Traditional Laser-induced Breakdown Spectroscopy Research Articles

Enhancing analytical merits of laser-induced breakdown spectroscopy of hydrogen isotopes using an orthogonal double-pulsing scheme

Accurate detection and quantification of hydrogen isotopes in solid materials are vital for diverse applications, including fusion energy, hydrogen storage, and tritium production. Laser-induced breakdown spectroscopy (LIBS) is a well-established, rapid, standoff method for this purpose, but it faces challenges related to the analytical merits required for isotopic analyses. In this study, we enhance the analytical and detection capabilities of traditional single-pulse LIBS by implementing an orthogonal double pulsing approach, focusing on the analysis of a range of 2H concentrations in Zircaloy-4 substrates (acting as a proxy for 3H). The double-pulse experiments employed an orthogonal re-heating configuration with two nanosecond Nd:YAG lasers. We systematically evaluated critical parameters affecting the signal intensity in double-pulse LIBS, including interpulse delay, ambient gas pressure, and heating laser energy. Our results demonstrate that employing an orthogonal double-pulse scheme significantly enhances 2Hα emission while minimizing line broadening and self-absorption, ultimately improving the technique's analytical capabilities.

Analysis of microscopy techniques to measure segregation in continuous-cast steel slabs.

The accurate characterisation of centreline segregation requires precise measurements of composition variations over large length scales (10 ) across the centreline of the cast product, while having high resolution, sufficient to quantify the significant composition variations between dendrites due to microsegregation at very small length scales (10 ). This study investigates the potential of a novel microscopy technique, named Synchrotron Micro X-ray Flurorescence (SMXRF), to generate large-scale high-resolution segregation maps from a steel sample taken from a thin slab caster. Two methods, Point Analysis and Regression Analysis, are proposed for SMXRF data calibration. By comparing with the traditional Laser-Induced Breakdown Spectroscopy (LIBS), and Electron Probe Micro Analyser (EPMA) techniques, we show that SMXRF is successful in quantitative characterisation of centreline segregation. Over large areas (e.g. 12 16 ) and at high resolution (10-50 pixel size) various techniques yield comparable outcomes in terms of composition maps and solute profiles. The findings also highlight the importance of both high spatial resolution and large field of view to have a quantitative, accurate, and efficient measurement tool to investigate segregationphenomena.

Multielement simultaneous quantitative analysis of trace elements in stainless steel via full spectrum laser-induced breakdown spectroscopy

Laser-Induced Breakdown Spectroscopy (LIBS) instruments are increasingly recognized as valuable tools for detecting trace metal elements due to their simplicity, rapid detection, and ability to perform simultaneous multi-element analysis. Traditional LIBS modeling often relies on empirical or machine learning-based feature band selection to establish quantitative models. In this study, we introduce a novel approach—simultaneous multi-element quantitative analysis based on the entire spectrum, which enhances model establishment efficiency and leverages the advantages of LIBS. By logarithmically processing the spectra and quantifying the cognitive uncertainty of the model, we achieved remarkable predictive performance (R2) for trace elements Mn, Mo, Cr, and Cu (0.9876, 0.9879, 0.9891, and 0.9841, respectively) in stainless steel. Our multi-element model shares features and parameters during the learning process, effectively mitigating the impact of matrix effects and self-absorption. Additionally, we introduce a cognitive error term to quantify the cognitive uncertainty of the model. The results suggest that our approach has significant potential in the quantitative analysis of trace elements, providing a reliable data processing method for efficient and accurate multi-task analysis in LIBS. This methodology holds promising applications in the field of LIBS quantitative analysis.

Design, construction, and validation of an in-situ groundwater trace element analyzer with applications in carbon storage

It is estimated that carbon emissions should reach net-zero by 2050 to meet important climate targets. Carbon capture is likely necessary to reach these targets, requiring a long-term storage solution such as geological carbon sequestration. However, as with any subsurface activity, leakage can occur, potentially impacting groundwater quality near the storage site. Rapid detection is essential to mitigate damage to this resource. Since CO2 will acidify groundwater, the concentrations of acid soluble minerals and associated cations will increase. Thus, an in-situ, real-time element analysis system based on laser-induced breakdown spectroscopy (LIBS) is under development to monitor these elements. The system splits the traditional LIBS system into a miniature, all-optical sensor head built around a passively Q-switch laser fiber coupled to a control unit. Previous work has validated the LIBS technique for use at high pressure as well as the split system design. In this work, a fieldable prototype sensor is developed and tested in an onsite monitoring well where trace elements concentrations (approx. 0–3 ppm) were tracked over 20 days. These concentrations varied in response to local rainfall, diluting with increased rain, demonstrating the ability of a LIBS-based sensor to track trace elements under real-world conditions.

Effect of cavity-confinement and microwave-assistance on the sensitivity of LIBS for detecting Cu content in pig feed

The laser-induced breakdown spectroscopy (LIBS) is a potential tool for detecting heavy metals in pig feed. In order to implement a highly sensitive LIBS system required for the detection of Copper in pig feed and achieve better detection results, this work combines cavity-confinement and microwave-assistance with the LIBS system. Based on the characteristic spectral intensity of Cu I 324.75 nm, four factors including delay time, laser energy, cavity-confinement diameter, and microwave-assisted power are optimized by using single factor method and response surface methodology (RSM) for obtaining suitable experimental parameters and detection performance. The detection results show that as compared with the single factor method, the optimal experimental parameters obtained by using RSM increase the intensity of the characteristic spectral lines by 21.69% and the detection limit is as low as 0.878 mg/kg. As compared with the traditional LIBS techniques, the use of cavity-confinement combined with microwave-assistance increase the detection sensitivity of LIBS technique by 18.6-fold. The results show that RSM effectively analyzes the interactions between factors and their effects on the response values to effectively obtain better values for each factor. This enhances the LIBS spectra by cavity-confinement and microwave-assistance, and improves the sensitivity of detection of Cu in the pig feeds, which is suitable for realizing the quantitative detection of low concentration elements in pig feeds.

Breakdown Spectroscopy Induced by Nonlinear Interactions of Femtosecond Laser Filaments and Multidimensional Plasma Gratings

Breakdown spectroscopy is a valuable tool for determining elements in solids, liquids, and gases. All materials in the breakdown region can be ionized and dissociated into highly excited fragments and emit characteristic fluorescence spectra. In this sense, the elemental composition of materials can be evaluated by detecting the fluorescence spectrum. This paper reviews the recent developments in laser-induced breakdown spectroscopy. The traditional laser-induced breakdown spectroscopy, filament-induced breakdown spectroscopy, plasma grating, and multidimensional plasma grating-induced breakdown spectroscopy are introduced. There are also some proposals for applications of plasma gratings, such as laser ablation, laser deposition, and laser catalysis of chemical reactions in conjunction with research on the properties of plasma gratings.

Rapid identification of volatile organic compounds and their isomers in the atmosphere

Isomers are widely present in volatile organic compounds (VOCs), and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere. In this work, laser-induced breakdown spectroscopy (LIBS) technology was developed to online distinguish VOCs and their isomers in the air. First, LIBS was used to directly detect halogenated hydrocarbons (a typical class of VOCs) and the characteristic peaks of the related halogens were observed in the LIBS spectra. Then, comparing the LIBS spectra of various samples, it was found that for VOCs with different molecular formulas, although the spectra are completely the same in elemental composition, there are still significant differences in the relative intensity of the spectral lines and other information. Finally, in light of the shortcomings of traditional LIBS technology in identifying isomers, machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs, and the recognition results were very good. It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.

Combined laser ablation-tuneable diode laser absorption spectroscopy and laser-induced breakdown spectroscopy for rapid isotopic analysis of uranium

Laser-induced breakdown spectroscopy (LIBS) can provide immediate in situ elemental characterisation of a sample from a stand-off distance with no sample preparation for bulk, minor and trace species. These attributes suggest the technique could be applied to many processes in the nuclear industry. However, at present, LIBS cannot quickly and easily be used to determine the isotopic composition of a sample, which limits its potential. We report the development of a system comprising laser ablation-tuneable diode laser absorption spectroscopy (LA-TDLAS) and LIBS which can maintain the benefits of traditional LIBS and enable isotopic analysis of certain elements, including lithium and uranium. In this feasibility study, we used this approach to analyse a uranium metal wire sample under ambient conditions of pressure and temperature. Simultaneously, from the same laser produced plasma, the 235U isotope fraction was determined with LA-TDLAS while the plasma emission was used to obtain the electron density of the plasma using Stark broadening of uranium and sodium emission lines. The accuracy of the isotopic analysis performed with LA-TDLAS was limited by the noise of the absorption spectra and low concentration of the minor 235U isotope (0.7%). The limit of detection was estimated to be 1.5 wt%. Using the Doppler broadening of absorption lineshapes, the plasma temperature was calculated to drop from 25,000 K to 2000 K during the plasma lifetime. The electron density rapidly decreased from 6 × 1016 cm−3 immediately after laser ablation to around 3 × 1016 cm−3 after a few μs. The combination of LIBS and LA-TDLAS opens the possibility of rapid elemental and isotopic analysis which would be useful across the nuclear fuel cycle. Furthermore, the LA-TDLAS technique could be further developed for a portable measuring instrument for nuclear forensics applications.

Three-dimensional topographic and multi-elemental mapping by unilateral-shift-subtracting confocal controlled LIBS microscopy

Laser induced breakdown spectroscopy (LIBS) is a promising analytical technique based on the interaction between laser and material, which can quantitatively analyse the composition and content of material from the perspective of spectroscopy. The element distribution of non-uniform samples, such as natural ore, can be obtained by pointwise scanning without pretreatment. LIBS excitation intensity is the highest near the focus, so low imaging speed and low focusing accuracy will lead to unreliable element maps. Hence, an ultrasensitive technique called unilateral-shift-subtracting confocal controlled LIBS microscopy (UCCLIBS) was prepared to rapidly acquire high spatial resolution multi-elemental maps of the sample surface, which utilizes a laser induced breakdown spectrometer attached to a unilateral-shift-subtracting confocal microscope. A surface axial focusing ability of approximately 18 nm under 20× objective lens with the N.A. value of 0.4 is obtained, which is more than two orders of magnitude higher than that of ever traditional LIBS approaches, and the inherent anti-drift capability is successfully realized. The chemometric method of principal component analysis (PCA) is applied to the multi-element analysis of agate ore, which improved the accuracy and efficiency of sample analysis. We show the multi-layer element map of a solid-state electrolyte with a tomographic resolution of 2.3 μm. With these excellent properties, the UCCLIBS might provide a new idea for the detection of three-dimensional elemental characterization of minerals and chemical materials.

Investigation of Shielding Effects on Picosecond Laser-Induced Copper Plasma Characteristics under Different Focusing Distances

In traditional laser-induced breakdown spectroscopy (LIBS) applications, the line intensity and analysis capability are susceptible to plasma shielding. To investigate the shielding effects on the characteristics of Cu plasma in air, a ~120-picosecond laser with a wavelength of 1064 nm was employed to produce plasma. The plasma temperature and electron density were calculated under the condition of local thermal equilibrium (LTE) and optically thin, while the relationships between the line intensity, plasma temperature and electron density were analyzed. Moreover, the LTE condition was validated by the McWhirter relation, plasma relaxation time and diffusion length, and the optically thin condition was observed through the variation in line intensity. The results indicated that when the focal point was below the target surface, the plasma shielding was the weakest, and the highest line intensity could be obtained. In addition, there was a positive correlation between the increased plasma temperature and the degree of shielding effect. When the focal point was above the target surface, the high-irradiance pulse directly broke down the free air and produced a shock wave. Under the high pressure of the over-heated shock wave, the line intensity, plasma temperature and electron density increased again. This study provides an important insight into the experiments and applications of picosecond LIBS.

Improvement of sample discrimination using laser-induced breakdown spectroscopy with multiple-setting spectra

Laser-induced breakdown spectroscopy (LIBS) is a promising multi-elemental analysis technique and has the advantages of rapidness and minimal sample preparation. In traditional LIBS measurement, sample spectra are generally collected based on a single set of fixed experimental parameters, such as laser energy and delay time. When samples have the same main components and similar component concentrations, the difference in their spectral intensities becomes less obvious. This can lower the sensitivity of LIBS measurement and pose a threat to the accuracy and robustness of LIBS qualitative analysis. In this work, we propose a new method to increase the spectral difference between similar samples, namely multiple-setting spectra. For each sample, it adopts different sets of experimental parameters and obtains a group of spectra to increase the fingerprint spectral information. The effectiveness of the proposed method is theoretically verified and then tested on 11 similar coal samples. Specifically, the sample spectra were collected with different laser energy and delay time, and processed by principal component analysis (PCA) and Davies-Bouldin index (DBI). The results show that the use of multiple-settings spectra can significantly improve the sample discrimination accuracy from 81.8% to 96.4%. In addition, the proposed method can maintain the efficiency and cost of LIBS measurement.

Improved signal stability using an auxiliary flow-based chamber for aerosol laser-induced breakdown spectroscopy

Signal stability is a fundamental requirement for an analytical spectroscopic technique. An auxiliary-flow based chamber is presented for emission signal stability in aerosol laser-induced breakdown spectroscopy (LIBS). The performance of the designed chamber was evaluated with the traditional aerosol LIBS scheme. Factors influencing optical emission including laser energy and particle size were carefully considered. Both intra-experiment and inter-experiment results exhibited excellent short-term and long-term stability of emission signals with the novel sampling scheme while traditional cross-chamber suffered 15% and 40% intensity decrease, respectively. The systematic air analysis before and after aerosol experiment determined that major cause of signal decrease in the cross-chamber was degraded optical transmission due to aerosol contamination on optical path which was eliminated in the auxiliary flow-based chamber. The proposed scheme can be used for the analysis of diverse aerosols types in various optical emission based analytical techniques.

High accuracy analysis of fiber-optic laser-induced breakdown spectroscopy by using multivariate regression analytical methods

Fiber-optic laser-induced breakdown spectroscopy (FO-LIBS), which delivers the laser energy through an optical fiber cable, is more suitable for remote analysis and applying in complex environment than traditional laser-induced breakdown spectroscopy (LIBS). However, since the laser fluence is limited by optical fiber loss and attenuation, FO-LIBS suffers more from spectral interference, matrix effect, and self-absorption effect. In this work, three multivariate quantitative analytical methods, including two linear models partial least squares (PLS) and sparse partial least squares (SPLS), one nonlinear model support vector machine (SVM), were utilized to carry out the quantitative analysis of four trace metal elements (Manganese (Mn), Chromium (Cr), Nickel (Ni), and Titanium (Ti)) in pig iron. And the quantitative analytical ability of linear model and nonlinear model was studied and compared. The results show that nonlinear SVM model has the best performance. Using the SVM model, the coefficients of determination (R2) of Mn, Cr, Ni, and Ti were 0.9705, 0.9849, 0.9882, and 0.9837, respectively, and the root mean squared errors of prediction (RMSEP) of Mn, Cr, Ni, and Ti were 0.0982 wt%, 0.0185 wt%, 0.0179 wt%, and 0.0178 wt%, respectively. This work demonstrates that nonlinear quantitative analytical methods can effectively overcome those nonlinear effects and improve the quantitative analytical accuracy of FO-LIBS

Time-resolved electron temperature and density of spark discharge assisted femtosecond laser-induced breakdown spectroscopy

In laser-induced breakdown spectroscopy (LIBS), spark-discharge (SP) is an effective auxiliary method to improve spectral emission intensity, and can effectively affect plasma temperature and electron density. In traditional LIBS technology, nanosecond laser is usually used as excitation source. Compared with nanosecond laser, femtosecond (fs) pulse laser has many advantages in the interaction between laser and matter. The SP can also enhance the emission intensity of fs-LIBS. However, the discussion on plasma temperature and electron density of SP assisted fs-LIBS is rare. In this study, we measured time-resolved spectra of fs-LIBS with the SP. By using the Boltzmann plot and the Stark broadening, we calculated time-resolved plasma temperatures and electron densities for different laser energies at different discharge voltages. We hope that this study can provide a better understanding for SP assisted fs-LIBS.

Detection of K in soil using time-resolved laser-induced breakdown spectroscopy based on convolutional neural networks

One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy (LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem, this paper investigated a combination of time-resolved LIBS and convolutional neural networks (CNNs) to improve K determination in soil. The time-resolved LIBS contained the information of both wavelength and time dimension. The spectra of wavelength dimension showed the characteristic emission lines of elements, and those of time dimension presented the plasma decay trend. The one-dimensional data of LIBS intensity from the emission line at 766.49 nm were extracted and correlated with the K concentration, showing a poor correlation of = 0.0967, which is caused by the matrix effect of heterogeneous soil. For the wavelength dimension, the two-dimensional data of traditional integrated LIBS were extracted and analyzed by an artificial neural network (ANN), showing = 0.6318 and the root mean square error of validation (RMSEV) = 0.6234. For the time dimension, the two-dimensional data of time-decay LIBS were extracted and analyzed by ANN, showing = 0.7366 and RMSEV = 0.7855. These higher determination coefficients reveal that both the non-K emission lines of wavelength dimension and the spectral decay of time dimension could assist in quantitative detection of K. However, due to limited calibration samples, the two-dimensional models presented over-fitting. The three-dimensional data of time-resolved LIBS were analyzed by CNNs, which extracted and integrated the information of both the wavelength and time dimension, showing the = 0.9968 and RMSEV = 0.0785. CNN analysis of time-resolved LIBS is capable of improving the determination of K in soil.

Portable fiber-optic laser-induced breakdown spectroscopy system for the quantitative analysis of minor elements in steel

In this paper, we developed a portable laser-induced breakdown spectroscopy (LIBS) using an optical fiber to deliver laser energy and used it to quantitatively analyze minor elements in steel. The R2 factors of calibration curves of elements Mn, Ti, V, and Cr in pig iron were 0.9965, 0.9983, 0.9963, and 0.991, respectively, and their root mean square errors of cross-validation were 0.0501, 0.0054, 0.0205, and 0.0245 wt%, respectively. Six test samples were used for the validation of the performance of the calibration curves established by the portable LIBS. The average relative errors of elements Mn, Ti, V, and Cr were 2.5%, 11.7%, 13.0%, and 5.6%, respectively. These results were comparable with most results reported in traditional LIBS in steel or other matrices. However, the portable LIBS is flexible, compact, and robust, providing a promising prospect in industrial application.

LIBS core imaging at kHz speed: Paving the way for real-time geochemical applications

This paper demonstrates the new capabilities of laser-induced breakdown spectroscopy (LIBS) to perform fast high-resolution multi-elemental mappings of geological samples. A rock sample with a 5-mm surface roughness and one with a plane surface were laser scanned at a repetition rate of 1 kHz with a spatial resolution of 50 μm, using the Mission: Coriosity platform from ELEMISSION Inc. The elemental mappings of the few cm2 surfaces for 6 elements were obtained, revealing high levels of detail and complexity in the element distribution. In addition, the distributions of 9 elements along linear segments on the rock surfaces reveal correlations between the elements which allow inferring the mineralogical content of the samples. The platform provides a novel approach for fast simultaneous mapping of several elements as it can acquire and process 1000 spectra per second, which was not technically possible with traditional LIBS instrumentation. In addition, the platform is coupled with advanced graphical algorithms allowing the direct visualization of the distribution of several elements on the same image.

Research on spectral characteristics of laser-induced plasma by combining Au-nanoparticles and magnetic field confinement on Cu

In order to enhance the intensity of emission spectra of laser-induced plasma, a method of combining magnetic field enhanced laser induced breakdown spectroscopy(LIBS) with nanoparticle enhanced LIBS (NELIBS) was proposed. Laser-induced breakdown of copper was respectively performed by using traditional LIBS, magnetic field-enhanced LIBS, NELIBS, and the combination of the magnetic field enhanced LIBS and NELIBS.Some parameters including electron temperature, electron density and signal-to-noise ratio were obtained and analyzed. The experimental results show that when the Au-nanoparticles(Au NPs) are combined with magnetic field in LIBS, the spectral intensity of plasma is effectively enhanced and, the signal-to-noise ratio is significantly improved, and the optimum is achieved when the laser pulse energy is 80 mJ; the electron temperature and the electron density do not change obviously, the ability of using LIBS to detect trace elements is significantly improved.

Investigation and performance evaluation of optically thin laser-induced breakdown spectroscopy without self-absorption

In order to avoid the self-absorption effects presented in the laser-induced breakdown spectroscopy (LIBS) for industrial application, a novel optically thin LIBS (OT-LIBS) technique has been developed, investigated and evaluated. By comparing the elemental doublet lines intensity ratios with the theoretical one, we can reset the delay time of exposure of the intensified CCD (ICCD) and obtain the non-self-absorption emission line directly. In this experiment, once the delay time is set to 500 ns, the traditional LIBS experimental setup has been converted to the OT-LIBS one. The experimental parameters that corresponded to OT-LIBS were optimized, and the optically thin condition of the induced plasma was validated. The linear correlation coefficients of the Boltzmann plot is larger than 0.99, as well as the SA coefficient reaches its maximum, which verify that the plasmas generated by OT-LIBS are indeed in optically thin condition. Univariate quantitative analysis results performed on several self-made pallets show that, compared to the traditional LIBS, OT-LIBS has improved the linear correlation coefficient R 2 of calibration line for aluminium from 0.86 to 0.98, and reduced the mean absolute measurement error from 1.2% to 0.13%. The measurement accuracy has been improved by nearly an order of magnitude, but the measurement repeatability has not been improved. In addition, also the boundary conditions, applicability and limitation of OT-LIBS are also investigated. It is certified that the limitations of concentration and pulsed laser energy are 0–20.8% and larger than 16.9 mJ, while the applicable concentration and pulsed laser energy are 0–15.9% and larger than 33.1 mJ. This OT-LIBS technique is expected to promote the practical processes of LIBS in industrial application.

In Situ Underwater Laser-Induced Breakdown Spectroscopy Analysis for Trace Cr(VI) in Aqueous Solution Supported by Electrosorption Enrichment and a Gas-Assisted Localized Liquid Discharge Apparatus.

Traditional laser-induced breakdown spectroscopy (LIBS) always fails to directly detect target in aqueous solution due to rapid quenching of emitted light and adsorption of pulse energy by surrounding water. A method is proposed for the in situ underwater LIBS analysis of Cr(VI) in aqueous solution freed from the common problems mentioned above by combining a gas-assisted localized liquid discharge apparatus with electrosorption for the first time. In this approach, the introduction of the gas-assisted localized liquid discharge apparatus provides an instantaneous gaseous environment for underwater LIBS measurement (that is, the transfer of sampling matrix is not needed from aqueous solution to dry state). The preconcentration of Cr(VI) is achieved by electrosorption with a positive potential applied around adsorbents, which can promote the adsorption of Cr(VI) and inhibit that of the coexisting cations leading to a good anti-interference. Amino groups functionalized chitosan-modified graphene oxide (CS-GO) is utilized for Cr(VI) enrichment, which can be protonated to form NH3+ in acidic condition promoting the adsorption toward Cr(VI) by electrostatic attraction. The highest detection sensitivity of 5.15 counts μg-1 L toward Cr(VI) is found for the optimized electrosorption potential (EES = 1.5 V) and electrosorption time (tES = 600 s) without interference from coexisting metal ions. A corresponding limit of detection (LOD) of 12.3 μg L-1 (3σ method) is achieved, which is amazingly improved by 2 or even 3 orders of magnitude compared to the previous reports of LIBS.