Zeta potential of shape-controlled TiO2 nanoparticles with surfactants

Zeta potential of shape- and size-controlled TiO2 nanoparticles obtained with the introduction of surfactants during synthesis was measured at different pH values. A unique finding is that TiO2 nanoparticles shaped by sodium dodecyl sulfate (SDS) have double isoelectric points (IEPs), while other shape-controlled TiO2 nanoparticles have only one IEP. The double IEPs might be due to the complex chemistry of TiO2 nanoparticles with the presence of impurities (Na, S, C, etc.). At neutral pH, shape- and size-controlled TiO2 nanoparticles have more negative zeta potential values and lower IEPs than TiO2 nanoparticles obtained without the addition of surfactants during synthesis and the commercial anatase TiO2 nanoparticles Degussa P-25. The lower IEPs could be attributed to the presence of carbonates on particle surfaces. The IEP value of TiO2 nanoparticles increases with an increase in calcination temperature. The results suggest that the zeta potential of TiO2 nanoparticles can be manipulated with the addition of surfactants during the synthesis process.