Showing papers in "Applied Spectroscopy in 2019"
TL;DR: This article shows that 2D-COS is useful for spectral band assignment in HSI applications and demonstrates its utility for detecting subtle correlations between spectra features, or between features from different imaging modalities in the case of heterospectral (multimodal) HSI.
Abstract: The last two decades have seen tremendous progress in the application of two-dimensional correlation spectroscopy (2D-COS) as a versatile analysis method for data series obtained using a large variety of different spectroscopic modalities, including infrared (IR) and Raman spectroscopy. The analysis technique is applicable to a series of spectra recorded under the influence of an external sample perturbation. Two-dimensional COS analysis is not only helpful to decipher correlations, which may exist between distinct spectral features, but can also be utilized to obtain the sequence of individual spectral changes. The focus of this review article is on the application of 2D-COS for analyzing spatially resolved data with special emphasis on hyperspectral imaging (HSI) study. In this review, we briefly introduce the fundamentals of the generalized 2D-COS analysis approach, discuss specific points of 2D-COS application to spatially resolved spectra and demonstrate essential aspects of data pre-processing for 2D-COS analysis of spatially resolved spectra. Based on illustrative examples, we show that 2D-COS is useful for spectral band assignment in HSI applications and demonstrate its utility for detecting subtle correlations between spectra features, or between features from different imaging modalities in the case of heterospectral (multimodal) HSI. Furthermore, a short overview on existing 2D-COS software tools is provided. It is hoped that this article represents not only a useful guideline for 2D-COS analyses of spatially resolved hyperspectral data but supports also further dissemination of the 2D-COS analysis method as a whole.
91 citations
TL;DR: Optical emission of laser-produced plasmas from solids, liquids, and gases has been comprehensively reported in multiple research manuscrip... as discussed by the authors, from their fundamentals to their potential applications.
Abstract: Optical emission of laser-produced plasmas from solids, liquids, and gases, from their fundamentals to their potential applications, has been comprehensively reported in multiple research manuscrip...
58 citations
TL;DR: The value portable GC-MS systems offer to warfighters in theater is outlined, some important aspects of the design of portable systems that makes their deployment to this type of end user possible, and methods that can be used to overcome challenges to successful deployment to non-scientists working within hostile environments are proposed.
Abstract: The use of portable gas chromatography-mass spectrometry (GC-MS) is an important capability that has been available commercially for almost 25 years. These systems have been used within a variety of different industries, including their extensive use by environmental scientists for the analysis of hazardous air pollutants. Recently, these systems were deployed to conventional military forces for use in theater to detect and identify toxic chemicals including chemical warfare agents (CWAs). The challenges of deploying such complex analytical instruments to these military users are unique. Among other things, these organizations have considerable and variable mission strains, complex and difficult logistics and coordination needs, and variability in user backgrounds. This review outlines the value portable GC-MS systems offer to these warfighters in theater, discusses some important aspects of the design of portable systems that makes their deployment to this type of end user possible, and proposes methods that can be used to overcome challenges to successful deployment of portable GC-MS to non-scientists working within hostile environments.
42 citations
TL;DR: It is shown that besides using the mathematical algorithm such as regularization, selecting a line pair with a large ΔE″ (>1390 cm−1) also reduces the reconstruction uncertainty at 300–2000 K.
Abstract: We report the influence of absorption line selection on the tomographic results for high-temperature flames by numerical and experimental methods. Different combinations of infrared H2O absorption ...
30 citations
TL;DR: The results show that LIBS can be used with deep learning for the detection of heavy metals in soil.
Abstract: In this study, a method based on laser-induced breakdown spectroscopy (LIBS) was developed to detect soil contaminated with Pb. Different levels of Pb were added to soil samples in which tobacco was planted over a period of two to four weeks. Principal component analysis and deep learning with a deep belief network (DBN) were implemented to classify the LIBS data. The robustness of the method was verified through a comparison with the results of a support vector machine and partial least squares discriminant analysis. A confusion matrix of the different algorithms shows that the DBN achieved satisfactory classification performance on all samples of contaminated soil. In terms of classification, the proposed method performed better on samples contaminated for four weeks than on those contaminated for two weeks. The results show that LIBS can be used with deep learning for the detection of heavy metals in soil.
28 citations
TL;DR: A long–short double pulse laser-induced breakdown spectroscopy method was employed to improve the analytical performance of LIBS for the measurement of manganese in steel samples, suggesting that the improvement in detection ability can be attributed to the pre-irradiation effect of long-pulse laser beam.
Abstract: A long-short double pulse laser-induced breakdown spectroscopy (long-short DP-LIBS) method was employed to improve the performance of LIBS for the measurement of manganese in steel samples The long pulse was generated by a Nd:YAG laser which was operated at free runing (FR) mode To investigate the detection ability without sample preparation, the steel washers were tested using SP-LIBS and long-short DP-LIBS, respectively The measurement results show that the long-short DP-LIBS method was able to record clear spectra from the rusty steel washers The steel washers were also measured after the polishing process The measurement results show that the signal intensity was enhanced by long-short DP-LIBS Through the observation with scanning electron microscope (SEM) on the laser craters, the results suggest that the improvement of detection ability can be attributed to the pre-radiation effect of long-pulse laser beam Next, the analytical performance for quantitative measurement of manganese was evaluated by employing ten standard steel samples The results show that the linearty fit (R2) of calibration curve is 0988 for long-short DP-LIBS, whereas, R2 is only 0810 for SP-LIBS under the same measurement conditions The five times repeated measurement results show that the average Relative Standard Deviation (RSD) of the tested samples is 293% for SP-LIBS and is 105% for long-short DP-LIBS The prediction results also show that the average Relative Error of Prediction (REP) is 949% for SP-LIBS and it 49% for long-short DP-LIBS The experimental results in current work demonstrate that long-short DP-LIBS is promising for the on line measurement of steel in the steelmaking plant
26 citations
TL;DR: It is demonstrated that cellular-level mapping can be accomplished using identical samples for both FT-IR and chemical labels, and higher-resolution results can be achieved using a deep convolutional neural network that integrates spatial and spectral features.
Abstract: Histological stains, such as hematoxylin and eosin (H&E), are routinely used in clinical diagnosis and research. While these labels offer a high degree of specificity, throughput is limited by the need for multiple samples. Traditional histology stains, such as immunohistochemical labels, also rely only on protein expression and cannot quantify small molecules and metabolites that may aid in diagnosis. Finally, chemical stains and dyes permanently alter the tissue, making downstream analysis impossible. Fourier transform infrared (FT-IR) spectroscopic imaging has shown promise for label-free characterization of important tissue phenotypes and can bypass the need for many chemical labels. Fourier transform infrared classification commonly leverages supervised learning, requiring human annotation that is tedious and prone to errors. One alternative is digital staining, which leverages machine learning to map IR spectra to a corresponding chemical stain. This replaces human annotation with computer-aided alignment. Previous work relies on alignment of adjacent serial tissue sections. Since the tissue samples are not identical at the cellular level, this technique cannot be applied to high-definition FT-IR images. In this paper, we demonstrate that cellular-level mapping can be accomplished using identical samples for both FT-IR and chemical labels. In addition, higher-resolution results can be achieved using a deep convolutional neural network that integrates spatial and spectral features.
25 citations
TL;DR: A rapid analytical method based on ultraviolet (UV) absorption spectroscopy that can achieve accurate detection of the concentration of the gas mixture in the conventional application range (including 4–10% C4F7N).
Abstract: As an alternative to sulfur hexafluoride (SF6) with great potential for application, heptafluoroisobutyronitrile-carbon dioxide (C4F7N-CO2) gas mixture has been applied in various gas-insulated equipment. The insulation performance of the gas mixture is closely related to the mixing ratio. Therefore, accurate quantification of C4F7N in the C4F7N-CO2 gas mixture has very important engineering significance. At present, there are few reports on the rapid quantitative detection of the concentration of C4F7N in the gas mixture. In this paper, a rapid analytical method for C4F7N concentration based on ultraviolet (UV) absorption spectroscopy is constructed. The UV spectral characteristics of C4F7N molecules are calculated by density functional theory. The appropriate bands that can be detected are determined by analyzing the calculated results. A concentration detection system of C4F7N based on UV absorption spectroscopy is built. Through analysis of the calculated results and experimental results, a quantitative detection method of C4F7N in the C4F7N/CO2 gas mixture is determined. The method can achieve accurate detection of the concentration of the gas mixture in the conventional application range (including 4-10% C4F7N). The coefficient of the determination R2 of the concentration inversion curve reaches 0.999 and the inversion error ratio does not exceed 5%. The related research results provide an important reference for the engineering application of the gas mixture.
19 citations
TL;DR: It is demonstrated that the Vis-NIR spectroscopic technique combined with appropriate chemometric methods could be useful in identifying AFB1 contamination of peanut kernels.
Abstract: Current methods for detecting aflatoxin contamination of agricultural and food commodities are generally based on wet chemical analyses, which are time-consuming, destructive to test samples, and r...
19 citations
TL;DR: The results suggest that similar LIBS systems could be packaged for use as an effective instrument for screening samples during collection activities in the field or to conduct process control measurements during the production of debris surrogates.
Abstract: This work describes the use of a laser-induced breakdown spectroscopy (LIBS) system to conduct macroscopic elemental mapping of uranium and iron on the exterior surface and interior center cross-se...
19 citations
TL;DR: A novel method to detect cosmic rays in deep ultraviolet Raman hyperspectral data sets adapted from existing cosmic ray removal methods applied to astronomical images, which identifies cosmic rays as outliers in the distribution of intensity values in each wavelength channel.
Abstract: Cosmic rays can degrade Raman hyperspectral images by introducing high-intensity noise to spectra, obfuscating the results of downstream analyses. We describe a novel method to detect cosmic rays i...
TL;DR: A rheo-optical characterization technique based on the combination of near-infrared (NIR) spectroscopy and mechanical analysis was applied to the nanocomposite consisting of hydroxyl-functionalized polypropylene (PPOH) and mesoporous silica (MPS) to probe the deformation behavior.
Abstract: A rheo-optical characterization technique based on the combination of near-infrared (NIR) spectroscopy and mechanical analysis was applied to the nanocomposite consisting of hydroxyl-functionalized...
TL;DR: Investigation of the effect of insulin given intracerebroventricular (ICV) before inducing a transient global ischemia by bilateral occlusion of the common carotid arteries in Mongolian gerbils supports the hypothesis of an insulin-dependent neuroprotection and antiapoptotic mechanism occurring in the brain of MG undergoing transient brain ischemies.
Abstract: Brain ischemia represents a leading cause of death and disability in industrialized countries. To date, therapeutic intervention is largely unsatisfactory and novel strategies are required for getting better protection of neurons injured by cerebral blood flow restriction. Recent evidence suggests that brain insulin leads to protection of neuronal population undergoing apoptotic cell death via modulation of oxidative stress and mitochondrial cytochrome c (CytC), an effect to be better clarified. In this work, we investigate on the effect of insulin given intracerebroventricular (ICV) before inducing a transient global ischemia by bilateral occlusion of the common carotid arteries (BCCO) in Mongolian gerbils (MG). The transient (3 min) global ischemia in MG is observed to produce neurodegenerative effect mainly into CA3 hippocampal region, 72 h after cerebral blood restriction. Intracerebroventricular microinfusion of insulin significantly prevents the apoptosis of CA3 hippocampal neurons. Histological observation, after hematoxylin and eosin staining, puts in evidence the neuroprotective role of insulin, but Raman microimaging provides a clearer insight in the CytC mechanism underlying the apoptotic process. Above all, CytC has been revealed to be an outstanding, innate Raman marker for monitoring the cells status, thanks to its resonant scattering at 530 nm of incident wavelength and to its crucial role in the early stages of cells apoptosis. These data support the hypothesis of an insulin-dependent neuroprotection and antiapoptotic mechanism occurring in the brain of MG undergoing transient brain ischemia. The observed effects occurred without any peripheral change on serum glucose levels, suggesting an alternative mechanism of insulin-induced neuroprotection.
TL;DR: Cyclic fluctuations of the amide I and amide II bands and a continuous increase of the EPS band were related to the starvation of bottom-layered bacteria caused by the nutrient gradient in E. coli colonies.
Abstract: Contrary to the planktonic state of bacteria, their biofilm form represents severe complications in areas such as human medicine or food industry due to the increasing resistance against harsh cond...
TL;DR: A novel charge-shifting lock-in approach permitting fast SERDS operation using a specialized dual-wavelength diode laser and a custom-built charge-coupled device enabling charge retention and shifting back and forth on the CCD chip is presented.
Abstract: Shifted excitation Raman difference spectroscopy (SERDS) can provide effective, chemically specific information on fluorescent samples. However, the restricted ability for fast alternating detection (usually < 10 Hz) of spectra excited at two shifted laser wavelengths can limit its effectiveness when rapidly varying emission backgrounds are present. This paper presents a novel charge-shifting lock-in approach permitting fast SERDS operation (exemplarily demonstrated at 1000 Hz) using a specialized dual-wavelength diode laser (emitting at 829.40 nm and 828.85 nm) and a custom-built charge-coupled device (CCD) enabling charge retention and shifting back and forth on the CCD chip. For six selected mineral samples (moved irregularly during spectral acquisition), results demonstrate superior reproducibility of the fast charge-shifting read-out over the conventional read-out (operated at 5.4 Hz). Partial least squares discriminant analysis revealed improved classification performance of charge-shifting (four latent variables, sensitivity: 99%, specificity: 94%) versus conventional read-out (six latent variables, sensitivity: 90%, specificity: 92%). The charge-shifting concept was also successfully translated to sub-surface analysis using spatially offset Raman spectroscopy (SORS). Charge-shifting SERDS-SORS spectra recorded from a polytetrafluoroethylene layer, concealed behind a 0.25 mm thick, opaque, heterogeneous layer, matched reference spectra much more closely and exhibited a signal-to-background-noise (S/NB) ratio two times higher than that achieved with conventional CCD read-out SERDS-SORS. The novel approach overcomes fundamental limitations of conventional CCDs. In conjunction with the inherent capability of the charge-shifting lock-in technique to suppress rapidly varying ambient light interference demonstrated by us earlier it is expected to be particularly beneficial with heterogeneous fluorescent samples in field applications.
TL;DR: A novel application of terahertz time-domain spectroscopy (THz-TDS) is described for the determination of permittivity and polarizability of organic crystals, as exemplified by measurements with the polymorph I form of crystalline aspirin.
Abstract: A novel application of terahertz time-domain spectroscopy (THz-TDS) is described for the determination of permittivity and polarizability of organic crystals, as exemplified by measurements with th...
TL;DR: Recognized as a label-free and background-free technique, the coherent Raman spectroscopy, complemented with a known high-resolution spectroscopic correlation analysis, has potential in studying the hydrogen-bonded pyridine-water complexes.
Abstract: Hydrogen bonding is a vital molecular interaction for bio-molecular systems, yet deep understanding of its ways of creating various complexes requires extensive empirical testing. A hybrid femtosec...
TL;DR: The benefits of different SLM devices as a part of Raman instrumentation are introduced and a variety of recent example applications which have benefited from their incorporation into a Raman system are provided.
Abstract: Advances in consumer display screen technologies have historically been adapted by researchers across the fields of optics as they can be used as electronically controlled spatial light modulators (SLMs) for a variety of uses. The performance characteristics of such SLM devices based on liquid crystal (LC) and digital micromirror device (DMD) technologies, in particular, has developed to the point where they are compatible with increasingly sensitive instrumental applications, for example, Raman spectroscopy. Spatial light modulators provide additional flexibility, from modulation of the laser excitation (including multiple laser foci patterns), manipulation of microscopic samples (optical trapping), or selection of sampling volume (adaptive optics or spatially offset Raman spectroscopy), to modulation in the spectral domain for high-resolution spectral filtering or multiplexed/compressive fast detection. Here, we introduce the benefits of different SLM devices as a part of Raman instrumentation and provide a variety of recent example applications which have benefited from their incorporation into a Raman system.
TL;DR: The development and validation of an in-line near-infrared (NIR) spectroscopic method for the determination of content uniformity of blends in a tablet feed frame is focused on.
Abstract: Process analytical technology (PAT) has shown great potential for in-line tableting process monitoring. The study focuses on the development and validation of an in-line near-infrared (NIR) spectroscopic method for the determination of content uniformity of blends in a tablet feed frame. An in-line NIR method was developed after careful evaluation of the impact of potential experimental factors on the robustness and model accuracy and precision. The NIR method was validated according to the principles outlined in International Conference on Harmonization-Q2 for validation of analytical procedures and was demonstrated to be suitable for monitoring blend content for the formulation under evaluation. Reliable measurements of blend homogeneity rely on representative sampling. To reach the appropriate scale of scrutiny for a unit dose, the study assessed factors that influence the effective sample size measured by NIR. Spectral averaging, integration time, and feed frame paddle wheel speed were found to influence the effective sample size measured by the NIR probe. The effective sampling size was also estimated by comparing the distribution of predicted values with the reference values. The development of a robust, in-line PAT method was facilitated by thorough understanding of the sensitivity of PAT sensors to factors affecting pharmaceutical processes and products.
TL;DR: A novel technique called AOSD@Job’s, combining asynchronous orthogonal sample design scheme (AOSD) with Job's method, is proposed to estimate the stoichiometric ratio of two substances that form a supramolecular aggregate under intermolecular interactions.
Abstract: A novel technique called AOSD@Job’s, combining asynchronous orthogonal sample design scheme (AOSD) with Job’s method, is proposed to estimate the stoichiometric ratio of two substances that form a ...
TL;DR: This research work demonstrates a simple approach that significantly improves remote Raman and LIBS capabilities for long range chemical detection with compact low laser power Ramanand LIBS systems.
Abstract: The remote detection of chemicals using remote Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) is highly desirable for homeland security and NASA planetary exploration programs. ...
TL;DR: A method of back propagation (BP) neural network modeling, which incorporates a genetic algorithm (GA), evaluates the method of parameter modeling and prediction based on GA to optimize the BP neural network (GA–BP), and realizes a quantitative analysis of the C(I) 247.86 nm line.
Abstract: Carbon content detection is an essential component of the metal-smelting and classification processes. An obstacle in carbon content detection by laser-induced breakdown spectroscopy (LIBS) of stee...
TL;DR: It was determined that faster exposure replicates can provide greater peak resolution with higher fidelity measurements but are limited with respect to the total analysis time (i.e., limited in detection timely separations).
Abstract: Automated introduction platforms integrated with inductively coupled plasma optical emission spectroscopy (ICP-OES) systems are continuously being improved. Expanding on the introduction systems, a newly developed automated ion chromatography system was explored for performing rapid in-line separations coupled to ICP-OES for the detection of trace elements in uranium. Trace elements are separated from a uranium material and the analytes are directed into the ICP-OES for subsequent detection. Detection parameters such as exposure time frequency, wavelength selection, and settling times were explored to gain insight on optimal detection schemes for in-line trace elemental analysis. The methodology was applied in the analysis of a uranium oxide (U3O8) certified reference material, CRM-124. It was found here that the sensitivity and uncertainty of the technique are greatly affected by how the ICP-OES is employed to collect data. Overall it was determined that faster exposure replicates can provide greater peak resolution with higher fidelity measurements but are limited with respect to the total analysis time (i.e., limited in detection timely separations). Zeta scores, which combine accuracy and uncertainty of certified values and experimental values, were used to validate the ICP-OES modes of operation.
TL;DR: An all-optical quartz-enhanced photoacoustic spectroscopy system (QEPAS) with quadrature point stabilization for trace gas detection was reported and the detection sensitivity was enhanced by a factor of ∼2.1 in comparison to the conventional QEPAS system.
Abstract: An all-optical quartz-enhanced photoacoustic spectroscopy system (QEPAS) with quadrature point stabilization for trace gas detection was reported. The extrinsic interferometry-based optical fiber F...
TL;DR: The investigations and results show an easy alternative and cheap way to detect small amounts or residue of harmful environmental pollutants, which has a direct bearing on food quality and thus on human health.
Abstract: Advanced gold (Au) and silver (Ag) nanostructures were produced by laser techniques on printer paper substrate. Surface-enhanced Raman spectroscopy (SERS) analyses of the fungicide mancozeb (Dithane DG) and insecticide thiamethoxam (Aktara 25 BG) in quantities smaller than usually applied in agricultural medicine were performed for the first time assisted by the structures fabricated. The investigations and results show an easy alternative and cheap way to detect small amounts or residue of harmful environmental pollutants, which has a direct bearing on food quality and thus on human health.
TL;DR: The obtained results of the Stark widths and shifts at the different temperatures and densities of electrons have been compared with the limited data available in the literature and regularities and similarities for said parameters are established.
Abstract: In this work, the Stark broadening parameters (widths and shifts) of the 2203.5 A and 4386.5 A Pb(II) spectral lines have been investigated and measured in laser-induced breakdown spectroscopy (LIB...
TL;DR: The results indicated that the developed fluorescence-based aptasensor was simple in design, easy to operate, and could be used to detect rapidly and accurately SDM in water and fish samples.
Abstract: Fluorescence-based aptasensors possess high sensitivity but are complicated and usually require multistep labeling and modification in method design, which severely limit the practical applications...
TL;DR: A cosmic ray artefact removal algorithm is proposed that works in a similar way to the double acquisition method but requires only a single capture, so long as a data set of similar spectra is available.
Abstract: Cosmic ray artifacts may be present in all photo-electric readout systems. In spectroscopy, they present as random unidirectional sharp spikes that distort spectra and may have an affect on post-processing, possibly affecting the results of multivariate statistical classification. A number of methods have previously been proposed to remove cosmic ray artifacts from spectra but the goal of removing the artifacts while making no other change to the underlying spectrum is challenging. One of the most successful and commonly applied methods for the removal of comic ray artifacts involves the capture of two sequential spectra that are compared in order to identify spikes. The disadvantage of this approach is that at least two recordings are necessary, which may be problematic for dynamically changing spectra, and which can reduce the signal-to-noise (S/N) ratio when compared with a single recording of equivalent duration due to the inclusion of two instances of read noise. In this paper, a cosmic ray artefact removal algorithm is proposed that works in a similar way to the double acquisition method but requires only a single capture, so long as a data set of similar spectra is available. The method employs normalized covariance in order to identify a similar spectrum in the data set, from which a direct comparison reveals the presence of cosmic ray artifacts, which are then replaced with the corresponding values from the matching spectrum. The advantage of the proposed method over the double acquisition method is investigated in the context of the S/N ratio and is applied to various data sets of Raman spectra recorded from biological cells.
TL;DR: An on–off–on reversible fluorescence probe for sensitive and specific monitoring Cu2+, Cys, and His has been prepared and can be used to test Cu2+ and Cys/His in live cells and human urine samples with great reliability.
Abstract: A simple coumarin-based Schiff base (probe L) was successfully developed. It showed strong green fluorescence emission at 527 nm with a 70.3% of fluorescence quantum efficiency (ΦF). However, after the addition of common metal ions, probe L can only combine with Cu2+ ions and displayed significant fluorescence quenching of > 96.2% (ΦF = 2.7%) due to the paramagnetic quenching action from Cu2+. Conversely, by the coordination action of cysteine (Cys) and histidine (His), the quenching fluorescence of the complex (L-Cu2+) between probe L and Cu2+ ions was recovered mostly because the Cys and His can usurp Cu2+ of L-Cu2+ and led to the liberation of probe L. Based on the fluorescence changes of probe L with the actions of Cu2+, Cys, and His, an on-off-on reversible fluorescence probe for sensitive and specific monitoring Cu2+, Cys, and His has been prepared. More importantly, the probe L and L-Cu2+ ensemble can be used, respectively, to test Cu2+ and Cys/His in live cells and human urine samples with great reliability.
TL;DR: The results suggest that the ambient temperature has great influences on laser-induced plasma, which needs to be taken into account in underwater LIBS measurement, especially on-site marine applications.
Abstract: Laser-induced breakdown spectroscopy (LIBS) has been successfully applied to ocean exploration, but the changes in marine environmental factors could have an important impact on the LIBS signals. T...