Abstract: The present invention relates to a formulation for preparing an optical metal oxide layer, the formulation comprising polyoxometalates (POMs) complexed to metal oxide nanoparticles (NPs); a method for preparing an optical metal oxide layer using said formulation; and an optical device comprising said optical metal oxide layer.

Abstract: Complexes of polyoxometalate (POM) cluster anions and nanoparticle (NP) cores, are disclosed, featuring inherent thermodynamic stability at least due to covalent bonds, which attach the POMs to the NP cores. The nanoparticles comprise a plurality of crystalline, polycrystalline or amorphous metal-oxide, metal oxyhydroxide and/or metal hydroxide compounds. The POM and NP, each independently, may comprise one, two, three or more different metal cations, particularly transition or main group metal cations. These complexes are highly soluble in water and inherently stable to oxidation and hydrolysis in a broad pH range. As such, the complexes are useful, inert alia, as improved soluble water-oxidation catalysts and stabilizers of metastable crystals.