Bar-shaped nanoparticles of iron(II) hydroxide

Formation of elongated nanoparticles was observed when was precipitated from solutions containing excess of Fe²⁺. The average diameter of the particles was 23 nm; the length to diameter ratio was up to 14. This shape was an unexpected phenomenon because bar- or needle-like nanoparticles have been earlier reported only for Fe(III)-based materials. Chemical analysis revealed Fe(OH)₂ nature of the obtained particles. In addition, this conclusion was verified with a new simple method for quantitative evaluation of the particle morphology. Application of this method to the mixed samples allowed to distinguish between the two different compounds and to attribute different morphologies to Fe(OH)₂ or Results indicate that bars are frequent shapes of nano-sized iron oxides/hydroxides.