Formation and Structure of a Tin-Iron Oxide Solid-State System with Potential Applications in Carbon Monoxide Sensing through the Use of Cyanogel Chemistry

The reaction of aqueous solutions of SnCl₄·5H₂O and K₄Fe(CN)₆ in a 2/1 Sn/Fe atomic ratio results in a hydrogelled polymeric material, characterized by bridging cyanides between the central metals of the adducts. Materials of this type have previously been noted upon reaction of PdCl₄^2- with cyanometalates in aqueous solution and have been referred to as cyanogels. Dehydration of Sn/Fe cyanogels results in xerogels that maintain the initial polymeric structure of the hydrogel. Thermal processing of such gels under an air atmosphere at 900 °C produces a solid homogeneous mixture of macrocrystalline SnO₂ and Fe₂O₃.