Selective formation of iron oxide and oxyhydroxide nanoparticles at room temperature: Critical role of concentration of ferric nitrate

Abstract

Formation of various iron oxides and oxy-hydroxides was monitored during the hydrolysis of ferric nitrate with hydrazine monohydrate under sonication. The hydrolysis of a concentrated solution (0.05 M) of ferric nitrate solution resulted in the formation of γ-Fe2O3 as the major product and that of a lower concentration (0.005 M) formed α-FeOOH as the major product and at intermediate concentrations, γ-FeOOH or a mixture of γ-FeOOH and α-FeOOH was formed. The shape of the particles varied from spherical to acicular to rod shaped as a result of the changes in the phases formed. The as-formed γ-Fe2O3 exhibited a saturation magnetization of 65 emu/g where as the as-prepared α-FeOOH exhibited a very weak magnetic moment of around 4 emu/g.