Nanopartículas de ouro suportadas em núcleos de óxido de ferro magnético revestidos por sílica

Abstract

Magnetic nanoparticles (NPMs), such as magnetite and maghemite, have aroused great technological interest due to the ability to adapt according to the purpose for which they will be employed. The possibility of coating with several types of binders, such as silica, would be one of its characteristics of interest for technological applications. Silica was chosen due to its low cost, great availability and to favor the dispersion of the magnetic nanoparticles in liquid medium, chemically functionalizing the surface, which makes the magnetic core more stable. In addition to the functionalization of magnetic materials, silica can still be used as support for other nanomaterials. Nanoparticulate gold is one of the potential materials to be supported by silica. Gold catalysts when supported and nanodispersed have the advantage of high activity and selectivity in various reactions at low temperatures. Compared to other noble metals such as platinum, palladium, titanium, rhodium, gold presents lower cost and greater stability in the trade balance making it more feasible for different applications. The magnetic iron oxide will be synthesized through the thermal decomposition method and its functionalization will be given by means of a sol-gel solution from the solubilized fumed silica. Subsequently gold nanoparticles were supported. The gold snanoparticles were synthesized from a solution of 1% HAuCl4 by the sol-gold method. The following materials were synthesized MagSili (50-50) 1st filtration (suspended material) and MagSili (50-50) 2nd filtration (decanted material) where the values in parentheses represent the ratios of the magnetic iron oxide and silica respectively. Tests of catalytic activity using methylene blue as a model molecule and hydrogen peroxide (H2O2) decomposition using the pressure equalization system were performed in order to evaluate the catalytic efficiency of the materials. The structural characterization was done by infrared, X-ray fluorescence (TXRF) and scanning electron microscopy (SEM). Thus, the objective of the present work was to coat a magnetic iron oxide with silica, to support gold nanoparticles which acted as catalysts in the process of methylene blue discoloration and decomposition of hydrogen peroxide.