Nanoscale water soluble self-assembled zero-valent iron: role of stabilizers in their morphology

Abstract

Self-assembled water soluble sheet-like zero-valent iron nano-composites have been prepared using a simple one-pot chemical reduction method using an aqueous solution of FeCl₃ and NaBH₄ both with and without cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). It was demonstrated that dark brownish precipitates were formed immediately after the addition of NaBH₄ into the ferric chloride solution. In the presence of CTAB and SDS, stable perfectly transparent brown colored iron sols were formed. UV-visible spectra show that both of the stabilizers (CTAB and SDS) formed a stable complex with Fe³⁺ ions. The synthesized Fe-nanoparticles were characterized using dynamic light scattering (DLS), energy dispersion X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible spectroscopy, and X-ray diffraction (XRD). The TEM results show that the average size of a zero-valent iron nano-sheet is about 144 to 625 nm in diameter. The mean particle size was estimated to be 203 nm with a standard deviation of 67 nm, which translated to a surface area of Fe-nanoparticles of ca. 2.0 m² g⁻¹. The role of surfactants and the mechanisms of nucleation and self-aggregation processes have been discussed for the first time.