Preparation of nano-needle hematite particles in solution

Uniform nano-needle hematite particles were prepared by forced hydrolysis, namely, by reflux of Fe(NO3)3 solution in the presence of organic chelating agent 1-hydroxyethy1-1,1′-diphosphonic acid (HEDP) and HNO3. Nano-needle hematite particles with a length of 90–100 nm and axial ratio of 9–12 were obtained. The effect of the concentration of HEDP and HNO3 on the morphology of the mematite particles was investigated by transmission electron microscopy (TEM). From the morphology of the particles extracted at different stages of hydrolysis, we think the amount of positive charges on the primary particle surface is crucial for the formation of nano-needle particles.