UV Excimer Research Articles

Improving Charge Storage of Biaxially-Oriented Polypropylene Under Extreme Electric Fields by Excimer Uv Irradiation.

Biaxially-oriented polypropylene (BOPP) is one of the most commonly used materials for film-based capacitors for power electronics and pulsed power systems. To address the pressing issue of performance-limiting loss under extreme electric-fields, here we demonstrate a one-step, high-throughput, and environment-friendly process based on very low-dose ultra-violet irradiation from KrCl (222nm) and Xe2 (172nm) excimer. The performance of commercial BOPP is boosted in terms of withstanding electric-field extremes (Weibull breakdown strength 694 to 811V μm-1 by 17% at 25°C and 428 to 651V μm-1 by 52% at 120°C), discharged energy density, and conduction losses. Importantly, the depth profile of space charge is precisely measured in-situ with a high resolution of 500nm by laser induced pressure pulse. Consequently, the space charge effect and electric-field distortion are reduced and related to the improved polymer films. It is demonstrated that energetic UV photons act as scissors for BOPP chains and dissociate oxygen molecules leading to the more thermally stable oxygen-containing structures, as deep traps to impede charge migration. This work provides a promising approach to produce polymers with customized microscopic characteristics that is compatible with the assembly lines of polymer-based capacitors. This article is protected by copyright. All rights reserved.

Inactivation of Coronavirus OC43 by Excimer Lamp, UV Lamp, and Deep UV-LED at Irradiation Wavelengths of 222 nm, 254 nm, and 275 nm

Inactivation of Coronavirus OC43 by Excimer Lamp, UV Lamp, and Deep UV-LED at Irradiation Wavelengths of 222 nm, 254 nm, and 275 nm

Effect of tungsten doping on laser ablation and graphitization of diamond-like nanocomposite films

Laser surface microstructuring of diamond-like nanocomposite (DLN) films is a promising technique to improve their properties. For industrial applications, UV excimer or IR lasers with high pulse repetition rate are commonly used. In this paper, we investigate the influence of metal (tungsten) doping of DLN film on the ablation and graphitization behavior of the films using KrF laser (λ = 248 nm, τ = 20 ns) and Yb:Yag laser (λ = 1030 nm, τ = 8 ps). The response is found to be sensitive to the laser wavelength and pulse duration. For UV ns-pulses, the ablation threshold is insensitive to W-doping, showing only a slight increase for the highest tungsten concentration of 27 at.%, while the ablation rate decreases. Conversely, an increase of tungsten content in the case of the irradiation by IR ps-pulses induces a drop in the ablation threshold and an increase in the ablation rate. The structural modification of the films is analyzed by Raman spectroscopy, which also allows us to estimate the thickness of a residual graphitized layer on the surface after laser irradiation. It is found that laser-induced graphitization is stronger for doped DLN films after multipulse irradiation.

Antibacterial properties of angle-dependent nanopatterns on polystyrene

Surface modification of polystyrene by a KrF pulse excimer UV laser under the angles of incidence of the laser beam of 0, 22.5 and 45° was proposed in this paper. The influence of the angle of incidence, laser fluence, number of pulses and a deposition of a thin gold layer on the physical and chemical properties of the surface was studied closely. Changes in the surface morphology, the formation of the periodic surface structures as well as the dependence of their dimension on the angle of incidence of the laser beam were determined by Atomic force microscopy and Scanning electron microscopy. Changes in the surface chemistry were studied by X-ray Photoelectron spectroscopy, which revealed a significant increase of oxygen concentration for all laser treated samples and also by electrokinetic analysis to further clarify the surface chemistry and charge changes occurring during the laser treatment. An optimal conditions for antibacterial surface construction was found on the basis of combination of silver nanolayer and PS treated under angle of laser beam incidence 45°. The potential application of laser-treated polystyrene foils can be found mainly in the biotechnological industry, as well as in various other fields dealing with surface modification and micro-patterning of solids.

Excimer ultraviolet-irradiated exfoliated graphite loaded with carbon-coated SnOx small nanoparticles as advanced anodes for high-rate-capacity lithium-ion batteries

This paper reports a fast and efficient excimer ultraviolet (EUV) radiation method to prepare carbon-coated mixed tin oxide-loaded exfoliated graphite (SnOx@C-G) nanocomposites. The SnOx small nanoparticles (SNPs) are isolated using oxidized sucrose and uniformly deposited onto mildly oxidized exfoliated graphite during the 20-minute EUV radiation process. XPS and ESR analyses suggest the existence of abundant oxygen vacancies in the SnOx SNPs. The electrochemical kinetics of SnOx@C-G, which are determined by in situ electrochemical impedance analysis, demonstrated a high reversible capacity of approximately 740 mA h g-1 after 250 cycles at a current density of 1.6 A g-1, and an impressive reversible rate performance exceeding 450 mA h g-1 can be obtained even at a high current density of 3.2 A g-1 when applied as an anode for lithium storage. This improved cycling stability and rate capability benefit from the carbon coating, which not only buffers the volume change of SnOx SNPs but also provides a path for electron transport on the surface of the SnOx SNPs during the electrochemical process. Furthermore, the oxygen vacancies in SnOx SNPs result in a large capacitive contribution to capacity. The EUV radiation method used to synthesize SnOx@C-graphite nanosheets is universally applicable to prepare a high-performance SNPs/carbon-based anode for lithium-ion batteries.

Construction and Properties of Ripples on Polymers for Sensor Applications

Surface modification of polystyrene and polyethylene naphthalate by a KrF pulse excimer UV laser under the angles of incidence of the laser beam in the range of 0 to 60° with a step of 7.5° was studied in this paper. The influence of the angle of incidence on the period of the resulting surface structures and the modified refractive index of the substrates was determined with all the other parameters of the laser radiation held constant. All data was acquired on the basis of surface analysis. Atomic force microscopy was used to study the morphological changes in the laser treated samples and to determine the period of the ripple-like surface structures, from which the modified refractive index was subsequently calculated. Selected samples were metallized with gold with aim to determine the influence of patterned substrate on consequently formed nanolayer. These information may be useful for consequently constructed SERS system based on ripple-metal system.

Unique laser coding technology to fight falsified medicines

Based on WHO statistics, counterfeit medicines represent 10% of the global drug trade. According to Directive 2011/62/EU as regards the prevention of falsified medicines from entering into the legal supply chain, a unique identification should be put on each box of drugs to be able to track and trace them. The objective of this study is to develop a technology to mark an individual traceability code directly on the surface of the tablet. By using this technique, anyone with a camera-enabled phone and a suitable application installed should be able to authenticate these drugs. By marking the medicine's surface, patients could be protected from fake drugs.The aim of the present work was to study how different types of lasers affect the film coating of the tablet during the laser marking intervention.To sum up, the present findings may contribute to efficient and reliable laser marking solutions in the unique identification procedure. Based on our measurement results, it can be stated that the excimer UV laser is clearly the most suitable marking instrument for anti-counterfeiting coding on solid coated tablet form as this caused the least amount of chemical degradation of the polymer film.

Compact single-pass X-ray FEL with harmonic multiplication cascades

The generation of X-ray radiation in cascaded single-pass free electron laser (FEL), which amplifies high harmonics of a two-frequency undulator, is studied. Power dynamics of FEL harmonics is explored with the help of the phenomenological model of a single pass FEL. The model describes both linear and non-linear harmonic generation, starting from a coherent seed laser and initial shot noise with account for main loss factors for each harmonic in each cascade individually: the energy spread and beam divergence, the coupling losses between FEL cascades, the diffraction etc. The model was validated with the experiment and with relevant 3-D simulations. It is employed for modeling the cascaded FELs with harmonic multiplication and analyzing the evolution of FEL harmonic power with the aim to obtain the maximum high harmonic power in the X-ray band at the shortest possible FEL length with the lowest possible seed frequency. The advantages of two-frequency undulators in HGHG FELs are elucidated. The requirements for the electron beam are studied; the need for low energy spread is evidenced: our evaluations yield σe<2×10−4. Several cascaded HGHG FELs with two-frequency undulators are modeled. Generation of soft X-ray radiation at λ=2.71nm, reaching ∼50 MW power with I0∼100 A in a cascaded FEL at just 40 m with 13.51 nm seed, matching peak reflectivity of Mo/Si, is demonstrated. The generation of 40 MW radiation power at λ=2.27nm with the beam current I0∼100 A, energy E=950MeV and the energy spread σe=2×10−4 is studied, using second and third harmonics in three-stage 45 m long FEL. The multistage FEL is modeled for generating radiation in nanometer band: ∼40 MW power at λ∼2.6 nm with I0∼175 A current in just ∼40 m long FEL with commercially available F2 excimer UV laser seed at 157 nm. The peak radiation power rises to ∼0.5 GW for ∼1 kA beam current.

Wettability of Dentin Structure after Exposure to Excimer UV Irradiation

Wettability of Dentin Structure after Exposure to Excimer UV Irradiation

Matrix-Assisted Pulsed Laser Evaporation: A novel approach to design mesoporous carbon films

We report on a fast synthesis method of porous carbon films on solid substrates. Thin carbon micro-structures tailored by processing conditions were synthesized for the first time by Matrix-Assisted Pulsed Laser Evaporation. The procedure consists of pulsed laser irradiation of a cryogenic target composed of phloroglucinol/glyoxylic acid organic precursors dissolved in different mixtures of solvents. An excimer UV KrF* pulsed laser was employed inside a vacuum chamber for material expulsion from the target and immobilization on a solid facing collector. By modifying laser energy or target solvents, thin polymeric coatings of hundreds of nanometers with various cross-linking degrees were obtained at room temperature in 10 min only. No drying or thermo-polymerization step is required even for high boiling point solvents such as dymethyl sulfoxide (DMSO). After thermal treatment, mesoporous carbon films exhibiting diverse nano-morphologies and surface areas up to 705 m2 g−1 determined by Kr adsorption were then directly obtained onto various collectors. Processing and assembling mechanisms of phenolic resins were investigated and two competing mechanisms, e.g., target absorption of laser wavelength and subsequent molecules transfer/interactions are accounted for the growth of high quality films as highlighted by several techniques.

Thermal stability of excimer laser melted films formed on the AA2024-T351 aluminium alloy: Microstructure and corrosion performance

Excimer UV laser radiation sources have recently employed for surface modification of aluminium alloys to provide melted layers with highly refined microstructure and superior pitting corrosion resistance. Moreover, the resultant rough appearance might be an excellent base for the later paint application. Unfortunately, during the paint baking process and depending on the exposure time, the temperature of the alloy may raise up to 200°C, thus affecting the stability of the melted film. In the present work, the excimer KrF laser source was employed to create a melted film on the aerospace AA2024-T351 aluminium alloy, which was subsequently evaluated under different heat treatments with the aim to evaluate its thermal stability in terms of microstructure and corrosion performance. Microstructural modification was analysed by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), whereas the corrosion performance was evaluated by anodic polarisation and immersion testing in deaerated 0.1M NaCl solution. The experimental results showed that above 160°C, heat treatment of the melted layer resulted in the precipitation of the strengthening Al2CuMg phase as well as the nucleation and coarsening of the Al(Cu,Fe,Mn) secondary phase from the solute segregation bands originally formed during laser surface melting (LSM). The formation of these particles influenced the pitting corrosion resistance in two different ways: diminishing the pitting potential (Epit), and increasing both corrosion and passivation current densities. Nevertheless, this reduction was relatively negligible for all the heat treatment conditions studied, when compared to the parent alloy.

Excimer Ultraviolet-Irradiated Carbon Nanofibers as Advanced Anodes for Long Cycle Life Lithium-Ion Batteries.

Carbon nanofibers (CNFs) bearing oxygen-containing functional groups and inhomogeneous nanopores are successfully prepared by excimer UV radiation. The CNFs demonstrate potential for use as an anodic material in rechargeable Li-ion batteries. Their improved electrochemical performances are attributed to the chemically bonded solid-electrolyte interface films on the CNF surface. This approach is also applicable to other carbonaceous electrode materials.

Surface analysis of ripple pattern on PS and PEN induced with ring‐shaped mask due to KrF laser treatment

The approach for ripple nanopattern construction on surface of two polymer substrates [polyethylene naphthalate (PEN) and polystyrene (PS)] exposed by a KrF pulse excimer UV laser through a contact lithographic mask with circular slit was proposed in this paper. Thin layer of gold was deposited on samples after the laser treatment. Changes in the morphology of the surface of both the shielded and exposed areas of the substrates, as well as the dimensions of the laser‐induced periodic surface structures, were determined (by atomic force microscopy, laser confocal microscopy and scanning electron microscopy), compared with observations and measurements made on samples treated directly (without a contact mask) under the same conditions. The morphology of the interface between the treated and untreated regions was also closely studied. Surface chemistry of treated samples was studied in detail by X‐ray Photoelectron Spectroscopy. The detailed study of surface chemistry of modified PEN and PS revealed a significant increase of oxygen concentration for laser treated PS and increase of carboxyl groups in case of PEN. The potential application of this research can be found in biotechnology, micro technology and several other fields. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Synergetic Effect Between Plasma and UV for Toluene Conversion in Integrated Combined Plasma Photolysis Reactor with KrCl/KrBr/XeCl/Xe2 Excilamp

An integrated combined plasma photolysis (CPP) reactor, which simultaneously produced dielectric barrier discharge (DBD) plasma and excimer UV radiation, was employed to decompose toluene gas. The study of toluene degradation by the separate processes, realized in three reactors (DBD, UV, and CPP), showed that toluene conversion by CPP was higher than the sum of the conversions for DBD and UV alone, indicating a synergetic effect in CPP between plasma and UV occurred. The degradation performance of gaseous toluene in CPP using different excimer UV sources (XeCl*, KrCl*, KrBr*, Xe2*) was compared, and a regression analysis showed that CPP can enhance toluene conversion by about 50 % and energy yield by 90 %. Radiant spectra and efficiency of excimer UV sources were recorded in detail. Further, it was observed that carbon balance and CO2 selectivity were greatly increased in the CPP in comparison with DBD, accompanied by NO, CO, and O3 being effectively suppressed. Intermediate products in effluent gas using CPP treatment for toluene included formic acid, acetic acid, benzene, benzaldehyde, phenol, benzoic acid, etc. Based on by‐product analysis and excimer UV radiant efficiency, we concluded that toluene degradation is due to electron impact dissociation, excited species and free radical reaction from background gases dissociation, direct photolysis by excimer UV, and synergy between plasma and UV. Among these, electron impact, free radical reaction, and plasma‐UV synergy played critical roles on toluene conversion, while direct UV contribution seems to be minor.

Defects induced in Yb3 +/Ce3 + co-doped aluminosilicate fiber glass preforms under UV and γ-ray irradiation

A set of Ce-/Yb-co-doped silica optical fiber preform cores, differing in terms of dopant concentrations are studied by Electron Paramagnetic Resonance (EPR) spectroscopy before and after irradiation of the samples with excimer UV laser light and γ-rays. Evidence of Yb3+ clustering in the case of high Yb content samples is observed on as prepared samples regardless of the presence of Ce3+ ions. Si-E′ and Al-OHC centers were identified upon photon irradiation. The results are correlated to the micro-structural origin of the photodarkening process occurring in Ce–Yb doped glass fibers.

Excimer UV Radiation in Dermatology

Ultraviolet B (UVB 290-320 nm) radiation has been used in the treatment of different skin diseases. Light sources with narrowband UVB output spectrum have been developed with the aim of increasing the rates of “beneficial to side effect” profile of the treatment. Narrowband UVB phototherapy using fluorescent lamps (TL01, 311&#x2213;2nm) has been widely adopted over the past 10 years. Monochromatic Excimer Light (MEL) represents a new source of narrow-band UVB emitting at 308 nm and guarantees a safe and effective approach to different chronic and recurrent skin diseases thanks to its potent and selective immunosuppressant action.

Effects of wavelength and water quality on photodegradation of N-Nitrosodimethylamine (NDMA)

N-Nitrosodimethylamine (NDMA) is a potent carcinogen that yields a cancer risk of 10−6 at concentrations as low as 0.7ngL−1. Tentative guideline values are set at 3ngL−1 in California, USA; 9ngL−1 in Ontario, Canada; 40ngL−1 nationwide in Canada; and 100ngL−1 by the World Health Organization. NDMA is a great concern in treating reclaimed water as well as drinking water. UV degradation can be considered effective degradation method. A 1-log reduction of NDMA is achieved by 1000mJcm−2 of a 254-nm low pressure (LP) mercury UV lamp. However, a higher degradation efficiency than that provided by LP lamps is desired in practical treatment. In this study, the effects of wavelength and water quality were investigated to achieve higher degradation efficiency. The effects of wavelength were examined by comparing three UV lamps: a 222-nm Kr Cl Excimer UV lamp, a 254-nm LP mercury UV lamp, and a 230- to 270-nm filtered medium pressure (FMP) mercury UV lamp. The 222-nm lamp and FMP lamp achieved 4 times and 2.8 times higher degradation efficiency, respectively, than the conventional 254-nm LP lamp. Effects on water quality were also simulated by using absorption spectrum data of nitrate solutions and process water from a drinking-water treatment plant. In the simulation, the 222-nm lamp was affected by UV-absorbing compounds in the water, whereas the FMP lamp showed more stable degradation efficiency. Appropriate use of these three types of lamps could enhance the efficiency of degradation of NDMA.

Enhancement of VUV Emission from a Coaxial Xenon Excimer Ultraviolet Lamp Driven by Distorted Bipolar Square Voltages

AbstractEnhancement of vacuum UV emission (172 nm VUV) from a coaxial xenon excimer UV lamp (EUV) driven by distorted 50 kHz bipolar square voltages, as compared to that by sinusoidal voltages, is investigated numerically in this paper. A self‐consistent radial one‐dimensional fluid model, taking into consideration non‐local electron energy balance, is employed to simulate the discharge physics and chemistry. The discharge is divided into two three‐period portions; these include: the pre‐discharge, the discharge (most intense at 172 nm VUV emission) and the post‐discharge periods. The results show that the efficiency of VUV emission using the distorted bipolar square voltages is much greater than when using sinusoidal voltages; this is attributed to two major mechanisms. The first is the much larger rate of change of the voltage in bipolar square voltages, in which only the electrons can efficiently absorb the power in a very short period of time. Energetic electrons then generate a higher concentration of metastable (and also excited dimer) xenon that is distributed more uniformly across the gap, for a longer period of time during the discharge process. The second is the comparably smaller amount of “wasted” power deposition by Xe+2 in the post‐discharge period, as driven by distorted bipolar square voltages, because of the nearly vanishing gap voltage caused by the shielding effect resulting from accumulated charges on both dielectric surfaces (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Electrical Approach of Homogenous High Pressure Ne/Xe/HCl Dielectric Barrier Discharge for XeCl (308 nm) Lamp

This paper reports the investigation of the excimer UV emission efficiency in Ne/Xe/HCl mixture in terms of the homogenous model of a dielectric barrier discharge. The computer model developed is based on the Ne/Xe/HCl gas mixture chemistry, the circuit and the Boltzmann equations. The effects of operating voltage, HCl concentration in the mixture as well as gas pressure on the discharge efficiency and the 172, and 308 nm photon generation, under typical experimental operating conditions, have been investigated and discussed. Calculations suggest that the overall conversion efficiency from electrical energy to VUV emission in the lamp is greater than 27%, and it will be very affected at high voltage amplitude and high gas pressure with a significant dependence on the HCl concentration in the gas mixture.

Simulation of gas-discharge UV sources based on a glow discharge in a xenon-chlorine mixture

A model is developed that makes it possible to calculate the concentration of excimer molecules, halogenides of inert gases, in the positive column of a glow discharge initiated in a chlorine-containing gas mixture. Using this model, one can quantitatively reproduce experimental dependences of the excimer UV power on the discharge current in wide ranges of the gas mixture compositions and pressures, provide satisfactory quantitative agreement between calculated and experimental radial distributions of the electron and excimer molecule concentrations, and give a physical explanation for the experimental dependences. To this end, this model, unlike other available ones, allows for the electron-impact dissociation of chlorine molecules, the radial nonuniformity of dissociation, and the radial nonuniformity of the gas temperature.