Ultraviolet Laser Radiation Research Articles

Manifestations of Laser-Induced Graphene under Ultraviolet Irradiation of Polyimide with Varied Optical Fluence.

In this work, we put forward a rigorous study on ultraviolet (355-nm) laser irradiation of polyimide for the realization of high-quality laser-induced graphene (LIG) with micron-scale features. High-quality material and micron-scale features are desirable—but often at odds—given that small features demand tightly focused beam spots, with a predisposition to ablation. As such, we investigate the synthesis of LIG by correlating the material characteristics, as gleaned from scanning electron microscopy and Raman spectroscopy, to the incident optical fluence, as a measure of applied optical energy per unit area. The study reveals that high-quality LIG, with ratios of Raman 2D-to-G peak heights approaching 0.7, can be synthesized with micron-scale features, down to 18 ± 2 μm, given suitable attention to the optical fluence. Optimal characteristics are seen at optical fluences between 40 and 50 J/cm2, which promote graphenization and minimize ablation. It is hoped that these findings will lay a foundation for the application of LIG in future integrated technologies.

Preparation of hierarchical Micro-Nano titanium dioxide structures via laser irradiation for enhancing water transport performance

Ultraviolet laser irradiation is a significant technique for creating functional materials with hierarchical micro-nano morphology. Herein, a facile laser irradiation method is developed to fabricate multi-scale titanium dioxide structures; their morphologies and compositions are evidenced by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. By analyzing the high-speed photography and spark distribution, we elucidate that the evolution of material ablation state accompanies with the unique spark area and number distribution attributing to the change of laser irradiation intensity, and these microcavities generated in violent ablation play an important role in the supplement of front water film for enhancing water transport performance. Moreover, the comprehensive analysis of equivalent laser intensity on different micro peaks and pits, global statistical data, and high-speed photography reveals the mechanism of microcavity abnormal narrowing with the increase of laser irradiation cycles. This work has significant implications for understanding the creation of micro-nano topology by laser irradiation for enhancing water transport performance and sheds light on application integration of such promising functional surfaces.

Characterizing the Grating-like Nanostructures Formed on BaF2 Surfaces Exposed to Extreme Ultraviolet Laser Radiation

Monocrystalline barium fluoride (BaF2) slab targets were irradiated by focused 46.9-nm laser radiation at various fluence levels above the ablation threshold. Well-developed ablation patterns with sharp edges were studied by AFM (atomic force microscopy). Their inner surfaces were uniformly covered by periodic structures. The spatial period of the ripples depends on the laser fluence. When the sample is rotated by 45°, the orientation of the grating-like structure changes accordingly. Thus, the grating vector of the periodic structure seems to be coupled to the crystallographic planes of the single crystal. This means that the XUV-laser induced ripples reported here differ from LIPSS (laser-induced periodic surface structures) associated with interference phenomena occurring on illuminated surfaces. Therefore, other mechanisms are discussed to explain the formation of the periodic nanostructures reported in this article.

Предпороговые эффекты при воздействии ультрафиолетовых лазерных импульсов на медь и ее сплавы

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 µm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic.

Prethreshold effects, when copper and its alloys were impacted to ultraviolet laser pulses

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1-1.0 J/sm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 μm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic. Keywords: plastic deformation, optoplastic effect, crystallographic slip, laser.

Effect of UV Laser Radiation on "Positive Regulation of Telomere Maintenance" in Saccharomyces cerevisiae.

Introduction: Excessive exposure to ultraviolet (UV) radiation may cause a variety of skin cancers and damage to the eye lens. The assessment of different aspects of UV damage has attracted researchers' interest. UV radiation to simple biological models such as Saccharomyces cerevisiae of yeast family could help to find out different molecular changes resulting from radiation. The assessment and network analysis of gene expression data about yeast cells radiated by the UV laser was the aim of this study. Methods: The gene expression profiles of S. cerevisiae samples in the presence of the UV laser at 30 seconds radiation and 15 minutes' post-radiation time are compared with the control profiles. The significant expressed genes interacted and the central nodes and related biological terms were identified. Results: The main connected component of the network including 427 nodes was analyzed and 11 central differentially expressed genes (DEGs) were determined. RPN11, UBI4, HSP82, and HSC82 as critical DEGs and "positive regulation of telomere maintenance" as a related biological term were introduced. Conclusion: The finding has provided a new perspective on laser application in the rejuvenation process. It seems that the laser can be used as a suitable agent against the aging process which is a limiting factor in human life.

Harnessing the Keratinolytic Activity of Bacillus licheniformis Through Random Mutagenesis Using Ultraviolet and Laser Irradiations.

Keratinase is one of the important proteases, which is widely used for converting keratin of the keratinaceous materials into various value-added products. In this study, a popular keratinase producer, Bacillus licheniformis PWD-1, was exposed to ultraviolet (UV) and He-Ne laser irradiations to develop high keratinase-producing mutants. Laser irradiation showed a higher lethality of cells (94%) than UV treatment (92%), whereas laser treatment required a longer time (75min) than UV treatment (20min). A total of 58 mutants were selected from 176 isolates to study protein and keratinase production capability of the mutants. The highest keratin-to-casein (K:C) ratio (1.43) was exhibited by LU11 mutant, which was obtained from the combined laser and UV irradiations. The purified keratinase (65kDa) of LU11 showed 40% yield 1.7-fold purity, while the respective value for wild enzyme was 29% and 1.3-fold. Both enzymes showed optimal activity at 55 ℃ and pH 8, with a Z value of 15.78 ℃ for LU11 and 19.72 ℃ for wild strain. The Vmax and specific constant (Kcat/Km) of the mutant enzyme were 357.17 U/ml and 33.11min-1mM-1, respectively, which were significantly higher than the respective values of wild enzyme (102.04 U/ml and 28.36min-1mM-1).

Microscopic Kinetics in Poly(Methyl Methacrylate) Exposed to a Single Ultra-Short XUV/X-ray Laser Pulse.

We study the behavior of poly(methyl methacrylate) (PMMA) exposed to femtosecond pulses of extreme ultraviolet and X-ray laser radiation in the single-shot damage regime. The employed microscopic simulation traces induced electron cascades, the thermal energy exchange of electrons with atoms, nonthermal modification of the interatomic potential, and a triggered atomic response. We identify that the nonthermal hydrogen decoupling triggers ultrafast fragmentation of PMMA strains at the absorbed threshold dose of ~0.07 eV/atom. At higher doses, more hydrogen atoms detach from their parental molecules, which, at the dose of ~0.5 eV/atom, leads to a complete separation of hydrogens from carbon and oxygen atoms and fragmentation of MMA molecules. At the dose of ~0.7 eV/atom, the band gap completely collapses indicating that a metallic liquid is formed with complete atomic disorder. An estimated single-shot ablation threshold and a crater depth as functions of fluence agree well with the experimental data collected.

High-performance ion source generated by ultraviolet laser irradiation of Cu crystals

Ultraviolet laser driven radiation pressure acceleration of Cu crystals is investigated by using particle-in-cell simulations. When an ultrathin Cu crystal is irradiated by a circularly polarized pulse with wavelength λ = 72 nm, waist radius w0=4λ, and normalized magnitude a0=20 (energy of 85 mJ), a plasma with a lattice structure is generated first. Then, an acceleration field of 14.2 TV/cm can be induced by the radiation pressure of the ultraviolet pulse in the target, which is about one order of magnitude larger than that of optical lasers for the same a0, and the lattice structure exerts effect on the acceleration only in the vicinity of the optimal target thickness. As a result, a quasi-monoenergetic Cu ion beam of energy of 5 GeV (75 MeV/nucleon), a charge of 0.12 nC, and the emittance of 7×10−9 m rad can be produced, which implies that using ultraviolet lasers instead of optical lasers should turn down the size and emittance of ion sources by orders lower than that of optical lasers. Therefore, a high-performance ion source is produced, which may have potential applications in medical therapy and ion radiography.

Photonic methods for rapid crystallization of LiMn2O4 cathodes for solid-state thin-film batteries

High temperature and prolonged thermal annealing for the crystallization of cathode in thin-film batteries (TFBs) restricts the choice of current collector and substrates and causes lithium loss in the cathode. This work explores photonic-based alternatives for cathode crystallization, specifically xenon flash-lamp annealing (FLA), ultra-violet excimer laser irradiation (UV-laser), and infrared laser (IR) annealing. The effect of these methods is systematically compared to that of thermal annealing in terms of processing time, crystal structure and electrochemical performance of the LiMn2O4 model thin-film cathode. FLA and UV excimer laser can crystallize LMO cathode in short periods of 6 min and 25 min, respectively, compared to the reference (ref.) thermal processing time of 60 min at 600 °C. The performance of the FLA-processed LMO cathodes (crystallinity, capacity, diffusion coefficient) is comparable to that of the thermal ref. with a capacity of 6 μAh cm−2 and 5 μAh/cm−2 at 15 C for FLA and thermal ref. respectively, with the practical limit of the 150 nm LMO film being 9.5 μAh cm−2. A thin-film FTO/LMO/Li3POxNy/Li solid-state battery was assembled and cycled at a high rate of 10 C with only a negligible capacity fade of 3.6% after 200 cycles. FLA can be used as an effective alternative for fast crystallization of thin-film cathodes on temperature-sensitive substrates and is suitable for upscaling processes.

Effect of Nanosecond Ultraviolet Laser Radiation on the Structure and Adhesion Properties of Metals and Alloys

t—The effect of ultraviolet (UV) laser radiation on the structure and adhesion properties of materials such as chromated bronze, stainless refractory austenitic chromium-nickel steels, and copper, has been experimentally studied. It has been shown that the surface microstructuring of elements of a diffusion-bonded joint improves its mechanical properties as to its tensile strength and tensile strain. Some results are presented for the laser perforation of a copper interlayer and the laser surface microstructuring of ceramic blanks which provide improvement in the mechanical properties of a Si3N4/Cu/Si3N4 welded joint.

深紫外激光辐照加速材料老化系统的光学设计

深紫外激光辐照加速材料老化系统的光学设计

A Comparative Study of Laser-Induced Graphene by CO2 Infrared Laser and 355 nm Ultraviolet (UV) Laser.

Laser-induced graphene (LIG) is an emerging technique for producing few-layer graphene or graphene-like material that has recently received increasing attention, due to its unique advantages. Subsequently, a variety of lasers and materials have been used to fabricate LIG using this technique. However, there is a lack of understanding of how different lasers (wavelengths) perform differently in the LIG conversion process. In this study, the produced LIG on polyimide (PI) under a locally water-cooled condition using a 10.6 μm CO2 infrared laser and a 355 nm ultraviolet (UV) laser are compared. The experimental investigations reveal that under the same UV and CO2 laser fluence, the ablation of PI show different results. Surface morphologies with micron-sized and nanometer pores were formed by the UV laser under different laser fluences, whereas micron-sized pores and sheet structure with fewer pores were produced by the CO2 laser. Energy dispersive spectrometry and three-dimensional topography characterization indicate that the photochemical effects were also involved in the LIG conversion with UV laser irradiation. It is also observed through experiments that the photothermal effect contributed to the formation of LIG under both lasers, and the LIG formed on PI substrates by the CO2 laser showed better quality and fewer layers.

UV laser decontamination of chemical warfare agent simulants CEPS and malathion

Ultraviolet (UV) laser irradiation was applied to decontaminate chemical warfare agent simulants chloroethyl phenyl sulfide (CEPS) and malathion, with results obtained from gas chromatography–mass spectrometry analysis. Exposure of CEPS to a 266 nm laser exhibited feasible decontamination by dominantly producing the byproduct diphenyl disulfide. However, decontamination in the cases with 355 and 532 nm exposure on CEPS as well as 266 nm exposure on malathion were relatively inefficient. Results also show a strong correlation between decontamination efficiency and absorption probability, which indicates the importance of selecting proper laser wavelengths and supports the photochemical mechanism of UV laser decontamination.

Ionization and dissociation of benzene and aniline under deep ultraviolet laser irradiation

We report a study on photo-ionization of benzene and aniline with incidental subsequent dissociation by the customized reflection time-of-flight mass spectrometer utilizing a deep ultraviolet 177.3 nm laser. Highly efficient ionization of benzene is observed with a weak C4H3+ fragment formed by undergoing disproportional C-C bond dissociation. In comparison, a major C5H6+· fragment and a minor C6H6+· radical are produced in the ionization of aniline pertaining to the removal of CNH· and NH· radicals, respectively. First-principles calculation is employed to reveal the photo-dissociation pathways of these two molecules having a structural difference of just an amino group. It is demonstrated that hydrogen atom transfer plays an important role in the cleavage of C-C or C-N bonds in benzene and aniline ions. This study is helpful to understand the underlying mechanisms of chemical bond fracture of benzene ring and related aromatic molecules.

ZnO Microwire-Based Fiber-Tip Fabry-Pérot Interferometer for Deep Ultraviolet Sensing

We propose a simple deep ultraviolet (UV) sensor consisting of a conventional single-mode optical fiber capped with a ZnO microwire. The ZnO microwire positioned on the fiber-tip acts as a Fabry-Pérot interferometer, of which the reflection spectrum can be employed for UV light monitoring. When ZnO microwire is exposed to UV irradiation, variations in the concentration of photogenerated carriers will result in the change of the refractive index (RI) of the ZnO microwire, and thus interference wavelengths of the proposed device exhibits red-shift with a sensitivity of 0.288 nm/(W·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) under 266-nm deep UV laser irradiation. Meanwhile, a fast response time of 0.56 ms is experimentally obtained. The results may pave a new way for fast responsive, highly spatial-resolved optical fiber UV sensors.

Ultrathin Highly Flexible Featherweight Ceramic Temperature Sensor Arrays.

We fabricated highly flexible Sr- and Ni-doped perovskite SmMnO3 thermistor film sensor arrays on an ultrathin (5 μm thick) and lightweight (21 mg) polyimide sheet for healthcare monitoring devices. The Ag nanowire and nanoparticle-impregnated carbon microcone array, which was prepared by precisely controlled surface laser carbonization of polyimide, showed sufficiently low resistance as a bottom electrode and good stability against sharp bending angles. The dot-shaped (diameter: 900 μm) perovskite thermistor film with a thickness of 900 nm was crystallized by pulsed ultraviolet laser irradiation of a precursor film printed with perovskite nanoparticle dispersion ink, and the film functioned well as the thermistor with a thermistor constant of 2820 K. The thermistor sensor sheet exhibited rapid responses to temperature variation and high stability in the temperature cycle tests over 1000 cycles between room temperature and 80 °C. The bending durability for a bending angle of 60° with a small bending radius (500 μm) was also high. During the bending test over 1000 cycles, the monitoring temperature variation was suppressed only within 0.1 °C. This ultrathin sensor array sheet can be mounted on surfaces with shape variations, and we used the sensor for real-time monitoring in healthcare to detect precise temperature variations on the human skin during physical exercise.

Nanosecond laser fabrication of superhydrophobic surface on 316L stainless steel and corrosion protection application

Herein, we developed an facile, cost-effective and efficient method to fabricate microstructures of different scales on 316 L stainless steel substrate surface by laser modification. By changing the laser parameters, such as various laser fluence (2.69, 3.96, 6.28, 8.14,9.55 J/cm2) during laser irradiation, different sizes of micro-cracks and brain-like microstructures can be obtained. The experimental results indicate that a static contact angle of 160 ± 5° and the sliding angle of 3 ± 0.5°, can be achieved at a scanning interval of 30.0 μm and laser fluence of 8.14 J/cm2, which has the best outstanding wettability. In addition, the microstructures and chemical compositions on the surface were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The corresponding corrosion resistance properties was evaluated by the means of potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The laser textured superhydrophobic surface was found to enhance the corrosion resistance dramatically. Also, after the laser modification, excellent self-cleaning performance was demonstrated based on tests with quartz sand particles. Particularly, we extensively discussed how the structures on the 316 L stainless steel were formed after the ultraviolet nanosecond laser irradiation and the interaction mechanism of the laser and substrate. This study not only provides important insights into the formation mechanism of laser textured surfaces, but also guides practical industrial applications as this approach is simple, low-cost and convenient for fabrication of large-area superhydrophobic surfaces on various metal materials.

Programmed Ultrafast Scan Welding of Cu Nanowire Networks with a Pulsed Ultraviolet Laser Beam for Transparent Conductive Electrodes and Flexible Circuits.

Metal nanowires (NWs) have shown superior advances for the next-generation transparent conducting (TC) materials. Most concerns were focused on uniform conductive films; however, fabrication of a programmed circuit is still lacking. Here, we demonstrate a programmable ultrafast welding method by pulsed laser beam scanning under ambient conditions to achieve a Cu NW pattern-free TC circuit as well as various size films. High-aspect ratio Cu NWs (> 3000) are synthesized through an oleylamine-mediated solution system. Pulsed ultraviolet laser irradiation together with a programmed moving station is set up for the welding of Cu NW networks. Finite element simulations reveal that the transient heating by efficient absorption of UV light (∼ 250 nm) could remove the organic residues on the surface and realize local welding of interlaced NW junctions. With only 10 ms pulsed irradiation, high optoelectronic performance (33 ohm/sq. at 87% transmittance at 550 nm) and excellent stability of the Cu NW TC film have been achieved. The line-by-line and selected route scanning modes could rapidly make large area TC films and directly write flexible circuits. Moreover, completely transparent micron-size UV and blue LED chips are fabricated and successfully lit with bright emission. This method opens up a future way of circuit and device fabrication by direct one-step laser writing.

Development of inorganic-organic hybrid nanostructured material for H2O2 sensing application

An organic-inorganic hybrid nanoparticle (HNPs) composed of Sm(TTA)3Phen, a coordination compound, and NaY0.78Er0.02Yb0.20F4, an upconversion nanoparticles (UCNPs), has been developed and used for H2O2 sensing application. Herein, Sm(TTA)3Phen absorbs ultraviolet (UV) light and gives fluorescence in yellow-red-near infrared (NIR) region. Whereas, the UCNPs absorb NIR radiations (980 nm) and consequently emit in green-red region through photon upconversion process. Two important optical phenomena are observed when HNPs are simultaneously excited with UV (266 nm) and NIR (980 nm) laser radiation- (i) an energy transfer from Sm3+ to Er3+ ions, and (ii) color tunable emission from red to green, if the power of 980 nm laser is varied. Further, the material is highly competent to sense H2O2 through fluorescence quenching of Sm3+ emission in presence of H2O2. The nature of quenching is conspicuously different for different concentration/volume range of H2O2. For lower volume range, the rate of decrease of emission/excitation intensity is linear, while for higher volume range the decay in intensity is exponential. The attained minimum detection limit for H2O2 is 2 μl, which is significant for sensing applications.