*4.1. Materials*

Titania P25 (TiO2) with a mixture of anatase (80%) and rutile (20%) crystal phase, and a specific surface area of 50.1 m<sup>2</sup> g<sup>−</sup>1, was kindly provided by Evonik, Essen, Germany. Silver nitrate (99%, Sigma Aldrich Chemie GmbH, München, Germany), sodium hydroxide pellets (99%, Carl Roth, Karlsruhe, Germany), methanol (99.9%, Carl Roth), and methylene blue (Sigma Aldrich) were used without further purification. Deionized water with a resistivity of 18.2 MΩ·cm was obtained from a Sartorius Arium 611 device (Sartorius Göttingen, Germany) and used for the preparation of all aqueous solutions and suspensions.
