Results Of Laser-induced Breakdown Spectroscopy Research Articles

Discriminating two bacteria via laser-induced breakdown spectroscopy and artificial neural network

Rapid and successful clinical diagnosis and bacterial infection treatment depend on accurate identification and differentiation between different pathogenic bacterial species. A lot of efforts have been made to utilize modern techniques which avoid the laborious work and time-consuming of conventional methods to fulfill this task. Among such techniques, laser-induced breakdown spectroscopy (LIBS) can tell much about bacterial identity and functionality. In the present study, a sensitivity-improved version of LIBS, i.e. nano-enhanced LIBS (NELIBS), has been used to discriminate between two different bacteria (Pseudomonas aeruginosa and Proteus mirabilis) belonging to different taxonomic orders. Biogenic silver nanoparticles (AgNPs) are sprinkled onto the samples’ surface to have better discrimination capability of the technique. The obtained spectroscopic results of the NELIBS approach revealed superior differentiation between the two bacterial species compared to the results of the conventional LIBS. Identification of each bacterial species has been achieved in light of the presence of spectral lines of certain elements. On the other hand, the discrimination was successful by comparing the intensity of the spectral lines in the spectra of the two bacteria. In addition, an artificial neural network (ANN) model has been created to assess the variation between the two data sets, affecting the differentiation process. The results revealed that NELIBS provides higher sensitivity and more intense spectral lines with increased detectable elements. The ANN results showed that the accuracy rates are 88% and 92% for LIBS and NELIBS, respectively. In the present work, it has been demonstrated that NELIBS combined with ANN successfully differentiated between both bacteria rapidly with high precision compared to conventional microbiological discrimination techniques and with minimum sample preparation.

Stability and accuracy improvement of element analysis in steel alloys using polarization-resolved laser-induced breakdown spectroscopy

The existence of the background signal is one of the factors leading to the uncertainty of spectral intensity, which dramatically affects the stability, repeatability, and quantitative accuracy of laser-induced breakdown spectroscopy (LIBS) measurements. In this work, the polarization-resolved LIBS (PR-LIBS) and partial least squares (PLS) regression models were proposed to improve the stability and accuracy of qualitative and quantitative analysis of steel alloy elements. The obtained spectra were pre-processed to select an appropriate number of variables, and the relationship between the spectral intensity and the certified concentration information of steel alloy samples was modeled using PLS. Compared to LIBS measurements, the relative standard deviation (RSD) and root-mean-square error (RMSE) of PR-LIBS decreased, while the signal-to-background ratio (SBR) and coefficient of determination (R2) increased. Finally, the quantitative results of LIBS and PR-LIBS of Si, Mn, Cr, and Ni in steel alloy samples using PLS were displayed and discussed. For the PR-LIBS dataset, the R2 has increased by at least 3.4%, and the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) have improved by at least 6.3% and 19.0%, respectively. These findings coupled with the simplicity of the experimental process indicate that PR-LIBS is a simple and low-cost solution that can increase the stability and accuracy of LIBS measurements.

Experimental investigation for pulsed laser nitriding of metals

Pulsed laser nitriding of active metals has been regarded as a promising method for performance enhancement of metals. Nevertheless, clarifying the complicated mechanisms of pulsed laser nitriding such as the nitrogen transport and the chemically active state of nitrogen poses challenges due to the rather fast and complex processes. In this work, the in situ momentum measurements, in situ laser-induced breakdown spectroscopy (LIBS) measurements, in situ transient off-axis Digital holography (TODH) measurements and energy dispersive spectroscopy measurements were implemented to investigate the pulsed laser nitriding. It was revealed experimentally that the laser-supported-detonation (LSD) may be the key, and the nitriding process could proceed effectively only when the illumination power density of laser can reach the threshold of generating LSD. The LSD-induced high-speed N+ ions and N atoms flow to the metal surface, which may be the major mechanism for the nitrogen transporting to the metal surface. Moreover, the experimental results of LIBS showed that the chemically active state of nitrogen is N+ ions and their lifetime is at the scale of 102 ns. The lifetime of N+ ions was found to be prolonged as the nitrogen pressure was increased. As indicated by TODH experimental results, the prolonged lifetime of N+ ions may be caused by the smaller shock wave velocity at the higher nitrogen pressure. These experimental findings in this work may clarify the nitrogen transport mechanism and the chemically active state of nitrogen, which may lead to a better understanding of the pulsed laser nitriding and provide the guidance for optimizing the related industrial design in the future.

Comparative Study on Determination of Selected Rare Earth Elements (REEs) in Ion Adsorption Clays Using Handheld LIBS and ICP-MS

The rare earth elements (REEs) are crucial components of green technology and are now considered critical raw materials. One of the emerging tools in mineral exploration, laser-induced breakdown spectroscopy (LIBS), was used by several studies to determine the REE contents of different geological materials. In this study, the concentrations of selected REEs (La, Ce, Pr, Nd, Sm, Gd, Dy, and Yb) in 11 ion adsorption clays (IACs) from El Nido, Palawan, Philippines were determined using a handheld LIBS analyzer. The REE contents of the samples were also determined using inductively coupled plasma mass spectrometry (ICP-MS) to compare LIBS with the established laboratory technique. The two-sided t-test shows no significant differences for the average La, Ce, Pr, Nd, Sm, and Gd results of LIBS and ICP-MS, whereas Dy and Yb have significant differences. Based on these results, it can be concluded that LIBS can be an alternative to ICP-MS for the rapid determination of some REE in IACs.

Combination of analytic techniques to chemical characterization and preservation of Jurassic clam shrimp carapaces from La Matilde Formation, Patagonia

Chemical studies of fossil clam shrimps have taken relevance in the possibility of inferring about fossilization processes. Laser–induced Breakdown Spectroscopy (LIBS) is an attractive technique for geological analyses because the laser can ablate a few micrograms directly from a small area on the solid sample. On the other hand, RAMAN spectroscopy is a technique that allows rapid and non-destructive in situ detection of the components of the samples and has been used in micropalaeontology to identify carbonaceous materials. In this study, the aim was an analysis of the preservation of the clam shrimp Eosolimnadiopsis? santacrucensis Gallego, 1994 from La Matilde Formation (Jurassic) using diverse methods including LIBS, RAMAN and X–ray fluorescence (XRF) techniques as well as surrounding rock. Afterwards LIBS results were evaluated using principal component analysis (PCA). According to XRF data, Si was the main element, indicating that the rock sample consists primarily of silicate minerals. Our results of LIBS and PCA analysis indicate chemical changes between the points from carapaces and rock matrix. Some areas of the carapace showed high peaks of Ca, Na, Mg and it was variable for Si, while in other parts of the carapace and rock matrix the Si remained at high intensity. Also, RAMAN spectroscopic analysis revealed the presence of amorphous carbon. This is the first report and evaluation on the LIBS and RAMAN techniques applied to fossil clam shrimps and contributes to obtaining a range of additional information to subsequently establish the different mechanisms involved in the taphonomic history of these organisms.

LIBS study of ITER relevant tungsten–oxygen coatings exposed to deuterium plasma in Magnum-PSI

We discuss the applicability of laser induced breakdown spectroscopy (LIBS) for deuterium retention analysis in compact and porous tungsten-oxide (W-O) coatings. Deuterium loading was performed by exposing the coatings to deuterium plasma in Magnum-PSI linear plasma device.The deuterium signals obtained by ex-situ LIBS had sufficiently good signal-to-noise ratio for reliable separation of essentially broadened hydrogen and deuterium lines as well as for comparison of the lateral and depth distributions of deuterium in the coatings. Strong deuterium signal was obtained for the first laser shot which corresponded to the surface layer of the W-O coatings whereas deeper in the coating the signal decreased to noise level. In addition, the deuterium signal was highest in the central region of compact W-O coating. For both coatings, depth profiles of elements obtained by LIBS match with those recorded by secondary ion mass spectroscopy (SIMS) in the lateral direction along the sample surface. The results of LIBS and SIMS results were supported by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) data which showed that the exposure to deuterium plasma resulted in remarkable changes in the surface morphology along the sample surface. The study demonstrates the LIBS potential in deuterium retention measurements in plasma facing components.

Highly accurate determination of Zn and Cu in human hair by ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy

Hair is an ideal biomarker for monitoring human health and environmental risks through the determination of trace elements in the hair. However, accurately quantifying trace elements in hair using laser-induced breakdown spectroscopy (LIBS) is a big challenge. A simple and low-cost method, ultrasound-assisted alkali dissolution (UAAD), was proposed for quantifying trace elements in human hair. In this work, three different solvents (deionized water, nitric acid mixture, and sodium hydroxide) were used to dissolve the hair assisted by ultrasound; and then the hair solution was dripped onto filter paper. The effect of alkali dissolution on enhancing the spectral intensity of zinc (Zn) and copper (Cu) was then analyzed. Using ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy (UAAD-LIBS), the limits of detection (LoDs) for determining Zn and Cu elements can reach to 0.3517 μg/g and 0.0146 μg/g, respectively. Based on this simple method with low LoDs, the quantitative analysis results of LIBS for three actual samples were compared with inductively coupled plasma optical emission spectrometry (ICP-OES). The relative errors of Zn and Cu between UAAD-LIBS and ICP-OES were less than 7.6% and 4.9%. These results show that using UAAD as a sample pretreatment process is an effective method of LIBS analysis.

Application of Laser Induced Breakdown in Air in Conjunction with Atomic Absorption Spectroscopy for Detection of Trace Elements in Fennel Seeds

A robust approach of laser-induced breakdown spectroscopy (LIBS) in ambient air has been employed to investigate concentration of the trace elements in fennel seeds (saunf) via generation of plasma through the second harmonic of solid state Nd: YAG pulsed laser 532 nm. Spectral emissions of saunf plasma were acquired with resolution of 0.06 nm in spectral range of 200–720 nm. The experimental determination showed the existence of elements namely, Ca, Al, K, Fe, S, P, Mg, Mn, Sr, Na, and Zn in the sample. However, no toxic elements such as Pb, Cr etc. were perceived. The relative concentrations of detected elements were measured through the intensity of the strongest peak, intensities of every emission from every specie, and calibration free (CF)-LIBS. To indorse the experimental determinations of LIBS, a comparative study was carried out with the outcomes of atomic absorption spectroscopy (AAS). The results of LIBS and AAS were compared by the statistical treatment.

Elemental analysis of packaging tapes by LA-ICP-MS and LIBS

Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) methods were developed and applied to the characterization and comparison of eight packaging tape samples manufactured in Asia. The application of LIBS for the analysis of tape samples is reported for the first time. The results of LIBS were compared to LA-ICP-MS as a reference technique and also to assess the complementarity of both techniques for the analysis of this type of sample. The developed methods can be applied to the forensic analysis of other types of tapes and, potentially, to the forensic analysis of other polymeric materials. The use of these laser-methods allowed for the detection of up to 7 elements by LIBS, and 11 elements by LA-ICP-MS. In addition, LIBS proved especially useful in detecting elements that were problematic by LA-ICP-MS such as lithium and potassium. Multivariate analysis of the data was used to visualize chemical similarities or differences obtained by each technique.The area under selected peaks was integrated after the spectra were normalized to the signal intensity. This strategy provided the best reproducibility and repeatability. From the comparison criteria evaluated in this study, ±5s produced the lower error rates for the comparison of packaging tapes for the selected elements. These results show that LIBS is a viable alternative to the previously reported LA-ICP-MS for forensic analyses and comparisons of tape evidence.

Mineral content analysis of root canal dentin using laser-induced breakdown spectroscopy.

ObjectivesThis study aimed to introduce the use of laser-induced breakdown spectroscopy (LIBS) for evaluation of the mineral content of root canal dentin, and to assess whether a correlation exists between LIBS and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) methods by comparing the effects of irrigation solutions on the mineral content change of root canal dentin.Materials and MethodsForty teeth with a single root canal were decoronated and longitudinally sectioned to expose the canals. The root halves were divided into 4 groups (n = 10) according to the solution applied: group NaOCl, 5.25% sodium hypochlorite (NaOCl) for 1 hour; group EDTA, 17% ethylenediaminetetraacetic acid (EDTA) for 2 minutes; group NaOCl+EDTA, 5.25% NaOCl for 1 hour and 17% EDTA for 2 minutes; a control group. Each root half belonging to the same root was evaluated for mineral content with either LIBS or SEM/EDS methods. The data were analyzed statistically.ResultsIn groups NaOCl and NaOCl+EDTA, the calcium (Ca)/phosphorus (P) ratio decreased while the sodium (Na) level increased compared with the other groups (p < 0.05). The magnesium (Mg) level changes were not significant among the groups. A significant positive correlation was found between the results of LIBS and SEM/EDS analyses (r = 0.84, p < 0.001).ConclusionsTreatment with NaOCl for 1 hour altered the mineral content of dentin, while EDTA application for 2 minutes had no effect on the elemental composition. The LIBS method proved to be reliable while providing data for the elemental composition of root canal dentin.

LIBS experiments for quantitative detection of retained fuel

Laser Induced Breakdown Spectroscopy (LIBS) provides chemical information from atomic and ionic plasma emissions generated by laser vaporization of a sample. At the ENEA research center, in collaboration with IPPLM, an equipment has been set up to qualitatively and quantitatively determine the chemical composition of impurities deposited on Plasma Facing Components (PFC). The strength of the LIBS, for its capability of light elements detection, is fully exploited to determine the deuterium content since this element can be considered as the best choice proxy for tritium; the latter being is of great importance in assessing safe conditions to assure the continuous operation in nuclear fusion tokamak.Here we present the results of the Double Pulse LIBS (DP-LIBS) probing of deuterated samples with the simultaneous optical detection by medium-resolution and high-resolution spectrometer. Deuterium emission at 656.1nm has been detected then the elemental composition has been quantified by applying the Calibration Free (CF) approach. The obtained results demonstrate that the DP-LIBS technique combined with CF analysis is suitable for the quantitative determination of tritium content inside the PFCs of next fusion devices like ITER.

Analysis and Discrimination of Sedimentary, Metamorphic, and Igneous Rocks Using Laser-Induced Breakdown Spectroscopy

This study deals with the analysis of rocks using laser-induced breakdown spectroscopy (LIBS) coupled with principal component analysis. The spectra of sedimentary, metamorphic, and igneous rock samples were recorded in the 200–900 nm spectral range. The atomic lines of elements such as Si, Ca, Mg, Fe, Na, and K along with lighter elements, namely C, H, N, and O, were observed in these spectra. Multivariate analysis in combination with LIBS was used to classify the samples. For principal component analysis, a 12 × 5849 data matrix was formed using the results of LIBS. The plot of the analysis revealed similarities between the sedimentary and metamorphic rock samples compared with the igneous rock sample. Thus, the present study demonstrates that LIBS coupled with principal component analysis can become an important tool for rapid classification and in-situ discrimination of rock samples.

Quantitative Analysis of Shilajit using Laser-Induced Breakdown Spectroscopy and Inductively Coupled Plasma/Optical Emission Spectroscopy

Laser-induced Breakdown Spectroscopy (LIBS) was used for the quantitative study of Shilajit samples using first harmonic (1064 nm) of a Q-Switched Nd:YAG laser by an appropriate detection system. The samples were chosen from the northern Himalayan mountainous range at locations namely Skardu, Gilgit, Chilas, Chitral, and Muzaffarabad. The relative concentrations of detected species were measured via integrated intensity of the strongest line of an element and via Calibration-Free CF-LIBS approach. Our findings recommend the altitudinal variations in Physico-chemical properties of Shilajit. Different functional groups were identified using Fourier Transform infrared (FTIR)-Spectroscopy. The results of LIBS were compared to results of Inductively Coupled Plasma/Optical Emission Spectroscopy (ICP/OES) with fine harmony.

A novel approach for investigation of chemical aging in composite propellants through laser-induced breakdown spectroscopy (LIBS)

Many methods have been developed in recent years for the analysis and evaluation of energetic materials. This work introduces a novel approach for the analysis and aging of solid composite propellants by laser-induced breakdown spectroscopy (LIBS). The results of the plasma spectrum were used to investigate the behavior of the aged samples. For this purpose, CN and AlO molecular bands of different samples were compared with each other. The samples were examined under inert argon atmosphere to study LIBS signal improvement. Some absent lines such as C and C2 swan bands were detected and reduction of air impact was carried out. Line intensity ratios of samples were changed for all samples during their aging. Differential scanning calorimetry (DSC) method was used to compare them with the output of LIBS’s technique. The results of LIBS and DSC methods show a similar trend in changing mechanical and thermal properties.

Determination of environmental safety level with laser-induced breakdown spectroscopy technique

This paper reports the quantitative estimation of heavy metals contamination in the soil, around the power station, by laser-induced breakdown spectroscopy (LIBS). Soil samples were collected from various distances (200–1000 m) and depths (10–50 cm) in the vicinity of the Iskandar power station in Johor, Malaysia. Samples were dried and pelletised prior to excitation. A Q-switched Nd:YAG laser was employed to ablate the sample and MayaPro spectrometer (Ocean Optics) for recording the emission spectrum of laser-induced plasma. Pb, Fe, Ni and Cu concentrations were estimated in the polluted soil with repeatability rate of above 96%. Quantitative results of LIBS were validated by flame atomic absorption spectroscopy (FAAS) and were found in good agreement. The concentration of the detected heavy metal elements was found within the safety limits set by Department of Environment (DOE) of Malaysia and the European standards.

Adaptive femtosecond laser-induced breakdown spectroscopy of uranium

Laser-induced breakdown spectroscopy (LIBS) is an established technique for material characterization applicable to a variety of problems in research, industry, environmental studies, and security. LIBS conducted with femtosecond laser pulses exhibits unique properties, arising from the characteristics of laser-matter interactions in this pulse width regime. The time evolution of the electric field of the pulse determines its interaction with sample materials. We present the design and performance of a femtosecond LIBS system developed to systematically optimize the technique for detection of uranium. Sample analysis can be performed in vacuum environment, and the spectral and temporal diagnostics are coupled through an adaptive feedback loop, which facilitates optimization of the signal-to-noise ratio by pulse shaping. Initial experimental results of LIBS on natural uranium are presented.

Comparison of gated and non-gated detectors for double-pulse laser induced plasma analysis of trace elements in iron oxide

Double-pulse laser-induced breakdown spectroscopy (LIBS) is an emerging technique for accurate compositional analysis of many different materials. We present results of collinear double-pulse LIBS for analysis of the trace elements aluminum, phosphorus and boron in sintered iron oxide targets. The samples were ablated in air by double-pulse Nd:YAG laser radiation (6ns pulse duration, laser wavelength of 532nm) and spectra were recorded with an Echelle spectrometer equipped either with a CCD (charge coupled device) or an ICCD (intensified charge coupled device) camera. For the trace elements aluminum and phosphorus, the use of the CCD detector system resulted in considerable higher signal-to-noise ratios and/or better limits of detection compared to the results achieved with the ICCD detector. The use of CCD double-pulse LIBS enables to detect low concentrations of phosphorus with a limit of detection of 10ppm by evaluating the UV line at 214.91nm, which overlaps with a Fe I line. Compared to the ICCD system, the CCD system requires the accumulation of a higher number of laser double-pulses to achieve acceptable signal quality. This can be disadvantageous for elements showing pronounced depletion effects as for the trace element boron in sintered iron oxide targets.

High-speed scanning laser-induced breakdown spectroscopy at 1000 Hz with single pulse evaluation for the detection of inclusions in steel

Spatially resolved information about the distribution and chemical composition of inclusions in steel are gained by scanning methods, such as scanning electron microscopy with energy dispersive X-ray spectroscopy, electron probe microanalysis or capillary-X-ray flourescence. Scanning laser-induced breakdown spectroscopy (LIBS) offers distinct advantages in contrast to these conventional methods. Sample polishing or high vacuum conditions are not necessary, a simple grinding of the sample is sufficient for the preparation. Analysing times can be reduced significantly. At Fraunhofer ILT a measuring system was developed enabling for the first time high-speed scanning LIBS with measuring frequencies of up to 1000 Hz. Sample surfaces with dimensions up to 110×45 mm2 can be analyzed. Light elements such as C, N, O, P, and S are detected, which is demonstrated by the identification of nonmetallic inclusions in steel. Principle, features and results of high-speed scanning LIBS with a spatial resolution&amp;lt;20 μm are presented.