**3. Materials and Methods**

The following reagents were used as received and without any further treatment: Cu2O powder (Fluka AG, in Sigma-Aldrich, Steinheim, Germany), In2O3 powder (Sigma-Aldrich, Steinheim, Germany), Fe2O3 powder (Sigma-Aldrich, Steinheim, Germany), anhydrous CuSO4 (BDH Chemicals ltd, Poole, England), In(NO3)3xH2O (Sigma-Aldrich, Steinheim, Germany), FeCl3 (Carlo Erba Reagents srl, Milano, Italy), NaOH pellets (Fluka AG in Sigma Aldrich, Steinheim, Germany), and L-Ascorbic Acid (Alfa Aesar GmbH, Karlsruhe, Germany). Deionized water was used for all syntheses in which a solvent was required.
