Synthesis and Photo-Catalytic Activity of Nanoparticles with Structure "Core/Shell": Fe3O4@SiO2@TiO2

D Chenchik,J Jandosov

doi:10.18321/ectj651

Abstract

In this work, the nanosized magnetic Fe3O4@SiO2@TiO2 photocatalyst was prepared by sol-gel methods. First the nuclei of magnetite nanoparticles were prepared by co-precipitation of iron (II&III) salts solutions. Secondly, the magnetite nanoparticles were dispersed in ethanol using sonication, and solutions of both ammonia and tetraethoxysilane were added to the suspension under intense stirring, since it was suggested that the introduction of an intermediate passive SiO2 layer between the Fe3O4 and TiO2 phases inhibits the direct electrical contact and hence prevents the photodissolution of the magnetite phase and deterioration of the surface photocatalytic properties. Finally, solution of tetrabutoxytitanium was added dropwise to the mixture of Fe3O4@SiO2 nanoparticles under sonication & intense stirring. The resulting particles were separated using a magnet, washed and dried to constant weight, the yield was 70%. The photocatalytic activity of Fe3O4@ SiO2@TiO2 nanoparticles was investigated by photodegradation of methyl orange in aqueous solution under UV light irradiation. The photodegradation dynamics revealed that even though the oxidation rate decreases over time, about 90% of methyl orange is oxidized during the first 35 min.

Highlights

Since the beginning of the titanium dioxide (TiO2) industrial production in early 20th century, it has been widely used as a pigment and filler [1] in sunscreens, paints, ointments, toothpastes, etc [2]
In 1972 Fujishima and Honda discovered the phenomenon of photocatalytic splitting of water under ultraviolet radiation on an electrode coated with titanium dioxide [3]
One of the promising practical applications of TiO2 and TiO2-based nanocomposites is purification of water by way of oxidation reaction of organic pollutants with peroxide anion-radicals formed under ultraviolet radiation in the process of photocatalysis [3]

Summary

Introduction

Since the beginning of the titanium dioxide (TiO2) industrial production in early 20th century, it has been widely used as a pigment and filler [1] in sunscreens, paints, ointments, toothpastes, etc [2]. One of the promising practical applications of TiO2 and TiO2-based nanocomposites is purification of water by way of oxidation reaction (photodegradation) of organic pollutants with peroxide anion-radicals formed under ultraviolet radiation in the process of photocatalysis [3]. The direct contact between the magnetic particles and photocatalysts lads to the photogenerated electron–hole recombination and the photodissolution of the Fe3O4 magnetic particles under the UV-irradiation. The photogenerated holes can oxidize neither the organicmolecules nor the water adsorbed to hydroxyl radicals, the direct contact core/shell catalysts have low activities[7]. To overcome the drawbacks of the low activities and the photodissolution, Cao and Chen pioneered a three-component magnetic photocatalyst of c-Fe2O3@SiO2@TiO2 in 1999, in which c-Fe2O3 was used as the magnetic core, SiO2 interlayer as insulator, and TiO2 as photocatalytic shell [8]. The photocatalysts can be immobilized with various metals to obtain a synergistic effect in enhancing their effectiveness [9]

Experimental part

Results and discussion

Conclusion