Bin Liu
Quartz dust exposure in the workplace is linked to fatal diseases. A wide range of micrometric to nanometric particles characterize mechanically fractured quartz dust. Due to the strong electrostatic adhesion forces that prevent the nanofraction from being isolated, little is known about how this nanometric fraction affects quartz's overall toxicity. Additionally, fractured silica dust has unique surface characteristics, such as nearly free silanols (NFS), which give quartz a membranolytic activity. Bottom-up methods can be used to make nanoquartz, but the surface chemistry of these crystals is very different from that of fracturing-produced nanoparticles. We present a top-down milling method for producing nanometric quartz with the same toxic surface properties as fractured quartz. By combining the dry and wet stages of ball milling, dispersing the material with water and varying the milling times and rotational speeds, the process was made more efficient. It was possible to obtain nanoquartz with a strong propensity to aggregate into sub micrometric sizes. Surfactants or simulated body fluids had no effect on the deagglomeration. A bimodal crystallite domain size and partial lattice amorphization were observed. Coherence with previous toxicological data was indicated by a moderate membranolytic activity that was correlated with the number of NFS. It was possible to obtain a membranolytic nanoquartz for use in toxicological studies.
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