Nanosecond Laser-induced Breakdown Spectroscopy Research Articles

Discrimination of cow, goat, and sheep milk by femtosecond and nanosecond laser-induced breakdown spectroscopy

In the present work, femtosecond Laser Induced Breakdown Spectroscopy, fs-LIBS, is applied for the first time for the analysis of the inorganic content and the identification of the animal origin of milk samples (i.e., cow, goat, and sheep). The fs-LIBS spectra were analyzed by different machine learning algorithms (i.e., multivariate statistical analysis), and their performance was assessed. The obtained classification accuracies of the milk samples based on the animal origin were found to attain values up to 95 %, depending on the algorithm used. For comparison purposes, LIBS experiments were also carried out employing nanosecond laser pulses, ns-LIBS. The obtained results from both the fs- and ns-LIBS experiments were found to be in excellent agreement between them. The present findings, using fs laser excitation, demonstrate and extend the capabilities of LIBS technique, for the identification of the animal origin of milk samples, thus making fs- and/or ns-LIBS technique a powerful and useful tool for milk authentication, quality, and safety control related research.

Metal micro/nanostructure enhanced laser-induced breakdown spectroscopy

This study used a femtosecond laser to ablate a Cu sample, forming a micro/nanostructural layer on the surface. And the effect of this structural layer on nanosecond laser-induced breakdown spectroscopy (LIBS) was discussed. Firstly, the effect of the micro/nanostructural layer on the intensity of laser-induced Cu plasma spectra was investigated. The micro/nanostructure could significantly enhance the spectral intensity of the Cu plasma by 82.5 times at 13.3 mJ laser energy. Secondly, the Cu plasma temperature and electron density were calculated. The micro/nanostructures could significantly increase Cu plasma temperature and electron density. Finally, the effect of micro/nanostructure surface on the spectral intensities of Pb and Cr elements in water was investigated for LIBS analysis. It was found that the detection limit of Pb and Cr trace metal elements in water was 1.85 ng/mL and 0.51 ng/mL at a lower laser energy (13.3 mJ), which was significantly better than other LIBS methods reported so far. The results show that the micro/nanostructure enhanced LIBS is a more sensitive method for detecting trace metal elements in the water.

Homogeneity Measurements of Li-Ion Battery Cathodes Using Laser-Induced Breakdown Spectroscopy.

We study the capability of nanosecond laser-induced breakdown spectroscopy (ns-LIBS) for depth-resolved concentration measurements of Li-Ion battery cathodes. With our system, which is optimized for quality control applications in the production line, we pursue the goal to unveil manufacturing faults and irregularities during the production process of cathodes as early as possible. Femtosecond laser-induced breakdown spectroscopy (fs-LIBS) is widely considered to be better suited for depth-resolved element analysis. Nevertheless, the small size and intensity of the plasma plume, non-thermal energy distribution in the plasma and high investment costs of fs-LIBS make ns-LIBS more attractive for inline application in the industrial surrounding. The system, presented here for the first time, is able to record quasi-depth-resolved relative concentration profiles for carbon, nickel, manganese, cobalt, lithium and aluminum which are the typical elements used in the binder/conductive additive, the active cathode material and the current collector. LIBS often causes high variations in signal intensity from pulse to pulse, so concentration determination is, in general, conducted on the average of many pulses. We show that the spot-to-spot variations we measure are governed by the microstructure of the cathode foil and are not an expression of the limited precision of the LIBS setup.

Direct comparison of ns LIBS and fs LIBS with high spatial and temporal resolution in gases

Spatial resolution is one of the most critical parameters for spectroscopic measurements especially when used in gases. However, the lateral resolution of femtosecond (fs) laser-induced breakdown spectroscopy (LIBS) in gases has not been thoroughly investigated. Here, we directly compare the differences and connections between nanosecond (ns) LIBS and fs LIBS through spatio-temporally resolved spectroscopy. At the time period we measured, unlike the ns LIBS plasma, the fs LIBS plasma does not show detectable expansion, and we do not find composition transport due to turbulence inside the fs LIBS. In other words, the local spectral emission in the fs LIBS can correlate precisely to the composition at that location before the arrival of the laser, while ns LIBS cannot. This feature allows fs LIBS to have much higher lateral resolution than ns LIBS. Finally, this paper verified that fs LIBS can be used for one-dimensional measurements capability with its lateral resolution of 50 μm.

Comparison of sample temperature effect on femtosecond and nanosecond laser-induced breakdown spectroscopy

In this paper, we investigated the emission spectra of plasmas produced from femtosecond and nanosecond laser ablations at different target temperatures in air. A brass was selected as ablated target of the experiment. The results indicated that spectral emission intensity and plasma temperature showed similar trend for femtosecond and nanosecond lasers, and the two parameters were improved by increasing the sample temperature in both cases. Moreover, the temperature of nanosecond laser-excited plasma was higher compared with that of femtosecond laser-excited plasma, and the increase of the plasma temperature in the case of nanosecond laser was more evident. In addition, there was a significant difference in electron density between femtosecond and nanosecond laser-induced plasmas. The electron density for femtosecond laser decreased with increasing the target temperature, while for nanosecond laser, the electron density was almost unchanged at different sample temperatures.

Accuracy improvement of Fe element in aluminum alloy by laser induced breakdown spectroscopy under spatial confinement combined with gradient descent

The concentration of Fe in aluminum alloy can affect the plasticity, heat resistance, strength and stress corrosion resistance of the alloy. The quantitative analysis of aluminum alloy composition is an important part of the online detection of alloy composition. To improve the quantitative analysis accuracy of Fe in aluminum alloy, the spatial confinement nanosecond laser-induced breakdown spectroscopy is combined with the gradient-descent method. By collecting laser-induced aluminum alloy plasma emission spectra, it is found that the plasma radiation intensity under the confinement of the plate space is significantly enhanced. The enhancement factor of the plasma emission spectrum with a plate spacing of 10 mm is 2.3. The internal standard method and the gradient descent method are used to establish the calibration models respectively, and the values of fitting coefficient (<i>R</i><sup>2</sup>), root mean square error (RMSE) and average relative error (ARE) of the two models are compared. Without plate spatial confinement, the R<sup>2</sup>, RMSEC, RMSEP and ARE of the Fe element calculated by the internal standard method are 90.66%, 0.1903%, 0.1910% and 9.2220%, respectively. The <i>R</i><sup>2</sup>, RMSEC, RMSEP and ARE of Fe element obtained by the gradient descent method are 97.12%, 0.1467% (weight concentration), 0.1124% (weight concentration) and 7.1373%, respectively. With the plate spatial confinement, the <i>R</i><sup>2</sup>, RMSEC, RMSEP and ARE of Fe element calculated by the internal standard method are 95.22%, 0.1409% (weight concentration), 0.1401% (weight concentration), and 6.8893%, respectively. The <i>R</i><sup>2</sup>, RMSEC, RMSEP and ARE of Fe element obtained by the gradient descent method are 99.22%, 0.0731% (weight concentration), 0.0756% (weight concentration) and 3.5521%, respectively. Comparing with the internal calibration model, the accuracy and stability of the gradient descent calibration model are improved. The spatial confinement LIBS combined with the gradient descent method can effectively reduce the influence of the alloy matrix effect and the self-absorption effect on the quantitative analysis.

Plasma-grating-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a useful tool for determination of elements in solids, liquids, and gases. For nanosecond LIBS (ns-LIBS), the plasma shielding effect limits its reproducibility, repeatability, and signal-to-noise ratios. Although femtosecond laser filament induced breakdown spectroscopy (FIBS) has no plasma shielding effects, the power density clamping inside the filaments limits the measurement sensitivity. We propose and demonstrate plasma-grating-induced breakdown spectroscopy (GIBS). The technique relies on a plasma excitation source—a plasma grating generated by the interference of two noncollinear femtosecond filaments. We demonstrate that GIBS can overcome the limitations of standard techniques such as ns-LIBS and FIBS. Signal intensity enhancement with GIBS is observed to be greater than 3 times that of FIBS. The matrix effect is also significantly reduced with GIBS, by virtue of the high power and electron density of the plasma grating, demonstrating great potential for analyzing samples with complex matrix.

Correlation between laser spectroscopic studies and mechanical characterization of zirconia-based multiwall carbon nanotube ceramic composites

The hardness of zirconium oxide-based ceramic nanocomposites was correlated with the laser spectroscopic studies by analyzing the samples through nanosecond and femtosecond laser to see the viability of this technique as a fast and in situ for assessment of mechanical properties in nuclear industry. Zirconia incorporated with different vol% of multiwall carbon nanotubes were processed by the high frequency induction heated sintering. The composites were characterized by the nanosecond laser-induced breakdown spectroscopy (LIBS) with optimized delay time of 1, 2, and 3 µs and 200 and 300 mJ energies generated by laser Nd:YAG (λ = 1064 nm). The plasma temperature resulted by the ablation of different samples was estimated through intensity of selected zirconium lines using the Boltzmann plot method. The samples were mechanically characterized by the Vickers hardness test. The estimated plasma temperature and the ratio of Zr(II) with different intensities of Zr(I) emission lines show rather weak dependency and increase with surface hardness. The samples were scrutinized by the femtosecond laser micromachining through variation in depth and surface morphology of machined areas. It is found that deeper circular groove and enhanced erosion of disk shape by femtosecond laser machining are achieved for less hard materials and are in agreement with the LIBS analysis.

Nanosecond laser induced breakdown spectroscopy for biofouling analysis and classification of fouling constituents

Marine biofouling refers to the undesirable growth and adhesion of marine organisms such as barnacles, macroalgae and microbial slimes on immersed structures. Biofouling composition is determined by collecting samples from marine structures and vessels and analyzing them in laboratories. Alternatively, an approach of online sensing based on Laser Induced Breakdown Spectroscopy (LIBS), which consists of analysis of the spectral emission from laser-induced plasma, can be considered for the elemental composition of biofouling. The study of marine biofouling using LIBS has not been attempted previously. In the present work, a laboratory-scale LIBS technique is used to analyze biofouling samples and its constituent common water-borne algae and bacterial species. First, LIBS database is created under controlled conditions for the selected biofilm constituent algae (Nitzschia sigma and Chaetoslorenzianus) and bacterial (Pseudomonas aeruginosa, Bacillus subtilis, E.coli) species. LIBS spectra are also acquired for Biofilm samples grown on Fiber Reinforced Plastic (FRP) and Stainless steel (SS) 316 L substrates suspended at a depth of 1 m in the tropical Indian Ocean. The studies are carried out for fouling growth period of 5, 10, 15 and 20 days in the intertidal region at a distance of 480 m from the shore. The study shows that the LIBS technique combined with the Principal Component Analysis (PCA) can be used for acquiring the spectra of biofouling species, its rapid classification and studying the growth characteristics. The LIBS database would serve as a means for early identification of marine fouling bacteria and algae species.

基于纳秒和飞秒及双脉冲激光诱导击穿光谱的燃煤热值定量分析

基于纳秒和飞秒及双脉冲激光诱导击穿光谱的燃煤热值定量分析

Spectroscopic analysis of high protein nigella seeds (Kalonji) using laser-induced breakdown spectroscopy and inductively coupled plasma/optical emission spectroscopy

The spectroscopic analysis of high protein nigella seeds (also called Kalonji) was performed using pulsed nanosecond laser-induced breakdown spectroscopy (LIBS) at 532 nm. The emission spectrum of Kalonji recorded with an LIBS spectrometer exposed the presence of various elements like Al, B, Ba, Ca, Cr, K, P, Mg, Mn, Na, Ni, S, Si, Cu, Fe, Ti, Sn, Sr, and Zn. The plasma parameters (electron temperature and electron density) were estimated using Ca–I spectral lines and their behavior were studied against laser irradiance. The electron temperature and electron density was observed to show an increasing trend in the range of 5802–7849 K, and (1.2–3.9) × 1017 cm− 3, respectively, in the studied irradiance range of (1.2–12.6) × 109 W/cm2. Furthermore, the effect of varying laser energy on the integrated signal intensities was also studied. The quantitative analysis of the detected elements was performed via the calibration curves drawn for all the observed elements through typical samples made in the known concentration in the Kalonji matrix, and by setting the concentration of P as the calibration. The validity of our LIBS findings was verified via comparison of the results with the concentration of every element find in Kalonji using the standard analytical tool like ICP/OES. The results acquired using LIBS and ICP/OES were found in fine harmony. Moreover, limit of detection was measured for toxic metals only.

Interface Instability of Fe-Stabilized Li7La3Zr2O12 versus Li Metal.

The interface stability versus Li represents a major challenge in the development of next-generation all-solid-state batteries (ASSB), which take advantage of the inherently safe ceramic electrolytes. Cubic Li7La3Zr2O12 garnets represent the most promising electrolytes for this technology. The high interfacial impedance versus Li is, however, still a bottleneck toward future devices. Herein, we studied the electrochemical performance of Fe3+-stabilized Li7La3Zr2O12 (LLZO:Fe) versus Li metal and found a very high total conductivity of 1.1 mS cm–1 at room temperature but a very high area specific resistance of ∼1 kΩ cm2. After removing the Li metal electrode we observe a black surface coloration at the interface, which clearly indicates interfacial degradation. Raman- and nanosecond laser-induced breakdown spectroscopy reveals, thereafter, the formation of a 130 μm thick tetragonal LLZO interlayer and a significant Li deficiency of about 1–2 formula units toward the interface. This shows that cubic LLZO:Fe is not stable versus Li metal by forming a thick tetragonal LLZO interlayer causing high interfacial impedance.

Determination of toxic and essential metals in rock and sea salts using pulsed nanosecond laser-induced breakdown spectroscopy.

A spectrometer based on pulsed nanosecond laser-induced breakdown spectroscopy (LIBS) was employed for the quantitative determination of heavy and essential metals in salts from various sources available in Pakistan. Six salt samples were collected from sea salt and rock salt. Toxic metals (Cu, Cd, and Ni) and other microessentials (Fe, Ca, Co, Mg, Mn, S, and Zn) were investigated from the recorded spectra. The detection system was calibrated using a parametric dependence study. The quantitative analyses were accomplished under the assumption of local thermodynamic equilibrium and optically thin plasma. The results by the LIBS technique were in agreement with the outcomes of the same samples studied using a more standard approach like inductively coupled plasma-atomic emission spectroscopy (ICP-AES). When the concentrations of heavy and essential metals were calculated using a calibration-free LIBS method that does not need a standard salt specimen and dilution, both LIBS and ICP-AES were also in good agreement. The limit of detection of the experimental set up was determined for the observed heavy metals in the studied samples.

Application of nanosecond laser induced breakdown spectroscopy to elemental analysis of cuttings samples

Application of nanosecond laser induced breakdown spectroscopy to elemental analysis of cuttings samples

Determination of deuterium depth profiles in fusion-relevant wall materials by nanosecond LIBS

The ablation and fuel-retention characteristics of aluminum–tungsten (AlW) and beryllium–tungsten (BeW) samples have been determined using Laser Induced Breakdown Spectroscopy (LIBS) and compared to results obtained using Secondary Ion Mass Spectrometry (SIMS). The measurements have been made both at vacuum (of the order of 10−4Pa) and at 50Pa of argon to especially enhance the intensities of the spectral lines of H and D. For reliable evaluation of the ablation rate of the samples the electron density ne and temperature Te of the LIBS plasma have been determined with the help of selected of spectral lines of Be, Al, and W. The electron density ne has been obtained from Stark broadening lines of Al I (308.7nm and 394.4nm) and Be I (457.3nm) and Te from the Saha–Boltzmann plot using W I and W II spectral lines having a higher value of the energy of upper states in order to prevent the influence of self-absorption on the results. The results indicate similar ablation characteristics between AlW (AlWD) and BeW (BeWD) samples but the inclusion of deuterium in the coating increases the ablation rate by a factor of 10 for both sample types. Concerning fuel retention more than one order of magnitude less D is retained in the AlWD sample than in BeWD. In the presence of background argon, the H and D lines were stronger and more easily distinguishable. This is a positive sign considering the real application in ITER where LIBS measurements are foreseen to be done during maintenance breaks. However the higher pressure gave a better signal, it is still far from the measurement conditions planned for ITER which need to be tested separately.

Standoff monitoring of aqueous aerosols using nanosecond laser-induced breakdown spectroscopy: droplet size and matrix effects.

Nanosecond laser-induced breakdown spectroscopy has been examined for the analysis of suspended matter in a free stream of air. The real-time monitoring of this scenario poses major challenges for an accurate categorization due to its changing characteristics such as composition, size, and density of particles. The effects of particle size and matrix in the optical emission responses registered from such scenarios have been evaluated. Distant (10 m) plasmas of saline solutions, containing either NaCl or Na2SO4 at different concentrations, have been induced by nanosecond laser pulses at a wavelength of 1064 nm. The effects of the droplet size and its concentration on differences in the laser-induced breakdown probability, the intensity of the characteristic lines, and the plasma emission continuum have been discussed. The quantification of sodium in distant water droplets has been proved. However, an initial knowledge on the average droplet size is required. The average droplet size could be determined from the slope of H I and O I lines versus the continuum plasma emission, which is only weakly influenced by the salt content in the droplets.

Determination of elemental concentration in geological samples using nanosecond laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) can be used for measuring the concentrations or ratios of various trace elements in solid samples.

Temperature and electron density in femtosecond filament-induced Cu plasma

Laser-induced breakdown spectroscopy (LIBS), which is also known as laser-induced plasma spectroscopy (LIPS), is a very promising spectral analysis technique for detecting elemental composition. The possibility of remote operation of LIBS is one of the properties, which expands the application scope of this technique. The remote LIBS technique is based on a long-range lens. With the increase of focusing distance, it is difficult to tightly focus laser pulse due to the diffraction limits. The size of focusing spot increases with focusing distance increasing. This will require extremely high laser energy. Femtosecond laser filamentation due to optical Kerr effect can be applied to the remote LIBS. During the filament propagation, the waist of laser beam is close to a constant value. The laser intensity inside the filament is about 1013 W/cm2 (intensity clamping). The intensity is sufficient to ablate sample and produce the plasma. It can overcome the influence of the diffraction limit in nanosecond LIBS. Although many researchers have studied the femtosecond geometrical focusing and femtosecond filamentation LIBSs, the spectral characteristics have not been completely understood. In this paper, we study the femtosecond laser filament-induced Cu plasma spectroscopy. Femtosecond laser system is an ultrafast Ti:sapphire amplifier (Coherent Libra). The full-width at the half maximum is 50 fs at a wavelength of 800 nm with a repetition rate of 1 kHz and its output energy is 3.5 mJ. A quartz lens with a focal length of 1 m is used to focus the laser to generate a filament channel. The spectral intensity of produced Cu plasma along the filament channel is measured by using the optical emission spectroscopy, and the distribution of Cu(I) intensity versus the distance between sample and focused lens is obtained. The results indicate that in a longer distance range along the filament, plasma spectroscopy has stronger emission due to the intensity clamping effect in femtosecond laser filamentation. In addition, we also calculate the plasma temperature and electron density by using the Boltzmann plot and the Stark broadening. The plasma temperature and electron density along the filament channel can be divided into three main regions: region 1) from 950 mm to 970 mm, in which the plasma temperature and electron density increase with the increase of distance; region 2) from 970 mm to 1030 mm, in which the change of plasma excitation temperature is opposite to the change of electron density; region 3) from 1030 mm to 1050 mm, in which the plasma temperature and electron density decrease with the increase of distance.

Sensitivity, stability, and precision of quantitative Ns-LIBS-based fuel-air-ratio measurements for methane-air flames at 1-11 bar.

Nanosecond laser-induced breakdown spectroscopy (ns-LIBS) is employed for quantitative local fuel-air (F/A) ratio (i.e., ratio of actual fuel-to-oxidizer mass over ratio of fuel-to-oxidizer mass at stoichiometry, measurements in well-characterized methane-air flames at pressures of 1-11 bar). We selected nitrogen and hydrogen atomic-emission lines at 568 nm and 656 nm, respectively, to establish a correlation between the line intensities and the F/A ratio. We have investigated the effects of laser-pulse energy, camera gate delay, and pressure on the sensitivity, stability, and precision of the quantitative ns-LIBS F/A ratio measurements. We determined the optimal laser energy and camera gate delay for each pressure condition and found that measurement stability and precision are degraded with an increase in pressure. We have identified primary limitations of the F/A ratio measurement employing ns-LIBS at elevated pressures as instabilities caused by the higher density laser-induced plasma and the presence of the higher level of soot. Potential improvements are suggested.

Optimized LWIR enhancement of nanosecond and femtosecond LIBS uranium emission

A carbon dioxide (CO2) transverse electrical breakdown in atmosphere (TEA), pulsed laser was used to enhance the laser-induced breakdown spectroscopy (LIBS) spectral signatures of uranium under nanosecond (ns) and femtosecond (fs) ablation. The peak areas of both ionic and neutral species increased by one order of magnitude for ns-ablation and two orders of magnitude for fs-ablation over LIBS when the CO2 TEA laser was used with samples of dried solutions of uranyl nitrate hexahydrate (UO2(NO3)2·6H2O) on silicon wafers. Electron temperature and density measurements show that the spectral emission improvement from using the TEA laser comes from plasma reheating.