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Tuning of Citrate-stabilized Laser Ablated Silver Nanoparticles for Glyphosate Detection
摘要： The recent advances in nanotechnology can help develop both fast and cost-effective detection techniques to verify if the presence of contaminants in water resources is under safe limits, increasing temporal and geographical test coverage. For a specific analyte, the detection performance of citrate-stabilized silver nanoparticles depends on their chemical affinity, as well as on the ensemble characteristic of the colloid upon its de-stabilization by a mediated aggregation process. This work presents the tuning of citrate-stabilized silver nanoparticles produced by pulsed laser ablation in liquids for glyphosate detection in water. For fixed geometry and laser pulse characteristics, the ablation time, surfactant concentration and interaction pH were studied. The resulting colloidal solutions of silver nanoparticles with glyphosate were interrogated employing optical fiber spectroscopy. Two interrogation techniques which are based on a controlled aggregation of the colloid were used: UV-Vis extinction and Surface Enhanced Raman scattering. Using a calibration curve for low concentrations, the obtained limits of detection for glyphosate in water were 6 μM (1.0 mg/L) and 7.5 μM (1.3 mg/L), respectively.
关键词： SERS,silver nanoparticles,Glyphosate detection,laser ablation,LSPR
更新于2025-09-11 14:15:04
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Synthesis of molybdenum oxide nanoparticles by nanosecond laser ablation
摘要： Phothermal therapy (PTT) is one of the most promising techniques to treat cancer. Finding the ideal PTT agent nanomaterial has remained a challenge and has brought the interest of several researchers. In this work, we report the synthesis of molybdenum oxide (MoOx) nanoparticles (NPs), which exhibit absorption in the biological optical window ~840 nm, by using the laser ablation of solids in liquids (LASL) technique with nanosecond (ns) pulses. An Nd:YAG laser was used to synthesize the NPs in deionized (DI) water, free of surfactants or additives, which were optically characterized by absorption spectroscopy and TEM-EDX microscopy. Semi spherical NPs with a suitable average size and shape for potential use as PTT agents were obtained by laser ablation and ablation + fragmentation. The calculated band gap is 3.1 eV, which corresponds to MoO3. Micro-Raman spectroscopy studies determined that these NPs are composed of amorphous molybdenum oxide hydrates (MoO3 ? xH2O).
关键词： Molybdenum oxide,nanoparticles fragmentation,Photothermal therapy,laser ablation,photothermal agent
更新于2025-09-11 14:15:04
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An investigation of recast behavior in laser ablation of 4H-silicon carbide wafer
摘要： 4H-silicon carbide (SiC) is a suitable semiconductor material for high-speed power devices but also a typical difficult-to-process and hard-brittle material. Laser ablation is an efficient approach to process SiC. However, recast layer is an inevitable thermal damage during laser ablation. The present study experimentally and numerically investigated the recast behavior in laser ablation of 4H–SiC. The recast humps are with height of 1.4–3.3 μm and width of 12–22 μm, consist of SiC, Si, and SiO2, where 15.08 wt% of oxygen is detected. Microcracks and pore clusters are observed on the recast humps under SEM. Recoil pressure and surface tension in the molten pool dominate the process of recast hump formation. The recoil pressure of Si vapor is 2.27 MPa at 5000 K, as high as 22 times of atmospheric pressure. The simulation results show that the fluid in the middle flows around while the surrounding fluid flows upwards. The upward flow is almost laminar while the flow at the bottom of the molten pool is turbulent entertaining air and forming bubbles. The vaporization-induced keyhole in the molten pool becomes deeper and the sidewall becomes more inclined over time, accompanying with the “growing” of the recast hump. There are mainly three reasons causing the increase of recast height and recast width with the increased average laser power: (a) increase of recoil pressure; (b) increase of temperature gradient in the molten pool, enhancing the Marangoni convection; and (c) enlarging the molten pool and leading to more materials melting. With the decrease of the laser scanning speed, more liquid molten material is evaporated in the molten pool instead of being ejected outward to form recast humps. The increase of the laser pulse frequency decreases the peak laser intensity and hence results in the decrease of the recoil pressure. Besides, it also leads to the weakening of the heating ability of laser and lessening of the liquid molten material that could be ejected.
关键词： Marangoni convection,Recoil pressure,4H-silicon carbide,Recast layer,Laser ablation
更新于2025-09-11 14:15:04
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Raman Spectroscopy Investigation of Polytetrafluoroethylene in Different Zones of Impact of Continuous CO2 Laser Radiation
摘要： The surface of polytetra?uoroethylene (PTFE) irradiated with an IR laser was investigated by Raman spectroscopy. The degree of change in the surface depends on the ?uence of the radiation and on the impact zones around the center spot of the laser beam. New absorption bands detected in the spectrum of the irradiated polymer indicate the formation of CF3 groups as a result of the destruction of the polymer chain. Polymer chain carbonization is also observed under laser irradiation. The process of structural changes in laser irradiated PTFE is re?ned on the basis of obtained microphotographs of the supramolecular structure. Density functional theory calculations are used to help in interpreting the Raman spectra.
关键词： Raman spectroscopy,CO2 laser ablation,supramolecular structure,polytetra?uoroethylene
更新于2025-09-11 14:15:04
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A DLTS Perspective on Electrically Active Defects in Plated Crystalline Silicon n <sup>+</sup> p Solar Cells
摘要： Laser ablation (LA) has been compared with standard wet etching for contact opening in crystalline silicon n+p solar cells, from a perspective of electrically active defects, assessed by Deep-Level Transient Spectroscopy (DLTS). Copper metallization is employed, including a plated nickel diffusion barrier. It is shown that a hole trap around 0.17 eV above the valence band is systematically present in the depletion region of the junctions, irrespective of the contact opening method. This level could correspond with the substitutional nickel donor level in silicon and indicates that Ni in-diffusion occurs during the contact processing. No clear evidence for the presence of electrically active copper has been found. In addition, two other hole traps H2 and H3, belonging to point defects, have been observed after wet etching and standard LA, while for the highest laser power (hard LA) a broad band develops around 175 K, which is believed to be associated with dislocations, penetrating the p-type base region. Evidence will also be given for the impurity decoration of the dislocations, which enhances their electrical activity.
关键词： Deep-Level Transient Spectroscopy (DLTS),copper metallization,electrically active defects,laser ablation,nickel diffusion barrier,wet etching,crystalline silicon n+p solar cells
更新于2025-09-11 14:15:04
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Polymer–Mineral Composites Mimic Human Kidney Stones in Laser Lithotripsy Experiments
摘要： Despite the widespread use of laser lithotripsy to fragment kidney stones in vivo, there is a lack of robust artificial stone models to replicate the behavior of human stones during lithotripsy procedures. This need for accurate stone models is particularly important as novel laser technologies are introduced in the field of lithotripsy. In this work, we present a method to prepare composite materials that replicate the properties of human kidney stones during laser lithotripsy. Their behavior is understood through the lens of near-IR spectroscopy and helps to elucidate the mechanism of laser lithotripsy in kidney stone materials.
关键词： composite materials,artificial kidney stones,near-IR absorption,biomineralization,laser ablation
更新于2025-09-11 14:15:04
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Intense vortex high-order harmonics generated from laser-ablated plume
摘要： In this study, we demonstrate intense extreme-ultraviolet optical vortices generated using laser-ablation plume as the nonlinear medium. We used two types of plumes that are known to generate intense high-order harmonics for driving lasers with Gaussian beam profiles, but through different mechanisms, namely, carbon (diatomic carbon molecules) and tin (resonance with the autoionizing state). We find that the harmonic fluxes for diatomic carbon molecules are similar for Gaussian and vortex driving fields. However, for harmonics from the autoionizing state of tin (~26.3 eV), the enhancement factor of the resonant harmonic intensity decreases by ~50% when using the vortex driving field. The intense extreme-ultraviolet optical vortices demonstrated in this study will be useful for many applications including a material characterization technique known as optical angular momentum dichroism as well as the spectroscopy of spin-forbidden electronic transitions.
关键词： optical angular momentum dichroism,laser-ablation plume,spin-forbidden electronic transitions,extreme-ultraviolet optical vortices,high-order harmonics,diatomic carbon molecules,autoionizing state
更新于2025-09-11 14:15:04
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Obtaining of nanoparticles of Sc, Ti, V, Cr, Mn, Fe, Co, Ni with controlled sizes and properties using laser ablation
摘要： Using laser ablation, nanoparticles of Sc, Ti, V, Cr, Mn, Fe, Co, Ni with controlled sizes and properties were obtained. To obtain nanoparticles of a given size, not only ablation of massive targets was used, but fragmentation (exposure to a mixture of micro- and nanoparticles by laser radiation). The evolution of the particle size distribution function in the process of their laser fragmentation is investigated and its key parameters determining it are established, such as the energy density of a laser beam in a medium and the peak power of laser radiation. Different schemes for introducing laser radiation into colloidal systems have been used. To obtain nanoparticles that do not contain oxide films, organic alcohols (ethanol and propanol-2) were used as the working fluid. The obtained nanoparticles met the following criteria: 1). at least 95% of the particles in the preparation have the specified diameter; 2). The shape of the nanoparticles is close to spherical; 3). The composition of the nanoparticles does not include a significant amount of impurities and oxides; 4). In most of the nanoparticles, a metal crystal lattice is observed, although under certain conditions it is possible to obtain nanoparticles, both with the outer oxide layer and entirely consisting of oxides. The stability of the obtained colloid nanoparticles was investigated. It is assumed that the solvent is saturated with molecular hydrogen to prevent oxidation of nanoparticles during storage.
关键词： size control,laser ablation,nanoparticles,transition metals,oxidation prevention
更新于2025-09-11 14:15:04
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Sterilization for Bacillus Subtilis var. natto by Low Pressure Sputtering and Laser Ablation Plasma using Metal Powder Target
摘要： Effect of plasma sterilization for bacillus subtilis var. natto was studied using pulsed laser ablation and low pressure RF plasma, which usually used for functional thin film deposition. In addition, bulk and powder were used as the targets and compared the effect for the sterilization . Experimental results suggest that bacillus subtilis var. natto was not sterilized in the only vacuum state. However, they can be sterilized using low pressure RF plasma and pulsed laser ablation plasma irradiation. The effect of the sterilization using powder target was higher than that of bulk target, and that of the pulsed laser ablation plasma was higher than RF plasma. Those results suggest that the effect of sterilization was decided by the density of the high-energy metal atoms and ions.
关键词： plasma sterilization,plasma process,pulsed laser ablation
更新于2025-09-11 14:15:04
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Femtosecond transient absorption spectroscopy of laser-ablated graphite and reduced graphene oxide for optical switching behavior
摘要： Carbon based materials are considered as a rewarding contestant for optical devices due to its novel properties. In this study, graphite is laser-ablated and di?erent analytical methods such as XRD and Raman spectroscopy are used to evaluate the crystalline nature. In XRD, it indicates the decreased intensity after laser ablation but no change in peak positions resulted as graphite is very strong and hard material. Scanning electron microscopy (SEM) used to evaluate structural characteristics shows the overlapping layered structure after ablation. Reduced graphene oxide (rGO) is prepared by using modi?ed Hummers' method and reduced it by thermal reduction method. UV–Vis spectra con?rmed the peaks of graphite and rGO at 274 nm and 267 nm, respectively. To study the carrier relaxation dynamics of graphite and rGO, ultrafast Visible-pump/NIR-probe femtosecond transient absorption spectroscopy was used. Carrier relaxation occurred between 260 and 309 fs even after laser ablation damage, which is useful for future application of optical switching under high laser repetition.
关键词： Optical switching,Graphite,Graphene,Laser ablation,Transient absorption spectroscopy,Ultrafast spectroscopy
更新于2025-09-11 14:15:04