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Ce2O2CN2 was firstly used as a promoter to improve the catalytic activity and stability of Fe–N–C for the ORR.

The intrinsic principle of the electronic property of Pt catalysts for the selective hydrogenation of 1,3-butadiene was systemically elucidated.

As a widely used artificially synthesized sweetener, saccharin faced numerous disputes associated with food safety. Therefore, its fast analysis in food is of crucial importance. In this study, an analytical method for the fast and reliable screening of saccharin in various beverages was established and validated, by combining HPTLC with densitometry and surface enhanced Raman spectroscopy. The diluted sample liquid was directly sprayed and separated on a silica gel plate using a mixture of ethyl acetate and acetic acid in the ratio of 9 : 1 (v/v) as the mobile phase. The separation realized full isolation of the analyte from background noises. Then, a densitometry analysis in the absorption-reflection mode (working wavelength 230 nm) was optimized to obtain quantitative data, showing a good linearity in the range of 40-200 ng per band (

Al-substituted Li7La3Zr2O12 samples processed under argon show enhanced Li-ion transport and interfacial properties in symmetrical cells with lithium electrodes, compared to those prepared in air. In particular, the samples prepared under argon have higher ionic conductivities and lower interfacial impedances in symmetrical lithium cells, and show better DC cycling characteristics. The electronic conductivities are also somewhat higher. Pellets subjected to thermal treatment under the two types of atmospheres have different colors but exhibit similar microstructures. X-ray diffraction experiments suggest that there are slight structural differences between the two types of samples, but few dissimilarities were observed in elemental composition, distribution of ions, oxidation states, or bond lengths using laser-induced breakdown spectroscopy (LIBS), x-ray photoelectron spectroscopy (XPS), and extended x-ray absorption fine structure spectroscopy (EXAFS) to analyze the materials. Additionally, there was no evidence that La or Zr were reduced during the processing under Ar. Possible explanations for the improved electrochemical properties of the sample prepared under Ar compared to the one prepared in air include differences in grain boundary chemistries and conductivities and/or a small concentration of oxygen vacancies in the former.

Measurements with Laser Ablation Molecular Isotopic Spectrometry (LAMIS) are usually performed in atmosphere for rapid isotope analysis, and an understanding of molecule formation via plasma–air chemical reactions is important for quantitative analysis by LAMIS. In this work, the expansion of a plasma plume from ablation of pure aluminum in air is studied with time- and space-resolved monochromatic imaging and emission spectroscopy. The distributions of neutral Al and O atoms and AlO radicals formed through plasma chemical reactions are characterized. The emission spectra of the AlO bands of a B2Σ+–X2Σ+ system are recorded and the rotational–vibrational temperature was obtained through fitting experimental spectra. Inter-molecular vibrational band interference is well re-constructed, and self-absorption of bandheads, especially for the (0–0) band, is corrected. Interpretation of the spatial–temporal evolutions of plasma species and plasma temperature provides insights into the formation mechanism of AlO radicals in laser-induced plasma.

We investigate experimentally spatiotemporal characteristics of fluorescence emission from fs-laser-induced filaments in air. Emissions accompanying the transitions of N

Laser ablation molecular isotopic spectrometry (LAMIS) was recently reported for isotope analysis of samples and for molecules formation mechanism investigation by analyzing the isotopologues in laser induced plasma. LAMIS was utilized to quantify the OD and OH molecules in fs-laser ablated plasma from moist water samples carried by pure Ar gas at ambient environment. A theoretical spectral fitting model for OD and OH molecules was developed and was used to extract the isotopic ratio OD/OH by fitting of experimental spectra. Time-resolved spectra were measured and the influences of spectrum intensity and signal to noise ratio (SNR) on isotopic quantitative analysis performance were evaluated. The relative concentration of OD and OH molecules in laser induced plasma from a set of water samples with D2O concentrations in the range of 0% to 99.8% are quantified, and a very good linear relationship between D concentration and D2O concentration was obtained. The linear curve exhibited R2 exceeding 0.9997 and a slope of 1.006. In addition, no standard sample is necessary for quantitative analysis, demonstrating the advantages of spectral fitting LAMIS.

We investigate atomic and molecular emission of laser-ablated nitromethane in an Ar or N2 buffer gas, with fs laser-induced breakdown spectroscopy. The electronic bands of CN, C2, and NH molecules and the atomic transition lines of C I, N I, and Hα are identified. The time series of the emissions are obtained, and the formation mechanisms of CN and C2 are deduced. The CN violet system, the B2Σ+-X2Σ+ (0-0) band, is chosen to extract plasma temperature from the experimental spectra.

© 2018 Optical Society of America. We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plume splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.

© 2015 Elsevier B.V. All rights reserved. A new remote sensing technology for real-time isotopic analysis is introduced: Femtosecond Filament-Induced Laser Ablation Molecular Isotopic Spectrometry (F2-LAMIS). The technique combines femtosecond (fs) laser filamentation and ablation-based molecular isotopic spectroscopy, thereby enabling isotopic analysis of samples at a distance, in ambient air and at ambient pressure conditions. Isotopic analysis of zirconium (Zr) samples by F2-LAMIS is demonstrated, and the molecular and atomic emission intensity, and properties of the filament-induced plasma generated at different filament propagation distances were investigated. Spectral fitting of F2-LAMIS spectra enabled semi-quantitative isotopic analysis without the use of calibration standards, which was independent of the filament propagation distance for the studied range. This technology provides new capabilities for direct isotopic ratio measurements at remote distances.

For the purpose of devising methods for minimally destructive multi-element analysis, we compare the performance of a 266 nm–213 nm double-pulse scheme against that of the single 266 nm pulse scheme. The first laser pulse at 266 nm ablates a mica sample. Ten ns later, the second pulse at 213 nm and 64 mJ cm − 2 orthogonally intercepts the gas plume to enhance the analyte signal. Emissions from aluminum, silicon, magnesium and sodium are simultaneously observed. At low 266 nm laser fluence when only sub-ng of sample mass is removed, the signal enhancement by the 213 nm pulse is especially apparent. The minimum detectable amount of aluminum is about 24 fmol; it will be a hundred times higher if the sample is analyzed by the 266 nm pulse alone. The minimum detectable mass for the other analytes is also reduced by about two orders of magnitude when the second pulse at 213 nm is introduced. The spectral and temporal properties of the enhanced signal are consistent with the mechanism of ultra-violet laser excited atomic fluorescence of dense plumes.

Direct chemical imaging is critical to understand and control processes that affect the performance and safety of Li-ion batteries. In this work, femtosecond-Laser Induced Breakdown Spectroscopy (fs-LIBS) is introduced for 3D chemical analysis of Li-ion solid state electrolytes in electrochemical energy storage systems. Spatially resolved chemical maps of major and minor elements in solid-state electrolyte Li7La3Zr2O12 (LLZO) samples are presented, with a depth resolution of 700 nm. We implement newly-developed visualization techniques to chemically image the atomic ratio distributions in a LLZO solid state electrolyte matrix. Statistical analysis, 2D layer-by-layer analysis, 2D cross-sectional imaging and 3D reconstruction of atomic ratios are demonstrated for electrolyte samples prepared under different processing conditions. These results explain the differences in the physical properties of the samples not revealed by conventional characterization techniques, and demonstrate the ability of fs-LIBS for direct 3D elemental imaging of Li-ion battery solid-state electrolytes.

With the hope of applying laser-induced breakdown spectroscopy (LIBS) to the geological logging field, a series of cutting samples were classified using LIBS coupled with chemometric methods. In this paper, we focused on a comparative investigation of the linear PLS-DA method and non-linear SVM method. Both the optimal PLS-DA model and SVM model were built by the leave-one-out cross-validation (LOOCV) approach with the calibration LIBS spectra, and then tested by validation spectra. We show that the performance of SVM is significantly better than PLS-DA because of its ability to address the non-linear relationships in LIBS spectra, with a correct classification rate of 91.67% instead of 68.34%, and an unclassification rate of 3.33% instead of 28.33%. To further improve the classification accuracy, we then designed a new classification approach by the joint analysis of PLS-DA and SVM models. With this method, 95% of the validation spectra are correctly classified and no unclassified spectra are observed. This work demonstrated that the coupling of LIBS with the non-linear SVM method has great potential to be used for on-line classification of geological cutting samples, and the combination of PLS-DA and SVM enables the cuttings identification with an excellent performance.

© 2017 American Chemical Society. Recently, laser ablated molecular isotopic spectrometry (LAMIS) has expanded its capability to explore molecules formation mechanism in laser-induced plasma in addition to isotope analysis. LAMIS is a powerful tool for tracking the origination of atoms that is involved in formation of investigated molecules by labeling atoms with their isotopic substitution. The evolutionary formation pathways of organic molecules, especially of C2dimers and CN radicals, were frequently reported. However, very little is known about the formation pathways for metallic radicals and heterodimers in laser ablated plasma. This research focuses on elucidating the formation pathways of AlO radicals in femtosecond laser ablated plasma from18O-labeled Al2O3pellet. Plasmas expanding with strong forward bias in the direction normal to the sample surface were generated in the wake of a weakly ionized channel created by a femtosecond laser. The formation mechanism of AlO and influence of air were investigated with multiple plasma diagnostic methods such as monochromatic fast gating imaging, spatiotemporal resolved optical emission spectroscopy, and LAMIS. An advanced LAMIS fitting procedure was used to deduce the spatiotemporal distributions of Al18O and Al16O number densities and also their ratios. We found that the Al16O/Al18O number density ratio is higher for plasma portion closer to the sample surface, which suggests that chemical reactions between the plasma plume and ambient air are more intense at the tail of the plasma. The results also reveals that direct association of free Al and O atoms is the main mechanism for the formation of AlO at the early stage of the plasma. To the contrast, chemical reactions between plasma materials and ambient oxygen molecules and the isotope exchange effect are the dominant mechanisms of the formation of AlO and evolution of Al16O/Al18O number density ratio at the late stage of the plasma.

LAMIS is an all-optical laser-ablation technique for isotope analysis at atmospheric ambient conditions. In this presentation, the theoretical principles of F2-LAMIS will be overviewed and its application for remote isotopic analysis will be discussed.

A new laser induced plasma temperature measuring method with two lines emitted from different elements with the same ionization degree is proposed, assuming local thermodynamic equilibrium condition of the plasma. The influence of measurement error on deduced temperature accuracy was simulated in theory. A solution containing Cu, K, and Cr elements was used as the sample. Plasma was generated at the surface of the solution, and time-resolved spectra were recorded. Two atomic lines, Cu I 324 nm and K I 766 nm, were used to determine the plasma temperature with the proposed method. Four atomic lines and two ionic lines of Cr were selected to deduce plasma temperature with the Saha–Boltzmann plot method for comparison. The temperatures deduced from the two different methods showed similar behavior as a function of time. The results suggested that this method can be useful in cases where only very few lines from a single element are available in the spectrum and Boltzmann or Saha–Boltzmann plots cannot be built.

The detection of manganese (Mn) in industrial wastewater and seawater plays an important role in pollution monitoring and the investigation of geochemical and biological processes in the ocean. An approach has been introduced in this work to improve the detection sensitivity of Mn in liquids by laser-induced breakdown spectroscopy with a filter paper as solid substrate. The calibration curves of Mn in aqueous solutions were obtained with the detection of a Czerny–Turner spectrometer and an echelle spectrometer, respectively. The results showed that the Czerny–Turner spectrometer equipped with an intensified charge-coupled device (ICCD) had a more sensitive detection of Mn in aqueous solution with this approach. The limit of detection (LOD) for Mn was down to 0.11 mg/L with laser pulse energy of 90 mJ. With the same approach, the compact echelle spectrometer equipped with an ICCD was used to verify the feasibility for rapid onsite detection. The calibration curves for Mn in simulated industrial wastewater and seawater were constructed to calculate relevant LODs. The LODs of Mn were 2.78 mg/L in mixed solutions and 2.73 mg/L in seawater by calculation. Both the calibration curves and LODs were affected slightly by the matrix effect in the experiment. In order to assess the accuracy, a mixed solution including Mn, Cr, Cd, and Cu with known concentrations was determined, and good agreement between the measured and real values were achieved. It demonstrated that this approach has significant potential for rapid onsite detection of Mn and other metal elements in industrial wastewater and seawater.

Al-substituted Li7La3Zr2O12 (LLZO) pellets with a grain size of 100–200 μm and a relative density of 94% were prepared by conventional solid-state processing at a sintering temperature of 1100 °C, 130 °C lower than previously reported. Morphological features and the presence of impurities were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Femtosecond Laser Induced Breakdown Spectroscopy (LIBS) was used to visualize the distribution of impurities. The results suggest that chemical composition of the powder cover strongly affects morphology and impurity formation, and that particle size control is critical to densification. These properties, in turn, strongly affect total ionic conductivity and interfacial resistance of the sintered pellets.

Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) are used simultaneously for spatially resolved mapping of major and trace elements and isotopes within a Bastnasite rare earth ore sample. The combination of the two techniques provides complementary measurements for elements that are separately unattainable due to low sensitivity and/or strong interferences. Two dimensional (2D) layer-by-layer mapping, 2D cross-sectional imaging and three-dimensional (3D) volume rendering of elements and isotopes in the Bastnasite matrix are presented. These results pave the way for improved 3D elemental imaging through simultaneously acquired LIBS and LA-ICP-MS measurements.

It is a big challenge to apply laser induced breakdown spectroscopy (LIBS) to ocean in situ detection, but there are ample opportunities for LIBS development too. In the present work, laboratory investigations of LIBS on natural seawater at different pressures from 0.1 to 40 MPa were carried out. Pressure and laser pulse energy effects on LIBS emission were investigated. The result showed that enhanced LIBS emission can be obtained under elevated ambient pressure conditions. The line broadening of lines increases as a function of pressure. The time resolved LIBS emission results demonstrated that plasma emission is weakly dependent on the ambient pressure during the early stage of plasma and the pressure has a significant influence on the plasma form during plasma evaluation at a later stage of plasma. The obtained results suggested that the LIBS technique has the potential to be developed as an in situ chemical sensing technique for ocean applications.

We investigate experimentally spatiotemporal characteristics of fluorescence emission from fs-laser-induced filaments in air. Emissions accompanying the transitions of N2 (C3Πu−B3Πg) and N 2+ (B2Σu+−X2Σg+) are dominant. The decay dynamics of fluorescence from different radial positions and longitudinal sections of a filament column are obtained along with high resolution spectra. A decay curve contains two exponential components: a fast one (with a decay time constant ∼10s ps), and a slow one (∼sub-ns). The lifetime of the N 2 fluorescence is about three orders shorter than its spontaneous emission lifetime, indicating that most of the N 2 molecules in the excited state (C3Πu) are de-excited through collision. Different de-excitation mechanisms of N 2 (C3Πu) molecules contributing to fluorescence decay constants, e.g., the e −−N2, N 2−N2, and O 2−N2 collisions, are elucidated. We analyze the variations of decay constants together with corresponding fluorescence intensities, and obtain temperature distributions by fitting band spectra of N 2 molecules and N 2+ ions with a synthetic spectral model. Our results suggest that the fast and slow decay processes originate from the e −−N2 and O 2−N2 collisions, respectively.

Laser ablation molecular isotopic spectrometry (LAMIS) for rapid isotopic analysis of zirconium at atmospheric pressure was studied with a femtosecond-laser system operated under high repetition rate (1 kHz) and low pulse energy (160 μJ). The temporal evolution of zirconium neutral-atomic and ionic lines, as well as zirconium oxide molecular bands, were studied. Six molecular bands, belonging to the d(3)Δ-a(3)Δ (i.e., the α system) and E(1)Σ(+)-X(1)Σ(+) transitions, were observed with appreciable isotopic shifts. The assignments of the isotopic bandheads were first based on theoretical predictions of the band origins and the associated isotopic shifts of various dipole-allowed ZrO electronic transitions, followed by an experimental confirmation with a (94)Zr-enriched ZrO2 sample. In this work, the α(0,1) band from the d(3)Δ3-a(3)Δ3 subsystem was utilized for Zr isotope analysis based on a compromise between the magnitude of isotopic shifts in emission wavelengths, emission strengths, signal-to-background ratios, and spectral interferences. The analysis was performed in a standardless calibration approach; the isotopic information was extracted from the experimentally measured molecular spectra through theoretical spectral fitting. The results demonstrate the feasibility to obtain isotopic information for a spectrally complicated element like zirconium, without the need to use isotopically labeled calibration standards. The availability of comprehensive molecular constants will further improve the analytical accuracy of this standardless calibration approach.

Dense LLZO (Al-substituted Li7La3Zr2O12) pellets were processed in controlled atmospheres to investigate the relationships between the surface chemistry and interfacial behavior in lithium cells. Laser induced breakdown spectroscopy (LIBS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, synchrotron X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) studies revealed that Li2CO3 was formed on the surface when LLZO pellets were exposed to air. The distribution and thickness of the Li2CO3 layer were estimated by a combination of bulk and surface sensitive techniques with various probing depths. First-principles thermodynamic calculations confirmed that LLZO has an energetic preference to form Li2CO3 in air. Exposure to air and the subsequent formation of Li2CO3 at the LLZO surface is the source of the high interfacial impedances observed in cells with lithium electrodes. Surface polishing can effectively remove Li2CO3 and dramatically improve the interfacial properties. Polished samples in lithium cells had an area specific resistance (ASR) of only 109 Ω cm(2) for the LLZO/Li interface, the lowest reported value for Al-substituted LLZO. Galvanostatic cycling results obtained from lithium symmetrical cells also suggest that the quality of the LLZO/lithium interface has a significant impact on the device lifetime.

Laser Induced Breakdown Spectroscopy (LIBS), as an in-situ, real time, multi-element analysis tool, has been used in many applications. While for oceanic applications, many difficulties arise due to lower ablation efficiency and shorter emission lifetime of LIBS in water. The complexity of ocean environment makes LIBS performance even worse. To evaluate the potential using of LIBS for oceanic application, extensive experimental investigations of LIBS have been carried out with a nickel sample submerged in water under both single pulse and dual-pulse laser ablation. It was found that, for short duration laser pulse ablation, the continuum emission lifetime was nearly equal to the duration of laser pulse, with nickel atomic emission hardly appeared. As the laser pulse duration going up to 50 ns, several nickel atomic lines were turned up on the continuum background. With dual-pulse laser ablation, the intensity of theses nickel atomic lines were enhanced significantly, which demonstrated that dual-pulse had better LIBS performance. The LIBS signals of nickel target within the wavelength range of 330nm-390 nm were obtained under dual-pulse laser ablation. And severe self-absorption phenomenon was observed among those nickel atomic emission lines. The possible reason for self-absorption has been discussed and was attributed to the relevant transmission energy levels. To verify the effect of cations in water, LIBS investigation was carried out with the nickel target submerged in Na+, K+ solution or deep-sea water. It was found that both intensity and signal to background ratio had been improved with the cations in water. All those obtained results suggested that LIBS had great potential to be used in oceanic application.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ chemical analysis in ocean observation. Extensive experimental investigations were carried out to understand the plasma-ambient pressure interaction mechanism in a liquid environment. Results shows that plasma temperature and electron density increase with increasing pressure. Under elevated pressure conditions, the electron density increases at the late plasma stage. The results indicate that plasma could be condensed, which leads to an increase in plasma temperature and electron density.

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We introduce the use of femtosecond laser plasma spectroscopy in chemical imaging of Li-ion battery system components. Spatially resolved mapping of major and minor elements of Li-ion batteries is presented and correlated to electrochemical performance.