Nearly free surface silanols are the critical molecular moieties that initiate the toxicity of silica particles

Inhalation of silica particles can induce inflammatory lung reactions that lead to silicosis and/or lung cancer when the particles are biopersistent. This toxic activity of silica dusts is extremely variable depending on their source and preparation methods. The exact molecular moiety that explains and predicts this variable toxicity of silica remains elusive. Here, we have identified a unique subfamily of silanols as the major determinant of silica particle toxicity. This population of “nearly free silanols” (NFS) appears on the surface of quartz particles upon fracture and can be modulated by thermal treatments. Density functional theory calculations indicates that NFS locate at an intersilanol distance of 4.00 to 6.00 Å and form weak mutual interactions. Thus, NFS could act as an energetically favorable moiety at the surface of silica for establishing interactions with cell membrane components to initiate toxicity. With ad hoc prepared model quartz particles enriched or depleted in NFS, we demonstrate that NFS drive toxicity, including membranolysis, in vitro proinflammatory activity, and lung inflammation. The toxic activity of NFS is confirmed with pyrogenic and vitreous amorphous silica particles, and industrial quartz samples with noncontrolled surfaces. Our results identify the missing key molecular moieties of the silica surface that initiate interactions with cell membranes, leading to pathological outcomes. NFS may explain other important interfacial processes involving silica particles

Few-Layered MoS2 Nanoparticles Covering Anatase TiO2 Nanosheets: Comparison between Ex Situ and In Situ Synthesis Approaches

MoS2/TiO2 nanostructures made of MoS2 nanoparticles covering TiO2 nanosheets have been synthesized, either via ex situ or in situ approaches. The morphology and structure of the MoS2/TiO2 hybrid nanostructures have been investigated and imaged by means of X-ray diffraction (XRD) analysis and high-resolution transmission electron microscopy (HRTEM), while the vibrational and optical properties have been investigated by Raman, Fourier-transform infrared (FTIR), and UV−visible (UV–vis) spectroscopies. Different stacking levels and MoS2 nanosheets distribution on TiO2 nanosheets have been carefully evaluated from HRTEM images. Surface sites on the main exposed faces of both materials have been established by means of in situ FTIR spectra of CO probe molecule adsorption. The results of the ex situ and in situ approaches are compared to underline the role of the synthesis processes affecting the morphology and structure of MoS2 nanosheets, such as curvature, surface defects, and stacking order. It will be shown that as a result of the in situ approach, the reactivity of the TiO2 nanosheets and hence, in turn, the MoS2–TiO2 nanosheets interaction are modified