Tuning the formation and structural polymorphs of FeOOH nanoparticles via iron precursor concentration

Abstract The influence of iron precursor concentration on the formation and structure of FeOOH nanoparticles synthesized via chemical hydrolysis reaction was investigated. Ferric chloride hexahydrate at varying concentrations (0.2 M, 1 M, and 2 M) was employed, with NaOH used as the hydrolyzing agent to systematically evaluate how precursor concentration affects nanoparticle properties. Characterization techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), ATR-FTIR spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA), revealed that all synthesis conditions produced ultra-small FeOOH particles. Notably, lower precursor concentrations favored the formation of goethite (α-FeOOH), while higher concentrations led to syntheses of akaganeite (β-FeOOH), attributable to chloride ion effect. The size and colloidal parameters showed minor variation, but the zeta potential shifted from negative to positive with increasing precursor concentration, indicating changes in surface charge. Thermal stability analyses confirmed dehydration and phase transformation behaviors consistent with the specific polymorphs. These findings offer valuable insights into tailoring FeOOH nanoparticles synthesis for controlled polymorph production, with specific applications.