A novel type of active site at the surface of crystalline SiO₂ (a-quartz) and its possible impact on pathogenicity

Abstract

A new type of surface site, different from those previously described, which gives rise to a paramagnetic oxygen species upon adsorption of 0 2 at low temperature, has been found at the surface of crystalline quartz. This site is abundant on freshly cleaved surfaces or on chemically etched ones but absent on crystal growth faces or on samples annealed at high temperature. The abundance of this site is not related to the other surface radicals characteristic of the quartz surface originated by mechanical grinding in air. The EPR spectral features of the signal suggest an ozonide type radical 03-. The adsorption of oxygen onto quartz dusts variously treated in order to modulate their fibrogenic potential in vivo indicates that a relationship may exist between the presence of this site and quartz pathogenicity.Key words: quartz, oxygen radical species, ozonide, silicosis, EPR.DOMINIQUE COSTA, BICE FUBINI, ELIO GIAMELLO et MARCO VOLANTE. Can. J. Chern. 69, 1427 (1991).On a trouvC i la surface du quartz cristallin un nouveau site de surface, diffkrent de ceux dCcrits anterieurement, qui conduit i une espkce d'oxygkne paramagnktique lors de l'adsorption de l'oxygkne i basse tempkrature. Ce site se trouve en abondance sur les surfaces fraichement coupCes ou sur celles qui sont dCcapCes alors qu'il est absent sur les faces des cristaux en croissance ou sur des Cchantillons condensCs i haute tempirature. L'abondance de ce site n'est pas reliC aux radicaux de surface caractCristiques de la surface du quartz travaillke par broyage mkcanique dans l'air. Les caractkristiques spectrales du signal en W E suggkrent un radical du type ozonide 0 3 -. L'adsorption de l'oxyg5ne sur de la poussikre de quartz, traitke de diffCrentes faqons dans le but de moduler leur potentiel fibrogknique in vivo, indique qu'il peut exister une relation entre la prCsence de ce site et la pathonCgicitC du quartz.

Ball Milling of Silica-Based Pyroclastic Scoriae: Measurement of Mechanochemical Reactivity by Radical Scavenging

“…In view of their relevance for different areas of research, SiO 2 surface radicals have been intensely studied in the past. − In principle, the fracture of SiO 2 crystalline and amorphous phases, as well as frictional processes at their surfaces, determines the formation of at least two types of surface sites . On the one hand, the homolytic cleavage of Si–O– chemical bonds gives rise to silyl ≡Si • and siloxyl ≡Si–O • radicals.…”

“…Indeed, the formation of radicals at the surface of inorganic phases subjected to mechanical activation provides a measure of the reactivity enhancement caused by the application of impulsive mechanical stresses . Being SiO 2 the majority component of Pozzolane Rosse , the results obtained can attract significant interest from one of the most active research areas in the field of mechanochemistry. − …”

Molecular Simulation of Oxygen Reactions with Realistic Carbon and Silica Surfaces at High Temperature

“…The (≡ Si⋅) defect has been extensively studied, and has been identified on irradiated and vacuum fractured quartz and amorphous silica using Electron Spin Resonance (ESR) 17,18 . ESR in conjunction with isotope effects have been used to identify the (≡ Si-O⋅) defect on irradiated amorphous SiO 2 .…”

Pulmonary toxicity following acute coexposures to diesel particulate matter and α-quartz crystalline silica in the Sprague-Dawley rat

“…The mechanism directing the toxicity of silica particles in the lung still remains ambiguous but is thought to stem from multiple attributes relating to the crystalline structure of silica and its reactivity based on either surface charge or silicon-containing groups present on the surface of silica due to disruptions made to its structure during crushing, grinding and drilling (Castranova & Vallyathan, 2000). In conjunction with this, reactive oxygen/nitrogen species (ROS/RNS) associated with the particles themselves or as products of the respiratory burst following activation of phagocytes have been shown to drive a prolonged state of inflammation in the lungs (Blackford et al, 1994; Costa et al, 1991; Vallyathan et al, 1992, 1995). Studies investigating pulmonary toxicity of diesel demonstrate DPM-induced inflammation and oxidative stress as well (Bayram et al, 1998; Kim et al, 2016; Ohtoshi et al, 1998; Sagai et al, 1993, 1996); however, unlike silica, DPM exposure does not have the same propensity to cause fibrosis.…”