1,721,010 research outputs found
Fundamental study and analytical applications of nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) of metals, semiconductors and insulators
No full textNanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) is a recently proposed method to efficiently increase the LIBS emission signal of metals up to 2 orders of magnitude, by depositing metal nanoparticles (NPs) on the sample surface (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Anal Chem 85). This considerable emission enhancement has been ascribed to two effects: (1) an improvement in the ablation effect, and (2) a more efficient production of seed electrons by field emission, in turn due to the enhancement of the laser electromagnetic field induced by the NPs themselves (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Acta Part B, 98)
Calibration-free inverse method for depth-profile analysis with laser-induced breakdown spectroscopy
No full textThe Calibration-free inverse method (CF-IM) is a variant of the classical CF approach that can be used for the determination of the plasma temperature using a single calibration standard. In this work, the IM was suitably modified in order to test its applicability to the depth-resolved elemental analyses of stratified samples. The single calibration standard was used as a sort of reference sample to model the acquisition conditions of the spectra, to investigate the effect of the acquisition geometry, and to account for possible crater-induced changes in the acquired spectra and plasma parameters. Thus, a depth profile of the standard sample was performed in order to obtain a plasma temperature profile, which in turn was employed, together with the experimental electron density profile, for the depth profile calibration-free analysis. The methodology was also applied to archaeological samples, with the purpose of testing the method with weathered and layered samples, and compared with the results of classical LIBS with calibration lines
Minimally invasive medical diagnosis through Laser-Induced Breakdown Spectroscopy (LIBS) coupled with machine learning
No full textUntargeted spectroscopic methods allow interrogating biomedical samples without prior hypotheses about specific pathways, and therefore they are a powerful diagnostic tool for poorly understood or initially asymptomatic diseases. In this work, we analyzed micro- drops of biological fluids from patients and animal models with Laser-Induced Breakdown Spectroscopy (LIBS) and coupled the spectra with supervised classification algorithms to distinguish healthy and diseased individuals. LIBS is the optical emission spectroscopy of laser-induced plasmas, and it can provide the elemental fingerprinting of a wide variety of samples [1]. In [2], we designed a voting algorithm based on the use of LIBS difference spectra, that we employed as a data-pretreatment and feature-selection method to couple with Quadratic Discriminant Analysis for Alzheimer's Disease diagnosis in living patients
Laser-induced breakdown spectroscopy in cultural heritage science
No full textThe potential of Laser-Induced Breakdown Spectroscopy (LIBS) for micro-destructive analysis of cultural heritage objects has been widely demonstrated, and the technique is now ready to be integrated in the permanent instrumentation of conservation laboratories. This chapter presents a review of recent results obtained by LIBS researchers with a focus on three main applications that exemplify the most representative contributions of this technique to cultural heritage science: noninvasive stratigraphic analysis of multilayered samples; feasibility and field studies with portable instrumentation; and underwater LIBS of submerged samples. An overview on the principles of LIBS and employed instrumentation is also provided, together with a discussion on its advantages and drawbacks as compared to well-established techniques for the analysis of cultural heritage
Micro-invasive depth profile analysis by laser-induced breakdown spectroscopy (LIBS): The case of mercury layers on Sasanian coins
No full textLaser-Induced Breakdown Spectroscopy (LIBS) was used for depth-profile analysis of one Sasanian coin of the emperor Khusro II (591-628) from the Coin Collection of the Kunsthistorisches Museum of Vienna. The peculiarity of this coin, also found in analogous samples of the same and other collections, was the presence of an external Hg layer. The thickness and homogeneity of the Hg layer were characterized with the calibration-free inverse method, a variant of the classical calibration-free LIBS approaches in which one sample of known concentration is used to determine the plasma temperature. We demonstrated the feasibility of the inverse method also in cases of unknown samples with matrices different from that of the employed standard. In this work, the standard was a Cu-based alloy and the sample was an Ag-based alloy, also containing Hg and other minor components. The LIBS results were in good agreement with two previous independent micro-XRF measurements performed with a destructive approach, i.e. using a cross section of the same sample. This confirmed the applicability of the inverse method to unconventional matrices, for which the use of matrix-matched standards may be unfeasible. The conclusions of this work strongly support the use of laser ablation techniques for calibration-free and micro-invasive analysis of layered samples, in particular when the integrity of samples has to be preserved
Nanoparticle Enhanced Laser Induced Breakdown Spectroscopy (NELIBS): effect of nanoparticles deposited on sample surface on laser ablation and plasma emission.
No full textIn this paper the use of metallic nanoparticles (NPs) for improving Laser Induced Breakdown Spectroscopy (LIBS) is discussed. In the case of conductors an emission signal enhancement up to 1-2 orders of magnitude was easily obtained depositing NPs on the sample surface by drying a micro-drop of colloidal solution. The basic mechanisms of Nanoparticles Enhanced LIBS (NELIBS) were studied and the main causes of the huge enhancement were found to be related to the effect of NPs on the laser ablation process, in terms of a faster and more efficient production of seed electrons with respect to conventional LIBS. The characteristics of NELIBS-produced plasma were investigated by fast emission spectroscopy and spectral resolved image, and in spite of similar plasma parameters , the NELIBS plasma was found to have larger emission volume and longer persistence than the LIBS one. On the other hand a methodology for determination of NPs concentration and size was pointed out when the NPs are deposited on insulators, proving the feasibility of LIBS as a fast detection tool for a preliminary characterization of NPs
The role of Continuum radiation in Laser Induced Plasma Spectroscopy
No full textThis paper focuses on the interpretation of the origin of the continuum radiation in Laser Induced Plasma (LIP) emission spectra, a subject that has received little consideration in the literature when compared to the analysis of the line emission spectrum. The understanding of the spectral peculiarities observed immediately after the laser pulse, when the continuum radiation prevails on discrete emission lines, can be extremely important to retrieve the initial conditions of LIP and to correlate the produced plasma to the ablation mechanism. In this work, in addition to a qualitative interpretation of the LIP continuum in the initial stage of expansion, a methodology is proposed for a better measurement of the atomic temperature in the expansion stage of the LIP. Such methodology is based on the analysis of the combined Boltzmann and Planck plots. The results obtained stress once again the importance of considering non equilibrium effects in the initial stage of LIP expansion
Diagnosis of Alzheimer's disease using laser-induced breakdown spectroscopy and machine learning
No full textAlzheimer's disease (AD) is a progressive incurable neurodegenerative disease and a major health problem in aging population. We show that the combined use of Laser-Induced Breakdown Spectroscopy (LIBS) and machine learning applied for the analysis of micro-drops of plasma samples of AD and healthy controls (HC) yields robust classification. Following the acquisition of LIBS spectra of 67 plasma samples from a cohort of 31 AD patients and 36 healthy controls (HC), we successfully diagnose late-onset AD (> 65 years old), with a total classification accuracy of 80%, a specificity of 75% and a sensitivity of 85%
Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy of metallic samples
No full textIn this paper an increase of 1-2 orders of magnitude in Laser Induced Breakdown Spectroscopy (LIBS) signals was obtained by depositing silver nanoparticles on metal samples. Nanoparticle-Enhanced LIBS (NELIBS) proved a robust and flexible tool for the chemical analysis of metals because the sample emission signal did not appear very affected by the size and concentration of deposited nanoparticles (NPs), respectively within a range of 10 nm of diameter and one order of magnitude of concentration. On the other hand, preliminary NELIBS tests on insulators and semiconductors did not show any significant enhancement with respect to conventional LIBS. In this paper we present a detailed investigation of the fundamental features of the NELIBS spectra, in addition to some examples of analytical applications to the quantitative analysis of metal alloys
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