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Geographical authenticity evaluation of Mentha haplocalyx by LIBS coupled with multivariate analyses
摘要： Mentha haplocalyx (mint) is a significant traditional Chinese medicine (TCM) listed in the Catalogue of “Medicinal and Food Homology”, therefore, its geographical origins (GOs) are critical to the medicinal and food value. Laser-induced breakdown spectroscopy (LIBS) is an advanced analytical technique for GOs certification, due to the fast multi-elemental analysis requiring minimal sample pretreatment. In this study, LIBS data of sampled mint from five GOs were investigated by LIBS coupled with multivariate statistical analyses. The spectral data was analyzed by two chemometric algorithms, i.e. principal component analysis (PCA) and least squares support vector machines (LS-SVM). Specifically, the performance of LS-SVM with linear kernel and radial basis function (RBF) kernel was explored in sensitivity and robustness tests. Both LS-SVM algorithms exhibited excellent performance of classification in sensitive test and good performance (a little inferior) in robustness test. Generally, LS-SVM with linear kernel equally outperformed LS-SVM based on RBF kernel. The result indicated the potential for future applications in herbs and food, especially for in situ GOs applications of TCM authenticity rapidly.
关键词： laser-induced breakdown spectroscopy (LIBS),geographical origin,herb authenticity,least squares support vector machines,Mentha haplocalyx
更新于2025-09-23 15:19:57
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Detail investigation of toxicity, bioaccumulation, and translocation of Cd-based quantum dots and Cd salt in white mustard
摘要： In this study, a model crop plant white mustard (Sinapis alba L.) was treated with an aqueous dispersion of silica-coated CdTe quantum dots (CdTe/SiO2 QDs) in a 72-hours short-term toxicity test. The toxicity was established via measurements of (i) the root length and (ii) the chlorophyll fluorescence. These results were compared to two other sources of cadmium, free Cd ions (CdCl2) and prime un-shell nanoparticles CdTe QDs. Tested compounds were applied in concentrations representing 20 and 200 μM Cd. The uptake and translocation of Cd were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and the spatial Cd distribution was investigated in detail applying laser induced breakdown spectroscopy (LIBS). The LIBS maps with a lateral resolution of 100 μm were constructed for the whole plants, and maps with a lateral resolution of 25 μm (micro-LIBS arrangement) were used to analyse only the most interesting parts of plants with Cd presence (e.g. root tips or a part crossing the root into the above-ground part). Our results show that the bioaccumulation patterns and spatial distribution of Cd in CdTe/SiO2 QDs-treated plants differ from the plants of positive control and CdTe QDs. Fluorescence microscopy photographs revealed that CdTe/SiO2 became adsorbed onto the plant surface in comparison to CdTe QDs. Further, a physico-chemical characterization of QDs before and after the test exposure showed only minor changes in the nanoparticle diameters and no tendencies of QDs for agglomeration or aggregation during the exposure.
关键词： nanoparticles,cadmium,laser-induced breakdown spectroscopy,Sinapis alba L.,uptake,translocation
更新于2025-09-23 15:19:57
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Spatial confinement effect on CN emission from nanosecond laser-induced PMMA plasma in air
摘要： In this paper, a PMMA target was ablated to study spatial confinement effect on CN emission of laser-induced PMMA plasma in air. Four cylindrical cavities with same depth and different diameters (4, 6, 8, and 10 mm) were used to confine the nanosecond laser-ablated PMMA plasma plume. Laser pulse energies were 40, 50, and 60 mJ. The influence of cavity diameter on emission band and vibration temperature of CN molecule was demonstrated, the results showed an obvious increase in the emission and vibration temperature of CN molecule by using the cylindrical cavity. When the cavity diameter was smaller at a fixed laser energy, the emission enhancement of CN molecule appeared earlier, and the CN molecule had stronger emission and vibration temperature. For a fixed diameter cavity, when the laser energy was higher, the CN molecule presented stronger emission and higher vibration temperature, and the emission enhancement also appeared earlier. The enhanced effect on the spatial confinement mainly comes from shock wave produced by the laser-induced PMMA plasma. The spatial confinement cavity can reflect the shock wave, and the shock wave compresses the plasma plume, resulting in an improvement in the temperature and density of the plasma. Therefore, the optical emission of CN molecule increases as the shock wave interacts with the PMMA plasma.
关键词： CN,PMMA,laser-induced breakdown spectroscopy,spatial confinement
更新于2025-09-23 15:19:57
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Multivariate analysis and laser-induced breakdown spectroscopy (LIBS): a new approach for the spatially resolved classification of modern art materials
摘要： The ever-increasing speed of exchange of ideas, information, and culture allows contemporary art to be in constant growth, especially concerning the choice of artistic materials. Their characterization is not only crucial for the study of artistic techniques but also for research into the stability of the material and, consequently, the best preservation practices. For this aim, an analytical method should have the advantages of not requiring sample preparation, performing superficial micro-analysis, and obtaining detailed spectral information. For this study, laser-induced breakdown spectroscopy (LIBS) was employed. It was used for the identification of modern paints composed of inorganic pigments and organic binders, such as acrylics, alkyds, and styrene-acrylics. Principal component analysis (PCA) was used to classify the different pure materials, above all, the polymeric binders. To distinguish the paint mixtures, whose LIBS spectral results were more complex due to the pigment/binder interaction, a statistical method recently employed in the cultural heritage field was chosen, namely, random decision forest (RDF). This methodology allows a reduction of the variance of the data, testing of different training data sets by cross-validation, an increase of the predictive power. Furthermore, for the first time, the distribution of different inorganic pigments and organic binder materials in an unknown sample was mapped and correctly classified using the developed RDF. This study represents the first approach for the classification of modern and contemporary materials using LIBS combined with two different multivariate analyses. Subsequent optimization of measurement parameters and data processing will be considered in order to extend its employment to other artistic materials and conservation treatments.
关键词： Laser-induced breakdown spectroscopy,Inorganic pigments,Random decision forest,Organic binders,Principal component analysis
更新于2025-09-23 15:19:57
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Lens-to-sample distance effect on the quantitative analysis of steel by laser-induced breakdown spectroscopy
摘要： The focusing position of the laser affects the characteristics of the laser-induced plasma, which in turn influences the signal stability and the quantitative analysis of laser-induced breakdown spectroscopy. In this study, six standard alloy steels are used as the samples, and the trace elements including Si, Mn, Cr are quantitatively analyzed by internal standard method. The variations of line intensity, background noise intensity, signal-to-background ratio (SBR), detecting sensitivity and detection of limit (LOD) of the element with lens-to-sample distance (LTSD) were investigated. The results show that both the intensities of the analytical line and the background noise reached a maximum when the LTSD is 94 mm. While the corresponding SBR is relatively low. For quantitative analysis, it is observed that the change of the detection sensitivity with LTSD has the similar trend with that of SBR. That is, the detection sensitivity has a lower value when the LTSD is 94mm. However, when the LTSD changes from 93mm to 99mm, LODs of the three elements are maintained at a small value. The present results indicate that for quantitative analysis of LIBS, the intensities of the analytical line and the background noise should be comprehensively considered when optimizing the laser focusing position.
关键词： Laser-induced breakdown spectroscopy,Quantitative analysis,Line intensity,Lens-to-sample distance
更新于2025-09-23 15:19:57
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A microfluidic paper-based laser-induced fluorescence sensor based on duplex-specific nuclease amplification for selective and sensitive detection of miRNAs in cancer cells
摘要： MicroRNAs (miRNAs) are considered as the potential biomarkers for many cancers. To determine miRNAs in cancer cells is significant for realizing these diseases. In this work, a microfluidic paper-based laser-induced fluorescence sensor based on duplex-specific nuclease (DSN) amplification was developed and applied to selectively and sensitively determine miRNAs in cancer cells. An interface for laser-induced fluorescence detection was firstly applied to perform the sample detection on the paper-based chip. Under the optimal conditions, DSN (3 μL 0.10 U) and Taqman probes (2 μL 2.5 × 10?7 M) were preserved on the circles (Diameter 4 mm) of the folded paper chip. When miRNA solution was added, the mixed solution could trigger fluorescence signal amplification by cyclically digesting hybrids of miRNAs and Taqman probes by DSN. The whole determination, including sample heating process, could be accomplished within 40 min. The detection limits for miRNA-21 and miRNA-31 were 0.20 and 0.50 fM respectively, corresponding to only 1.0 and 1.5 zmol consumption of miRNAs. The testing of mismatched miRNAs showed that the method had good specificity. Finally, the method was applied to determine miRNA-21 and miRNA-31 in lysates of cancer cells of A549 and HeLa, and hepatocyte LO2. MiRNA-21 and miRNA-31 could be successfully found from the two cancer cells. The concentrations for miRNA-21 and miRNA-31 were 1.74 × 10?13 M and 6.29 × 10?14 M in HeLa cell lysate (3.75 × 104 cells/mL), 3.07 × 10?15 M and 3.28 × 10?15 M in A549 cell lysate (8.33 × 106 cells/mL) respectively. The recoveries ranged from 87.30% to 111.83%, indicating the results were reliable. The developed method was effective, selective and sensitive in the determination of miRNAs in cancer cells.
关键词： microRNA,Duplex-specific nuclease,Paper-based sensor,Laser-induced fluorescence,Cancer cell
更新于2025-09-23 15:19:57
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Difference in laser-induced damage behavior between back and front surfaces
摘要： When nanosecond-pulsed laser induces transmission element damage, the coupling effect of plasma and laser affects the damage process of the back and front surfaces, thereby determining the final damage morphology. This study presents the effects on the suppression and enhancement of plasma on particle ejection, the intensity of laser absorption and obstruction, and the surface morphology and drilling efficiency of multi-pulse laser processing. The difference between the back and front surface damage was compared, and the causes and function process were analyzed. Experiments are helpful to understand the role of plasma and the difference in damage between the back and front surfaces so that the thermal mechanism damage is clarified.
关键词： plasma,back and front surface,laser-induced damage,particle ejection
更新于2025-09-23 15:19:57
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Laser-induced graphene hybrid photoelectrode for enhanced photoelectrochemical detection of glucose
摘要： The combination of electrocatalyst with semiconductor light-absorber is of great importance to increase the efficiency of photoelectrochemical (PEC) glucose detection. Here, in-situ and synchronous fabrication of Ni-based electrocatalyst (NiEC) and CdS semiconductor in laser-induced graphene (LIG) on indium?tin oxide glass is demonstrated via a one-step laser-induced solid phase transition. A series of component and structural characterizations suggest that the laser-induced NiEC uniformly disperses in the hybrid nanocomposite and exists mainly in the form of Ni0 and NiO state. Moreover, both electrochemical and PEC investigations confirm that the as-prepared hybrid photoelectrode exhibits excellent photoelectrocatalytic ability towards glucose, which is not only attributed to the strong synergistic interaction between CdS and NiEC, but also benefited from the high conductivity as well as 3D macroporous configuration of the simultaneously formed LIG, providing the key factor to achieve sensitive non-enzymatic PEC glucose sensors. Therefore, the laser-induced hybrid photoelectrode is then applied to the PEC detection of glucose, and a low detection limit of 0.4 μM is obtained with good stability, reproducibility, and selectivity. This study provides a promising paradigm for the facile and binder-free fabrication of electrocatalyst?semiconductor?graphene hybrid photoelectrode, which will find potential applications in sensitive PEC biosensing for a broad range of analytes.
关键词： nickel electrocatalyst,hybrid nanocomposite,cadmium sulfide,photoelectrochemical sensing,laser-induced graphene,glucose
更新于2025-09-23 15:19:57
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Data on eosin Y solutions for laser-induced fluorescence in water flows
摘要： Dye tracing techniques involve the tagging of a sample of water with dye, providing important qualitative and quantitative information. This article presents physical and fluorescence properties of dye solutions obtained by diluting a pharmaceutical aqueous solution of eosin Y with distilled water. Sample solutions with eosin concentrations ranging from 0 to 20 g/L were examined under various temperatures and laser powers. The data include measurements of dynamic viscosity, surface tension and pH. Fluorescence emission spectra as well as laser beam attenuation and photobleaching measurements are also reported. The datasets provide guidelines for obtaining optimal dye mixtures and suitable optical configurations to implement eosin fluorescence techniques.
关键词： Dye-water solution,Surface tension,Viscosity,Laser-induced fluorescence,pH
更新于2025-09-23 15:19:57
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Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence
摘要： A detailed study of the ?ows of ion and neutral argon populations in a helicon plasma was carried out. Understanding the principle ion sinks and sources of neutral fueling is essential to understanding the ability of helicon wave heating to create high density plasmas. This heating mechanism and the neutral fueling required to sustain it and perhaps manipulate the axial density pro?le in long cylindrical plasmas are an active research topic for advanced plasma wake?eld accelerator concepts. Using laser induced ?uorescence (LIF) of ion and neutral argon species, an ion ?ux of up to 2:5 (cid:2) 1021 m(cid:3)2 s(cid:3)1 was measured leaving the core of a helicon plasma with a peak electron density of 4:0 (cid:2) 1018 m(cid:3)3. Taking the divergence of the axial ion ?ux pro?le yields a minimum ionization rate estimate of 2 (cid:2) 1021 m(cid:3)3 s(cid:3)1, and including the radial divergence increases the estimated ionization rate to approximately 1022 m(cid:3)3 s(cid:3)1. Neutral ?ow velocities measured using LIF reveal a circulatory fueling and loss mechanism with distinct zones where radial or axial sources and sinks dominate.
关键词： laser induced fluorescence,ionization source rate,argon,helicon plasma,particle balance
更新于2025-09-23 15:19:57