Potential Of Laser-induced Breakdown Spectroscopy Research Articles

Effect of buffer gas on the analysis of Dunhuang murals by laser-induced breakdown spectroscopy technology

• Damage of laser ablation can be minimized in the buffer gas condition of Helium, while the quality of LIBS spectra was improved. • Buffer gas jet was supplied in open atmosphere through a high-pressure gas cylinder instead of a vacuum target chamber, is more suitable for in-situ analysis. • The strategies performed in this work can also applied in other cultural heritage for the purpose of reducing LIBS damage. In this work, the potential of laser-induced breakdown spectroscopy (LIBS) on micro-destructive analysis of mural pigmented layers was studied under different buffer gases of air, Ar, N 2 , O 2 and He. In order to maintain the intrinsic advantages of LIBS for in-situ analysis, the buffer gas jet was supplied in open atmosphere through a high-pressure gas cylinder instead of a vacuum target chamber. Three kinds of red pigments, cinnabar, red lead, and red ochre that were widely used in Dunhuang murals, were utilized to prepare “mock-up” blocks. The effects of buffer gas on pigment discoloration, ablated crater, intensity of emission signal, signal-to-noise ratio (SNR) and stability of emission signal were studied. For practical application, the flow rates of buffer gas were optimized. It was found that the diameter of the ablated crater is the largest, the pigment discoloration around the crater is more serious in air after laser ablation, followed by Ar, N 2 , and O 2 . On the contrary, in buffer gas of He, these effects are the smallest. Moreover, Ar can enhance radiation of plasma to produce the strongest intensities of spectra, and He is the best choice for obtaining the best SNR and spectral stability among these buffer gases. The optimal gas flow rate for reducing damage and improving LIBS signal is around 5000cm 3 /min. In addition, the influence mechanism of different buffer gases on plasma was discussed qualitatively by combining the physical properties and plasma temperature. Finally, the buffer gas He was applied to analyze the actual mural fragments, and it was conclusively confirmed that He can reduce the damage to the pigment layer and the discoloration caused by high temperature in LIBS experiment.

Quantitative Compositional Analyses of Calcareous Rocks for Lime Industry Using LIBS.

Here, the potential of laser-induced breakdown spectroscopy (LIBS) in grading calcareous rocks for the lime industry was investigated. In particular, we developed a system equipped with non-intensified detectors operating in scanning mode, defined a suitable data acquisition protocol, and implemented quantitative data processing using both partial least squares regression (PLS-R) and a multilayer perceptron (MLP) neural network. Tests were carried out on 32 samples collected in various limestone quarries, which were preliminarily analyzed using traditional laboratory X-ray fluorescence (XRF); then, they were divided into two groups for calibration and validation. Particular attention was dedicated to the development of LIBS methodology providing a reliable basis for precise material grading. The congruence of the results achieved demonstrates the capability of the present approach to precisely quantify major and minor geochemical components of calcareous rocks, thus disclosing a concrete application perspective within the lime industry production chain.

Short-Pulse Lasers: A Versatile Tool in Creating Novel Nano-/Micro-Structures and Compositional Analysis for Healthcare and Wellbeing Challenges.

Driven by flexibility, precision, repeatability and eco-friendliness, laser-based technologies have attracted great interest to engineer or to analyze materials in various fields including energy, environment, biology and medicine. A major advantage of laser processing relies on the ability to directly structure matter at different scales and to prepare novel materials with unique physical and chemical properties. It is also a contact-free approach that makes it possible to work in inert or reactive liquid or gaseous environment. This leads today to a unique opportunity for designing, fabricating and even analyzing novel complex bio-systems. To illustrate this potential, in this paper, we gather our recent research on four types of laser-based methods relevant for nano-/micro-scale applications. First, we present and discuss pulsed laser ablation in liquid, exploited today for synthetizing ultraclean “bare” nanoparticles attractive for medicine and tissue engineering applications. Second, we discuss robust methods for rapid surface and bulk machining (subtractive manufacturing) at different scales by laser ablation. Among them, the microsphere-assisted laser surface engineering is detailed for its appropriateness to design structured substrates with hierarchically periodic patterns at nano-/micro-scale without chemical treatments. Third, we address the laser-induced forward transfer, a technology based on direct laser printing, to transfer and assemble a multitude of materials (additive structuring), including biological moiety without alteration of functionality. Finally, the fourth method is about chemical analysis: we present the potential of laser-induced breakdown spectroscopy, providing a unique tool for contact-free and space-resolved elemental analysis of organic materials. Overall, we present and discuss the prospect and complementarity of emerging reliable laser technologies, to address challenges in materials’ preparation relevant for the development of innovative multi-scale and multi-material platforms for bio-applications.

Analysis of lead-based archaeological pottery glazes by laser induced breakdown spectroscopy

The aim of this study was to demonstrate the potential of Laser-Induced Breakdown Spectroscopy (LIBS) in the analysis of pottery shards, which are commonly the most abundant artefacts recovered at archaeological sites. The analytical capability of LIBS in identification of elements characteristic to inorganic pigments used for decoration was assessed. Based on the specific elements detected in the LIBS spectra of glazes, correlations between the elemental composition of the glaze and the colours of the glazed surface were established. The results were in accordance with the previously reported Energy Dispersive X-ray Fluorescence (EDXRF) and Raman analyses of some of the samples, and with the presently performed XRF analysis. Two important parameters for plasma characterization, temperature and electron number density, were estimated from the spectral data. A potential use of LIBS for depth profiling was also investigated by analysing the silicon to aluminium intensity ratio as a function of the number of laser shots applied. Profilometry analysis of the damages created on the glazed surfaces by laser shots was used to estimate the average ablation depth and ablated mass.

Elemental analysis of fish feed by laser-induced breakdown spectroscopy

In this study, the potential of laser-induced breakdown spectroscopy (LIBS) as an efficient multi-elemental quantification tool for fish feed is determined. A particular focus of this paper is total chromium, an essential element that has the potential to be toxic and carcinogenic. In total six elements, four macro-elements (Ca, Fe, K and Mg) and two micro-elements (Cr and Rb), were modelled using LIBS spectra of aquafeed samples. Reference analysis was conducted via inductively coupled plasma mass spectrometry (ICP-MS) and showed good agreement with LIBS predictions. These results provide evidence that LIBS has the potential to be utilized in the field as a real-time screening tool for establishing the elemental composition of a range of fish feeds.

Direct analysis of calcium in liquid infant formula via laser-induced breakdown spectroscopy (LIBS)

The present work illustrates the potential of laser-induced breakdown spectroscopy (LIBS) for the direct analysis of liquid food products. The aim of the experiment was to predict calcium content in ready-to-feed infant formula. The analysis was performed by a LIBS system coupled to a liquid sample chamber with a rotatory wheel that presents the liquid to the laser beam as a thin film. Multivariate analysis with partial least squares regression (PLSR) was performed to correlate LIBS spectral data to reference calcium contents. The obtained PLSR model exhibited a good fit and linearity, as indicated by the coefficients of determination for calibration (Rc2) and cross-validation (Rcv2), with values of 0.96 and 0.89, respectively. The robustness of the calibration model was assessed by external validation showing a root-mean-square error of prediction of 6.45 mg 100 mL−1. These results demonstrated the potential of LIBS for real-time analysis of liquid food products.

Discrimination between the authentic and fake Egyptian funerary figurines “Ushabtis” via laser-induced breakdown spectroscopy

Abstract The potential of laser-induced breakdown spectroscopy (LIBS) in differentiating between types of genuine and fake Ushabtis was studied. For this goal, the present study was initiated by a comprehensive spectrochemical analytical study of four archeological Ushabti statues, dated back to the late Ptolemaic period (332–330 B.C), which have been excavated south of El-Shawaf pyramid in Saqqara, Giza, Egypt. This study was followed by performing the same investigations on several imitated Ushabtis, which were purchased from the touristic marketplace in the region of the pyramids. For the archeological samples, optimization of LIBS experimental parameters in terms of temporal detection conditions along with laser wavelengths and their corresponding ablation rate was performed. The spectrochemical analyses of the genuine archaeological samples were carried out both superficially and stratigraphically. Main surface elements such as Ca, Na, Al, Si, Cu, Fe, and Mn were detected while large amounts of Ca and Sr represent their bulk elements. The LIBS results were validated by results obtained by SEM-EDX technique, which provided complementary information such as surface morphological images and quantitative composition of the samples’ constituents. Under the optimum experimental conditions, LIBS spectral emission of the imitated samples was acquired and compared to those for true archeological ones for the sake of possible discrimination between them. Successful utilization of LIBS in examining the authenticity of suspect Ushabtis has been accomplished and presented. This study may suggest the need for archeologists to be equipped with portable LIBS systems in the excavation sites or museums, which facilitate the immediate discrimination process when LIBS data of genuine samples are initially available.

Determination of zinc and iron in wheat using laser-induced breakdown spectroscopy

The potential of laser-induced breakdown spectroscopy (LIBS) has been used to determine the micronutrients (iron and zinc) in wheat, which is a staple food and the most widely cultivated crop in Pakistan. Wheat samples consisted of commercial and candidate varieties and a fortified wheat flour (FWF). The LIBS spectrum were recorded from wheat flour pellets using a Q-switched Nd:YAG laser focused on the surface of the wheat sample. Twenty-five single shot spectra were recorded at different sites of the same pellet. The data were normalized to exclude shot-to-shot laser energy variations and then the averaged emission spectrum was used for further analysis. According to the NIST atomic data base and the related literature, the most intense emission lines of zinc at 202.54, 206.20 and 213.85 nm and iron at 238.20, 259.93, 275.57, 344.06 & 373.48/373.71 nm have been detected in the LIBS spectra of wheat genotypes, which has been used to determine their relative intensities. Significant variation among the genotypes was identified for these minerals. In addition, principal component analysis (PCA) has been performed to statistically classify the wheat varieties based on their iron and zinc emission intensities. The PCA grouped the data into clusters based on the similarities in their micronutrient. The highest zinc was identified in NR-488, Zincol-2006 and NARC-2011. Likewise, the strongest iron intensities were observed in FWF, Borlaug-2016 and NR-486. These findings may assist breeders in the selection of genotypes with high micronutrients coupled with high grain yield, and other desirable traits essential for variety release. The present study has validated LIBS as a characterization tool for inferring micronutrients in the staple food.

Laser-induced breakdown spectroscopy (LIBS) for rapid analysis of ash, potassium and magnesium in gluten free flours

Gluten free (GF) diets are prone to mineral deficiency, thus effective monitoring of the elemental composition of GF products is important to ensure a balanced micronutrient diet. The objective of this study was to test the potential of laser-induced breakdown spectroscopy (LIBS) analysis combined with chemometrics for at-line monitoring of ash, potassium and magnesium content of GF flours: tapioca, potato, maize, buckwheat, brown rice and a GF flour mixture. Concentrations of ash, potassium and magnesium were determined with reference methods and LIBS. PCA analysis was performed and presented the potential for discrimination of the six GF flours. For the quantification analysis PLSR models were developed; R2cal were 0.99 for magnesium and potassium and 0.97 for ash. The study revealed that LIBS combined with chemometrics is a convenient method to quantify concentrations of ash, potassium and magnesium and present the potential to classify different types of flours.

Selective Surface Sintering Using a Laser-Induced Breakdown Spectroscopy System

Titanium metal injection molding allows creation of complex metal parts that are lightweight and biocompatible with reduced cost in comparison with machining titanium. Laser-induced breakdown spectroscopy (LIBS) can be used to create plasma on the surface of a sample to analyze its elemental composition. Repetitive ablation on the same site has been shown to create differences from the original sample. This study investigates the potential of LIBS for selective surface sintering of injection-molded titanium metal. The temperature created throughout the LIBS process on the surface of the injection-molded titanium is high enough to fuse together the titanium particles. Using the ratio of the Ti II 282.81 nm and the C I 247.86 nm lines, the effectiveness of repetitive plasma formation to produce sintering can be monitored during the process. Energy-dispersive X-ray spectroscopy on the ablation craters confirms sintering through the reduction in carbon from 20.29 Wt.% to 2.13 Wt.%. Scanning electron microscope images confirm sintering. A conventional LIBS system, with a fixed distance, investigated laser parameters on injection-molded and injection-sintered titanium. To prove the feasibility of using this technique on a production line, a second LIBS system, with an autofocus and 3-axis translation stage, successfully sintered a sample with a nonplanar surface.

The potential of laser-induced breakdown spectroscopy for industrial at-line monitoring of calcium content in comminuted poultry meat

The presence of bone particles, and hence the calcium content, is a key quality parameter for mechanically separated poultry meat (MSM). A method for fast at-line monitoring of the calcium content in MSM during production is therefore requested by the industry. Laser-induced breakdown spectroscopy (LIBS) is an interesting technique in this regard because it is fast and potentially enables direct detection of minerals in a sample with minimal sample preparation. Nine commercial MSM samples, representing the common range of calcium contents in MSM, a hand-deboned sample and minced poultry meat were measured by LIBS using sample preparation suitable for an industrial at-line monitoring setting. In the spectra obtained, emission lines from sodium, potassium and calcium were identified. Using inductively coupled plasma optical emission spectrometry (ICP-OES) as the reference method, and partial least squares regression (PLS) as calibration model, including three calcium lines adjusted by potassium, it was possible to separate samples according to three calcium levels with LIBS. Very low (<20 mg/100 g Ca), intermediate (20–90 mg/100 g Ca), and high (>90 mg/100 g Ca).

A novel approach to sensitivity evaluation of laser-induced breakdown spectroscopy for rare earth elements determination

We report the potential of Laser-Induced Breakdown Spectroscopy (LIBS) for the determination of lanthanum and yttrium in soils and rocks.

Analysis of Roman-Hispanic Archaeological Ceramics using Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a useful tool for characterization of archaeological samples because it involves little or no sample preparation, and it allows on-site rapid and nondestructive analysis. In this study, ceramics from the archaeological site of Labitolosa (Huesca) were analyzed qualitatively and quantitatively. Furthermore, a protocol is described for the determination of iron in archaeological materials by interpolating calibration graphs and standard addition. Moreover, the potential of LIBS for direct quantitative analysis of iron in real archaeological materials was evaluated, and optimum analytical conditions were determined. The reproducibility of LIBS spectra from different archaeological samples was investigated as a function of the number of laser shots. The results were compared with those of a reference material.

Laser-induced breakdown spectroscopy for in situ qualitative and quantitative analysis of mineral ores

In this work, the potential of laser-induced breakdown spectroscopy (LIBS) for discrimination and analysis of geological materials was examined. The research was focused on classification of mineral ores using their LIBS spectra prior to quantitative determination of copper. Quantitative analysis is not a trivial task in LIBS measurement because intensities of emission lines in laser-induced plasmas (LIP) are strongly affected by the sample matrix (matrix effect). To circumvent this effect, typically matrix-matched standards are used to obtain matrix-dependent calibration curves. If the sample set consists of a mixture of different matrices, even in this approach, the corresponding matrix has to be known prior to the downstream data analysis. For this categorization, the multielemental character of LIBS spectra can be of help. In this contribution, a principal component analysis (PCA) was employed on the measured data set to discriminate individual rocks as individual matrices against each other according to their overall elemental composition. Twenty-seven igneous rock samples were analyzed in the form of fine dust, classified and subsequently quantitatively analyzed. Two different LIBS setups in two laboratories were used to prove the reproducibility of classification and quantification. A superposition of partial calibration plots constructed from the individual clustered data displayed a large improvement in precision and accuracy compared to the calibration plot constructed from all ore samples. The classification of mineral samples with complex matrices can thus be recommended prior to LIBS system calibration and quantitative analysis.

An assessment of the potential of laser-induced breakdown spectroscopy (LIBS) for the analysis of cesium in liquid samples of biological origin.

The present study describes the development of an analytical method for the determination of cesium in biological fluid samples (human urine and blood samples) by laser-induced breakdown spectroscopy (LIBS). The developed method is based on sample presentation by liquid-to-solid conversion, enhancing the emission signal by drying the liquid into small "pockets" created in a metal support (zinc plate), and allows the analysis to be carried out on as little as 1 μL of sample volume, in a closed sample cell. Absolute detection limits on the Cs I 852.1 nm spectral line were calculated by the IUPAC 3σ method to be 6 ng in the urine sample and 27 ng in the blood serum sample. It is estimated that LIBS may be used to detect highly elevated concentration levels of Cs in fluid samples taken from people potentially exposed to surges of Cs from non-natural sources.

Novel estimation of the humification degree of soil organic matter by laser-induced breakdown spectroscopy

Soil organic matter (SOM) constitutes an important reservoir of terrestrial carbon and can be considered an alternative for atmospheric carbon storage, contributing to global warming mitigation. Soil management can favor atmospheric carbon incorporation into SOM or its release from SOM to atmosphere. Thus, the evaluation of the humification degree (HD), which is an indication of the recalcitrance of SOM, can provide an estimation of the capacity of carbon sequestration by soils under various managements. The HD of SOM can be estimated by using various analytical techniques including fluorescence spectroscopy. In the present work, the potential of laser-induced breakdown spectroscopy (LIBS) to estimate the HD of SOM was evaluated for the first time. Intensities of emission lines of Al, Mg and Ca from LIBS spectra showing correlation with fluorescence emissions determined by laser-induced fluorescence spectroscopy (LIFS) reference technique were used to obtain a multivaried calibration model based on the k-nearest neighbor (k-NN) method. The values predicted by the proposed model (A-LIBS) showed strong correlation with LIFS results with a Pearson's coefficient of 0.87. The HD of SOM obtained after normalizing A-LIBS by total carbon in the sample showed a strong correlation to that determined by LIFS (0.94), thus suggesting the great potential of LIBS for this novel application.

Potential of laser-induced breakdown spectroscopy for discrimination of nano-sized carbon materials. Insights on the optical characterization of graphene

Since its invention in 2004, graphene has attracted considerable interest worldwide. Advances in the use of graphene in materials science and engineering require important increases in the quality of the final product for integration in photonic and electronic devices. To meet this demand, which will become increasingly strict in the future, analytical techniques capable of differentiating between the starting materials and graphene need to be developed. The interest in the use of laser-induced breakdown spectroscopy (LIBS) for this application rests on the rapid progress experienced by this technology for identification of carbon-based materials of close chemical composition. The potential of LIBS has been explored here by a careful investigation of the spectral properties of both multi-layer and few-layer graphene, graphite and graphene oxide. Results reveal significant differences in the specific optical emission responses of these materials, expressly reflected on the behavior of CN and C2 molecular emissions. These differences result from the particularities of the materials, such as the number of carbon layers and the carbon hybridization in the bonding structure, together with the post-ablation evolution of the concerned plasma plume. In short, this interconnection between ablation and emission events generated from each material allows its characterization and its differentiation from other materials with highly similar chemical composition.

Laser-induced breakdown spectroscopic characterization of impurity deposition on the first wall of a magnetic confined fusion device: Experimental Advanced Superconducting Tokamak

Our recent investigations have indicated the potential of laser-induced breakdown spectroscopy (LIBS) for analysis of the co-deposited layers on the first wall in the Experimental Advanced Superconducting Tokamak (EAST) in the vacuum environment. Detailed information of compositions at the superficial and in-depth positions of the first wall of divertor tiles can be obtained by analyzing the spectra from 200 to 980nm. The decrease in concentrations of the depositional elements (such as D, Li) was clearly observed in the depth from 0 to 100μm, but the concentrations of the substrate elements were found to be relatively uniform in the depth after dozens of laser pulses. The linear correlation approach has been applied for improving the impurity depth profile accuracy and identifying the interface boundary between the deposition layer and the substrate for the first time. This would help us to develop LIBS technique to monitor the fuel retention and impurity deposition on the first wall of EAST.

Fast quantitative determination of platinum in liquid samples by laser-induced breakdown spectroscopy

The potential of laser-induced breakdown spectroscopy (LIBS) for the rapid determination of platinum in liquid silicone oils has been evaluated in the framework of on-line process control. A comparison of LIBS sensitivity between three setups designed for liquid analysis (static, liquid jet and flowing liquid) was performed using a 266 nm Nd/YAG laser irradiation. Best results were obtained using the flowing liquid setup and a similar limit of detection was obtained using the liquid jet. The effect of different buffer gases (Ar, He, N(2), etc.) on the signal sensitivity was studied in liquid jet analysis and best values were obtained with a nitrogen sheath gas. Detection limits were in the 100 mg/kg range for both setups. Quantitative determination of platinum in real liquid samples was also investigated using both liquid jet and flowing liquid setups. Calibration curves were plotted for Pt with the liquid jet and the flowing liquid setups under optimised temporal acquisition parameters (delay time and gate width). A normalisation using a silicon line was applied and recovery ranged from 3 to 15% for Pt in catalyst samples with both setups showing that LIBS is a sensitive and accurate method for on-line applications.

Discrimination of biological and chemical threat simulants in residue mixtures on multiple substrates

The potential of laser-induced breakdown spectroscopy (LIBS) to discriminate biological and chemical threat simulant residues prepared on multiple substrates and in the presence of interferents has been explored. The simulant samples tested include Bacillus atrophaeus spores, Escherichia coli, MS-2 bacteriophage, α-hemolysin from Staphylococcus aureus, 2-chloroethyl ethyl sulfide, and dimethyl methylphosphonate. The residue samples were prepared on polycarbonate, stainless steel and aluminum foil substrates by Battelle Eastern Science and Technology Center. LIBS spectra were collected by Battelle on a portable LIBS instrument developed by A3 Technologies. This paper presents the chemometric analysis of the LIBS spectra using partial least-squares discriminant analysis (PLS-DA). The performance of PLS-DA models developed based on the full LIBS spectra, and selected emission intensities and ratios have been compared. The full-spectra models generally provided better classification results based on the inclusion of substrate emission features; however, the intensity/ratio models were able to correctly identify more types of simulant residues in the presence of interferents. The fusion of the two types of PLS-DA models resulted in a significant improvement in classification performance for models built using multiple substrates. In addition to identifying the major components of residue mixtures, minor components such as growth media and solvents can be identified with an appropriately designed PLS-DA model.