole, pointing to the fact that the gain depends on hole geometry, and less on the position where the electron enters. The detection probability map strongly changes with the field strength above the TGEM surface, in relation to the change of the actual surface field configuration. The results can be confronted with position-dependent simulations of TGEM electron transfer and gas multiplication.

Compensation to positive as well as negative lenses can occur in chicks reared in bright UV lighting

An earlier report describing a lack of compensation to imposed myopic and hyperopic defocus in chicks reared in UV lighting has led to the belief that the spatial resolving power of the UV cone photoreceptor network in chicks is not capable of decoding optical defocus. However this study used dim light rearing conditions, of less than 10lx. The purpose of the current study was to determine if emmetropization is possible in young chicks reared under higher luminance, UV lighting conditions. Young, 4day-old chicks were reared under diurnal near UV (390nm) illumination set to either 20 or 200lx while wearing a monocular defocusing lens (+20, +10, −10 or −20D), for 7days. Similarly treated control groups were reared under diurnal white lighting (WL) of matching illuminance. The WL and UV LED sources were set to equivalent illuminances, measured in “chick lux”, calculated from radiometer readings taken through appropriate narrow band interference filters, and a mathematical model of the spectral sensitivity of the chick visual system. High resolution A-scan ultrasonography was undertaken on days 0 (before lenses were fitted), 2, 4, and 7 to track ocular dimensions and refractive errors were measured by retinoscopy on days 0 and 7. Compensation to negative lenses was unaffected by UV illuminance levels, with near full compensation being achieved under both conditions, as well as under both WL conditions. In contrast, compensation to the positive lenses was markedly impaired in 20lx UV lighting, with increased instead of decreased axial elongation along with a myopic refractive shift being recorded with the +10D lens. Compensation under both WL conditions was again near normal for the +10D lens. However, with the +20D lens, myopic shifts in refractive error were observed under both dim UV and WL conditions. The spatial resolving power of the UV cone photoreceptor network in the chick is sufficient to detect optical defocus and guide the emmetropization response, provided illumination is sufficiently high. However, compensation to imposed myopic defocus may be compromised, when either the amount of defocus is very high or illumination low, especially when the wavelength is restricted to the UV range.