*2.1. Synthesis of SiO2@TiO2 Coating Coupled with Sonochemistry*

For TiO2 sol production, titanium Iso-propoxide (97%, Sigma Aldrich, St. Louis, MO, USA) was added dropwise into an organic solvent (isopropyl alcohol, 99%, Sigma Aldrich), previously stirred under an inert nitrogen atmosphere for 5 min.

For SiO2 synthesis, sonotrode equipment (Hielscher Ultrasound Technology UP200Ht, Teltow, Germany) was used working at 100% cavitation and 20% amplitude. A solution of distillated water, absolute ethyl alcohol and oxalic acid, in a 5/5/0.1 molar relation was prepared and stirred sonochemically for 15 min. Afterwards, tetraethyl orthosilicate was added dropwise and the mixture was stirred sonochemically for 3 min. Next, polydimethylsiloxane was added dropwise and continuously stirred for 3 min.

Finally, the titanium dioxide sol and the silicon dioxide sol were mixed. Beforehand, sonotrode working conditions were modified from the initial conditions to 100% cavitation and 60% amplitude. Immediately after mixing, 10 mL of distilled water was added and mixed continuously using sonotrode conditions for 20 min. The resultant mixture was applied on glass and mortar surfaces and left to dry at room temperature.
