Elemental analysis by Au-nanopartciles enahnced LA-ICP-MS

Introduction A preliminary study of nanoparticles-enhanced LA-ICP-MS is presented. It represents an analytical strategy to improve the analytical performance of the LA-ICP-MS in terms of sensitivity and LOD, preserving its excellent characteristics (simplicity, rapidity, etc.), without any changes in the experimental set-up. Methods Some drops of Gold Nanoparticles (AuNPs) colloidal dispersion were deposited on the sample’s surface, the solvent evaporated before the analysis. Spherical AuNPs dispersions in aqueous citrate buffer (Sigma Aldrich Co.) or naked PLAL (Pulse Laser Ablation in Liquid) [1] AuNPs of different size were used on certified standard target (Copper, Titanium, Bronze, Brass, Silicon and Glass). Results A considerable increase of the measured signal intensity was observed in the presence of AuNPs. By analogy with results already obtained with Laser Induced Breakdown Spectroscopy [2,3], when a critical number of NPs are deposited on the target surface, the laser pulse electromagnetic field induces the collective oscillation of the conduction electrons of the NPs that in turn results in a strong enhancement of the field. The improvement is probably induced by the best quality of the nanoparticles' agglomerate generated during the laser ablation. Metallic elements show enhancement also in non-conductive matrices. Different metallic elements show different enhancement in the same matrix, as well as the same element shows different enhancement in different matrices. It should be noted the AuNPs can be completely removed after the analysis. Conclusions The existence of an improvement of sensitivity in LA-ICP-MS signal via AuNPs allows to identify and quantify elements without damaging significantly the sample's surface unlike conventional LA-ICP-MS. Novel Aspect The AuNPs allow to improve the sensitivity of LA-ICP-MS technique almost in a nondestructive mode, which can be extremely useful in many fields as forensic sciences and cultural heritage

Nanoparticles-enhanced laser-ablation ICP-MS of metallic samples

This research shows a preliminary study of nanoparticles-enhanced LA-ICP-MS, which aims to obtain an analytical procedure in order to improve the analytical performance of the technique in terms of sensitivity and LOD, without any changes in the experimental configuration. The undoubted strength of this approach is represented by its simplicity, affordability and fast performance. Laser parameters or the type and flow of gas carrier can be changed to improve the ablation of the sample. Otherwise, the sample can be altered in order to increase its response to laser, preserving its chemical properties. This second method has been used, and in particular some drops of AuNPs colloidal dispersion were deposited on the sample’s surface, and the solvent evaporated before it had been ablated. A remarkable increase in the measured signal intensity is observed due to the presence of nanoparticles. In analogy of what has already proved with Laser Induced Breakdown Spectroscopy [1,2], when a critical number of NPs are deposited on the target surface, the laser pulse electromagnetic field induces the collective oscillation of the conduction electrons of the NPs that in turn results in a strong enhancement of the field. The latter allows to switch the seed electron production in the ablation process from multiphoton ionization to electron field emission. In this frame a more efficient and homogeneous ablation can be obtained. In this work preliminary results of this approach during LA-ICP-MS of metallic alloys are shown and discussed with a systematic comparison of conventional LA-ICP-MS and nanoparticle enhanced LA-ICP-MS

Physical-Chemical characterization of Sea-silk and its crafting phases

The sedentary mollusc Pinna nobilis L. produces fine but strong filaments of fibre beard called “byssus”. This fibre has the task of fixing itself to the sea grass and withstand the flow. Byssus was the basic raw material used to make Sea-silk, but this Mediterranean species is protected since 1992 [1] and production of its iridescent golden textile is therefore impossible. In the history of textile, Sea-silk constitutes a very small part, it is proven that the use of Sea-silk dates back to at least the Roman age while, today, Sardinia and Apulia (Taranto), are the production centres of Sea-silk and keep their importance. We studied samples of sea-silk kept at Commodity Science Museum of Bari University, where one valve, some pearls and all the different phases of crafting of this textile are represented, starting from the raw byssal threads up to the woven textile. The aim of this research is to characterize the threads from a morphological and chemical point of view considering above all the evolution and changing of the material with the different working phases. Due to the samples uniqueness, the smallest amount possible is taken from the byssal threads (about 20 mg). We used different techniques like optical microscopy (OM) and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) aimed to the observation of the morphological changing of the fibers examined in their different handmade production steps and ICP-MS for the determination of metal composition in some fibers after their mineralization and in deionized water, observing the metal lost characteristic of the desalination process. The results obtained show how the metal concentrations analysed, decrease after the different crafting steps, and the fiber of the Sea-silk change its microscopic aspect until to obtain the golden “soul of the sea”. [1] http://www.muschelseide.ch/it/biologie/byssus/faseranalyse.htm

The Tetris game of scientific investigation. Increase the score embedding analytical techniques. Raw materials and production technology of Roman glasses from Pompeii

A collection of 18 intensely coloured and variously decorated Roman glass coming from Pompeii and preserved at the National Archaeological Museum of Naples were investigated. The objects analyzed embrace a wide colour palette and several molding and decoration techniques. The analytical strategy here pursued embedded the use of optical microscopy (OM), scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS), Raman spectroscopy and laser ablation-inductively coupled plasma-mass (LA-ICP-MS) aimed at understanding raw materials and production technology. The results achieved point out how, by means of analytical techniques sensibly integrated, archaeological questions can be solved and significant marks in know-how glass production can also be gained. The source of colours resulted in calcium antimonate (for white), lead-tin-antimony oxides (for yellow), copper (for red), iron and copper (for green), cobalt (for blue), manganese (for brown), calcium antimonate and copper/iron (for turquoise) and iron-sulphur chromophore for black/amber colour. Differently coloured parts belonging to the same object resulted made of glass of different compositions (soda-lime or lead-based). One fragment, notwithstanding the compatible glass matrix, did not seem consistent with Roman age glasses, because of the evidences (never observed before for Roman glasses) of a chrome-based raw material for green and calcium arsenate for white

Raw materials and technological changes in lime mortars and plasters from Egnatia in the Roman Age

This study reports investigations on painted plasters and mortars from Egnatia. The investigations allowed to identify raw material and pigments and to reconstruct the technology employed in the manufacturing of painted plasters from the 2nd cent. BCE to 1st cent. CE. The pigments observed by Raman analyses highlighted Fe oxyhydroxide (terre rosse), cinnabar and hematite to obtain red colour, yellow ocher for yellow, charcoal for black, calcite for white, blue Egyptian for blue and glauconite (terra verde) for green. As concerns the technology, observations by optical and electronic microscopies showed that the pigments were fixed on the plaster still wet by the technique called “a fresco”. The same observations allowed also to point out the structural aspects of the supports of painted plasters. In most cases, supports are calcarenitic-type, characterized by fragments of spathic calcite, fossil and micritic limestones. Above the natural support, we observed plasters manufactured more or less accurately: in some cases the lime putty was mixed with well-selected material (crushed calcite with homogeneous particle size), in others not. The pigments appeared clearly penetrating the plaster. Petrographical (OM), mineralogical (XRPD) and chemical (XRF) data suggest the use of the same limestone (Calcare di Bari formation) to produce lime through times, although the quality of lime putty is quite different. While the bedding mortars were frequently prepared using littoral sand, in plasters of Imperial age it was observed the presence of spathic calcite only in the finishing layer, associated with preparation layers containing cocciopesto or littoral sand. The presence of straw in some preparation layers was probably aimed to delay the carbonatation, since the finishing layer with spathic calcite was applied. Hydraulic mortars with cocciopesto are mainly present in the plaster stratification of the thermal baths, only in one sample is part of a floor

A pottery jigsaw puzzle: distinguish true and false pieces in two Apulian red figured vases by a poli-technique action plan

Apulian red figured pottery is part of the most recognizable and appreciated artworks of Italian cultural heritage. The initial objective of the research was checking the non-authenticity of some parts of two important Apulian red figured vases, stored in the National Archaeological Museum of Naples and subjected, through the ages, to several unrecorded restorations. The results obtained, in addition to achieve the set goal, revealed the non-authenticity of the whole upper part of one of the two vases, supplied further knowledge on nineteenth century restoration techniques, for these vases never adequately described, but mostly underlined how the answers to the archeological questions can only arise from a detailed characterization of the materials, succeeded by a scientific multi-technique strategy. Specifically, the complete chemical–physical characterization of the samples was accomplished by inductively coupled plasma mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and Fourier transform infrared spectroscopies

“Indagini archeometriche su vasi della collezione Intesa Sanpaolo” Atti del Convegno. Giornata di Studi. SAVOIR-FAIRE ANTICHI E MODERNI Pittori e officine ceramiche nell’Apulia di V e IV secolo a.C.

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Impact of Metals on (Star)Dust Chemistry: A Laboratory Astrophysics Approach

International audienceLaboratory experiments are essential in exploring the mechanisms involved in stardust formation. One key question is how a metal is incorporated into dust for an environment rich in elements involved in stardust formation (C, H, O, Si). To address experimentally this question we have used a radiofrequency cold plasma reactor in which cyclic organosilicon dust formation is observed. Metallic (silver) atoms were injected in the plasma during the dust nucleation phase to study their incorporation in the dust. The experiments show formation of silver nanoparticles (~15 nm) under conditions in which organosilicon dust of size 200 nm or less is grown. The presence of AgSiO bonds, revealed by infrared spectroscopy, suggests the presence of junctions between the metallic nanoparticles and the organosilicon dust. Even after annealing we could not conclude on the formation of silver silicates, emphasizing that most of silver is included in the metallic nanoparticles. The molecular analysis performed by laser mass spectrometry exhibits a complex chemistry leading to a variety of molecules including large hydrocarbons and organometallic species. The reactivity of silver atoms/ions with acetylene was also studied in a laser vaporization source. Key organometallic species, AgnC2Hm (n=1-3; m=0-2), were identified and their structures and energetic data computed using density functional theory. This allows us to propose that molecular Ag-C seeds promote the formation of Ag clusters but also catalyze hydrocarbon growth. Throughout the article, we show how the developed methodology can be used to characterize the incorporation of metal atoms both in the molecular and dust phases. The reported methodology is a demonstration laying down the ground for future studies on metals of astrophysical interest such as iron