Diamond is considered as a very promising material for the development of devices for radiation detection. Unlike other conventional photoconductive detectors diamond-based devices should provide high discrimination between UV and visible radiation. In this work we present the electro-optical properties of devices based on randomly oriented diamond films, synthesized in a microwave plasma enhanced chemical vapor deposition reactor. A comparative study on devices with coplanar interdigitated Cr/Au electrodes (with different interelectrode pitches) made of films grown simultaneously on intrinsic and p-doped silicon (100) substrates has been performed. The chemical-structural, morphological, electrical and optical properties of ROD films have been studied. In particular, the optical response has been measured in air using a Xe flash lamp coupled with an optical quartz fiber and a properly tailored front-end electronics based on a charge sensitive amplifier. Experimental results gave indications on how the device performances are dependent on the two types of employed substrates.

Laser Induced Breakdown Spectroscopy (LIBS) is an appealing technique to study laser-induced plasmas(LIPs), both from the basic diagnostics point of view and for analytical applications. LIPs are complexdynamic systems, expanding at supersonic velocities and undergoing a transition between differentplasma regimes. If the Local Thermodynamic Equilibrium (LTE) condition is valid for such plasmas, severalanalytical methods can be employed and fast quantitative analyses can be performed on a variety ofsamples. In the present paper, a discussion about LTE is carried out and an innovative application to theanalysis of the alexandrite gemstone is presented. In addition, a study about the influence of plasmaparameters on the performance of LTE-based methods is reported for bronze and brass targets.

The interaction of nanoparticles with proteins has emerged as a key issue in addressing the problem of nanotoxicity. We investigated the interaction of silver nanoparticles (AgNPs), produced by laser ablation with human ubiquitin (Ub), a protein essential for degradative processes in cells. The surface plasmon resonance peak of AgNPs indicates that Ub is rapidly adsorbed on the AgNP surface yielding a protein corona; the Ub-coated AgNPs then evolve into clusters held together by an amyloid form of the protein, as revealed by binding of thioflavin T fluorescent dye. Transthyretin, an inhibitor of amyloid-type aggregation, impedes aggregate formation and disrupts preformed AgNP clusters. In the presence of sodium citrate, a common stabilizer that confers an overall negative charge to the NPs, Ub is still adsorbed on the AgNP surface, but no clustering is observed. Ub mutants bearing a single mutation at one edge ? strand (i.e. Glu16Val) or in loop (Glu18Val) behave in a radically different manner. Human ubiquitin forms amyloids on the surface of silver nanoparticles produced by laser ablation, which induce clustering of the nanoparticles and thioflavin T fluorescence. In the presence of sodium citrate as a stabilizer, ubiquitin only forms a protein corona. A single mutation (Glu16Val) at one edge ? strand of the protein can deeply influence the amyloid transition (see figure). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser-induced breakdown spectroscopy (LIBS) has been in use for decades, but only recently the technique has progressed so to allow the construction of efficient handheld, self-contained commercial instruments featuring a large range of capabilities. In particular, the development of portable handheld instruments able to perform noninvasive, spatially resolved, multielement, in-situ analysis has provided an impressive impulse to the scientific investigation of cultural heritage materials. In this work, the design of a handheld LIBS instrument and the first test measurements performed on a fragment of a sedimentary rock monument are presented. A full broadband LIBS emission spectrum with a point and shoot operation was recorded directly within few seconds, so providing information on the elements present in the weathered layer in comparison to the stone surface. Further, the Calibration Free (CF)-LIBS approach was used to test the possibility to obtain a suitable quantitative composition of the main elements present in the sample.

Laser cleaning is widely used to remove black crusts from weathered limestone monuments. The cleaning efficiency is commonly tested using conventional analytical techniques, which do not allow to analyze the same sample before and after the treatment. In this paper, micro computed tomography (?-CT) and micro X-ray fluorescence spectroscopy (?-XRF) techniques were used for the first time to evaluate the laser cleaning efficiency on two different encrusted quoins collected from a limestone monument. Analyses were carried out non-destructively on the same portion of the two lithotypes before and after the treatment. ?-XRF confirmed the presence of gypsum in the black crust, and showed a marked decrease of S and other typical elements after laser cleaning of both samples. ?-CT clearly showed the different structure of limestone before and after cleaning and the crust portion removed by the laser. The combination of the two techniques allowed to assess that, even if the two samples had a similar chemical composition, their response to laser cleaning was different on dependence of their different fabric/structure. In fact, in one sample calcium sulphate was still partially retained also after the black crust removal, whereas in the other sample the sulphate layer was almost completely ablated due to its more compact structure. In both cases, laser cleaning operation was shown not to cause any structural modification or mechanical damage of the original stone material. In conclusion, the use of these novel techniques appears very promising for studying the effects of laser ablation on rock samples in order to set the best working conditions for their cleaning.

Although the first nanoseconds to microseconds rule the resulting process yield of laser ablation in liquid, a comprehensive view involving combination of time-resolved measurement techniques is still lacking. In this paper, fundamental aspects of laser ablation of metals in water during the production of nanoparticles are discussed. Three fast diagnostic methods have been applied simultaneously. These are Optical Emission Spectroscopy for the plasma characterization, fast shadowgraph for plasma and cavitation bubble dynamics and laser scattering for the mechanisms of delivery of the produced materials in the liquid. Moreover, in order to validate the discussion, the effect on cavitation dynamics of the ablation of bulk and wire-shaped targets has been investigated together with the relative nanoparticles production yield. Unusual arrow-bow ejection phenomena between the cavitation bubble and the wire result in suppressed material back-deposition, causing efficient ejection of ablated matter into the liquid. The presented nanosecond and microsecond-resolved analysis allows estimating the timescale and role of the basic mechanisms involved in laser ablation in liquids as well as the thermodynamic characteristics of the processes.

The study of the degradation mechanisms of materials constituting historical buildings is very relevant in the context of cultural heritage preservation. In this work, a limestone sample collected from the masonry blocks of the entrance gate of historic Castello Svevo, Bari, Italy, was subjected to depth profile elemental analysis of the ablated black crust and the underlying limestone by double pulse laser-induced breakdown spectroscopy. The specific elemental components were identified and their concentrations along the sample profile analyzed, so allowing to identify the boundary between the weathered and unaltered rock. The laser-induced plasma stability, i.e., the absence of parameter changes during ablation, was verified to be constant and not to affect the elemental peak sizes during the entire depth analysis process when the plasma is confined in the ablation crater.

The present work aims to evaluate the alteration conditions of historical limestone rocks exposed to urban environment using the Laser-Induced Breakdown Spectroscopy (LIBS) technique. The approach proposed is based on the microscale three dimensional (3D) compositional imaging of the sample through double-pulse micro-Laser-Induced Breakdown Spectroscopy (DP-?LIBS) in conjunction with optical microscopy. DP-?LIBS allows to perform a quick and detailed in-depth analysis of the composition of the weathered artifact by creating a 'virtual thin section' (VTS) of the sample which can estimate the extent of the alteration processes occurred at the limestone surface. The DP-?LIBS analysis of these thin sections showed a reduction with depth of the elements (mainly Fe, Si and Na) originating from atmospheric dust, particulate deposition and the surrounding environment (due to the proximity of the sea), whereas, the LIBS signal of Ca increased in intensity from the black crust to the limestone underneath.

Laser-induced breakdown spectroscopy (LIBS) is a fast and reliable technique suitable for the simultaneous qualitative and quantitative analysis of major and trace elements in samples of various nature and origin. In last decades, the use of metal accumulator plants, in combination with compost, has become a cheap and sustainable alternative technique to lower soil contamination by toxic heavy metals. In the present work, theLIBS technique has been applied to measure the concentrations of selected elements, including Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Sr, and Zn, in two composts of different origin and nature and four accumulator plant species (Atriplex halimus, Brassica alba, Brassica napus, and Eruca vesicaria). The plant samples were analyzed either as bulk plant material or as specific organs (i.e. shoots and roots). The concentrations measured by LIBS were assessed by complementary induced coupled plasma-optical emission spectroscopy. The significant correlation found between the data obtained by the two techniques (R=0.732-0.999) supports the feasibility of LIBS for fast screening of major, trace and toxic elements in plant and compost samples. In conclusion, the LIBS technique shows promising for further applications in soil remediation as well as in agriculture.

Non-equilibrium effects in hydrogen plasmas have been investigated in different systems, ranging from RF plasmas to corona discharges. The existing measurements of vibrational and rotational temperatures, obtained by different spectroscopical techniques, are reported, rationalized by results calculated by kinetic models. Input data of these models are discussed with particular attention on the dependence of relevant cross sections on the vibrational quantum number. Moreover, the influence of the vibrational excitation of H(2) molecules on the translational distribution of atoms in ground and excited levels is shown. Finally, a collisional radiative model for atomic hydrogen levels, based on the coupling of the Boltzmann equation for electron energy distribution function (EEDF) and the excited state kinetics, is presented, emphasizing the limits of quasi-stationary approximation. In the last case, large deviations of the EEDF and atomic level distributions from the equilibrium are observed.

A handheld laser-induced breakdown spectroscopy (LIBS) instrument is proposed as a novel tool that is able to provide information on the nature of meteorites and discriminate among iron, stone, stony-iron meteorites and meteor-wrongs. Further, a novel fuzzy logic-based inference algorithm is applied to broadband LIBS spectra for the identification of meteorites and their classification according to their origin and nature. The identification of meteorites is a decision-making problem based on a compromise among human experience, visual evidence and analytical data, which fuzzy logic is proved to be able to solve. The final model is able to correctly classify 25 out of 26 samples and provides a set of IF-THEN rules that describe how some selected wavelengths are involved in the classification task.

In the present work, laser ablation of a graphite target submerged inpure water was tested as a methodology for the production of carbon-basednanoparticles. The effect of varying the external pressure imposed to the liquidwas investigated for the first time, in the range from 1 to 146 atm. Single or doublelaser pulses were used to ablate the target and the produced nanoparticles werecharacterized by atomic force microscopy (AFM) and by Raman spectroscopy. Aspectroscopic study of the laser induced plasma features was carried out with a Titarget and interpreted in terms of laser-induced cavitation phenomena. Tubularnanoparticles of 25 nm average diameter were obtained only by single pulse (SP)ablation of graphite, while particles formed with the double pulse (DP) techniquemainly consisted of graphite particulates. At 1 atm, these tubular nanoparticles were few and mixed with diamondlike carbon,while at 146 atm they were produced in a larger amount, suggesting that the high density effect induced by pressure plays a keyrole for their generation.

The laser cleaning process combined with laser-induced breakdown spectroscopy (LIBS) were applied to restoreand characterize altered limestones of the ancient jamb of the historic entrance gate of Castello Svevo, Bari, Italy.This area of the masonry blocks of the limestone castle was chosen because of its evident degradation with anapparent deposit of black crusts. The combination of a Q-switched Nd:YAG pulsed laser with the diagnostics typicalof the LIBS technique was shown to be very effective for monitoring, controlling and characterizing the lasercleaning process of limestone. The different elemental compositions of the black encrustations covering the stonesurface and the underlying stone allowed to evaluate and avoid over-cleaning and/or under-cleaning. Further,coupling LIBS to the cleaning process provided important information about the optimal experimental conditionsto be used for evaluating the conservation status and determining the most proper cleaning restoration procedurebefore operating the consolidation of the blocks. Thus a sufficient removal of unwanted layers could beachieved without modifying the surface underneath and ameliorating the effectiveness of traditional cleaningtechniques. In this work, the elemental composition of the ablated black crust and the underlying stone weredetermined by the spectroscopic study of plasma emitted from either a single pulse (SP) or a double pulse(DP) LIBS configuration. With respect to SP LIBS, a marked enhancement of the signal emission was observedby DP-LIBS used after a previous stratigraphic DP-LIBS assessment of the cleaning depth.

A fast procedure for chemical analysis of different meteorites is presented, based on LIBS (Laser Induced Breakdown Spectroscopy). The technique is applied to several test cases (Dhofar 019, Dhofar 461, Sahara 98222, Toluca, Sikhote Alin and Campo del Cielo) and can be useful for rapid meteorite identification providing geologists with specific chemical information for meteorite classification. Concentration profiles of Fe, Ni and Co are simultaneously detected across the Widmanstatten structure of the iron meteorite Toluca with a view to determining cooling rates. The LIBS analysis of meteorites is also used as a laboratory test for analogous studies on the respective parent bodies (Mars, asteroids) in space exploration missions where one clear advantage of the proposed technique is that no direct contact with the sample is required.

Laser-Induced Breakdown Spectroscopy (LIBS) is a fast and reliable technique suitable for the simultaneous qualitative and quantitative analysis of major and trace elements in samples of various nature and origin. In last decades, the use of compost as an organic amendment has become a very common, cheap and sustainable agricultural practice to provide soil with organic matter and nutrients, although the content of heavy metals in compost may often represent a risk for its agronomic use. In the present work, the detection and concentration of selected macro- and micronutrients and heavy metals, including Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Sr, and Zn, in two commercial composts of different origin have been measured comparatively by LIBS and conventional Induced Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) techniques. In general LIBS data are in good agreement with the corresponding ICP-OES data. The best correlation of LIBS values with ICP-OES values are obtained at the laser wavelength of 532 nm for Al, Ca, K, Mg, Mn and Na, and at the wavelength of 355 nm for Cr, Cu, Fe, Pb, Sr and Zn. In conclusion, our results confirm the feasibility of LIBS for the quantitative analysis of several elements in composts with several advantages including no need of (or minimal) sample preparation, rapidity and relatively low costs, showing promising for further applications. However, a number of instrumental and substrate factors still need to be optimized to obtain a better performance for accuracy and precision of LIBS analysis for each element.

Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds.

This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis. © 2014 Elsevier B.V. All rights reserved.

A modified version of the calibration-free (CF) method was applied to the analysis of a set of archaeological brooches made of various copper-based alloys and coming from the archaeological site of Egnatia (Apulia, Southern Italy). The developed methodology consists in determining the plasma temperature by reversing the set of equations employed in the usual CF algorithm, and it is thus referred to as "inverse method". The plasma temperature is determined for one certified standard, by using its known elemental composition as an input data, and then applied to the set of unknown samples to evaluate their composition in a CF mode. The feasibility of such an approach is demonstrated by comparing the results obtained with classical LIBS (drawing calibration lines with a series of matrix-matched certified standards) and with independent measurements performed with a conventional technique (LA-ICP-MS). © 2014 Elsevier B.V.

The excitation temperature of Laser Induced Plasmas (LIPs) of copper-based alloys was determined with an alternative approach, which reverses the procedure of calibration-free methods for quantitative analysis through Laser Induced Breakdown Spectroscopy (LIBS).The inverse method here proposed is based on the Local Thermodynamic Equilibrium (LTE) equations, which were applied to simulate the elemental composition of certified samples at different temperatures, assuming that the actual plasma temperature was the one providing the best agreement with certified data. This procedure was validated for a set of bronze and brass standard samples and in different experimental conditions, by changing laser pulse width (7 ns and 250 fs) and laser wavelength (1064 nm, 532 nm and 355 nm). The temperature determined with the inverse method was then employed to determine the elemental composition of archeological findings of different copper-based alloys from Southern Italy sites (from VII century B.C. to VII A.D.), in order to test its validity for the analysis of actual unknown samples. The obtained weight percentages showed a good correlation with those obtained with the calibration line method, which provided a further confirmation of the assumptions made. (C) 2012 Elsevier B.V. All rights reserved.

In 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 obtained depositing NPs on the sample surface by drying a micro-drop of colloidal solution. The basic mechanisms of Nanoparticle Enhanced LIBS (NELIBS) were studied and the main causes of this significantly large 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 emission spectroscopy and spectrally resolved images. In spite of similar plasma parameters, the NELIBS plasma was found to have larger emission volume and longer persistence than the LIBS one. A method to determine NP concentration and size was also proposed, which involved depositing NPs on non-interacting substrates, and proved the feasibility of LIBS as a fast detection tool for a preliminary characterization of NPs. © 2014 Elsevier B.V.

State-to-state non-equilibrium plasma kinetics is widely used to characterize cold molecular and reentry plasmas. The approach requires a high level of dynamical information, and demands a large effort in the creation of complete databases of state-resolved cross sections and rate coefficients. Recent results, emphasizing the dependence of elementary process probability on both the vibrational and rotational energy content of the H2 molecule, are presented for those channels governing the microscopic collisional dynamics in non-equilibrium plasmas, i.e. electron-impact induced resonant processes, vibrational deactivation and dissociation in atom-diatom collisions and atomic recombination at the surface. Results for H2 plasmas, i.e. negative ion sources for neutral beam injection in fusion reactors, RF parallel-plate reactors for microelectronics, atmospheric discharges and the shock wave formed in the hypersonic entry of vehicles in planetary atmosphere for aerothermodynamics, are discussed.

In this paper emission spectra of the plasma produced by laser-matter interaction are discussed in terms of the correlation between the elementary plasma processes and the evolution of plasma parameters during the expansion. Three main stages have been identified and discussed in details: high density plasma, near equilibrium plasma and non-equilibrium plasma including molecular formation. In order to develop a comprehensive point of view on the correlation between plasma mechanisms and spectral emission features several concepts already discussed and elucidated in the plasma science have been adapted to the description of the laser induced plasma and to its ionizing and recombining character.

Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.

Laser Induced Breakdown Spectroscopy (LIBS) is an analytical technique based on the optical emission spectroscopy of the plasma generated by high energy laser pulse and solid sample. LIBS allows to perform stand-off and in situ analysis with immediate response and a limit of detection (in the range of mgkg-1), and for these peculiarities is particularly suitable for analysis in the environmental field. In this work is presented a case of study where the elemental analysis of some polluted soils are obtained either with the classical calibration curve (CC) method or with a Local Thermodinamic Equilibrium (LTE)-based Calibration-Free (CF) method, in order to demonstrate the capability of this technique. It is important to underline that the latter methodology does not require the use of preliminary experiments with standard samples and so it does not have any limitation due to the matrix effect.Several polluted soil samples were analyzed by drawing calibration lines to determine the concentration of some trace metals (e.g., Cr, Pb, Cu, Zn, Sr, Ni), as well as those of some major elements (e.g., Fe, Mn, Mg). The elemental concentration (normalized by Fe concentration) was measured with ICP-OES and LIBS techniques respectively. For what concern LIBS measurements, a comparison was done between two different data treatment: the LTE-CF based method and the classical CC method. For some elements a comparison was tried between calibration lines and calibration-free data, in order to validate the latter techniques also for complex matrices such as soils.

Laser Induced Breakdown Spectroscopy (LIBS) is a fast and multi-elemental analytical technique particularly suitable for the qualitative and quantitative analysis of several elements in solid samples including metal alloys for metallurgy and jewellery, and cultural heritage materials. Due to negligible or virtually absent pre-treatments of samples, high sensitivity, simultaneous multielemental detection of major and trace elements, and especially capability for microanalysis with low sample consumption, LIBS has been recently used also for analysis of environmental samples, i.e., meteorites, soils, sediments, and vegetables.In the present work, the authors test the feasibility of the LIBS technique to be used during the remediation/restore of soils by plants (phytoremediation) and compost application. In detail, Cr, Cu, Fe, Pb, and Zn content were investigated in four plant species (i.e., Atriplex halimus, Brassica napus, Rucola sativa, and Sorghum bicolor) and two different composts, and concentration values compared with those obtained by ICP-OES.Although the LODs for the LIBS-detected elements were sometimes quite higher if compared with other analytical techniques, data obtained underline the capability of LIBS method for the monitoring of the studied elements in plants growing in polluted soils, also allowing to calculate a "translocation" factor between roots and leaves. Good results were obtained also for composts.Furthermore, as some metals like Cu and Fe have to be considered, below certain concentrations, micronutrients, the authors propose the application of the LIBS in investigating deficit in plant uptake (e.g., Fe-chlorosis), and/or to evaluate the concentration of nutrients (e.g., Ca, Mg, Mn) in amendments/fertilizers.