PREPARATION OF A TIO2 NANOPARTICULATE FILM USING A 2-DIMENSIONAL SOL-GEL PROCESS

The preparation of a TiO2 thin film was investigated by a newly develo ped two-dimensional (2D) sol-gel process. When a chloroform solution o f monomer or tetramer of tetrabutoxytitanium (TBT) was spread on the s urface of an aqueous subphase, the TBT was hydrolyzed and polycondense d at the air/water interface to give floating gels. These gels were ga thered by 2D compression to yield a uniform gel film on the water surf ace. The addition of chelating agents such as acetic acid and acetylac etone to the aqueous subphase or spreading solution was effective in s uppressing the 2D hydrolysis/polycondensation reactions and in increas ing the stability of the floating gel film. Up to 20 layers of the flo ating gel film prepared on aqueous acetic acid could be quantitatively transferred onto a suitable substrate using Langmuir-Blodgett techniq ues. The addition of n-octadecyl acetoacetate in the spreading solutio n of monomeric Ti butoxide and ethoxide resulted in quantitative trans ference of the gel films onto substrates without a limitation on the n umber of depositions. The deposited TiO2-based gel films could be conv erted into nanothick TiO2 films by calcination at 773 K for 30 min. It was suggested that the oxide films prepared from gel films of less th an a few tens of layers were composed of quantum-size TiO2 particulate s. The thickness and the density of the nanoparticulate TiO2 films cou ld be controlled by the number of deposited gel film layers and the su rface pressure of the gel film layer during deposition. The controllab le thickness of the TiO2 film by one deposited gel film layer was esti mated to be 2-3 Angstrom.