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.

An innovative approach of double pulse laser-induced breakdown spectroscopy (DP-LIBS) coupled with optical microscopy was applied to the characterisation and quantitative analysis of the Agoudal iron meteorite in bulk sample and in petrographic thin section. Qualitative analysis identified the elements Ca, Co, Fe, Ga, Li and Ni in the thin section and the whole meteorite. Two different methods, calibration-free LIBS and one-point calibration LIBS, were used as complementary methodologies for quantitative LIBS analysis. The elemental composition data obtained by LIBS were in good agreement with the compositional analyses obtained by traditional methods generally applied for the analysis of meteorites, such as ICP-MS and EDS-SEM. Besides the recognised advantages of LIBS over traditional techniques, including versatility, minimal destructivity, lack of waste production, low operating costs, rapidity of analysis, availability of transportable or portable systems, etc., additional advantages of this technique in the analysis of meteorites are precision and accuracy, sensitivity to low atomic number elements such as Li and the capacity to detect and quantify Co contents that cannot be obtained by EDS-SEM.

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.

Biochar has gained agricultural importance as a soil amendment because of its important agricultural properties such as water retention, plant nutrient supplier, promoter of microorganism growth, sequestration action of atmospheric CO2, etc. Further, it is a low cost material being produced by recycling. Due to its active sites, biochar can adsorb nutrients so acting as a soil fertilizer. Thus the rapid assessment of nutrients in these materials is essential to ensure quality control for agricultural purposes. This work aimed to develop a simple analytical method based on Laser-Induced Breakdown Spectroscopy (LIBS) to determine Ca in biochar-based fertilizers. In particular, biochar samples enriched with Ca were prepared from peanut shells, residues of eucalyptus and banana fibers. The calibration standards were prepared by matrix matching using a biochar from eucalyptus residues. Different spectral preprocessing were evaluated to enhance the precision and accuracy of the method. However, the matrix effects demanded the use of internal standardization as the appropriate methodology to obtain the best accuracy. A linear correlation coefficient of 0.989 and a linear work range of 1.51-11.23% Ca were obtained using the proposed method, which yielded limits of detection and quantification of 0.45% e 1.51%, respectively. Calcium contents determined by LIBS in biochar-based fertilizers were in good agreement (paired t-test at 95% confidence level) with those determined by using High-Resolution Continuous Source Atomic Absorption Spectrometry (HR-CS FAAS) as the reference technique. Thus, the importance of internal standardization was demonstrated to be successful for the quantitative analysis of Ca in complex matrices like biochar-based fertilizers.

The C cycle in the Brazilian forests is very important for issues related to climate changes. Assessing and understanding C dynamics in Amazonian soils can help scientists to improve models and anticipate scenarios. Development of new methods for soil C measurements in situ is crucial in this region due to the financial costs and times needed for collecting and sending soil samples from the forest to the research laboratory. Laser-induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy which uses a highly energetic laser pulse for the plasma production. In this technique sample preparation is typically minimized or unnecessary. Furthermore, LIBS is able to perform a simultaneous semi-quantitative and multi-element analysis in few seconds, thus allowing the monitoring and comprehensive analysis of soil in situ. In this study, the feasibility of a portable and low resolution LIBS system for the in situ quantitative analysis of soil C was investigated in two typical forest Brazilian soils, a Spodosol (Amazon Forest) and an Oxisol (Atlantic Forest). The intensities of LIBS C lines were analyzed in fifty-three soil samples. In particular, two C lines were evaluated, at 193.03 nm and 247.86 nm. The line at 247.86 nm showed a very strong interference with iron and titanium lines, which made impossible any quantitative analysis. The line at 193.03 nm showed interference by atomic and ionic aluminum emission lines, but the analytical conditions were better than those at 247 nm. To solve this problem a correction method was proposed and tested for the C line at 193.03 nm. A strong correlation was found between the C data measured by LIBS and those measured by the reference technique (CHN elemental analysis). The Pearson's coefficient value of R = 0.91 supported the efficiency of the used correction.

An ultrashort (100 fs) Ti:Sapphire pulsed laser has been employed in order toproduce nanostructures by pulsed ablation of a graphite target in water. Different (10-100-1000 Hz) repetition rates have been used, and the features of material produced have beeninvestigated by surface enhanced Raman spectroscopy (SERS) and scanning electron micro-scopy (SEM). SERS spectra show that a broad asymmetric band associated with diamond-likecarbon (DLC) is observed when repetition rates of 10 or 100 Hz are used. On the contrary,ablated species produced with 1 kHz pulses present a narrow peak at 1333 cm -1 , the typicalmode of diamond, which is, however, embedded in a DLC band centered at 1540 cm -1 . SEMimages show the presence of dispersed octahedral-shaped structures having a size from 1 to 5 ?m,in the case of 10 or 100 Hz repetition rates, and agglomerates of particles having a dimensionbelow 300 nm, when 1 kHz pulses are used.

Photodetectors based on polycrystalline diamond (PCD) films are of great interest to many researches for the attractive electronic, mechanical, optical and thermal properties. PCD films are grown using the Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) method. First, we characterized films by means of structural and morphological analysis (Raman spectroscopy and scanning electron microscopy), then we evaporated a pattern of coplanar interdigitated Cr/Au contacts with an inter-electrode spacing of 100 um in order to perform the electrical characterization.We carried out measurements of dark current and impedance spectroscopy to investigate the film properties and conduction mechanisms of films and the effects of post-growth treatments. Finally we developed acharge sensing pre-amplifier to read-out the signal produced by UV photons in the detector.

Soil carbon sequestration is one approach to mitigate greenhouse gases. However, to reliably assess the quantities sequestered of carbon in several productive systems, new methods and equipment for large scale determination are needed. Laser-induced breakdown spectroscopy (LIBS) is a well-known analytical technique to analyses of solid, liquid, gaseous and aerosol samples. Furthermore, the interest in this technique has grown because it does not require chemical treatment for sample preparation, thus LIBS technique can be considered environmentally clean, without chemical waste. However, it shows a lower sensitivity when compared to other spectrometric methods. One way to overcome this limitation is to use a double pulse (DP) configuration. Few papers are found in the literature using DP systems in the analysis of soils. This study aimed to build and characterization of an apparatus DP-LIBS for the soil study. The soils samples were collected from two different Brazilian regions, North (Amazon) and Southeast (Sao Paulo). Tropical soils have large amounts of iron and aluminum in their compositions, so the main carbon lines in 247.86 nm and 193.03 nm, respectively, endures strong interference of these elements. A comparative study between conventional (single pulse) LIBS and DP-LIBS was performed. Also, the influence of the excitation wavelength on the ablation and re-heating were compared. Two different Nd:YAG lasers operating at the wavelength 532 nm and 1064 nm (IR), respectively, were used and the total Carbon and some micronutrients of the soil were investigated. The collinear DP-LIBS system built enhanced the intensity of emission lines of these elements more than twice, when compared with conventional single pulse LIBS, and reduced the continuum emission. Preferably the IR laser was indicated to re-heating of the plasma. In general, DP-LIBS improved the analytical performances of the technique.

With 6.5 m of peat accumulated during the past ca. 15,000 years, Etang de la Gruère (EGr) represents thelongest continuous record of atmospheric dust deposition in northern hemisphere. This paper presents acomparative study of the mineralogical composition of Sphagnum peat samples and their correspondinghumic acids (HA) from a peat core collected at EGr bog. The purpose of this study was to better understandthe dominant process responsible for the amount and distribution of mineral matter in ombrotrophic (i.e., rain-fed) peat. Specifically, the goal was to separate the relative importance of the changing rates of atmospheric mineral dust deposition (during the past two millennia) from the mineralization of organic matter (OM), for the distribution of the ash fraction of the peat profile.The results suggest that variations in ash content at EGr are mainly the result of an increase in the rate ofsupply of dust particles and cannot be attributed simply, or exclusively, to differences in the degree of OMdecay: evidence is provided by both acid insoluble ash (AIA) profiles and the correlations among lithogenicelements (Al, Si, Ti, Y, and Zr), total ash content and AIA. Moreover, our findings suggest that part of theAIA occurring in peat extremely is stable, and is unaffected by the extreme chemical conditions used toextract the HA fraction: this may be partly due to the inherent stability of quartz and "heavy minerals"such as zircon and rutile, but organic coatings developed on mineral surfaces during peat diagenesis, orthe formation of some other kind of organo-mineral complex, might also play a role. Consequently, testimonies of past dust depositions can be observed also into the recalcitrant HA fraction of the peat.

Diamond films exhibit interesting properties, such as a wide bandgap (5.5 eV) and very low electron affinity which favours the electron photoemission. Diamond based cold photocathode is well known and demonstrated, due also to its chemical stability and mechanical robustness.In this work, a comparative study on photoemission of nanocrystalline diamond (NCD) film and nanodiamond (ND) layers obtained by microwave plasma enhanced chemical vapour deposition and pulsed spray technique, respectively, is presented and discussed evidencing advantages and drawbacks. The first technique permits to obtain thin NCD films at high deposition temperature (650-900 °C) with excellent homogeneity and adhesion; whereas the second one allows to deposit thin ND layer at a temperature of 120 °C with poor adhesion and low uniformity. Both NCD film and ND layers have been characterized by Raman spectroscopy, atomic force microscopy (AFM) and photoemission measurements.

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.

Laser-induced breakdown spectroscopy (LIBS) has attracted a lot of attention due to its potential to rapidly identify and quantify any chemical element with minimal sample preparation. Despite continuous improvements, the sensitivity of this technique still remains a challenge. In order to increase LIBS intensity, a laser-induced fluorescence (LIF) system can be coupled with LIBS to re-excite a transition of the element in the plasma by employing very expensive optical parametric oscillators (OPO). In this work, a homemade tunable continuum wave-diode laser (CW-DL) has been developed and coupled to a double pulse (DP) LIBS system to enhance the sensitivity of Pb detection in a soil sample at the transition 6s26p2-3P2 -> 6s26p7s -3P1 at 405.78 nm. Before sample analysis, the production of no scattered light by the plasma was ascertained, and the optimal temperature of 10,000 K was estimated for this transition, feasible to be achieved in DP-LIBS systems. An increase of approximately 100% for the Pb I transition at 405.78 nm was obtained by DP-LIBS-CW-DL-LIF with respect to the DP-LIBS system alone. This result opens a new promising line of research to improve LIBS sensitivity using the CW-DL approach.

A spark discharge system was coupled to laser-induced breakdown spectroscopy (SD-LIBS) to improve sensitivity in the determination of P in fertilizers. A LIBS system consisting of a Q-switched Nd:YAG laser operating at 1064 nm and emitting pulses at 50 mJ with a fluence of 70 J cm-2 at the focal point was used. Results of preliminary experiments suggested that the most appropriate wavelength to measure P was the P (I) line at 214.9 nm, which did not show interferences by Fe, Cu and Zn. The electrical discharge was provided by a homemade high-voltage electronic circuit consisting of two cylindrical tungsten electrodes at the optimized output voltage of 4.5 kV, with tips arranged at the optimal distances of 4 mm between them and 2 mm above the sample surface. To minimize the expected matrix effects calibration standards of P2O5 in the range of 4.8 and 33.3% were prepared by mixing various amounts of a phosphate rock reference material (SRM-120c) with a mixture of CaCO3, CaSO4, (NH2)2CO and KCl at a 1:1:1:1 mass ratio. The calibration curves obtained at a 4.5 kV SD-LIBS output voltage showed correlation coefficients >=0.993, RSD <=8% and LOQ 5.3% (m/m) P2O5. Data obtained by analyzing commercial samples by the proposed system were in good agreement, at 95% confidence level, with those obtained by using high-resolution continuum-source flame atomic absorption spectroscopy.

The purpose of this work was to develop and optimize the key parameters that influence the double-pulse laser-induced breakdown spectroscopy technique in the orthogonal beam geometry when applied to the elemental analysis of environmental samples.

A soil, a plant and a fertilizer sample were investigated by double-pulse (DP) laser-induced breakdown spectroscopy (LIBS) in orthogonal beam geometry using a reheating configuration. The DP-LIBS signal enhancement was evaluated with respect to the corresponding single-pulse (SP) LIBS as a function of the interpulse delay at various ablation energies. The maximum signal enhancement measured was 155-fold when low ablation energy (4 mJ) and an interpulse delay of 10 ?s were used. At high laser energies (>= 16 mJ) and interpulse delay of 0.6 ?s, the maximum signal enhancement was up to 3-fold. The effect of excitation energies and interpulse delays on emission line intensities was discussed in the various conditions used. The emission line enhancement measured for ionic lines was always higher than that of atomic lines. Plasma excitation temperature and electron density measured as a function of interpulse delays at various ablation energies were shown to be related to the emission line intensities.

Organic fertilizers are obtained from waste of plant or animal origin. One of the advantages of organic fertilizers is that, from the composting, it recycles waste-organic of urban and agriculture origin, whose disposal would cause environmental impacts. Fast and accurate analysis of both major and minor/trace elements contained in organic mineral and inorganic fertilizers of new generation have promoted the application of modern analytical techniques. In particular, laser induced breakdown spectroscopy (LIBS) is showing to be a very promising, quick and practical technique to detect and measure contaminants and nutrients in fertilizers. Although, this technique presents some limitations, such as a low sensitivity, if compared to other spectroscopic techniques, the use of double pulse (DP) LIBS is an alternative to the conventional LIBS in single pulse (SP). The macronutrients (Ca, Mg, K, P), micronutrients (Cu, Fe, Na, Mn, Zn) and contaminant (Cr) in fertilizer using LIBS in SP and DP configurations were evaluated. A comparative study for both configurations was performed using optimized key parameters for improving LIBS performance. The limit of detection (LOD) values obtained by DP LIBS increased up to seven times as compared to SP LIBS. In general, the marked improvement obtained when using DP system in the simultaneous LIBS quantitative determination for fertilizers analysis could be ascribed to the larger ablated mass of the sample. The results presented in this study show the promising potential of the DP LIBS technique for a qualitative analysis in fertilizers, without requiring sample preparation with chemical reagents.

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.

The deposition of as-received nanodiamond (ND) particles on silicon substrate was performed by the pulsed spray technique, using a dispersion of 250nm ND in 1,2-dichloroethane. A set of samples was sprayed by varying the number of pulses from 1 to 500. The morphology of the samples was characterized and monitored by means of optical, atomic force, and confocal microscopies. At a low number of pulses, sparse diamond particles were observed, whereas at a high number of pulses dense/quasi-continuous ND layers were formed. The electrical conductivity measurements of surface silicon substrate evidenced a remarkable change for the presence of ND particles. This behavior is also found by theoretical simulations (finite element method). Finally, a comparison between the electrical resistances measured on these samples versus the pulse number and the inverse current density calculated as a function of the number of ND particles, showed a good agreement. The experimental results highlighted an increase of the electrical current by using a number of pulses <100, whereas the simulation results proved the enhancement of current density and its surface rectification by employing a specific number of particles. The current increased by increasing the temperature and during the heating-cooling cycles hysteresis was observed. (a) Scheme of the sprayed ND particles on silicon substrate, (b) 3D AFM image 5×5?m² of 10 pulses sample, (c) trends of measured R and calculated 1/J.

Meteorites are rocks that once were part of planets or large asteroids, and usually contain a great amount of extra-terrestrial iron. Nowadays, the meteorite business is booming and the demand is increasing all over the world, whereas supply (originating especially from Morocco and Algeria) is limited. Thus, specimens presented as meteorites often turn out to be common Earth rocks or old smelter and castoff iron dubbed as a 'meteor-wrong'. In the present study, a compact handheld instrument based on fast-response multi-elemental analysis technique, i.e., laser induced breakdown spectroscopy (LIBS), has been used to identify specific major elements (Ni and Co) and trace elements (Ga and Ir), in order to discriminate a certified iron meteorite with respect to a suspected meteorite fragment and a pig iron product. Furthermore, a calibration freeLIBS method has been used to quantify the main elements Fe, Ni and Co in the iron meteorite and Fe, Mn, Si and Ti in the other two fragments.

The behavior of hydrogen spectral emission of the plasmas obtained by Laser-Induced Breakdown Spectroscopy (LIBS) measurement of four metal targets (Au, Cu, Mn, Pb) in air was investigated. The plasma was produced by a pulsed Nd:YAG laser emitting in the fundamental wavelength. A systematic study of the spatial-integrated plasma emission obtained by an in-depth scanning of the target was performed for each metal, both in single pulse and collinear double-pulse configurations. Further, a spatial-resolved analysis of the emission of plasma produced on the Al target by a single laser pulse was performed, in order to describe the spatial distribution of emitters deriving from the target and air elements. The line intensities of the main plasma components (target metal, nitrogen, oxygen and hydrogen) were measured in both experimental conditions. Results show that the hydrogen line intensity varies greatly as a function of the metal considered, and exhibits a marked decrease after the first laser shots. However, differently from emission lines due to surface impurities, the hydrogen line intensity reaches a constant level deep inside the target. The spatial-resolved measurements indicate that hydrogen atoms in the plasma mainly derive from the target surface and, only at a minor extent, from the dissociation of molecular hydrogen present in the surrounding air. These findings show that the calculation of plasma electron number density through the measurement of the Stark broadening of hydrogen Balmer alpha line is possible also in depth scanning measurements.

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.

The study of enstatite chondrites (ECs) may play an important role in understanding theevolution of Earth, inner Solar System and asteroid belt. ECs are very scarce among chondriticmeteorites. The chemical composition of their silicates, sulphides and metals reflect their formationunder highly reducing conditions. Most ECs are completely dry and lack any evidenceof hydrous alteration, thus ECs were formed likely within the snow line and are good candidatesto be considered the building blocks of inner planets, like Mercury. ECs represent themost reduced group among chondrites, featuring enstatite chondrules (FeO < 1 wt%), low olivinecontent, Fe-Ni alloy, and oxygen isotopic ratios that match the terrestrial fractionation line(TFL) and are subdivided in two groups: EH and EL, i.e. high and low Fe-metal content, respectively(Keil, 1968).In this work a thin section of the EC labelled Sahara 97072 EH3 previously investigated bymulti-analytical approach (Manzari, 2010), was studied by means of Laser Induced BreakdownSpectroscopy (LIBS). LIBS advantages with respect to conventional analytical techniques are:simultaneous multi-element qualitative and quantitative analysis in real time, high sensitivity,stratigraphic analysis of a sample by profiling, especially sensitive to light elements such as C,B, Be, H and Li, no need of an analytical chamber, sampling and surface treatment (Senesi,2014). Recently, the potentiality of LIBS was exploited even in remote elemental analysis ofextraterrestrial rocks. LIBS technique was installed onboard of NASA Mars Science Laboratoryrover named Curiosity, as part of ChemCam to provide chemical analyses on Martian rocks(Wiens et al., 2013; Gordon et al., 2014). In this study, an innovative LIBS prototype (Fig. 1a),operating with a Nd:YAG laser in double pulse configuration, was used coupled with a petrographicmicroscope (micro-LIBS) that allows chemical investigations directly on the thin section(Fig. 1b). This innovative approach enables to perform chemical analyses preserving a qualitative knowledge of the phases in a thin section taking into account the distribution of thegrains, the texture and any preferred orientations at the microscale. In particular, qualitativemicro-LIBS data (Fig. 1c) of metal-sulfide-nodules consisting of kamacite Fe, Ni, Cr-troilite,and oldhamite CaS resulted in good agreement with data previously obtained by SEM-EDS.Future investigations on martian meteorites using micro-LIBS will be carried out to validatethe data obtained in remote mode by ChemCam.

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.

Over the past two decades an intense activity has been conducted in the study anddevelopment of the analytical technique of laser-induced breakdown spectroscopy (LIBS) in severalfields of academic and applicative research, including agriculture. LIBS is a fast and reliabletechnique suitable for the simultaneous qualitative and quantitative analysis of major and traceelements in samples of various nature and origin. This review reports and discusses some works onLIBS applications and his feasibility to the study of agriculture with focus on soils, plants andcomposts. Results obtained on element detection and quantification, identification anddiscrimination are reviewed and briefly discussed. In particular, we would focus the attention onhow LIBS could be adopted on the Brazilian environment with promising results. For example, newmethods that allow soil C measurements in-situ are crucial for Amazonian soils and an encouragingresolution method to quantify C in Brazilian soils would be given by means of atomic emissionlines obtained by a portable LIBS system. Furthermore, field measurements are also possible byusing compact portable LIBS apparatus really helpful in hostile environment, e.g., Amazoniaregion.

A number of phosphate rocks and organomineral P fertilizers was analyzed comparatively by laser-induced breakdown spectroscopy (LIBS) in both single- and double-pulse modes associated with two chemometric methods, i.e., principal components analysis (PCA) and partial least squares regression (PLSR). PCA was demonstrated to be a valuable method for the identification of spectral differences between similar samples with only minor compositional differences. The raw and normalized LIBS spectra were able to provide effective identification and discrimination at a 95% confidence level and in good agreement with the reference concentrations. Results obtained confirm the promising potential of LIBS for the rapid classification of P fertilizers in situ.

Laser-induced breakdown spectroscopy is an optical emission technique quite suitable for the analysis of recalcitrant materials as it eliminates complex procedures of sample preparation. However, for some simple LIBS instrumentation the detection limits are still higher compared to those of consolidated spectroscopic techniques. The aim of the present work was to develop a method for the determination of K in new biochar-based fertilizer samples using a simple single pulse LIBS arrangement. Due to the low K detectability, which made impossible to obtain calibration curves, an exploratory qualitative study was performed aiming to evaluate the influence of the addition of easily ionizable elements (EIE) on the sensitivity. To this aim different salts containing EIE (K, Li and Na) and other cations (Cu and Mg) have been evaluated. Results obtained showed that salts containing EIE cations increased the spectral emission signals of some elements in samples previously submitted to charring. In particular, the strategy of using Li+ was applied to the determination of K in biochar-based fertilizers. The addition of Li+ allowed to develop an analytical method for K determination featuring a linear dynamic range from 0.8% to 21.56% K, and limits of detection and quantification of 0.2% and 0.8%, respectively.

Laser-induced breakdown spectroscopy (LIBS) is a technique increasingly used to perform fast semi-quantitative multi-elemental analyses of various materials without any complex sample preparation, being also suitable for in situ analyses. Few studies have been performed to understand the influence of laser wavelength on LIBS analytical performance on environmental samples. The main goal of this study was to perform a comparative elemental analysis of a number of soils, citrus leaves, and synthetic solid matrices using two different wavelengths, i.e., 532 and 1064 nm of Nd:YAG lasers, and a spectrometer coupled to a non-intensified charge-coupled device camera as the detection system. The emission lines with higher upper energy level, i.e., C I--193.03 (7.685 eV) and Si I--212.41 nm (6.616 eV), were more intense when using the 532 nm than the 1064 nm laser light, whereas the opposite occurred for elements with lower upper energy level, i.e., Ti I--336.12 nm (3.716 eV) and Fe I--368.75 nm (4.220 eV). The observed increase in LIBS signal between the two wavelengths is about 30-50%. The relationship between the line emission intensities and the used excitation wavelengths were associated to the upper level energy of the element.

Laser induced breakdown spectroscopy (LIBS) in single pulse (SP) and double pulse (DP)configuration in collinear beam geometry at atmospheric air pressure was used to determinethe limit of detection (LOD) for the macronutrients Ca, Mg and P, the micronutrients Fe, Na,Mn and Zn and the trace elements Al, Cr, Cu and V in 26 samples of organic and inorganicfertilizers of different matrix composition. Inductively coupled plasma optical emissionspectroscopy (ICP-OES) was used as a reference technique. A comparative study wasperformed to optimize key parameters, such as excitation wavelength, delay time andinterpulse, for improving LIBS performance in the SP and DP configurations. Results show aconsiderable improvement in linear correlation between the DP LIBS signal and elementconcentration measured by ICP-OES compared to SP LIBS. LOD values obtained by DPLIBS increased up to five times as compared to SP LIBS. In general, LIBS results show amarked improvement in the simultaneous quantitative determination of various elements inorganic and inorganic fertilizers.

A relevant and still unsolved issue in the characterization of diamond coatings deposited on ceramic materials such as hexagonal boron nitride (h-BN) is to enhance the resistance of the substrate to erosion by Kr+ or Xe+ ions generated in the plasma propulsion systems. In this work, diamond films were grown by microwave plasma enhanced chemical vapour deposition on h-BN substrates untreated, for the first time, and pre-treated for short (31-65 min) and long (285-296 min) process times. The morphology of diamond films was analysed by scanning electron microscopy, and atomic force microscopy, and their chemistry and structure by Raman spectroscopy. Microscopy analysis revealed that non-continuous (at short process time) and continuous (at long process time) films were formed, respectively, on both untreated and pre-treated h-BN substrates. In particular, diamond films grown on untreated h-BN substrates exhibited roughness values higher than those of h-BN substrates pre-treated by a conventional ultrasonic method.

Diamond coating has been proposed in different patents where prosthetic joints integrate diamond-coated load bearing surfaces in order to reduce friction and to increase the useful life of the joint [1], or where diamond coatings replace plastic (such as Ultra High Molecular Weight Poly-Ethylene)/ceramic (such as Zirc-alloy) materials suitable for ginglymous, enarthrodial implants or digital joints [2]. Concerning femoral prostheses, diamond coated silicon nitride has been considered as total hip replacement material [3]. Moreover, wear-debris-induced periprosthetic bone loss and aseptic loosening are the main long-term problems for total hip replacements, and amorphous diamond (a-D) coatings could reduce the wear debris for articulating surface [4]. In alternative, multilayered nanocrystalline diamond coatings have been studied in order to improve incredible hardness and excellent wear-resistance for articulating surfaces of structural implant devices [5]. Recently, diamond like carbon (DLC) have been considered about reducing friction and wear of orthopaedic implants [6]. In this direction nano- and ultranano-crystalline diamond (NCD and UNCD) and polished poly-crystalline diamond coatings exhibiting very low roughness, could bring to better mechanical properties if compared with DLC/a-D ones. Results of recent studies on NCD coatings applied to medical implants, has shown the high diamond biocompability and positive bioactivity [7]. We propose in this work to investigate and to fabricate tailored biocompatible NCD coatings addressed to low roughness (and consequent low friction) behavior. The used technology will be based on MicroWave Plasma Enhanced Chemical Vapour Deposition (MWPECVD) technique [8], able to improve superior hardness and Young's modulus for low temperature NCD [9]. The optimized approach will be focused on the grain surface characterization and on the mechanical properties of NCD coatings grown at different deposition temperature values (650-884°C). The surface morphology will be studied by Atomic Force Microscopy (AFM) technique, and the chemical-structural features of all coatings will be analyzed by Raman spectroscopy. Some important mechanical aspects will be discussed in details.

Nanodiamond (ND) layers are produced by the pulsed spray technique on a heated silicon substrate. By varying the number of pulses it was possible to obtain a quasi-continuous layer on the substrate surface. The use of atomic force and confocal microscopies allowed to evidence the presence of self-assembled pillar structures. The pillar formation is due to the evaporation of 1,2-dichlorethane solvent in which 250 nm nanodiamonds were dispersed and its mechanism is based on the coffee stain effect as described in detail in ref. 1. Simple bio-chips on glass and silicon substrates can be fabricated spraying ND spots arranged in an array configuration (see Figure 1a) through a mask, and are suitable for bio-applications. Specifically, the presence of nitrogen vacancy (N-V) color center in ND particles is also promising as bio-markers2. An example of spot is illustrated in Figure 1b where pillars are present (see the zoomed area of Figure 1b). Additionally, the control of the pillar position represents an important challenge for micro-functionalised emitters arranged in a chip matrix suitable for bio-screening.

Two fragments of an iron meteorite shower named Dronino were characterized by a novel technique, i.e. Double-Pulse micro-Laser Induced Breakdown Spectroscopy (DP-?LIBS) combined with optical microscope. This technique allowed to perform a fast and detailed analysis of the chemical composition of the fragments and permitted to determine their composition, the alteration state differences and the cooling rate of the meteorite. Qualitative analysis indicated the presence of Fe, Ni and Co in both fragments, whereas the elements Al, Ca, Mg, Si and, for the first time Li, were detected only in one fragment and were related to its post-falling alteration and contamination by weathering processes. Quantitative analysis data obtained using the calibration-free (CF) - LIBS method showed a good agreement with those obtained by traditional methods generally applied to meteorite analysis, i.e. Electron Dispersion Spectroscopy - Scanning Electron Microscopy (EDS-SEM), also performed in this study, and Electron Probe Microanalysis (EMPA) (literature data). The local and coupled variability of Ni and Co (increase of Ni and decrease of Co) determined for the unaltered portions exhibiting plessite texture, suggested the occurrence of solid state diffusion processes under a slow cooling rate for the Dronino meteorite.

Soil organic matter (SOM) constitutes an important reservoir of terrestrial carbon and can be considered an alternative for atmospheric carbon storage, contributing to global warming mitigation. Soil management can favor atmospheric carbon incorporation into SOM or its release from SOM to atmosphere. Thus, the evaluation of the humification degree (HD), which is an indication of the recalcitrance of SOM, can provide an estimation of the capacity of carbon sequestration by soils under various managements. The HD of SOM can be estimated by using various analytical techniques including fluorescence spectroscopy. In the present work, the potential of laser-induced breakdown spectroscopy (LIBS) to estimate the HD of SOM was evaluated for the first time. Intensities of emission lines of Al, Mg and Ca from LIBS spectra showing correlation with fluorescence emissions determined by laser-induced fluorescence spectroscopy (LIFS) reference technique were used to obtain a multivaried calibration model based on the k-nearest neighbor (k-NN) method. The values predicted by the proposed model (A-LIBS) showed strong correlation with LIFS results with a Pearson's coefficient of 0.87. The HD of SOM obtained after normalizing A-LIBS by total carbon in the sample showed a strong correlation to that determined by LIFS (0.94), thus suggesting the great potential of LIBS for this novel application. © 2014 Elsevier B.V.

Soil organic matter (SOM) constitutes an important reservoir of terrestrial carbon and can be considered analternative for atmospheric carbon storage, contributing to global warming mitigation. Soil management canfavor atmospheric carbon incorporation into SOM or its release from SOM to atmosphere. Thus, the evaluationof the humification degree (HD), which is an indication of the recalcitrance of SOM, can provide an estimationof the capacity of carbon sequestration in soils under various managements. The HD of SOM can be estimatedby using various analytical techniques including fluorescence spectroscopy. In the present work, the potential ofLaser-Induced Breakdown Spectroscopy (LIBS) to estimate the HD of SOM was evaluated for the first time. In aLIBS experiment a high-energy laser pulse irradiates the sample and the energy absorbed by the sample causesa local heating of the material that results in its evaporation or sublimation. The high temperature of the ablatedmaterial generates a small plasma plume and, as a result of the plasma temperature, the ablated material breaksdown into excited atomic and ionic species. During the plasma cooling, the excited species return to their lowerenergy state emitting electromagnetic radiation at characteristic wavelengths. In a LIBS spectrum the measurementof the characteristic emission wavelengths provides qualitative information about the elemental composition ofthe sample, whereas the intensities of the signals can be used for quantitative determinations. The LIBS potentialfor the analysis of organic compounds has been explored recently by using the emission lines of elements that arecommonly present in organic compounds, such as the predominant C, H, P, O and N. LIBS elemental emissionswere correlated to fluorescence emissions determined by Laser-Induced Fluorescence Spectroscopy (LIFS), whichwas considered as the reference technique. The HD of SOM determined by LIBS showed a strong correlation tothat determined by LIFS, suggesting a great potential of LIBS for this novel application.

Soybean and its derivatives are one of the most valuable and traded agricultural commodities worldwide. The major problem faced by the producers is the reduction of soybean yield due to diseases. In Brazil, the green stem and foliar retention (GSFR) was recently described as affecting soybean plants and causing concerns. Unfortunately, no effective methods of early diagnosis and treatments are known. In an attempt to better investigate the plant changes caused by GSFR infection, soybean leaves collected from healthy and sick plants of two varieties from two different places of Brazil were evaluated comparatively for their content of the three macronutrients Ca, K and Mg by laser-induced breakdown spectroscopy (LIBS). Atomic absorption spectrometry (AAS) was used as the reference technique. In general, the relative simplicity of LIBS instrumentation and the minimal sample preparation required makes it a valuable tool for agriculture application, including nutritional investigation and disease diagnosis of plant samples. The Pearson coefficients obtained for the correlation between LIBS and AAS data were close to 0.80 for the three nutrients analyzed. The results obtained by applying the Student t-test and Principal Component Analysis (PCA) to experimental data allowed to discern between healthy and sick plant leaves. LIBS data analyzed by the classification via regression (CVR) method associated with Partial Least Square Regression (PLSR) yielded success rates higher than 80% in class differentiation. This study demonstrates the possibility of using LIBS as a convenient analytical tool to discern between healthy and GSFR infected plants by analyzing the three macronutrient Ca, K and Mg, thus providing an early GSFR diagnostic tool.

The aim of this study was to develop a quantitative method to determine phosphorus in fertilizers of different matrix compositions using the laser induced breakdown spectroscopy (LIBS) technique. The LIBS spectra were acquired on 26 samples of organic and inorganic fertilizers by using a low cost, portable, gated CCD system in the atmospheric environment. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique. A method was developed to remove the outlier spectra and perform the baseline correction and peak normalization. By applying the proposed corrections, the linear correlation between LIBS and ICP increased from R 1/4 0.76 to R 1/4 0.95. An average error of 15% found in cross-validation of LIBS quantification appeared feasible for P quantification in fertilizers. Two reference samples with different matrix compositions were also analyzed, and the absolute error in the quantification was below 5%. Further, no significant fluctuation was found in P quantification when LIBS was performed over 150 days.

Highly efficient MWPECVD diamond based photocathodes have been demonstrated to be more stable than conventional materials such as CsI in UV detection. Poly- and nano-crystalline diamond films are still investigated and tested. Many research groups have found that photoemission properties are function of grain size, surface morphology and presence of defects (sp2 carbon bonding, carbon-hydrogen bond) within the grain boundaries [1]. One of the issues of diamond application in photocathodes, if compared with the CsI, is the very high temperature used during its growth, thus restricting the application fields. In this work, we present a study of photocathodes based on diamond layer deposited at low temperature by spray technique [1]. Diamond powders, with different grain sizes, were dispersed in the non-polar 1,2-dichloroethane (DCE) solvent by sonication for 30 minutes and successively sprayed on the substrates.The sprayed diamond films have been characterized by Raman spectroscopy, Atomic Force Microscopy and Photoemission measurements.Quantum efficiency (QE) measurements of the photocathodes have been assessed at normal incidence in reflective mode in the UV spectral range (150-210 nm) by means of a 30 W deuterium lamp (Mc Pherson TM) under vacuum. The photocathode was mounted in a multi-wire proportional chamber, not operating in electron multiplication mode. The absolute QE was evaluated by means of a NIST calibrated standard photodiode.The results have shown a QE dependence on the grain sizes and properties of the starting diamond powders. Moreover, the photoemissive properties of the low temperature (100 °C) sprayed diamonds are comparable with MWPECVD ones, these last produced at high temperature (>= 700 °C).

The C cycle in the Brazilian forests is very important, mainly for issues addressed to climate changes and soil management. Assessing and understanding C dynamics in Amazonian soils can help scientists to improve models and anticipate scenarios. New methods that allow soil C measurements in situ are a crucial approach for this kind of region, due to the costs for collecting and sending soil samples from the rainforest to the laboratory. Laser-induced breakdown spectroscopy (LIBS) is a multielemental atomic emission spectroscopy technique that employs a highly energetic laser pulse for plasma production and requires neither sample preparation nor the use of reagents. As LIBS takes less than 10 s per sample measurement, it is considered a promising technique for in situ soil analyses. One of the limitations of portable LIBS systems, however, is the common overlap of the emission lines that cannot be spectrally resolved. In this study a method was developed capable of separating the Al interference from the C emission line in LIBS measurements. Two typical forest Brazilian soils rich in Al were investigated: a spodosol (Amazon Forest) and an oxisol (Atlantic Forest). Fifty-three samples were collected and analyzed using a low-resolution LIBS apparatus to measure the intensities of C lines. In particular, two C lines were evaluated, at 193.03 and 247.86 nm. The line at 247.86 nm showed very strong interference with Fe and Si lines, which made quantitative analysis difficult. The line at 193.03 nm showed interference with atomic and ionic Al emission lines, but this problem could be solved by applying a correction method that was proposed and tested in this work. The line at 247.86 was used to assess the proposed model. The strong correlation (Pearson's coefficient R = 0.91) found between the LIBS values and those obtained by a reference technique (dry combustion by an elemental analyzer) supported the validity of the proposed method.

Diamond powders of various size ranging from few nanometers to tens of micrometers arecommonly used to treat the silicon substrate in order to enhance the nucleation process beforethe growth of thin diamond films by chemical vapor deposition (CVD) techniques[1 and refs.therein]. Recently a great attention is paid to nanodiamond (ND) particles which include stablenitrogen-vacancy (N-V) color centers [2]. In this work we propose the spray technique [3] todirectly deposit natural ND layers on silicon substrate using particles of 250 nm. ND particles weredispersed in the apolar solvent 1, 2 - dichloroethano (DCE) by sonication for 30 minutes. Then thedispersion was sprayed on the Si substrate, obtaining the highest ND density in the middle of it.The obtained ND films were analyzed by Raman spectroscopy, atomic force microscopy (AFM) and3D confocal microscopy. The first technique allows the measurement of the chemical andstructural composition and the photoluminescent properties, whereas the other ones measure thetopography and morphology of the layers.A careful morphological analysis showed the existence of pillar-like self-assembled structuresdistributed in an irregular way. The highest pillar density was found far from the center of thesample, where the ND layer is non-uniform. The evolution of the structures were well observed bythe 3D image analysis performed by confocal microscopy and AFM. The studyon the formationmechanisms of ND self-assembled structures will be presented and discussed.

Pillar-like structures of nanodiamonds on a silicon substrate are self-Assembled for the first time by a pulsed spray technique. This technique allows us to deposit nanodiamond layers by using high quality nanocrystals of 250 nm dispersed in 1,2-dichloroethane (DCE) solvent. The analysis of 2D/3D confocal and atomic force microscopy images evidences the presence of self-Assembled pillar-like structures distributed in an irregular way. The proposed method is simple, easy and cheap, and does not require complex growth processes or structured materials, ideal for upscaling toward industrial biochip implementation and photonic applications. The suggested formation mechanisms of self-Assembly are based on the so-called coffee stain effect, i.e., on the time evolution of DCE evaporation.

The self-assembly of pillar-like structures in nanodiamond (ND) layers has been obtained for the first time by pulsed spray technique [1]. This technique has enabled to directly deposit ND layers on silicon substrate using natural nanocrystals of 250 nm. ND particles were dispersed in the apolar solvent 1, 2 - dichloroethane (DCE) by sonication for 30 minutes, then the dispersion was sprayed on the substrate. Various samples were sprayed at different number of pulses, ranging from 1 to 500. The obtained ND layers were analyzed by Raman spectroscopy, atomic force microscopy (AFM), 3D confocal microscopy, and contact angle measurements. The Raman spectroscopy allowed the measurement of the chemical and structural composition and the photoluminescent properties, the microscopic techniques measured the topography and morphology of the layers and contact angle measurements established the hydrophilic/hydrophobic nature of substrate/ND layers surfaces. A careful morphological analysis evidenced the existence of self-assembled pillar-like structures. The formation mechanisms of self-assembly, based on the so-called coffee stain effect, i.e. on the time evolution of DCE evaporation will be presented and discussed. Theoretical electrical aspects of the single pillar will also be discussed.

Laser-induced breakdown spectroscopy (LIBS) is showing to be a promising, quick, accurate, and practical technique to detect and measure metal contaminants and nutrients in urban wastes and landfill leachates. Although conventional LIBS presents some limitations, such as low sensitivity, when used in the single pulse configuration if compared to other spectroscopic techniques, the use of the double-pulse (DP) configuration represents an adequate alternative. In this work DP LIBS has been applied to the qualitative and quantitative analysis of mercury (Hg) in landfill leachates. The correlation analysis performed between each intensified charge-coupled device pixel and the Hg concentration allowed us to choose the most appropriate Hg emission line to be used for its measure. The normalization process applied to LIBS spectra to correct physical matrix effects and small fluctuations increased from 0.82 to 0.98 the linear correlation of the calibration curve between LIBS and the reference data. The limit of detection for Hg estimated using DP LIBS was 76 mg Kg-1. The cross validation (leave-oneout) analysis yielded an absolute average error of about 21%. These values showed that the calibration models were close to the optimization limit and satisfactory for Hg quantification in landfill leachate.

Laser-induced breakdown spectroscopy (LIBS) is a well-known consolidated analytical technique employed successfully for the qualitative and quantitative analysis of solid, liquid, gaseous and aerosol samples of very different nature and origin. Several techniques, such as dual-pulse excitation setup, have been used in order to improve LIBS's sensitivity. The purpose of this paper was to optimize the key parameters as excitation wavelength, delay time and interpulse, that influence the double pulse (DP) LIBS technique in the collinear beam geometry when applied to the analysis at atmospheric air pressure of soil samples of different origin and texture from extreme regions of Brazil. Additionally, a comparative study between conventional single pulse (SP) LIBS and DP LIBS was performed. An optimization of DP LIBS system, choosing the correct delay time between the two pulses, was performed allowing its use for different soil types and the use of different emission lines. In general, the collinear DP LIBS system improved the analytical performances of the technique by enhancing the intensity of emission lines of some elements up to about 5 times, when compared with conventional SP-LIBS, and reduced the continuum emission. Further, the IR laser provided the best performance in re-heating the plasma.

Thick (around 3 um) and thin (48-310 nm) nanocrystalline diamond (NCD) films have been produced from Ar-rich CH4/Ar/H2 (1/89/10 %) and H2-rich CH4/H2 (1/99 %) microwave plasmas, respectively.The deposition rate and the nucleation enhancement have been monitored in situ and in real time by pyrometric and laser reflectance interferometry for micrometer- and nanometer-thick films. For thick films, an improvement of the NCD films' smoothness has been obtained by a buffer layer between the films and the treated Si substrate. For thin films, a combinatorial approach, i.e., a treatment of the Si substrate in a suspension of mixed diamond powders of 250 nm and 40-60 um, has been utilized. The present experimental results show that the buffer layer procedure allows good preservation of the surface of the treated Si substrate and the combinatorial approach promotes effectively the seeding of the Si surface.

Characteristics of soil organic matter (SOM) are important, especially in the Amazon region, which represents one of the world's most relevant carbon reservoirs. In this work, the concentrations of carbon and differences in its composition (humification indexes) were evaluated and compared for several horizons (0 to 390 cm) of three typical Amazonian podzol profiles. Fluorescence spectroscopy was used to investigate the humic acid (HA) fractions of SOM isolated from the different samples. Simple and labile carbon structures appeared to be accumulated in surface horizons, while more complex humified compounds were leached and accumulated in intermediate and deeper Bh horizons. The results suggested that the humic acids originated from lignin and its derivatives, and that lignin could accumulate in some Bh horizons. The HA present in deeper Bh horizons appeared to originate from different formation pathways, since these horizons showed different compositions. There were significant compositional changes of HA with depth, with four types of organic matter: recalcitrant, humified, and old dating; labile and young dating; humified and young dating; and little humified and old dating. Therefore, the humification process had no direct relation with the age of the organic matter in the Amazonian podzols.

Nanocrystalline diamond (NCD) coatings with thickness of about 3 um were grown on silicon substrates at four deposition temperatures ranging from 653 to 884 degrees C in CH4/H2/Ar microwave plasmas. The morphology, structure, chemical composition and mechanical and surface properties were studied by means of Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Raman spectroscopy, nanoindentation and Water Contact Angle (WCA) techniques. The different deposition temperatures used enabled to modulate the chemical, structural and mechanical NCD properties, in particular the grain size and the shape. The characterization measurements revealed a relatively smooth surface morphology with a variable grain size, which affected the incorporated hydrogen amount and the sp(2) carbon content, and, as a consequence, the mechanical properties. Specifically, the hydrogen content decreased by increasing the grain size, whereas the sp(2) carbon content increased. The highest values of hardness (121 +/- 25 GPa) and elastic modulus (1036 +/- 163 GPa) were achieved in NCD film grown at the lowest value of deposition temperature, which favored the formation of elongated nanocrystallites characterized by improved hydrophobic surface properties. (C) 2014 Elsevier B.V. All rights reserved.

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.