Alessandro Lo Giudice

A diamond-based biosensor for the recording of neuronal activity.

We have developed a device for recording the extracellular electrical activity of cultured neuronal networks based on a hydrogen terminated (H-terminated) conductive diamond. GT1-7 cells, a neuronal cell line showing spontaneous action potentials firing, could maintain their functional properties for days in culture when plated on the H-terminated diamond surface. The recorded extracellular electrical activity appeared in the form of well-resolved bursts of fast and slow biphasic signals with a mean duration of about 8ms for the fast and 60ms for the slow events. The time courses of these signals were in good agreement with those recorded by means of conventional microelectrode array (MEAs) and with the negative derivative of the action potentials intracellularly recorded with the patch clamp technique from single cells. Thus, although hydrophobic in nature, the conductive H-terminated diamond surface is able to reveal the spontaneous electrical activity of neurons mainly by capacitative coupling to the cell membrane. Having previously shown that the optical properties of H-terminated diamond allow to record cellular activity by means of fluorescent probes (Ariano, P., Baldelli, P., Carbone, E., Giardino, A., Lo Giudice, A., Lovisolo, D., Manfredotti, C., Novara, M., Sternschulte, H., Vittone, E., 2005. Diam. Relat. Mater. 14, 669-674), we now provide evidence for the feasibility of using diamond-based cellular biosensors for multiparametrical recordings of electrical activity from living cells.

Average energy dissipated by mega-electron-volt hydrogen and helium ions per electron-hole pair generation in 4H-SiC

The pulse height response for He and H ions with energies between 1 and 6 MeV incident upon n-type 4H-SiC epitaxial Schottky diodes has been investigated. The average amount of energy, e, given up by the incident radiation to form electron-hole pair in this material was obtained by comparison with the average energy loss per pair in silicon detectors and it was found to be (7.78±0.05)eV at room temperature. This value is smaller than that foreseen by Klein’s semiempirical linear relationship between e and the semiconductor band gap.

Cathodoluminescence investigations on the Popigai, Ries, and Lappajärvi impact diamonds

Abstract Twenty impact diamond samples from the Popigai, Ries, and Lappajärvi astroblemes were analysed using cathodoluminescence (CL) at room temperature (RT). Five of the samples were further investigated at liquid nitrogen temperature (LNT). Cathodoluminescence images allowed for the discrimination of diamond from graphite, thus contributing to a better understanding of the reciprocal relationships between these carbon polymorphs and their overall textural features. Cathodoluminescence spectral measurements of the diamonds revealed emission bands and peaks located at 1.8 eV (688 nm), 2.23 eV (556 nm), 2.32 eV (534 nm), 2.39 eV (519 nm), 2.49 eV (498 nm), and 2.8-2.9 eV (443-427 nm). The bands at 2.8-2.9 eV and at 1.8 eV, observed at RT, were related respectively to vibronic levels (involved in electronic transitions), located at dislocation defects and to dislocations. Regarding the other lines, which were only visible at LNT, there may be a relationship between the peaks at 2.32 eV, 2.23 eV, and 2.39 eV, and the content of amorphous carbon phases. Some spectral features may be considered a possible signature of impact diamonds. In particular, the band at 1.8 eV, which is uncommon in terrestrial natural diamonds, and the peaks at 2.23 eV and 2.32 eV, are present in all the samples studied.

In-air broad beam ionoluminescence microscopy as a tool for rocks and stone artworks characterisation.

AbstractBroad beam ionoluminescence (IL) microscopy is a promising technique for the non-destructive characterisation of rocks and stone objects. Luminescence imaging by means of broad ion beams has been sporadically used by other authors but, to our knowledge, its potential has not yet been fully investigated, neither in geological science nor in other fields. The in-air broad beam IL microscope was developed and installed at the INFN-LABEC external microbeam in Florence. Similar to the cathodoluminescence (CL) microscope, the apparatus exploits a CCD colour camera collecting images (few square millimetres wide, with ∼10-μm spatial resolution) of the luminescence emitted by the sample hit by a defocused megaelectron volt (MeV) proton beam. The main differences with the well-established and widespread CL are the possibility of working in air (no sampling or conductive coatings required) and the possibility of combining the analysis with microbeam analysis, such as, for example, μ-IL and μ-PIXE (particle-induced X-ray emission). To show the potential of the technique, IL images of thin sections of lapis lazuli are compared with those obtained by means of an in-vacuum cold CL. An application to the study of stone artworks is also reported. This technique and apparatus will provide a valuable help for interdisciplinary applications, e.g. in geological sciences and in the cultural heritage field. FigureExperimental setup of the broad beam IL microscopy apparatus on the external microbeam line of the INFN-LABEC in Firenze during the analysis of a lapis lazuli rock

µ-XRF Analysis of Trace Elements in Lapis Lazuli-Forming Minerals for a Provenance Study.

This paper presents new developments on the provenance study of lapis lazuli started by our group in 2008: during the years a multi-technique approach has been exploited to obtain minero-petrographic characterization and creation of a database considering only rock samples of known provenance. Since the final aim of the study is to develop a method to analyze archeological findings and artworks made with lapis lazuli in a completely non-invasive way, ion beam analysis techniques were employed to trace the provenance of the raw material used for the production of artifacts. Continuing this goal and focusing the analysis on determination of more significant minero-chemical markers for the provenance study of trace elements in different minerals, the method was extended with the use of micro X-ray fluorescence (µ-XRF), to test the potential of the technique for this application. The analyzes were focused on diopside and pyrite in lapis lazuli samples of known provenance (Afghanistan, Tajikistan, and Siberia). In addition, µ-XRF data were compared with micro proton-induced X-ray emission (µ-PIXE) results to verify the agreement between the two databases and to compare the analytical performance of both techniques for this application.

Protocol for lapis lazuli provenance determination: evidence for an Afghan origin of the stones used for ancient carved artefacts kept at the Egyptian Museum of Florence (Italy)

Despite that the Badakhshan Province (Afghanistan) remains the most plausible hypothesis for the lapis lazuli used in antiquity, alternatives proposed in literature are worth to study to confirm or disprove their historical reliability. In this work, a protocol for determining the provenance of lapis lazuli rocks used for carved artefacts is described. Markers for the univocal attribution of the raw material to a source were identified analysing 45 rocks of known provenance (among which 15 georeferenced) from 4 quarry districts. To the best of our knowledge, this reference database is the widest in provenance studies on lapis lazuli. All the markers are recognisable by means of Ion Beam Analysis (IBA) techniques, in particular micro-proton-induced x-ray emission (PIXE) and micro-ionoluminescence (IL). These techniques are non-invasive and applicable in air, allowing to analyse artworks and rocks of practically any shape and dimension without sample preparation.The protocol was applied to determine the provenance of raw material used for carved lapis lazuli artefacts kept at the Egyptian Museum of Florence, the second most important Egyptian museum in Italy, second only to the museum of Turin. The collection in Florence has a great historical value and includes several lapis lazuli pendants, scarabs, small statuettes and amulets ascribable mainly to the first millennium BC. Following the protocol, 11 of these artefacts were analysed by means of IBA techniques. Results ascribe the raw material to the Afghan quarry district.

Average and core silver content of ancient-debased coins via neutron diffraction and specific gravity

The measurement of the fineness of debased ancient silver coins has proven to be a very difficult issue, which has been studied for a long time. In this paper, this subject is analysed, and the various consequences of the silver surface enrichment (SSE) are discussed exploiting the most recent investigations. A new model is proposed for the complex object that is an ancient-debased silver coin, based on the silver profiles measured on some sectioned specimens. The model is applied to a sample of 43 coins, mainly Roman victoriati, Cisalpine and Illyrian drachms (from late III to I century B.C.). The coins are investigated in two different ways: neutron diffraction (ND) and specific gravity (SG). The results of the two measurements are combined via the proposed model to provide a more complete numismatic information of the original fineness of the monetary alloy. As a result, a relation between SSE thickness and SG is derived, which, for these coinages, allows to estimate the original alloy silver content from a simple SG measurement; the same method can be used to study other debased coinages, provided that all the procedure (ND and SG) is applied.

Modification of the electrical and optical properties of single crystal diamond with focused MeV ion beams

In this paper an overview is given on recent results obtained in the framework of an Italian/Croatian collaboration aimed to explore the potential of techniques based on focused MeV ion beams to locally modify the structural, electrical and optical features of diamond. Experiments were carried out using light (H, He, C) ion beams with energies of the order of MeV, focused to micrometer-size spot and raster scanned onto the surface of monocrystalline (IIa or Ib) diamond samples. Different energies, ion species and fluences were used, in conjunction with variable thickness masks and post annealing processes, to define three-dimensional structures in diamond, whose electrical/optical/structural properties have been suitably characterized. Finite element numerical methods have been employed in the modeling of the material modification and in device design.

Performances of epitaxial diamond in the field of X-ray diagnostics

A thin epitaxial single crystal CVD (Chemical Vapour Deposited) diamond detector has been used in order to monitor the X-ray pulses coming out from a standard, portable, medical X-ray apparatus. The current pulses have been acquired and digitized in order to obtain the pulse shape, timing and dose. The obtained data were successfully compared with standard X-ray monitors like air ionization chambers and silicon detector arrays. The results strongly suggest a possible use of CVD epitaxial diamond in the field of X-ray diagnostics for energies up to 120 keV and doses up to 125 mGy and for X-ray pulse timing from 0.1 s or below and 2 s or more.

Ion Beam Analysis of Single Crystal CVD Diamond

IBIC ( Ion Beam Induced Charge ) represents a powerful method to investigate the homogeneity of the response of semiconductor nuclear detectors from the point of view of charge collection efficiency ( cce ) with a spatial resolution of few microns. Polycrystalline materials like CVD diamond displayed in the past non-uniform cce maps, in which it was easy to notice the appearance of single grains. Moreover, the presence of traps in the defective regions around the grain boundaries caused strong polarization effects which in practice impeded in many cases to get reasonable cce maps. With the availability of new homoepitaxially grown CVD diamond samples the situation is now very much improved : maps are very uniform and the non-homogeneous broadening of peaks with the consequent worsening of energy resolution is extremely reduced. In this paper, both proton and alpha microbeams of energies 3 and 4.5 MeV were used for the investigation of single crystal CVD homoepitaxial diamond, with a beam diameter spot of about 1.2 mm over scanned areas of more than 1 mm2, sampled in regions of interest from 450x450 um down to 150x150 um and below. The good spatial homogeneity together with a cce value of about 50 % made it possible to reach energy resolutions of 1.3 % FWHM, including a not negligible electrical noise. These values compare quite well with Si performances, which in the same conditions reached 0.85% FWHM. The stability and reproducibility of the detector was very good without any preliminary priming and polarization effects were reduced to a minimum. The detector was pushed in some cases up to 700 cps with apparently no cce losses and with only a slight worsening of energy resolution.