Prevention of particle agglomeration in sol–gel synthesis of TiO₂ nanoparticles via addition of surfactant

Three surfactants, namely, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyethylene glycol (PEG), were used to prevent particle agglomeration in TiO₂ nanoparticle synthesis. The nanoparticles were produced using the sol–gel and ball milling (dry–wet–dry) techniques. Structural and morphological analyses were performed via X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to explain the effect of the surfactants on TiO₂ nanoparticle agglomeration and particle size reduction. XRD results showed that the crystal structures of non-surfactant had pure anatase, whereas those obtained using PEG (sample PEG-TiO₂), SDS (sample SDS-TiO₂), and CTAB (sample CTAB-TiO₂) had a rutile phase. SEM morphological results showed that the use of these surfactants could prevent agglomeration. TEM analysis results showed that PEG-TiO₂, SDS-TiO₂, and CTAB-TiO₂ had smaller particles than those synthesized without surfactants. Particle analysis showed that the particle sizes were in the following order: CTAB-TiO₂ < SDS-TiO₂ < PEG-TiO₂. The use of CTAB resulted in the most significant change. The formation of the rutile phase and agglomeration reduction with the use of CTAB was due to the faster hydrolysis process (compared with the hydrolysis processes with the use of the other surfactants) and a quantum size effect. The details of the hydrolysis mechanism and agglomeration prevention are also discussed.