Facile and controllable synthesis of iron nanoparticles directed by montmorillonite and polyvinylpyrrolidone

Porous host-hybridized metal nanoparticles are of great potential in sorption and catalysis related processes. The objective of this study was to synthesize property-controllable iron nanoparticles in montmorillonite and polyvinylpyrrolidone involved borohydride reduction system. In this system, mixed primary and secondary iron nanoparticles were readily generated. These resulting nanoparticles displayed an a-Fe@iron-oxide@polyvinylpyrrolidone core-double-shell architecture, in which the oxide shells protect the alpha-Fe cores from thorough oxidation in essential. In hybridization process, a polymer barrier was developed on the clay mineral surfaces. Due to the barrier-related steric hindrances and/or the alkaline pH-derived electrostatic repulsions, the clay mineral particles built a card-house flocculation structure, which can be converted to a semi-card-house form in dry products by suitable washing and drying treatments. The binding of the polymer to the iron and clay mineral surfaces would be mainly through hydrogen bonding. In general, the card-house pores and polymer layers made the hybridized iron nanoparticles much smaller and more dispersed than their bare counterparts. Specifically, by adjusting the molar mass and concentration of the polymer and the reductant amount, the hybridized iron nanoparticles could be further optimized. This synthesis route is carried out in situ under ambient temperature and atmosphere, greatly simplifying the process for iron nanoparticles preparation.