Chemical variability of artificial stone powders in relation to their health effects

The occurrence of highly severe silica-related diseases among the resin- and silica-based artificial stone workers was claimed, associated to an extremely short latency. High levels of exposure and intrinsic properties of AS are thought to modulate the development of silicosis and auto-immune diseases. This study compares parent materials and processed dusts, to shed light on changes of AS occurring in the manufacturing process, through an XRF, EPR and XAS investigation. We point out the extremely wide variability of the materials, the occurrence of chemical signatures impressed by the processing techniques, and the unprecedented generation of stable radicals associated to the lysis of the Si-O chemical bond inside the resin coated respirable crystalline silica. These results suggest that the AS processing in industrial stone workshops can create respirable dusts with peculiar physical and chemical properties, to be correlated to the observed clinical evidences

Synthesis, characterization and biological activity of novel Cu(II) complexes of 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehy de-4N-substituted thiosemicarbazones

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained

Spin concentration in a possible ESR dosimeter: An electron spin echo study on X-irradiated ammonium tartrate

Several single crystals and powder samples of ammonium tartrate, recently proposed as a possible ESR dosimeter, have been X-irradiated with different doses. The total radical concentration has been determined by quantitative cw ESR, by comparison with a standard. The samples have been studied by electron spin echo spectroscopy. The two-pulse echo decay has been obtained and simulated by a single exponential function for different values of the microwave power of the pulses and for different pulse lengths. The dependence of the phase memory time TM on the microwave power has been exploited to get information on the contribution of the instantaneous diffusion to spin dephasing. At room temperature in the range of radical concentrations of 1E18-1E19 spins/cm3 the instantaneous diffusion is the dominant spin dephasing mechanism. The linear dependence of the instantaneous diffusion on the total concentration of the radicals is in agreement with the theory. From the latter result we conclude that the average radical-radical distance corresponds to a random distribution of the radicals in the matrix. A simple method of measuring the radical concentration by the ESE decays in powder samples of irradiated ammonium tartrate is described

Characterisation of the Fe(III):H+ Defect Centre in Natural Amethyst

A natural single crystal of amethyst was investigated by means of continuous-wave and pulsed Electron Paramagnetic Resonance (EPR), with the aim of structurally characterizing the substitutional S2 Fe(III):H+ centre. In this centre, Fe(III) replaces Si(IV) in the tetrahedral site, whereas H+ is coupled to Fe(III) to maintain the charge balance. The spectroscopic investigations, mainly the interpretation of the Electron Spin Echo Envelope Modulation, allowed a detailed localisation of the proton to be obtained. H+ occurs in the channels crossing the crystal parallel to the crystallographic c axis, in a largely eccentric position. The Fe(III)-H+ distance, evaluated in 2.70\ua0\uc5, is found associated with a non-negligible isotropic hyperfine coupling, which can be linked to the relative stability of the S2 centre in natural amethyst

An insight into the metal coordination and spectroscopic properties of artistic Fe and Fe/Cu logwood inks

Fe- and Fe/Cu-based logwood inkswere synthesized following recipes in nineteenth and early twentieth century manuals andwere characterized by EPR, ESI-MS, FTIR, and Raman spectroscopies. Thismulti-technique approach allowed us to shed light on the structures of the complexes responsible for the inks\u2019 colors and to obtain vibrational signatures that can be used to identify the different inks in works of art and in historic documents. Information on the nature and chemical properties of the complexes formed between a dye and a mordant is important as these determine, at least in part, their lightfastness. EPR permitted to determine the coordination environment of the metallic ions. The results of the ESI-MS analysis demonstrated, for the first time, the breakdown of the hematein molecule during the ink preparation, and that the colorants are formed by the complexation of themetallic ions by hematein breakdown products,mainly catechol and/or bicyclic compounds. The FTIR spectra obtainedwere found to be dominated by bands due to the bindingmediumand sulfates used as reagents. The Raman analysis showed that the characteristic features for the different inks studied depend on the historic recipe used, attesting to the challenges that their identification and characterization inworks of art present. In the Raman spectra of the inks applied on paper, broadening of bands in the 750\u2013400 cm 121 range are observed when compared to the spectra of the inks\u2019 powders, possibly due to the interaction of the compoundswith the cellulose in the substrate

One-dimensional clusters of 16-doxyl-stearate radicals in organic nanochannelsas studied by electron paramagnetic resonance (EPR)

In this paper we report a variable temperature EPR investigation on auto-assembling inclusion compounds of tris(o-phenylenedioxy)cyclotriphosphazene (TPP), the nitroxide radical methyl ester of the 16-doxyl-stearic acid (16-dox), and diamagnetic co-guests of various polarities. By playing with the nature of the co-guest and the concentration of the radical we obtained radicals isolated, or in 1D clusters. Local order, dynamics and orientation of the guests have been obtained by simulations of the spectra of spin-carrying guests envisaged as probes. For the simulations, intra-channel and inter-channel radical pairs and trimers magnetic interactions have been modellized. The interest of similar compounds for 1D magnetic materials is discussed