Evolution of mesoporous TiO2 during fast sol–gel synthesis

Abstract

Mesoporous TiO2 nanoparticles were synthesized by a fast sol–gel method using polyethylene glycol (PEG) and polyacrylamide as bi-template followed by two-step calcination under nitrogen and air atmosphere. The effects of factors such as the solvent volume, amount of water, medium pH, and amount and molecular weight of PEG on the sol–gel reaction rate were studied based on analysis of zeta potential measurements. The results showed that lower ethanol volume, lower pH, greater water volume, and higher PEG molecular weight led to faster sol–gel reaction rate with shorter gelation time, with pH and water volume being the most influential amongst these factors. The evolution during the fast sol–gel process was also investigated based on the infrared (IR) spectrum. The results indicated that the fast sol–gel process occurred due to intermolecular hydrogen bonding between hydrolysates of Ti alkoxides and the bi-template. The samples were characterized by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and N2 adsorption–desorption measurements, revealing high crystallinity with small crystallite size and large specific surface area.