**2.1 Materials**

Lanthanum nitrate hexa-hydrate (La(NO3)3·6H2O, ≥99.9% purity), copper nitrate (Cu(No3)2, ≥99.9% purity), and iron nitrate nonahydrate (Fe(NO3)3·9H2O, ≥99.9% purity) were obtained from Alfa Aesar.
