Polymer-Hematite Nanocomposites: Templating Effect of Commercial Ion-Exchangers in the Growth of Size-Controlled Iron Oxide Nanoparticles

The commercially available ion-exchange resin Amberlite IR120 has been used as the stabilizing agent for the preparation of a size controlled nanostructured hematite phase. The employed synthetic approach, based on the loading of Fe³⁺ by ion exchange and the subsequent treatment with an aqueous base solution, produces a nanocomposite material with a remarkably high content of oxide nanoparticles (iron content = 18.8% w/w, corresponding to 24.9% w/w of Fe₂O₃). Scanning electron microscopy and energy dispersive X-ray spectroscopy investigation show that the iron distribution is egg-like and parallels the distribution of the sulfonic groups of the ion-exchanger. Transmission electron microscopy characterization reveals that the size of the ferric oxide nanoparticles in the nanocomposites is narrowly distributed in the 4–6 nm range and that it is the same after the first and the fifth ion-exchange-precipitation cycle. Selected area Electron Diffraction (SAED) analysis of the nanostructured oxide after five ion-exchange-precipitation cycles indicates that it is hematite with a distorted structure.