Evaluation of potsherds features using hyperspectral maps generated by μ-LIBS scanner

The micro-laser induced breakdown spectroscopy (µ-LIBS) technique allows performing fast elemental analyses, without sample preparation and thus making it specifically useful in the analysis of the composition of ancient potsherd. The µ-LIBS instrument is equipped with a microscope and a scanning system allowing to realize small craters (about Ø = 25 µm) in order to obtain detailed hyperspectral surfaces maps (up to a maximum size of one square centimeter). The data are processed by Self-Organizing Maps (SOMs) method to visualize in 2D representations allowing significant information on the technological features of ceramic samples.The micro-laser induced breakdown spectroscopy (µ-LIBS) technique allows performing fast elemental analyses, without sample preparation and thus making it specifically useful in the analysis of the composition of ancient potsherd. The µ-LIBS instrument is equipped with a microscope and a scanning system allowing to realize small craters (about Ø = 25 µm) in order to obtain detailed hyperspectral surfaces maps (up to a maximum size of one square centimeter). The data are processed by Self-Organizing Maps (SOMs) method to visualize in 2D representations allowing significant information on the technological features of ceramic samples

Micro-chemical evaluation of ancient potsherds by μ-LIBS scanning on thin section negatives

In the study of ancient pottery, thin section analysis represents the basic approach to study mineralogical and petrografic features in order to obtain preliminary information about the production technology and origin of archaeological ceramics. However, even if thin section analysis allows investigating the textural and structural characteristics of potteries, peculiar features related to clay paste and temper composition, as well as provenance issues, can be detailed addressed only by quantitative mineralogical and chemical studies. In the realization of thin sections, a negative face is always produced, similar to the thin section itself; these remains can be used for additional analyses, such as high spatial resolution micro-chemical studies using, for example, a micro-laser induced breakdown spectroscopy (LIBS) scanner. LIBS is a spectroscopic technique that, exploiting the laser radiation, is able to bring into the plasma state micrometric portions of the sample, and to analyse its content through the study of the optical emission of the plasma itself. Unlike other techniques, LIBS can detect and quantify also light elements such as aluminium and magnesium. Images produced by the micro-LIBS instrument show the spatial distribution of the chemical elements within a portion of the sample, which may have dimensions from a few hundred microns up to several centimeters. The combination of these images with algorithms derived from image processing techniques may return interesting information and supporting data to in-depth investigate pottery components detected by optical microscopy observations. In this work, we present the results of an experimental study performed on thin-section negatives with different grain size, surface treatments and aggregates, coming from some Neolithic Italian sites, exploring the potential of the LIBS method in micro-chemical studies of ancient potsherds

Multivariate calibration in Laser-Induced Breakdown Spectroscopy quantitative analysis: The dangers of a ‘black box’ approach and how to avoid them

The introduction of multivariate calibration curve approach in Laser-Induced Breakdown Spectroscopy (LIBS) quantitative analysis has led to a general improvement of the LIBS analytical performances, since a multivariate approach allows to exploit the redundancy of elemental information that are typically present in a LIBS spectrum. Software packages implementing multivariate methods are available in the most diffused commercial and open source analytical programs; in most of the cases, the multivariate algorithms are robust against noise and operate in unsupervised mode. The reverse of the coin of the availability and ease of use of such packages is the (perceived) difficulty in assessing the reliability of the results obtained which often leads to the consideration of the multivariate algorithms as ‘black boxes’ whose inner mechanism is supposed to remain hidden to the user. In this paper, we will discuss the dangers of a ‘black box’ approach in LIBS multivariate analysis, and will discuss how to overcome them using the chemical-physical knowledge that is at the base of any LIBS quantitative analysis

COVID-19 Detection from Mass Spectra of Exhaled Breath

According to the World Health Organization, the SARS-CoV-2 virus generated a global emergency between 2020 and 2023 resulting in about 7 million deaths out of more than 750 million individuals diagnosed with COVID-19. During these years, polymerase-chain-reaction and antigen testing played a prominent role in disease control. In this study, we propose a fast and non-invasive detection system exploiting a proprietary mass spectrometer to measure ions in exhaled breath. We demonstrated that infected individuals, even if asymptomatic, exhibit characteristics in the air expelled from the lungs that can be detected by a nanotech-based technology and then recognized by soft-computing algorithms. A clinical trial was ran on about 300 patients: the mass spectra in the 10-351 mass-to-charge range were measured, suitably pre-processed, and analyzed by different classification models; eventually, the system shown an accuracy of 95% and a recall of 94% in identifying cases of COVID-19. With performances comparable to traditional methodologies, the proposed system could play a significant role in both routine examination for common diseases and emergency response for new epidemics.Comment: 15 page

Multi-technique characterization of madder lakes: A comparison between non- and micro-destructive methods

The chemical characterization of paint material is paramount for the understanding of painting techniques, provenance studies and for assessing conservation strategies. In particular, the chemical characterization of both the organic and inorganic fraction of lakes is fundamental to assess the technologies used in their production. In this short note, we present a pilot study by comparing several micro-destructive and non-destructive methods for the comprehensive characterization of the organic and inorganic fraction of reference madder lakes. In the final procedure, the chromophores-containing molecules were separated using a sample preparation procedure based on acid hydrolysis and solvent extraction, and analysed by high-pressure liquid chromatography with UV-Vis detector (HPLC-UV/Vis). Laser induced breakdown spectroscopy (LIBS) and X-Ray Fluorescence (XRF) were used for the study of the elemental composition. Multispectral Imaging was also applied in order to evaluate its potentialities to distinguish amongst different red lakes. The final multi-technique method allowed for the characterization of both organic and inorganic fraction from the same lake micro sample

Fast quantitative elemental mapping of highly inhomogeneous materials by micro-Laser-Induced Breakdown Spectroscopy

In this work, a fast method for obtaining a quantitative elemental mapping of highly inhomogeneous samples by µ-LIBS maps is proposed. The method, transportable and cheap, allows the analysis of large maps through the use of a Self-Organizing Map clustering method coupled to Calibration-Free LIBS for quantification of cluster prototypes. The method proposed has been verified on heterogeneous materials such historical lime mortars but it can be easily applied to a larger class of inhomogeneous materials for very different applications (modern building materials, biological samples, industrial materials, etc.)

Sintesi "green" di nanoparticelle e loro applicazione nella tecnica Laser Induced Breakdown Spectroscopy (LIBS)

Il presente lavoro di tesi si inserisce all'interno dell'attività di ricerca svolta presso il laboratorio di Spettroscopia Laser Applicata (ALS) del CNR di Pisa, relativa allo sviluppo e alla applicazione di metodologie di analisi mediante l'utilizzo della tecnica Laser Induced Breakdown Spectroscopy (LIBS). L'obiettivo di questo studio è quello di individuare, tra la letteratura esistente, uno o più metodi che permettano la sintesi di nanoparticelle di argento adatte ad una analisi NE-LIBS, attenendosi a requisiti di semplicità operativa, costi contenuti e sintesi “verde”. Una volta selezionato il metodo, le nanoparticelle sono state caratterizzate mediante spettroscopia di assorbimento UV-Vis e microscopia a trasmissione di elettroni (TEM) presso i laboratori NEST (National Enterprise for nanoScience and nanoTechnology) di Pisa. Sono state quindi utilizzate per le analisi NE-LIBS, impiegando la strumentazione disponibile presso il laboratorio di ALS. I parametri strumentali sono stati ottimizzati utilizzando dispersioni colloidali di nanoparticelle di argento certificate e le prestazioni delle nanoparticelle preparate sono state messe in relazione con i risultati ottenuti con le dispersioni certificate. Sono state effettuate analisi LIBS e NE-LIBS su materiali di riferimento certificati per la costruzione e la comparazione delle curve di calibrazione. È stata infine testata l'efficacia delle nanoparticelle preparate su campioni "reali" in modo da esplorare la potenzialità di una applicazione della NE-LIBS a campioni di matrice diversa: lamine di rame commerciali, foglie di tabacco liofilizzate provenienti da piante coltivate su terreni contaminati con cadmio e cromo e sedimenti marini

Rapid Identification of Beached Marine Plastics Pellets Using Laser-Induced Breakdown Spectroscopy: A Promising Tool for the Quantification of Coastal Pollution

The rapid identification of beached marine micro-plastics is essential for the determination of the source of pollution and for planning the most effective strategies for remediation. In this paper, we present the results obtained by applying the laser-induced breakdown spectroscopy (LIBS) technique on a large sample of different kinds of plastics that can be found in a marine environment. The use of chemometric analytical tools allowed a rapid classification of the pellets with an accuracy greater than 80%. The LIBS spectrum and statistical tests proved their worth to quickly identify polymers, and in particular, to distinguish C-O from C-C backbone pellets, and PE from PP ones. In addition, the PCA analysis revealed a correlation between appearance (surface pellets roughness) and color (yellowing), as reported by other recent studies. The preliminary results on the analysis of metals accumulated on the surface of the pellets are also reported. The implication of these results is discussed in view of the possibility of frequent monitoring of the marine plastic pollution on the seacoast