Luminescent polymer films from simple processing of coronene and europium precursors in water

We describe the preparation and optical characterisation of a coronene tetracarboxylate salt (CS) in polyvinyl alcohol (PVA) thin film solutions processed from water, neat or mixed with varying ratios of a europium tris(hexafluoroacetylacetoanto) diaquo complex [Eu(hfac)₃(H ₂O)₂]. Neat CS-PVA showed not only well-defined fluorescence peaks but also a long-lived phosphorescence emission, persisting for more than 1 second. Interaction between the CS and Eu^III molecules, mediated by means of carboxylate coordination to the Eu ^III, was attained by simple incorporation into the PVA polymer matrix and resulted in energy transfer from the coronone antenna to the europium centre. Under various blend ratios of CS and the Eu^III complex, total photoluminescence quantum yields of typically around 30 % were achieved. The straightforward processing of this type of self-assembled chromophore-lanthanide system into a luminescent polymer film offers potential for application to other chromophores, lanthanides and polymers.