Application Of Laser-induced Breakdown Spectroscopy Research Articles

Assessment of gunshot residue detection on a large variety of surfaces by portable LIBS system for crime scene application

The application of Laser-Induced Breakdown Spectroscopy (LIBS) in forensic science has garnered increasing attention. The ability to perform real-time, on-site analysis of Gunshot Residue (GSR) particles and potential elements originating from bullets or projectile cores on various surfaces holds the potential to assist in resolving firearms-related cases. This includes facilitating trajectory determination by locating distinct impact points and identifying the types of ammunition used. This study evaluates the utilization of a portable LIBS device for ballistic forensic purposes. Additionally, it focuses on the assessment of potential false positives and false negatives arising from the different materials where the shots have been fired. Since the system performs laser ablation of both surface particles and the substrate, it emphasizes the importance of conducting preliminary screening in an area with the same composition as the impact zone to minimize potential false positives during direct surface analysis. Furthermore, the results demonstrate the capability to detect the constituent elements of characteristic gunshot residue particles (GSR particles): lead (Pb), antimony (Sb), and barium (Ba) adhering to bullets, as well as the principal elements composing the jacket or core of the projectile: lead (Pb), copper (Cu), and zinc (Zn) through direct analysis, without the need for a sampling kit, on different surfaces such as walls, furniture, or fabrics. Analyses conducted a month after the shots were fired indicate the potential for finding residues in the vicinity of the bullet hole. Analyses conducted a month after the shots were fired indicate the possibility of finding residues in the area around the bullet hole.

Application of laser-induced breakdown spectroscopy for the analysis of pig bones

An application of the laser-induced breakdown spectroscopy technique (LIBS) for the elemental analysis of pig shoulder bone samples is reported. Measurements were performed using a compact laboratory-made LIBS system based on the TEA CO2 laser and time-integrated signal detection. The recorded spectra consisted of well-defined atomic and single-charged ionic lines of bone matrix elements (Ca and P) and other constituent elements (e.g. Mg, Zn, Na, K, and C) with a good signal-to-noise ratio suitable for chemical analysis. Based on the elemental composition of bone samples measured by inductively coupled plasma emission spectroscopy, limits of detection (LOD) of LIBS analysis were estimated for several elements. LOD ranged from 2.2 ppm (K) to 16 ppm (Zn). Carbon and Hα spectral lines were used for plasma diagnostics by measuring Stark widths. Optical profilometry was used to assess the capability of LIBS for depth profile analysis. For laser fluence between 13.0 and 18.2 J cm−2, the ablation rate per pulse ranged from 6 to 10 μm.

Advancing Elemental and Isotopic Analysis of Uranium Mineral Inclusions: Rapid Screening via Laser-Induced Breakdown Spectroscopy and High-Resolution Laser Ablation-ICP-MS Mapping

The work presented herein employs two laser-based analytical techniques (laser-induced breakdown spectroscopy (LIBS) and laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS)) to spatially determine the elemental and isotopic composition of uranium bearing minerals. Uniquely, this work leverages the high-speed applicability of LIBS to “screen” the sample(s) for their elemental constituents. After determining the location of the uranium inclusions (via LIBS), high-resolution LA-ICP-MS was employed to further characterize the inclusions. The high-resolution (sub-µm) capabilities of LA-ICP-MS were able to extract important information from the uranium minerals including discerning its chemical form (e.g., finchite from carnotite, Sr- and K-bearing uranyl vanadates, respectively) as well as their 235U/238U isotopic composition. This approach, LIBS followed by LA-ICP-MS, significantly reduces the analysis time (∼95 %) in comparison to employing a LA-ICP-MS only approach. Furthermore, this work presented a novel approach to analyzing inclusions via a particle/inclusion analysis tool which is commercially available within the iolite 4 software. This tool allowed for a more accurate characterization of the isotopic distribution of the inclusions, as well as allowing for rapid sizing of the inclusions. This analytical approach could readily be applied to other sample types in which the target species (e.g., µm-sized inclusions) are embedded in complex matrices (e.g., cm-sized samples).

Laser-induced breakdown spectroscopy in inhomogeneous fuel sprays: A novel calibration methodology for local stoichiometry

This paper presents a novel calibration for estimating the local stoichiometry of inhomogeneous sprays when using Laser-Induced Breakdown Spectroscopy (LIBS). The LIBS spectrum in inhomogeneous sprays appears to consist of coexisting spectra. This renders the traditional curve-fit calibration method inapplicable and impedes the determination of local equivalence ratios. A hypothesis is proposed that the spray LIBS spectra can be regarded as a discrete superposition of regions in the detection area with distinct compositions. A novel calibration approach is then proposed to test the simplest version of this hypothesis by identifying the best correlation between the spray LIBS spectra and a binary superposition of the calibration spectra. A local equivalent stoichiometry can then be estimated for the best correlated match. This approach generates spectra with high correlation to the test spray spectra for the majority of sparks, and hence provides a novel insight into LIBS application for inhomogeneous fuel/air mixtures. Test cases where the leaner region already contains fuel (ϕlean > 0) have high probability of successful ignition.

Application of Laser-Induced Breakdown Spectroscopy for Depth Profiling of Multilayer and Graded Materials.

Laser-induced breakdown spectroscopy (LIBS) has emerged as a powerful analytical method for the elemental mapping and depth profiling of many materials. This review offers insight into the contemporary applications of LIBS for the depth profiling of materials whose elemental composition changes either abruptly (multilayered materials) or continuously (functionally graded or corroded materials). The spectrum of materials is discussed, spanning from laboratory-synthesized model materials to real-world products including materials for fusion reactors, photovoltaic cells, ceramic and galvanic coatings, lithium batteries, historical and archaeological artifacts, and polymeric materials. The nuances of ablation conditions and the resulting crater morphologies, which are instrumental in depth-related studies, are discussed in detail. The challenges of calibration and quantitative profiling using LIBS are also addressed. Finally, the possible directions of the evolution of LIBS applications are commented on.

Elemental Analysis of Printing Ink with the Application of Laser-Induced Breakdown Spectroscopy (LIBS)- A Review

Forgery cases involving printed documents have recently increased due to advanced printing technologies. As a result, various analytical instruments are currently applied in forensic document examination to analyse printing ink. Analyses of printing ink are primarily focused on the ink’s chemical components, namely colourants, vehicles, and additives. Previous studies on ink analysis show an increasing trend in the use of spectroscopy methods including the application of Laser-Induced Breakdown Spectroscopy (LIBS). This instrument is favoured by document examiners in analysing printing ink due to its versatility, simple preparation, multi-elemental detection, minimal destruction, and precise readings. The examination of printing ink using LIBS is reviewed in this publication in addition to findings from previous research. The strengths and drawbacks of this technique, as well as contemporary approaches, are also explored in this article.

Investigation of thermodynamic properties in picosecond laser-produced plasmas on silicon

The validity of local thermodynamic equilibrium (LTE) in plasma is a long-term concern for laser-induced breakdown spectroscopy applications. In this paper, the spatial and temporal dependence of LTE deviation in picosecond laser-induced plasmas has been proved. A picosecond (∼20 ps) laser operated at 532 nm was used to ablate a silicon target to produce plasma at a pressure of 10−5 mbar. A general electron energy distribution function was used to provide access to the insight into population ratios of different energy levels for the spatially and temporally resolved optical emission intensity of laser-induced plasma. A precise temporal and spatial LTE boundary of plasma generated in picosecond laser ablation was obtained, and the results showed that only at delay times of 180–300 ns, the plasma away from the surface (>4 mm) is in LTE.

Application of Laser-Induced Breakdown Spectroscopy for Quantitative Analysis of the Chemical Composition of Historical Lead Silicate Glasses

The study of the chemical composition of historical glasses is widely used in archaeometry. The results of such analyses provide information on the probable date, place, and technological features of their production. Over time, a weathered layer may form on the surface of the glass, which differs in composition from the original one. To determine the initial composition using conventional methods (for example, X-ray fluorescence spectroscopy), the weathered layer should be removed. For historical objects, such manipulation is unacceptable and should be minimized. One of the methods for analyzing the chemical composition with minimal damage to a sample is laser-induced breakdown spectroscopy. The aim of this work was to develop a LIBS method, which makes it possible to perform a quantitative analysis of lead silicate glasses, including glasses containing a weathered layer. Reference glasses with a variable content of potassium, silicon, and lead oxides were synthesized, and based on the LIBS spectra, a calibration dependence was obtained that made it possible to measure the concentration of lead and potassium oxides in glasses within 70–85 and 5–20 wt%, respectively. The method was applied to analyze the composition of the glaze on a historic glazed tile from the burial church in the Euphrosinian monastery in Polotsk (the second half of the 12th century AD). The crater formed with the laser beam on the glazed surface was about 200 microns. Such damage is negligible compared to the total surface area of the tile (~10 cm2). The thickness of the weathered glaze layer was 70 microns, which was determined using variation in lead oxide content.

Radial characteristics of laser-induced plasma under the influence of air pressure

Air pressure is one of the key factors affecting laser-induced breakdown spectroscopy (LIBS), and the mechanism of its influence on the spatial–temporal evolution of laser-induced plasma (LIP) is still not fully understood due to complex physical processes. In this study, the spatially and temporally resolved LIP’s spectra at different pressures were collected from the direction of laser incidence, and the radial distribution characteristics of LIP along the target surface under the influence of air pressure were studied. Furthermore, the spatial–temporal evolution of the radial distribution of the electron density n e and electron temperature T e was studied using Stark broadening and a Boltzmann plot. Finally, the radial distribution of LIP satisfying the McWhirter criterion and the influence of air pressure on its spatial–temporal evolution were studied. It was found that air pressure has a significant effect on the radial distribution of LIP. The spectral intensity, electron density n e, and the electron temperature T e of the LIP decrease faster against distance r from the LIP core and slower with the delay time T d in a higher air-pressure environment. Furthermore, the LIP will gradually fail to satisfy the McWhirter criterion with the increase in the radius r and delay time T d; in addition, the lifetime of LIP, which satisfies the McWhirter criterion, is longer at higher pressure. This study is helpful in clarifying the influence of air pressure on the spatial–temporal evolution of LIP, optimizing the experimental parameters of LIBS, and providing a reference for application of LIBS.

Progress Toward Machine Learning Methodologies for Laser-Induced Breakdown Spectroscopy With an Emphasis on Soil Analysis

Optical emission spectroscopy of laser-produced plasmas, commonly known as laser-induced breakdown spectroscopy (LIBS), is an emerging analytical tool for rapid soil analysis. However, specific challenges with LIBS exist, such as matrix effects and quantification issues, which require further study in the application of LIBS, particularly for the analysis of heterogeneous samples, such as soils. Advancements in the applications of machine learning (ML) methods can address some of these issues, advancing the potential for LIBS in soil analysis. This article aims to review the progress of LIBS application combined with ML methods, focusing on methodological approaches used in reducing matrix effect, feature selection, quantification analysis, soil classification, and self-absorption. The performance of various adopted ML approaches is discussed, including their shortcomings and advantages, to provide researchers with a clear picture of the current status of ML applications in LIBS for improving its analytical capability. The challenges and prospects of LIBS development in soil analysis are proposed, offering a path toward future research. This review article emphasizes ML tools for LIBS soil analysis, which are broadly relevant for other LIBS applications.

Analysis of Rare Earth Ores Using Laser-Induced Breakdown Spectroscopy and Laser Ablation Time-of-Flight Mass Spectrometry

Rare earth elements are gaining significant importance in the scientific and technological fields for their exciting physical properties and characteristics. The aim of the present study was to determine rare earth elements (REEs) in geological ores found in the Northern Areas of Pakistan. We present the application of laser-induced breakdown spectroscopy (LIBS) and laser ablation time-of-flight mass spectrometry (LA-TOF-MS) for the elemental analysis of geological ore samples containing REEs. The laser-induced plasma plume exhibits a wide array of emission lines, including those of rare earth elements such as Ce, La, and Nd. Furthermore, the spectral range, from 220 nm to 970 nm, encompasses emission lines from C, Fe, Ti, Na, Mg, Si, and Ca. The qualitative analysis of the constituent elements in the samples was performed by comparing the LIBS spectrum of the unknown sample with that of the spectroscopically pure rare earth elements (La2O3, CeO2, and Nd2O3, with 99.9% metals basis) recorded under the same experimental conditions. The quantitative analysis was performed using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS), LA-TOF-MS, and energy-dispersive X-ray (EDX) techniques. The results obtained by CF-LIBS were found to be in good agreement with those obtained using the LA-TOF-MS and EDX analytical techniques. LIBS is demonstrated to yield a quick and reliable qualitative and quantitative analysis, of any unknown geological sample, comparable to that of the other analytical techniques.

Preliminary study of laser-induced breakdown spectroscopy for non-destructive pressure measurement in confined vacuum interlayers

The pressure measurement within a closed vacuum chamber is a crucial indicator for evaluating vacuum performance. The commonly used puncture and sampling method is destructive to the device. This paper presents a new method based on laser-induced breakdown spectroscopy (LIBS) to evaluate the pressure inside a confined, transparent vacuum sandwich. The intensity of the emission spectra of copper sheets inside the sandwich was tested at different pressures, and three cylindrical cavities of different heights were subjected to experiments. The results show that the Cu and O intensity ratio varies linearly with gas pressure in the 1–103 Pa range, which can be used to predict the pressure inside the interlayer. It is fast, non-destructive, and remotely detectable. This work extends the application of LIBS for spatial confinement effects to enhance the spectral intensity and provides a new idea for pressure measurement in confined devices.

Analytical approaches for food authentication using LIBS fingerprinting

Laser-induced breakdown spectroscopy (LIBS) is a widely acknowledged elemental analysis approach used in various study domains due to its rapid measurement capability and minimal sample-preparation requirements. Recently, there has been an increase in interest in the applications of LIBS in the realm of food safety and quality. Given that the majority of commonly consumed foods exhibit only modest trace-element variations, discovering predictive spectral patterns through multivariate analysis is crucial for the data-analysis pipeline. The efficacy of multivariate analysis and machine-learning algorithms to identify the most predictive spectral features, conduct class recognition and classification was evaluated in this paper, utilizing both a custom-developed benchtop LIBS system and a commercially available portable one. Specifically, this study's objective was to evaluate the performance of spectral variable selection using elastic-net multinomial logistic regression. The data processing pipeline and the LIBS hardware were evaluated in the context of food authentication and identification, a rising field of research addressing the issue of food fraud. Our findings indicated that classifying food samples with carefully selected fewer variables reduces model overfitting and improves the accuracy of LIBS pattern classification. In a broader sense, the results support the continued development of field-deployable, portable LIBS equipment designed for food authentication and fingerprinting activities.

Using laser-induced breakdown spectroscopy for the study of chloride diffusion in mortar and concrete

In this work, the applicability of Laser-Induced Breakdown Spectroscopy (LIBS) for the analysis of chloride diffusion in mortar and concrete has been studied. The high resolution of this technique allows it to obtain a mapping of the chloride ions distribution in these materials upon being exposed to salted environments, thus providing an image of how chlorides diffuse inside them. The technique has been applied to mortar samples submerged in a salt-saturated solution for 3, 9, and 30 months. It has been demonstrated that the penetration profiles fit reasonably well Fick’s second law in a modified version. The apparent diffusion coefficients for these samples were obtained (D3months = (5.94 ± 0.05) × 10−13 m2/s; D9months = (3.6 ± 0.6) × 10−13 m2/s; D30months = (2.1 ± 0.8) × 10−13 m2/s). These results are in the range of the values found in other similar studies. The study of the evolution of these parameters over time revealed an age-factor α = 0.449 ± 0.006. Finally, LIBS was also applied to a concrete sample submitted to a long-period (60 months) immersion in the salt-saturated solution, giving similar good results (D60months = (1.81 ± 0.03) × 10−13 m2/s), which demonstrates its suitability for the study of chloride diffusion in this type of material.

A data selection method for matrix effects and uncertainty reduction for laser-induced breakdown spectroscopy

Severe matrix effects and high signal uncertainty are two key bottlenecks for the quantitative performance and wide applications of laser-induced breakdown spectroscopy (LIBS). Based on the understanding that the superposition of both matrix effects and signal uncertainty directly affects plasma parameters and further influences spectral intensity and LIBS quantification performance, a data selection method based on plasma temperature matching (DSPTM) was proposed to reduce both matrix effects and signal uncertainty. By selecting spectra with smaller plasma temperature differences for all samples, the proposed method was able to build up the quantification model to rely more on spectra with smaller matrix effects and signal uncertainty, therefore improving final quantification performance. When applied to quantitative analysis of the zinc content in brass alloys, it was found that both accuracy and precision were improved using either a univariate model or multiple linear regression (MLR). More specifically, for the univariate model, the root-mean-square error of prediction (RMSEP), the determination coefficients (R 2) and relative standard derivation (RSD) were improved from 3.30%, 0.864 and 18.8% to 1.06%, 0.986 and 13.5%, respectively; while for MLR, RMSEP, R 2 and RSD were improved from 3.22%, 0.871 and 26.2% to 1.07%, 0.986 and 17.4%, respectively. These results prove that DSPTM can be used as an effective method to reduce matrix effects and improve repeatability by selecting reliable data.

Interactive three-dimensional chemical element maps with laser-induced breakdown spectroscopy and photogrammetry

Imaging the spatial distribution of chemical elements at a sample surface is a common application of laser-induced breakdown spectroscopy with vast scientific and technological applications. Yet, typical imaging solutions only explore the creation of two-dimensional maps, which can limit the interpretability of the results and further diagnostics in three-dimensional settings. Within this context, this work explores the combination of spectral imaging techniques and photogrammetry to deploy a versatile solution for the creation of three-dimensional spectral imaging models. First, by making use of a numerical algorithm that is able to match features in the spectral image with those of the three-dimensional model, we show how to match the mesh from distinct sensor modalities. Then, we describe a possible visualization workflow, making use of dedicated photogrammetry and visualization software to easily deploy interactive models. Overall, the results demonstrate the versatility of our approach and pave for the development of novel spectral imaging diagnostic strategies that are able to deliver better qualitative analysis and insight in the three-dimensional space.

On the use of laser-induced breakdown spectroscopy data for mineralogical investigations – constraints and application of a clustering method

This study examines how laser-induced breakdown spectroscopy (LIBS) data collected using a downhole deployable LIBS prototype for geochemical analysis in a fashion that imitates downhole deployment may be used for mineralogical investigations. Two chemically and mineralogically practically identical felsic rocks, namely granite and microgranite, are used to assess the effects of rock texture on mineral classification and high-resolution SEM-TIMA (scanning electron microscope coupled with TESCAN's integrated mineral analyser) mineral maps are used to reveal mineralogical composition of each LIBS ablation crater. Additionally, in order to extend the LIBS application for fast mineralogical studies to a greenfield scenario (i.e. no previous knowledge) a clustering methodology is presented for mineralogical classification from LIBS data. Results indicate that most LIBS spot analyses sample mineral mixtures, 91.2 and 100% for granite and microgranite, respectively, which challenges mineralogical classification, particularly for fine-grained rocks. Positive identification and classification of minerals of slightly different compositions relative to the bulk rock (i.e. fluorite and biotite in granitic rocks) demonstrates how minerals or minerals groups of distinct and interesting chemical compositions (e.g. sulfides or oxides in silicate-dominated rocks) can be rapidly recognized in a mineral exploration scenario. Strategies for overcoming mineral mixture issues are presented and recommendations are given for effective workflows for mineralogical analysis using LIBS data in different mineral exploration stages. Supplementary material : Complete LIBS analyses for granite and microgranite samples (Appendix A); modal mineralogy results for each LIBS ablation crater based on TIMA analysis (Appendix B); and TIMA mineral maps for granite and microgranite samples are available at https://doi.org/10.6084/m9.figshare.c.6444482

Application of Machine Learning and Laser-Induced Breakdown Spectroscopy to Flame Spray Pyrolysis for the Prediction of Catalyst Properties

Flame spray pyrolysis (FSP) can rapidly synthesize nanomaterials with desired physical and chemical properties. However, the broad parameter space of FSP and postcharacterizations of the synthesized nanomaterials can slow down the material discovery process. In this work, we applied laser-induced breakdown spectroscopy (LIBS) and machine learning (ML) models to characterize catalysts’ properties, which can decrease the number of postcharacterizations. The LIBS spectra are used as the descriptor to predict crystalline phase information, lattice constants (Å), and oxygen vacancy percentages (OV % s) of Ce–Mn–Zr solid solution catalysts by support vector classifiers and regressors. The balanced accuracies of making a correct prediction of phase information can reach 0.796, 0.829, 0.765, and 0.886 for tetragonal ZrO2, tetragonal α-MnO2, tetragonal β-MnO2, and tetragonal Mn3O4 phases, respectively. The lattice constants and OV % s of the testing samples can be predicted with root-mean-squared errors of 0.04 and 0.05, respectively. These accuracies indicate that ML models can identify an inferred relation between emission spectra and catalysts’ quality to determine the phase information, lattice constant (Å), and OV % of solid solution samples. Implementing LIBS and ML to FSP can provide rapid optimization of process parameters and rational guidance on novel material synthesis.

Evaluation of the nutrients in milk supplements suitable for children using LIBS and PAS technique

The presence of macro and micro nutrients essential for human health in four milk supplements is quickly identified using Laser-induced Breakdown Spectroscopy (LIBS) and Photoacoustic Spectroscopy (PAS). In addition to the minerals reported by the manufacturers, some additional spectral signatures of the elements like Na and K are also observed in the LIBS spectra which are not listed by some manufacturers. The ratio of various minerals like Ca/Mg, Na/Mg, etc. has been evaluated, and found a good correlation with the nutritional value listed on the product packaging. The organic elements C, H, N, and O together with the CN molecular band observed in the LIBS spectra of milk supplement indicate the presence of organic molecules. PAS is used for the identification of organic compounds such as Vitamins, Proteins, Fat, Taurine, and Sucrose in milk supplements. The results of the present study help in selecting milk supplements suitable for children suffering from chronic kidney diseases and diabetes. Based on the presence of minerals and their relative concentration, milk supplements are classified into three groups by applying Principal Component Analysis (PCA). Therefore, the results from the present work extend the application of LIBS and PAS together with PCA for the identification of the nutrients in milk supplements.

Comprehensive Analysis of Copper Plasma: A Laser-Induced Breakdown Spectroscopic Approach

The emergence of diversified applications of laser-induced breakdown spectroscopy in the biomedical field, electronics, space physics, and material processing necessitates a comprehensive understanding of plasma parameters. The present work delineates the structure and evolution of copper plasma under different ambient pressures (0.01 mbar to 100 mbar) along with other plasma parameters. The study reveals the role of ambient pressure in the increase of plasma temperature (Te), electron density (Ne), number of particles in the Debye sphere, plasma frequency, inverse bremsstrahlung absorption coefficient, electron thermal velocity, electron–ion collision frequency and in the decrease of Debye length (λD) and plasma skin depth (PSD). The experimental techniques and the theoretical explanations for the variation of plasma parameters and their applications are also detailed. As the ambient pressure increases, the motion of plasma species becomes restricted, resulting in the increase of Te, calculated using the Boltzmann plot. From the values of λD, PSD, and Ne, it is understood that the copper plasma under investigation is thermally non-relativistic and satisfies McWhirter’s criterion, thus, revealing the local thermodynamic equilibrium condition of plasma. The effects of Debye shielding and stark broadening on the spectral lines are also investigated. Thus, the study helps bring newfangled dimensions to the application of plasma by exploring the possibility of tailoring plasma parameters.