Abstract
Nanoparticles are coated in-flight with a plasma-enhanced chemical vapor deposition (PECVD) process at ambient or elevated temperatures (up to 300 °C). Two silicon precursors, tetraethyl orthosilicate (TEOS) and hexamethyldisiloxane (HMDSO), are used to produce inorganic silica or silica-organic shells on Pt, Au and TiO2 particles. The morphology of the coated particles is examined with transmission electron microscopy (TEM) and the chemical composition is studied with Fourier-transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It is found that both the precursor and certain core materials have an influence on the coating composition, while other parameters, such as the precursor concentration, aerosol residence time and temperature, influence the morphology, but hardly the chemical composition. The coated particles are used to demonstrate simple applications, such as the modification of the surface wettability of powders and the improvement or hampering of the photocatalytic activity of titania particles.
Highlights
Coated nanoparticles, often called core-shell particles, are used in numerous applications
The morphology of the coated particles is examined with transmission electron microscopy (TEM) and the chemical composition is studied with Fourier-transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS)
Published work focused on silica coating with tetraethyl orthosilicate (TEOS) as the precursor at ambient temperature, since it allows the formation of coatings on thermally unstable materials
Summary
Often called core-shell particles, are used in numerous applications. The sol-gel process can be used for the coating of particles with silica and silica-organic (organosilica) coatings for medical applications [4]. This method is not ideal from a practical standpoint, since many commercial nanoparticles with high production volumes are produced in the gas phase (e.g., flame synthesis of TiO2). Such particles would require two separate process environments (gas and liquid) for the production of core-shell structures
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