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Formation of ordered defect structures in lithium niobate crystals of different chemical composition at non-equilibrium processes of different nature
摘要： Ordered defective structures in lithium niobate crystals have been established. The phenomenon is a result of non-equilibrium processes of a different nature: photo-induced light scattering, laser ablation, and creation of cracks during relieving mechanical stresses. The shape of such structures depends on the nature and energy that affect a crystal. A number of concentric areas with a different density of laser-induced defects with a changed refractive index appear during photoinduced light scattering. Concentric clusters of microdomains appear in a macrodomain of another sign at laser ablation as a result of local switching under impulse laser radiation. A number of microcracks with a fractal structure appear near main macro-crack during cracking under mechanical stress. Thus, appearance of ordered defective structure occurs not only in the local spot of direct exposure to laser radiation, mechanical stress, etc., but also in some volume of a crystal around it.
关键词： Doping,Laser ablation,Lithium niobate,Mechanical stress,Defective structure,Photorefractive effect
更新于2025-11-21 11:24:58
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Fractional laser ablation for the targeted cutaneous delivery of an anti-CD29 monoclonal antibody – OS2966
摘要： Monoclonal antibodies targeting cytokines are administered parenterally for the systemic treatment of severe psoriasis. However, systemic exposure to the biologic increases the risk of side-effects including immunosuppression, whereas only a small fraction of the active molecules actually reaches the target organ, the skin. This preclinical study examines the feasibility of delivering a humanized anti-CD29 monoclonal antibody (OS2966) topically to skin using minimally-invasive fractional laser ablation. This approach would enable the targeted use of a biologic for the treatment of recalcitrant psoriatic plaques in patients with less widespread disease while minimizing the risk of systemic exposure. First, the effect of a wide range of laser poration conditions on skin permeation and deposition of OS2966 was tested in vitro to determine optimal microporation parameters. Subsequently, confocal laser scanning microscopy was employed to visualize the distribution of fluorescently-labelled OS2966 in skin. The results demonstrated that delivery of OS2966 into and across skin was feasible. Above fluences of 35.1 J/cm2, skin deposition and permeation were statistically superior to passive delivery reaching values up to 3.7 ± 1.2 μg/cm2 at the most aggressive condition. Selective targeting of the skin was also possible since ≥70% of the OS2966 was delivered locally to the skin. Although nanogramme quantities were able to permeate across skin, these amounts were orders of magnitude lower than levels seen following subcutaneous or intravenous injection and would result in minimal systemic exposure in vivo. The diffusion of fluorescently-labelled OS2966 into the skin surrounding the pores was clearly higher than in intact skin and demonstrated the feasibility of delivering the antibody at least as deep as the dermo-epithelial junction, a critical border region where inflammatory cells cross to promote disease progression. These preliminary results confirm that fractional laser ablation can be used for the cutaneous delivery of OS2966 and now preclinical/clinical studies are required to demonstrate therapeutic efficacy.
关键词： fractional laser ablation,cutaneous delivery,OS2966,psoriasis,monoclonal antibodies
更新于2025-11-21 11:08:12
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Controllable preparation of phase-separated Pb/Zn heterogeneous nanoparticles by laser ablation and their application in the growth of PbS tipped ZnS nanorods heterostructures
摘要： Phase-separated Pb/Zn heterogeneous nanoparticles (Pb/Zn HNPs) with a controllable phase ratio were firstly prepared by long-pulse-width millisecond laser ablation of Pb/Zn binary metal target immersed in anhydrous ethanol under room conditions. The phase ratio in the as-ablated Pb/Zn HNPs was mainly determined by the molar ratio of Pb/Zn in the initial binary metal target and the structure of Pb/Zn HNPs was partly influenced by the pulse laser width. Then the PBS tipped ZnS nanorods heterostructures (PbS/ZnS heterostructures) were grown by simply heating the mixture of the as-ablated Pb/Zn HNPs and thioacetamide (TAA) at 450 (cid:1)C in a tube furnace. The size and morphology of Pbs/ZnS heterostructures were decided by the original absolute size and relative size between phase-separated Pb and Zn nanoparticle. The formation of Pbs/ZnS heterostructures was the result of the diffusion-limited of S atoms in the Pb/Zn HNPs. This study not only provides a new strategy for the controllable preparation of phase-separated bimetallic nanoparticles that can be used for the growth of specific heterostructures but a new view on the fundamental physical and chemical aspects of nanocrystal formation after laser ablation of solids in liquids.
关键词： Heterostructure,Phase-separated,Heterogeneous nanoparticles,Laser ablation,Binary metal target,Diffusion-limited
更新于2025-11-14 17:04:02
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Increased UV absorption properties of natural hydroxyapatite-based sunscreen through laser ablation modification in liquid
摘要： Sunfilters based on hydroxyapatite (HAp) and iron-containing compounds (Fe2O3 and calcium iron phosphates) are of increasing interest, as they show UV absorption without generating health endanger free radicals (usually observed when other inorganic sunscreens are used). In this paper, laser ablation of solids in liquids has been applied to improve the UV absorption properties of a HAp based Fe-containing sunscreen powder derived from cod fish bones. Two different laser wavelengths were explored (532 and 1064 nm, green and infrared respectively); an improved experimental device was used, to allow a fine control of the volume of the irradiated particles. Results show an increased UV absorbance for the laser-treated powders in comparison with the untreated ones; this can be explained considering the smaller particle size and increased surface area; the higher iron concentration in the powders may also be determinant. Enhanced absorption was also observed in the near-infrared range, making the powders even more suitable for sunscreen applications. The green laser was more effective than the infrared one. Overall, laser ablation showed to be a powerful technique to control the size of the sunscreen particles and tailor their optical properties.
关键词： hydroxyapatite,Liquid laser ablation,UV protection,sunscreen
更新于2025-11-14 15:25:21
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Photocatalytic performance of TiO2 thin film decorated with Cu2O nanoparticles by laser ablation
摘要： Cu2O nanoparticles decorated TiO2 thin films were fabricated by laser ablation. The effects of Cu2O nanoparticles on the structure, optical properties and photocatalytic performance of TiO2 thin film were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectrometer system, optical absorption and photocatalytic evaluation system, respectively. XRD patterns indicate that the decoration has the effect of lowering the grain orientation of Cu2O. The photocatalytic performance in hydrogen generation of Cu2O decorated TiO2 composite thin film was significantly improved compared with that of either Cu2O nanoparticles or TiO2 single layer thin film with 1.70 and 1.77 times, respectively. The oxidation of Cu2O was demonstrated to dominate the photocatalytic performances of Cu2O/TiO2 composite thin films by varying the laser ablation powers.
关键词： Heterojunction,Cu2O nanoparticles,Laser ablation,Photocatalytic performance,TiO2 thin film
更新于2025-10-22 19:40:53
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Electrostatically Directed Assembly of Nanostructured Composites for Enhanced Photocatalysis
摘要： It is well established that the activity of photocatalysts can be improved by deposition of redox catalysts, which can effectively extract the photogenerated charge carriers, enhance the rate of interfacial reactions, and thus suppress undesired recombination processes. For optimum performance, a high degree of control over the loading, size, and surface catalytic properties of redox catalyst particles is desirable. Herein, a novel, highly controllable, and versatile method for preparation of TiO2 catalyst composites is reported. It starts with the generation of “naked” (ligand-free) nanoparticles of CuOx or FeOx by pulsed laser ablation of metal oxide targets in water. In the next step, a nearly quantitative colloidal deposition of CuOx and FeOx nanoparticles onto anatase TiO2 substrate is achieved by adjusting the pH in order to establish electrostatic attraction between the colloids and the substrate. The resulting TiO2–CuOx and TiO2–FeOx assemblies with optimum catalyst amount (≈0.5 wt%) exhibit photocatalytic rates in degradation of 2,4-dichlorophenoxyacetic acid enhanced by a factor of ≈1.5 as compared to pristine TiO2 under simulated solar irradiation. The electrostatically directed assembly of TiO2 with ligand-free catalyst nanoparticles generated by pulsed laser ablation is thus demonstrated as a viable tool for preparation of composites with enhanced photocatalytic performance.
关键词： photocatalysis,titanium dioxide,laser ablation,colloidal deposition,nanoparticles
更新于2025-09-23 15:23:52
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Laser synthesis of iron nanoparticle for Fe doped hydroxyapatite coatings
摘要： Thin films of iron doped hydroxyapatite have been prepared by nanosecond Pulsed Laser Deposition (PLD). The composite target used for the deposition has been obtained by mixing commercial hydroxyapatite powder with iron-based nanoparticles produced by femtosecond laser ablation in liquid (LAL) (4% of iron nanoparticles). In fact, LAL technique allows to obtain metallic nanostructures without any toxic chemicals and reagents, with a green approach that is crucial for application in biological and medical technologies. Films have been prepared with substrate temperature growing from room temperature (RT) to 500 °C. The effect of deposition temperature on morphology, composition and structural properties of coatings has been investigated. Films deposited at higher temperature result dense and crystalline, they present microscale and nanoscale structures, an average surface roughness of 0.3 μm and magnetic properties suitable for biomedical applications.
关键词： PLD,Iron doped hydroxyapatite,Laser ablation in liquid,Regenerative orthopedic applications
更新于2025-09-23 15:23:52
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Effect of different hardness and melting point of the metallic surfaces on structural and optical properties of synthesized nanoparticles
摘要： The relations between macroscopic and microscopic characteristics of materials are of utmost importance for synthesis of multi-atomic structures with advanced properties. We analyze the influence of pulse duration, pulse energy and temperature of liquid on the process of formation of nanoparticles (NPs) of the metals (In, Sn, Zn and W) with different hardness and melting temperature by laser ablation in liquid environment. Composition, morphology dynamics and properties of nanoparticle suspensions are studied using TEM analysis and Z-scan technique. The nonlinear optical properties of NPs are analyzed at 800 and 400 nm using 60 fs and 200 ps pulses. We show that the temperature of liquid environment influences the formation of NPs and their nonlinear optical properties. In addition, pulse energy have little influence on the formation, morphology and size of NPs during ablation of low hardness and melting point metal (In). However, pulse duration plays a very important role during the formation of NPs, especially the ultra-short pulse has a positive effect on the preparation of NPs with smaller particle size.
关键词： nonlinear optical properties,metal nanoparticles,laser ablation in liquid
更新于2025-09-23 15:23:52
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Surface structural alteration of multi-walled carbon nanotubes decorated by nickel nanoparticles based on laser ablation/chemical reduction methods to enhance hydrogen storage properties
摘要： The catalytic effect of nickel is addressed to decorate the multi-walled carbon nanotubes for the purpose of hydrogen storage. The hydrogen sorption/desorption are investigated using the volumetric technique. Nickel nanoparticles are distributed on the surface of nanotubes using the laser ablation/chemical reduction treatments. The hydrogen uptake is elevated at higher nickel population up to a certain value and then experiences a significant drop for larger nickel content. The laser treatment is accompanied by the induced pores around nanotubes. This gives rise to the creation of the larger pores at higher laser doses leading to decrease the hydrogen trapping. Despite the pore size distribution strongly alters during both synthesis methods, however the abundance of small pore size in laser treatments is relatively higher than the that of the other technique. In comparison, the laser ablation demonstrates a relatively smaller desorption temperature against chemical one, mainly owing to the formation of larger pore size/volume. Generally, the hydrogen trapping efficiently takes place in the laser treated samples against chemical reduction method. The highest value of hydrogen storage ~1% (0.6% weight) is corresponding to 12.3% (13% weight) of nickel loading via the laser ablation (chemical reduction).
关键词： Hydrogen uptake,Nickel nanoparticles,Laser ablation,Chemical reduction,Pore size
更新于2025-09-23 15:22:29
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High-throughput laser generation of Si-nanoparticle based surface coatings for antibacterial applications
摘要： High-productivity regime of nanosecond IR-laser ablative generation of silicon colloidal solutions in water for anti-bacterial applications was found in terms of GW/cm2-level laser intensity and scanning velocity by measuring multi-shot ablative mass loss and extinction coefficients of the colloids as sub-linear and third-power intensity functions, respectively. This advantageous regime implies sub-linear mass loss versus laser intensity at the simultaneous third-power yield of nanoparticles, resulting from the subcritical-density, opaque ablative plasma regulating the sample ablation rate and the related plasma-mediated dissociation (dispergation) of the ablation products. In contrast, at higher intensities, there is a drastic increase in mass loss with the corresponding increased yield of (sub) micrometer-sized particles owing to intense plasma-driven expulsion of micro-scale melt droplets and the corresponding saturation of the extinction coefficient of the colloidal solutions because of their dynamic local “self-limiting” effect during the high-rate ablation. The optimal low-intensity regime for Si nanoparticle production demonstrates the monotonous correlated increase of mass loss and extinction coefficient in terms of increasing laser scanning velocity, indicating the diminished cumulative effects. Surface coatings prepared from the generated Si nanoparticles exhibit minor surface oxidation, as acquired as their elemental composition via energy-dispersive X-ray spectroscopy, making their contact angle for water droplets (≈51°) close to that of bare Si wafer (≈58°) with its nanometer-thick native oxide layer. Owing to good wetting, the nanoparticle-based surface coatings show strong antibacterial response regarding Gram-negative Pseudomonas auereginosa bacteria even despite their minor oxidative passivation.
关键词： Silicon nanoparticles,Colloids,Surface oxidation,Extinction coefficient,Wetting,Antibacterial tests,Gram-negative bacteria Pseudomonas auereginosa,Sub-critical ablative plasma,Nanosecond laser ablation,Mass loss
更新于2025-09-23 15:21:21