Simple synthesis of water-dispersible and photoactive titanium dioxide nanoparticles using functionalized poly(ethylene oxide)s

Versatile and direct synthesis of water-dispersible titanium dioxide (TiO₂) nanoparticles in the presence of functionalized poly(ethylene oxide)s (PEO) having carboxylic acid groups is presented. The functionalized PEOs, such as PEO-folate conjugate and PEO-b-poly(maleic acid) (PEO-b-PMAc) as polymeric surfactants, were employed for in situ synthesis of TiO₂ nanoparticles through hydrolytic sol-gel process of titanium tetrachloride as a precursor in eco-friendly alcoholic media at a relatively low temperature. Both of the two polymers were found to be very effective for stabilizing TiO ₂ nanocrystals, exhibiting not only fairly good photocatalytic activities but also water-dispersible property. The core TiO₂ crystallites in the size range of 8∼11 nm could be readily controlled in ethanol at a relatively low reaction temperature (70°C), irrespective of the incipient reaction condition, which showed mixed polymorphs. The TiO ₂ nanoparticles consist of a few percentages (<10%) of brookite and mostly anatase phases. This process provides a simple and useful in situ preparative route to obtain water-dispersible TiO₂ nanoparticles. [Figure not available: see fulltext.]