3.4. Plausible mechanism for the SSL protective Al(OH)3 coating removal
To explain the quality of Al(OH)3 coating and a mechanism of its disruption, zeta potential measurements of TiO2 nanoparticles with an Al(OH)3 layer (MT 500SA) and pure rutile TiO2 to mimic the main constituents of SSL but without the organic layer were performed for comparison (Fig. SI 6). In addition, the effect of various SPW ingredients on zeta potential of SSL at the original pH and pH 6 is given in Table SI 2. Moreover, zeta potential of rutile TiO2 and MT 500SA nanoparticles subjected to Ca2+, SO42−, and CaSO4 × 2H2O are given in Table SI 3.
According to Petryshin and colleagues, the analysis of the acid–base interactions of water molecules with alkaline and acidic surface functional groups close to point of zero charge (PZC) is as follows [40]:
equation(1)
single bondTisingle bondOH2+(S) ↔ single bondTisingle bondOH(S) + H+
equation(2)
single bondTisingle bondOH(S) ↔ single bondTisingle bondO−(S) + H+