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Characterization of the Chinese Traditional Medicine <i>Artemisia annua</i> by Laser-Induced Breakdown Spectroscopy (LIBS) with 532?nm and 1064?nm Excitation
摘要： In order to investigate the influence of laser wavelength on the detection of the metals in Artemisia annua, pulsed lasers operating at wavelengths of 1064 nm and 532 nm for laser-induced breakdown spectroscopy (LIBS) have been employed to generate the plasma. The spectral lines of Mg (II) at 279.54 nm, CN at 388.29 nm, Ca (II) at 393.37 nm and Fe (II) at 404.27 nm were used to evaluate the optical emission at various delay times for the 532 nm and the 1064 nm laser. The effects of the data acquisition delay time on the line intensity, signal-to-background ratio and the characteristic parameters of laser plasma have been investigated as well. The results show that the 1064 nm beam induced plasmas with higher signal-to-background ratios and temperatures than the 532 nm beam. However, the 532 nm laser beam produced plasma with higher electron densities than the 1064 nm laser beam. In addition, a significant influence has been found: the spectral intensities of the ions were stronger than the spectral intensities of the atoms independent of whether the laser was operated at 532 nm or 1064 nm.
关键词： laser induced plasma,Artemisia annua,laser induced breakdown spectroscopy (LIBS)
更新于2025-09-12 10:27:22
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Spatial Molecular AlO Temperature Distributions in Laser-Induced Plasma
摘要： Spatially resolved, line-of-sight measurements of aluminum monoxide emission spectra in laser ablation plasma are used with Abel inversion techniques to extract radial plasma temperatures. Contour mapping of the radially deconvolved signal intensity shows a ring of AlO formation near the plasma boundary with the ambient atmosphere. Simulations of the molecular spectra were coupled with the line profile fitting routines. Temperature results are presented with simultaneous inferences from lateral, asymmetric radial, and symmetric radial AlO spectral intensity profiles. This analysis indicates that shockwave phenomena in the radial profiles, including a temperature drop behind the blast wave created during plasma initiation were measured.
关键词： laser-induced plasma,Abel transform,plasma spectroscopy,molecular spectroscopy,plasma dynamics,laser-induced breakdown spectroscopy,diatomic spectroscopy
更新于2025-09-12 10:27:22
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Lithium Distribution in Structured Graphite Anodes Investigated by Laser-Induced Breakdown Spectroscopy
摘要： For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.
关键词： laser-induced breakdown spectroscopy,3D battery,lithium-ion battery,ultrafast laser ablation,graphite anode
更新于2025-09-12 10:27:22
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Femtosecond laser-induced breakdown spectroscopy of a preheated Cu target
摘要： We present a study detailing femtosecond laser-induced breakdown spectroscopy (LIBS) of Cu with the sample preheated to di?erent temperatures (22–120 °C). The detected spectral intensity of the plasma emission increased with the target temperature. Additionally, laser-induced plasma temperature was calculated by Boltzmann plot method. The plasma temperature rose along with the target temperature, indicating an enhanced interaction between the laser and the target in the case of a higher target temperature. We also simulated the thermal behavior of Cu irradiated by the femtosecond laser via a two-temperature model. As the sample temperature increased from 22 °C to 120 °C, the increase in the lattice temperature under femtosecond laser irradiation was approximately 200–300 K, and the ablated depth increased. The simulated results suggested that increasing the sample temperature led to an increase in the ablated mass. Based on this work, it can be seen that the method of preheating the ablation target can help enhance the spectral intensity and the detection sensitivity of femtosecond LIBS.
关键词： LIBS,Sample temperature,Femtosecond laser,Laser-induced breakdown spectroscopy
更新于2025-09-12 10:27:22
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Simultaneous measurements of fuel concentration and temperature in gas jets by laser induced breakdown spectroscopy
摘要： Laser induced breakdown spectroscopy (LIBS) enables quantitative measurements of the equivalence ratio in flames, spray and gas jets. Although there are always considerable temperature differences between the calibrations and the LIBS measurements in flames and fuel jets, the temperature effects on LIBS were rarely mentioned and not corrected in the previous LIBS measurements. In this study, a novel method to simultaneously measure the equivalence ratio and the gas temperature by LIBS in a single laser shot is proposed. This method can correct the temperature effects based on the linear correlation between the peak intensity ratio (PIR) of atomic lines and the gas temperature. The PIR of H656/N746 and the full width at half maximum (FWHM) of H656 are employed to establish calibration curves with the equivalence ratio and the gas temperature, respectively, and both of calibrations show high coefficients of determination (R2). Then, the measurement accuracy and precision of the proposed method are discussed in detail. The total uncertainties in measurements of equivalence ratio and gas temperature are estimated by 5.6% and 5.8%, respectively. Finally, the simultaneous measurements of equivalence ratios and gas temperatures in methane jets at different positions and at different injection pressures are conducted. The comparison of equivalence ratios before and after correction of the temperature effects indicates that the accuracy of the fuel concentration measurements by LIBS would be remarkably degraded if the temperature variations were neglected.
关键词： Measurement uncertainties,Laser-induced breakdown spectroscopy (LIBS),Equivalence ratio,Gas temperature,Full width at the half maximum (FWHM)
更新于2025-09-12 10:27:22
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Investigation of compositional variations in chromitite ore with imaging Laser Induced Breakdown Spectroscopy and Spectral Angle Mapper classification algorithm
摘要： This paper focusses on the applicability of the Spectral Angle Mapper (SAM) algorithm for supervised classification of imaging Laser Induced Breakdown Spectroscopy (LIBS) data. Our main objective is to investigate variations in the chemical/mineralogical composition of complex ore from the sub-millimetre to the metre scale, which may offer novel and barely investigated interpretation opportunities for exploration purposes. This research is based on coarse chromitite ore from Merensky Reef, represented by a drill core and a small section through the upper chromitite layer. Detailed LIBS-based imaging measurements were accompanied by space-resolved reference measurements based on SEM/MLA and EDXRF, as well as bulk chemical analyses for multiple core slices. The SAM algorithm was applied for classification of LIBS hyperspectral images with respect to differences in mineral chemistry. Our investigations focused on the pre-processing of LIBS spectra prior to SAM classification, on spectral library development, as well as on the validation of the classified data. The SAM classification algorithm, which is solely based on ratios between spectral intensities, was found insensitive to normal shot-to-shot plasma variations and to chemically induced matrix effects. However, the algorithm may become inaccurate at low signal to noise ratios, at the border between different mineral grains (mixed spectra), or when classifying chemically similar phases such as pyrite and pyrrhotite. The extent of mixed spectra depends both on the size of the mineral grains as well as on the spot size of the LIBS laser. The SAM algorithm was successfully applied for classification of several base metal sulphides, rock-forming minerals, accessory minerals, as well as several mixed phases representing the main borders between different mineral grains. The resulting classified LIBS image shows the spatial distribution of the different phases, which is in very good agreement with the space-resolved reference measurements based on EDXRF and SEM/MLA. The results also highlight the extremely heterogeneous distribution of e.g. the sulphide phases in the investigated core piece. The applicability of the LIBS-SAM classification image for estimating metal concentrations based on point counting has been explored for Cu, Ni, S, and Cr. We conclude that this approach, when applied on sufficiently large surfaces, enables semi-quantitative data analysis, as well as the possible detection of trace elements (e.g. Pt, Pd) that occur in very small nuggets.
关键词： Chromitite Ore,Core Scanner,Spectral Angle Mapper,Geochemical Exploration,Laser Induced Breakdown Spectroscopy (LIBS),Mineral Classification
更新于2025-09-12 10:27:22
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Comparison of Calibration Approaches in Laser-Induced Breakdown Spectroscopy for Proximal Soil Sensing in Precision Agriculture
摘要： The lack of soil data, which are relevant, reliable, a?ordable, immediately available, and su?ciently detailed, is still a signi?cant challenge in precision agriculture. A promising technology for the spatial assessment of the distribution of chemical elements within ?elds, without sample preparation is laser-induced breakdown spectroscopy (LIBS). Its advantages are contrasted by a strong matrix dependence of the LIBS signal which necessitates careful data evaluation. In this work, di?erent calibration approaches for soil LIBS data are presented. The data were obtained from 139 soil samples collected on two neighboring agricultural ?elds in a quaternary landscape of northeast Germany with very variable soils. Reference analysis was carried out by inductively coupled plasma optical emission spectroscopy after wet digestion. The major nutrients Ca and Mg and the minor nutrient Fe were investigated. Three calibration strategies were compared. The ?rst method was based on univariate calibration by standard addition using just one soil sample and applying the derived calibration model to the LIBS data of both ?elds. The second univariate model derived the calibration from the reference analytics of all samples from one ?eld. The prediction is validated by LIBS data of the second ?eld. The third method is a multivariate calibration approach based on partial least squares regression (PLSR). The LIBS spectra of the ?rst ?eld are used for training. Validation was carried out by 20-fold cross-validation using the LIBS data of the ?rst ?eld and independently on the second ?eld data. The second univariate method yielded better calibration and prediction results compared to the ?rst method, since matrix e?ects were better accounted for. PLSR did not strongly improve the prediction in comparison to the second univariate method.
关键词： laser-induced breakdown spectroscopy,soil nutrients,elemental composition,proximal soil sensing,LIBS
更新于2025-09-12 10:27:22
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Influence of distance between target surface and focal point on CN emission of nanosecond laser-induced PMMA plasma in air
摘要： Laser-induced breakdown spectroscopy (LIBS) is a technique for spectral composition analysis of materials containing atomic and ionic emission lines, as well as a few molecular emission bands. Here we focused our study on molecular emission from CN (B2∑+→X2∑+) based on LIBS method. Polymethyl methacrylate (PMMA) was ablated by employing a Nd:YAG laser system in air under atmospheric pressure. In the ultraviolet range, the molecular emission intensities of CN violet bands were observed with a spectrometer equipped with an intensified CCD detector. The effect of distance between sample surface and focal point (DTSFP) on the intensities of molecular emission was studied in detail. The results showed that the molecular emission intensities of CN violet bands exhibited a strong dependence on the DTSFP. As the surface of the PMMA sample approached the focal point gradually, the emission intensity of CN increased at first and then dropped down. In addition, vibrational temperature of CN molecule was also calculated. The vibrational temperature showed the similar change in the emission intensity, while the position at the maximum vibrational temperature was inconsistent with the position at the CN intensity.
关键词： CN,distance between sample surface and focal point,laser-induced breakdown spectroscopy,PMMA
更新于2025-09-12 10:27:22
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APPLICATION OF LASER-INDUCED BREAKDOWN CAVITATION BUBBLES FOR CELL LYSIS IN VITRO
摘要： Objective: Understanding the basic mechanism of the cavitation bubble action on living cells as a crucial step of development and application of sophisticated methods based on controlled cavitation in cell behaviour manipulation. Optimisation of parameters in order to expand cell lysis region created by a single bubble. Methods: The cavitation bubbles are generated by the laser-induced breakdown method. The impact of controlled cavitation bubble on the biological system is synchronously monitored under a microscope and recorded. Visualization of the cavitation bubble course is monitored by a high-speed camera. The impact of technology on the healthy confluent cell layer is verified. Evaluation of the cavitation bubbles′ effect on cells in real time and by subsequent analysis of the cell lysis region and impact of the cavitation bubble on cell viability is carried out by optical visualization and life/dead fluorescence staining. Results: Cavitation bubble induced in distance of 1.5 mm from the cell surface overcomes properties of sessile bubble and enables to create cell lysis region over 1000 μm in diameter due to transient shear stress produced by liquid displaced by the bubble expansion. Conclusion: Cell lysis region is strongly dependent on the spot laser energy (SLE) and the bubble induction distance from cells. This knowledge is crucial for application in chemical free cell lysis in vitro, wound induction for experimental purposes and cell layers patterning in desired scale.
关键词： Laser-induced breakdown,Cavitation bubble,Cell viability,Cell lysis
更新于2025-09-12 10:27:22
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Ionization-field instability in the laser-induced breakdown of nanoporous dielectric
摘要： The theory of ionization-?eld instability in a continuous homogeneous medium is generalized to the heterogeneous nanoporous one with the purpose to clear and analyze the mechanism of nanograting formation during the optical breakdown process in a transparent dielectric (fused silica) containing multiple small inclusions (nanobubbles) with a lowered ionization threshold. Based on the Maxwell Garnett approximation extended to include the size effect caused by the ?nite ratio of the bubble sizes to the scale of unstable perturbations, we have obtained the equation system describing the spatiotemporal evolution of the plasma density, average ?eld, and effective dielectric permittivity and have derived the characteristic equation connecting the temporal growth rate of these perturbations with their spatial period. Analysis of the roots of this equation shows that the unstable periodic perturbation structure having the maximal growth rate is close in character to the nanogratings observed experimentally (modulation in the direction of the pump wave polarization with the period approximately equal to the half-wavelength in the host material).
关键词： laser-induced breakdown,nanograting formation,nanoporous dielectric,Maxwell Garnett approximation,ionization-field instability
更新于2025-09-12 10:27:22