TiO$_2$ nanoparticles are used in numerous technological processes. Since they are insoluble, suspensions must be stabilized to prevent their aggregation, which leads to the separation of nanoparticles. We attempted to achieve this by suspending the nanoparticles in mixtures of water and methanol, ethanol, and propan-2-ol. In addition, we varied the pH by adjusting the suspensions to pH values of 2, 7, and 10. We analyzed the effect of the medium composition and pH value on the stability of the suspensions by measuring the zeta potential and the hydrodynamic radius of the nanoparticles. We found that the absolute value of the zeta potential of TiO$_2$ nanoparticles is lowest in the presence of propan-2-ol and highest in systems with methanol. Nanoparticle aggregates are largest where the zeta potential is lowest.
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