G. Panczer

Mineral maturity and crystallinity index are distinct characteristics of bone mineral

The purpose of this study was to test the hypothesis that mineral maturity and crystallinity index are two different characteristics of bone mineral. To this end, Fourier transform infrared microspectroscopy (FTIRM) was used. To test our hypothesis, synthetic apatites and human bone samples were used for the validation of the two parameters using FTIRM. Iliac crest samples from seven human controls and two with skeletal fluorosis were analyzed at the bone structural unit (BSU) level by FTIRM on sectionsxa02–4xa0μm thick. Mineral maturity and crystallinity index were highly correlated in synthetic apatites but poorly correlated in normal human bone. In skeletal fluorosis, crystallinity index was increased and maturity decreased, supporting the fact of separate measurement of these two parameters. Moreover, results obtained in fluorosis suggested that mineral characteristics can be modified independently of bone remodeling. In conclusion, mineral maturity and crystallinity index are two different parameters measured separately by FTIRM and offering new perspectives to assess bone mineral traits in osteoporosis.

Long-term in vivo clearance of gadolinium-based AGuIX nanoparticles and their biocompatibility after systemic injection.

We previously reported the synthesis of gadolinium-based nanoparticles (NPs) denoted AGuIX (activation and guiding of irradiation by X-ray) NPs and demonstrated their potential as an MRI contrast agent and their efficacy as radiosensitizing particles during X-ray cancer treatment. Here we focus on the elimination kinetics of AGuIX NPs from the subcellular to whole-organ scale using original and complementary methods such as laser-induced breakdown spectroscopy (LIBS), intravital two-photon microscopy, inductively coupled plasma optical emission spectrometry (ICP-OES), transmission electron microscopy (TEM), and electrospray ionization mass spectrometry (ESI-MS). This combination of techniques allows the exact mechanism of AGuIX NPs elimination to be elucidated, including their retention in proximal tubules and their excretion as degraded or native NPs. Finally, we demonstrated that systemic AGuIX NP administration induced moderate and transient effects on renal function. These results provide useful and promising preclinical information concerning the safety of theranostic AGuIX NPs.

Influence of external β-irradiation in oxide glasses

Abstract Radiation effects in oxide glass as external β-irradiation has been investigated by Raman spectroscopy, Cr3+ luminescence and EPR spectroscopy to analyze microstructure evolution. Comparison between simplified and complex glasses (high-level nuclear waste glass analogue) was undertaken. Migration and segregation of sodium have been confirmed on simplified irradiated glasses by a polymerization increase and dissolved oxygen presence. Densification under irradiation has also been demonstrated with the increase of three-membered silicate rings in silicate glass and the decrease of the average Si–O–Si angle in the borosilicate glass. In both glasses, Cr3+ crystal field was increased, suggesting a Cr–O length decrease. The complex borosilicate glass responds differently: densification effect and Na segregation were not detected. Under β-irradiation, electron-trapping processes on Cr6+ occurred, forming Cr4+ and Cr5+ species.

Laser-induced time-resolved luminescence spectroscopy of minerals: a powerful tool for studying the nature of emission centres

The paper summarises new data and results referring to the characterization of the nature of luminescence centres in minerals that were published during the last 8xa0years. Besides well-established luminescence centres, such as Mn2+, Fe3+, Cr3+, divalent and trivalent rare-earth elements, S2−, and Pb2+, several other centres were proposed and substantiated, such as Mn3+, Mn4+, V2+, Ni2+, Pb+, Mn3+, Sb3+, Tl+, and radiation-induced centres. Also, a relatively new type of luminescence excitation mechanism is discussed briefly, namely plasma-induced luminescence. Here, the emission takes place when the matrix, where the formation of plasma is caused by irradiation with a beam of laser light, is capable to luminescence and contains luminescence centres.

From optical spectroscopy to a concentration quenching model and a theoretical approach to laser optimization for Yb3+-doped YLiF4 crystals

A spectroscopic characterization was carried out to identify crystal-field levels for magnetic-dipole transitions of Yb3+ ions located in the Y3+ dodecahedral S4 crystallographic site in YLiF4 (YLF) crystals which were grown either by the Czochralski technique or by the laser heated pedestal growth (LHPG) technique. The concentration dependence of the measured decay time of the 2F5/2 excited level of Yb3+ was analysed in order to understand relevant concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to trace rare-earth impurities (Er3+, Tm3+) has been observed over the visible region and interpreted by a limited-diffusion process within the Yb3+ doping ion subsystem to the impurities. The principal parameters useful for a theoretical approach for potential laser applications of Yb3+-doped YLiF4 crystals have also been given.

Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

A comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320xa0keV Ar+ ions at fluencies ranging from 1xa0×xa01012 to 2xa0×xa01016 cm−2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013xa0cm−2 and second at about 1015xa0cm−2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials.

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1xa0to 24 hrxa0after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 μm. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:xa0elemental, molecular, or cellular.

Luminescent centres in pezzottaite, CsBe2LiAl2Si6O18

Pezzottaite, CsBe 2 LiAl 2 Si 6 O 18 , is a rare new pink mineral found in central Madagascar and Afghanistan, exhibiting a beryl-like trigonal reduced symmetry ( R 3 c ). Numerous data on its optical properties, Raman, IR, absorption spectra as well LIBS data are available, while it is described as a non-luminescent mineral under UV light. However, pezzottaite shows several laser-induced red emissions and a particular unusual blue luminescence. LIBS analysis reveals the presence of Sc, Ca, Sr, Na, K and Rb as substituted trace elements, but these elements cannot be considered as the centres responsible for the observed emissions. Time-resolved analyses under different excitations (266, 355, 514 and 532 nm) at room and liquid nitrogen temperatures allow the identification of Fe 3+ (730 nm) and Cr 3+ (699 nm) as red emitting centres, while Tl + is considered responsible for the blue fluorescence (420–425 nm). Photoluminescence proves effective for identifying the presence of these luminescent trace elements even below the LIBS detection limit (a few ppm), but without yet attaining a quantitative resolution.

Exploration of megapixel hyperspectral LIBS images using principal component analysis

Laser-Induced Breakdown Spectroscopy (LIBS) has achieved promising performance as an elemental imaging technology, and considerable progress has been achieved in the development of LIBS over the last several years, which has led to great interest in the use of LIBS in various fields of applications. LIBS is a highly attractive technology that is distinguished by its table top instrumentation, speed of operation, and operation in ambient atmosphere, able to produce megapixel multi-elemental images with micrometric resolution (10 μm) and ppm-scale sensitivity. However, the points that limit the development of LIBS are undeniably the expertise and the time required to extract a relevant signal from the LIBS dataset. The complexity of the emission spectra (e.g., elemental responses, structure of the baseline), the high dynamic range of measurement (i.e., possibility to image major to trace elements), and the large number of spectra to process require new data analysis strategies. Such new strategies are particularly critical for multi-phase materials. In this paper, we report a new methodology based on the well-known Principal Component Analysis (PCA) approach for the multivariate hyperspectral analysis of LIBS images. The proposed methodology is designed for large, raw, and potentially complex series of LIBS spectra, that allows various and exhaustive levels of information to be extracted (including the characterization of mineral phases, assessment of the measurement and identification of isolated elements) and facilitates the manipulation of such hyperspectral datasets.

New development in time-resolved micro-photoluminescence spectroscopy of heterogeneous natural and synthetic inorganic materials

Abstract Inorganic materials with optical properties and especially naturally multidoped geomaterials often present micro-scale heterogeneities (growth zoning, inclusions, devitrification, micro-phasesxa0…). Identification and optical effects of such heterogeneities have more and more to be taken into account. To reach the microscopic scale during photoluminescence studies, a microscope has been modified in order to allow pulsed laser injection (from UV to visible), beam focus with micro-scale resolution on the sample, as well as collection of micro- fluorescence. Such equipment allows now undertaking time-resolved measurements of micro-phases. Applications on phosphors, devitrified glass and geomaterials are presented.