Polysaccharide films as templates in the synthesis of hematite nanostructures with special properties

Cationic chitosan can form polyionic complexes with anionic polysaccharides such as pectin, which can be cast into films in a similar manner to that of chitosan-starch blends. We report the use of such films as templates in the synthesis of hematite nanoparticles. Mechanistically, the interaction of the iron(II) centers with the carboxyl, amino and other functional groups in the film, after their adsorption into the pores of the template is the key to subsequent synthesis of nanoparticles through calcination. The spatial separation that the specificity of interaction provides is amply made use of through controlled calcination resulting in monodisperse nanoparticles of hematite nanoparticles. This paper also highlights the specific advantages such as rhombohedral shape, ∼40 nm intensity average diameter, narrow size distribution and weak ferromagnetic properties of using the polyion films at pH 2 as templates over polysaccharides either alone or in combination in solution or as blends.

► Chitosan forms self-assembled films with pectin and blends with starch. ► Compared to chitosan-pectin solutions, films offer better size tuning. ► Films carrying adsorbed Fe2+ on calcination generate hematite nanoparticles. ► Template governs magnetic properties of synthesized hematite nanoparticles. ► Films provide for weak-ferromagnetism.