QCM-D experiments were carried out to assess the effective- ness of the membrane surface modification procedure. A clean gold sensor was spin-coated with PSf, dried in a desiccator, and then tested in pure DI water to adjust the initial reading to
0 ng/cm2. After the reading had stabilized for 15 min, the DI water
was replaced by TiO2 solution to deposit the first TiO2 layer on the PSf surface of the sensor. As evidenced in Fig. 3, the mass on the sensor surface increased very fast, indicating that TiO2 nanoparti- cles were quickly adsorbed on the PSf surface. After about 2 h, the mass change slowed down significantly and stabilized at about
34 mg/cm2, indicating that the adsorption of TiO2 on the PSf
reached its capacity. Since the QCM-D measurements (i.e., sensor