Sonochemical Synthesis Of Fe₃O₄ Nanocrystal

With the rapid development of ultrasonic equipments and the research about new material synthesis, ultrasound has been widely used in chemical synthesis, materials science, biological and chemical engineering. Due to the special physical and chemical effects caused by ultrasound in liquid, it can be deemed as a new method for materials synthesis, typically for nano-materials fabrication. In this work, sonochemical method was applied to fabricate Fe3O4 nanocrystals. The effect of reaction conditions on the strucure and the morphology of products and their magnetic properties were investigated.The as-prepared Fe3O4 nanocrystals were used as core to fabricate recyclable core-shell structure Fe3O4/SiO2/TiO2 photocatalysta and the content of TiO2 was changed to optimize their photocatalytic property.Two-demisional plate-like Fe3O4 nanocrystals were synthesized by the reaction of Fe2+and NaOH under ultrasonic irradiation. The structure of the products was examined and the possible growth mechanism was discussed. Fe(OH)2 with plate-like morphology was formed by the reaction of Fe2+andexcessive OH". Thefinal products inherit its plate morphology by oxidization under ultrasonic irradiation to convert into magnetite. When Fe2+and Fe3+both acted with alkali solution under ultrasonic irradiation and single-crystalline Fe3O4 nanoparticles with uniform size were formed.The as-prepared products had the smallest size when the ratio of Fe2+and Fe3+ was 1:2. Changing the ratio of cations and raising the reaction temperature would accelerate the ripen process of Fe3O4, leading to a large average crystal size.The core-shell structured photocatalysts were prepared using above-prepared Fe3O4 nanocrystals as core and the shells of SiO2 and TiO2 were consequently coated on them by sol-gel method, the property of the photocatalysts was evaluated by decomposing RhB. The photocatalytic properties had been optimized by turning the fraction of TiO2.The results indicated that the catalyst with Fe3O4 nanoplate as core had better degradation performancecompared with those having Fe3O4 nanoparticles core. The performance of catalysts was improved with higher TiO2 content under UV irradiation. While too high content of TiO2wouldreduce the pore distribution on the surface and decrease the specific surface area.