The effect of metal ligands on the adsorption of metal coordination complexes on polystyrene nano-beads

Nanostructured metal oxides showing geometrically controlled shape are often shaped by the calcination of selected metal coordination complexes adsorbed on sacrificial polystyrene beads (PSB) in aqueous suspensions. The design of an alternative, more sustainable, method to guide the adsorption of titanium oxide precursors on sacrificial carriers into specific morphologies has been explored as part of a global strategy to produce new nano-engineered metal oxides. Among various titanium coordination complexes, ligands like β-diketones or β-ketoesters have been often investigated due to their chelating and stabilizing effect on the titanium. In particular, titanium coordination complexes like Titanium(IV)bis(ammonium lactato) dihydroxide and titanium diisopropoxide bis(acetylacetonate) have been largely applied in the fabrication of nanostructured titanium oxide films in last-generation photovoltaic devices. To date the driving force for the spontaneous adsorption of precursors on non-modified PSB had not been investigated. We propose that a major driver is the interaction between the polystyrene surface of PSB and the molecular structure of the organic ligands of the metal-complexes. The proposed mechanism is supported by proton nuclear magnetic resonance spectroscopy of the starting colloidal suspensions and by electron microscopy of the resulting nanostructured metal oxides.