Sol-gel synthesis and characterization of magnetic TiO2 microspheres

We tried to prepare magnetic TiO2 microspheres as thermoseeds for hyperthermia of cancer by a sol–gel process from titanium tetraisopropoxide (TTIP) in a water-in-oil emulsion. The microspheres were prepared by the addition of diethanolamine (DEA) as stabilizer, methanol (CH3OH) as dispersant and colloidal γ-Fe2O3 nanoparticles as origin of magnetization. The γ-Fe2O3 nanoparticles were prepared by an oxidation–precipitation method in FeCl2–NaNO3–NaOH system. The diameter of microsphere was controlled by optimizing preparation conditions, i.e., molecular ratio of reactants and stirring speed. Mono-dispersed magnetic TiO2 microspheres 10–30 µm in diameter were sucessfully obtained by adding a certain amount of water phase with the molar ratio of TTIP/DEA/CH3OH/H2O = 1:1.7:7:22 into kerosene with surfactant (sorbitan monooleate/sorbitan monostearate = 3:1 in weight ratio) 16 wt % of the total amount of oil phase. They contained up to 26.7 wt % γ-Fe2O3 and their saturation magnetization and coercive force were 20.4 Am2/kg and 10 kA/m, respectively.