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Numerical Investigation of Ultrashort Laser-Ablative Synthesis of Metal Nanoparticles in Liquids Using the Atomistic-Continuum Model
摘要： We present a framework based on the atomistic continuum model, combining the Molecular Dynamics (MD) and Two Temperature Model (TTM) approaches, to characterize the growth of metal nanoparticles (NPs) under ultrashort laser ablation from a solid target in water ambient. The model is capable of addressing the kinetics of fast non-equilibrium laser-induced phase transition processes at atomic resolution, while in continuum it accounts for the effect of free carriers, playing a determinant role during short laser pulse interaction processes with metals. The results of our simulations clarify possible mechanisms, which can be responsible for the observed experimental data, including the presence of two populations of NPs, having a small (5–15 nm) and larger (tens of nm) mean size. The formed NPs are of importance for a variety of applications in energy, catalysis and healthcare.
关键词： metal nanoparticles,femtosecond laser ablation,dual nanoparticle distribution,pulsed laser ablation in liquids
更新于2025-09-16 10:30:52
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Laser-Ablative Synthesis of Isotope-Enriched Samarium Oxide Nanoparticles for Nuclear Nanomedicine
摘要： Nuclear nanomedicine is an emerging field, which utilizes nanoformulations of nuclear agents to increase their local concentration at targeted sites for a more effective nuclear therapy at a considerably reduced radiation dosage. This field needs the development of methods for controlled fabrication of nuclear agents carrying nanoparticles with low polydispersity and with high colloidal stability in aqueous dispersions. In this paper, we apply methods of femtosecond (fs) laser ablation in deionized water to fabricate stable aqueous dispersion of 152Sm-enriched samarium oxide nanoparticles (NPs), which can capture neutrons to become 153Sm beta-emitters for nuclear therapy. We show that direct ablation of a 152Sm-enriched samarium oxide target leads to widely size- and shape-dispersed populations of NPs with low colloidal stability. However, by applying a second fs laser fragmentation step to the dispersion of initially formed colloids, we achieve full homogenization of NPs size characteristics, while keeping the same composition. We also demonstrate the possibility for wide-range tuning of the mean size of Sm-based NPs by varying laser energy during the ablation or fragmentation step. The final product presents dispersed solutions of samarium oxide NPs with relatively narrow size distribution, having spherical shape, a controlled mean size between 7 and 70 nm and high colloidal stability. The formed NPs can also be of importance for catalytic and biomedical applications.
关键词： nuclear nanomedicine,samarium (Sm) oxide nanoparticles,pulsed laser ablation in liquids,femtosecond laser ablation and fragmentation
更新于2025-09-16 10:30:52
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Selective rear-side ablation of aluminum thin layers with ultrashort-pulsed laser radiation
摘要： In recent years, several applications for laser ablation of thin metal layers from the fused silica substrate side have been studied. The rear-side ablation is a highly effective ablation method for thin layer structuring and reveals a high structuring quality. Therefore, the present work dealt with the selective rear-side ablation of thin aluminum layers (10–50 nm) on fused silica with ultrashort-pulsed laser radiation (λ = 1028 nm, ??H = 0.2–10 ps and w0,86 = 15.2 μm). The influences of pulse duration and layer thickness on the ablation thresholds as well as the incubation coefficients were determined. For layer thicknesses of 30 and 50 nm, a decrease of the ablation threshold with increasing pulse duration was determined. Whereas, the ablation threshold remained constant for layer thicknesses of 10 and 20 nm. Different morphologies were observed depending on the process parameters. The rear-side ablation of aluminum proceeded over the melting phase and no lift-off process had taken place. In addition to experimental investigations, calculations were carried out to determine the theoretical threshold fluences. The theoretical values were compared to experimental data. With the help of these investigations, the quality of the structuring of aluminum layers can be improved.
关键词： ultrashort-pulsed laser radiation,incubation coefficients,aluminum thin layers,laser ablation,rear-side ablation
更新于2025-09-16 10:30:52
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Synthesis of colloidal aluminum nanoparticles by nanosecond pulsed laser and the effect of external electric field and laser fluence on ablation rate
摘要： In this paper, the ablation of aluminum was induced by a Q-switched Nd:YAG laser (1064 nm, ~10 ns and 10 Hz) in ethanol at room temperature for producing colloidal nanoparticles. Two different experimental schemes (i.e. the electric field parallel, and perpendicular to the laser propagation path) were used to investigate the dependence of ablation rate on the external electric field characteristics and the laser fluence. The results show that at a constant laser fluence, regardless of the type of scheme, the ablation rate is increased in the presence of electric field. However, the characteristics of craters strongly depend on the direction of the electric field. The results also show that at both schemes with a constant electric field, the ablation rate rises when the laser fluence is increased. According to the results, it can be concluded that the ablation rate enhanced by applying electric field and increasing laser pulse energy.
关键词： Ablation rate,Laser materials processing,Laser ablation efficiency,Electric field,Ethanol interaction ambient
更新于2025-09-16 10:30:52
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[IEEE 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) - Berlin, Germany (2019.7.23-2019.7.27)] 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Hyperspectral imaging for thermal effect monitoring in in vivo liver during laser ablation
摘要： Thermal ablation is a minimally invasive technique used to induce a controlled necrosis of malignant cells by increasing the temperature in localized areas. This procedure needs an accurate and real-time monitoring of thermal effects to evaluate and control treatment outcome. In this work, a hyperspectral imaging (HSI) technique is proposed as a new and non-invasive method to monitor ablative therapy. HSI provides images of the target object in several spectral bands, hence the reflectance/absorbance spectrum for each pixel. This paper presents a preliminary and original HSI-based analysis of the thermal state in the in vivo porcine liver undergoing laser ablation. In order to compare the spectral response between treated and untreated areas of the organ, proper Regions of Interest (ROIs) were chosen on the hyperspectral images; for each ROI, the absorbance variation for the selected wavelengths (i.e., 630, 760, and 960nm, for deoxyhemoglobin, methemoglobin, and water respectively) was assessed. Results obtained during and after laser ablation show that the absorbance of the methemoglobin peaks increases up to 40% in the burned region with respect to the non-ablated one. Conversely, the relative change of deoxyhemoglobin and water peaks is less marked. Based on these results, absorbance threshold values were retrieved and used to visualize the ablation zone on the images. This preliminary analysis suggests that a combination of the absorbance information is essential to achieve a more accurate identification of the ablation region. The results encourage further studies on the correlation between thermal effects and the spectral response of biological tissues undergoing thermal ablation, for final clinical use.
关键词： laser ablation,absorbance spectrum,in vivo porcine liver,hyperspectral imaging,thermal ablation
更新于2025-09-16 10:30:52
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Comparison of Perioperative Costs between Stereotactic Laser Ablation and Craniotomy for Hypothalamic Hamartoma
摘要： Hypothalamic hamartoma (HH) is a congenital intracranial lesion associated with precocious puberty and gelastic epilepsy in children. Surgical management of HH to treat refractory epilepsy is a mainstay of treatment. Our aim was to compare the demographic characteristics and perioperative costs associated with resection by craniotomy and stereotactic laser ablation (SLA) by reviewing our institutional experience with SLA and comparing these data to a national database for craniotomy and resection. Retrospective chart review was conducted for the Texas Children’s Hospital cohort of patients who underwent SLA for HH between 2011 and 2013. Information about the craniotomy cohort representing historical cases of craniotomy was obtained from the Kids’ Inpatient Database for years 2003, 2006, and 2009. The cohort definition for patients undergoing craniotomy for HH was modified from published adult literature to identify pediatric patients with refractory epilepsy secondary to HH. Our study has shown that children undergoing SLA for HH have a shorter length of stay and lower cost of hospitalization compared with those who underwent craniotomy and resection for the same diagnosis. Together with previous findings from our institution regarding the safety and efficacy of SLA, our findings suggest that SLA may represent an attractive alternative to craniotomy for the treatment of refractory epilepsy secondary to HH.
关键词： hypothalamic hamartoma,epilepsy,hospitalization charges,gelastic seizures,stereotactic ablation,laser ablation,cost
更新于2025-09-16 10:30:52
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Nucleate boiling heat transfer performance of different laser processed copper surfaces
摘要： Present study reports the nucleate pool boiling characteristics of micro structured copper surface developed by utilizing two different laser systems, namely, pulsed Nd:YAG laser and continuous wave laser. Tests are conducted at atmospheric pressure and saturation temperature by using water as pool liquid. Enhancement in heat transfer coefficients was observed over all laser processed surfaces. The maximum enhancement in heat transfer coefficient was found to be 136% and 93% for the micro structured surfaces developed by using continuous wave and pulsed laser, respectively, compared to the reference smooth surface. The enhancement in heat transfer performance of micro structured surfaces are due to the presence of surface pores, grooves and micro cavities generated due to laser melting process.
关键词： micro cavities,continuous wave laser,laser ablation,Nd:YAG,nucleate pool boiling,pulsed laser
更新于2025-09-16 10:30:52
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Femtosecond lasers for high-precision orthopedic surgery
摘要： Laser micromachining with ultrashort pulses has shown great promise for clean, safe surgical treatment of bone tissue. However, comparisons of performance and development of “best practice” have been hampered by the difficulty of comparing results across a wide variety of experimental approaches and under surgically irrelevant conditions (e.g., dried, dead bone). Using a femtosecond (fs) pulsed laser system (τ = 140 fs, repetition rate = 1 kHz, λ = 800 nm), a comprehensive study of femtosecond laser microsurgery using the standard metrics of laser micromachining (ablation threshold, incubation effects, ablation rates, effect of focal point depth within the material and heat affected zone (HAZ)) was conducted on live, freshly harvested bovine and ovine cortical bone. Three important points of optimism for future implementation in the surgical theatre were identified: (1) the removal of material is relatively insensitive to the focal point depth within the material, removing the need for extreme depth precision for excellent performance; (2) femtosecond laser ablation of fresh bone demonstrates very little incubation effect, such that multiple passes of the laser over the same region of bone removes the same amount of material; and (3) the complete absence of collateral damage, heat- or shock-induced, on both the macro- and microscopic scales can be achieved readily, within a broad parameter range. Taken together, these results indicate a handheld or robotic deployed fiber laser platform for femtosecond laser microsurgery is a very viable prospect.
关键词： Laser ablation,Ultrafast laser micromachining,Femtosecond microsurgery,Laser micromachining,Orthopedic surgery
更新于2025-09-16 10:30:52
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Fundamentals and Applications of Fourier Transform Mass Spectrometry || Fourier transform ion cyclotron resonance mass spectrometry and laser: A versatile tool
摘要： The coupling of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with laser combines the attributes of laser mass spectrometry with the analytical capabilities of a mass spectrometer having high resolution, high mass measurement accuracy, long ion-observation times, and exceptional ion isolation capabilities required for ion-molecule reaction or ion fragmentation studies [1–3]. The laser may be used for different purposes in mass spectrometry. The most standard one is to generate ions from the surface of the laser-irradiated sample. Two regimes have to be considered in respect with the laser fluence (energy deposit per surface unit in J/cm2) or the laser power density also named irradiance (power density deposit per surface unit in W/cm2). At low laser fluence, laser desorption/ionization (LDI) may take place. When the laser fluence increases, the regime of laser–matter interaction is modified and laser ablation (LA) occurs. In both cases, the ionization phenomenon and the transfer of the atoms or molecules to the gas phase are the direct result of the laser matter interaction. LDI and LA are well suited to the analysis of a wide range of organic, inorganic and also biological compounds. For complex matrices, it is important to note that information may be obtained on both organic and inorganic species. This is of first importance for the study of environmental or composite samples for example, in which organics, inorganics and/or polymers are intimately associated.
关键词： laser,Fourier transform ion cyclotron resonance mass spectrometry,laser desorption/ionization,organic compounds,mass spectrometry imaging,inorganic compounds,laser ablation
更新于2025-09-16 10:30:52
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X-ray radiation protection aspects during ultrashort laser processing
摘要： Ultrashort pulse laser processing of materials allows for precise machining with high accuracy. By increasing the repetition rate to several 100 kHz, laser machining becomes quick and cost-effective. Ultrafast laser processing at high repetition rates and peak intensities above 1013 W/cm2 can cause a potential hazard by generation of unwanted x-ray radiation. Therefore, radiation protection must be considered. For 925 fs pulse duration at a center wavelength of 1030 nm, the x-ray emission in air at a repetition rate of 400 kHz was investigated up to a peak intensity of 2.6 × 1014 W/cm2. Based on the presented measurements, the properties of potential shielding materials will be discussed. By extending our previous works, a scaling of the x-ray radiation emission to higher peak intensities up to 1015 W/cm2 is described, and emitted x-ray doses are predicted.
关键词： laser-induced x-ray emission,ultrashort pulse laser processing,laser ablation,radiation protection
更新于2025-09-16 10:30:52