Structural and morphological properties of titanium dioxide nanoparticles doped by Boron atoms

The phase composition and morphology of boron-containing TiO2 nanoparticles obtained by the sol-gel method were investigated. The solution of titanium aqua complex [Ti (OH2)(6)](3+)center dot 3Cl(-) was used as a precursor. Borate acid H3BO3 (promoter of the formation of rutile) was used as a modified reagent. A single-phase rutile TiO2 was obtained at a concentration of borate acid in the reaction mixture, which causes the formation of a 0.5B-TiO2 sample. The particles of 0.5.-TiO2 samples were in the villi-form, with a diameter of 0.8-1.2 nm, and a length of 16-24 nm. With an increase of the H3BO3 concentration in the reaction mixture, synthesized oxide materials (samples of 1.0B-TiO2 and 1.5B-TiO2) contain 70 % and 57% of anatase respectively, in addition to rutile phase. Meanwhile, anatase proto-particles with a diameter of 3-7 nm were combined into units of 60-100 nm in size in a two-phase composite mixture. Titanium-borate monodentate molecules Ti(OH)(3)OB(OH)(2)center dot 2H(2)O were formed during the synthesis of the 0.5B-TiO2 rutile sample. These molecules in the polycondensation process serve as centers of origin, growth, and crystallization of TiO2 proto-particles. The interatomic distance of Ti-O in these particles is commensurate with the average length of the Ti-O - bond of TiO6 rutile octahedra. During the polycondensation process, the distance of the Ti-O molecule-promoter was reproduced as a pattern in the following octahedra of rutile crystals. Two types of titanium-borate molecules are formed in the reaction medium, during the synthesis of 1.0B-TiO2 and 1.5B-TiO2 samples. Molecules with a bidentate mononuclear structure Ti(OH)(2)OB(OH)(2)center dot 2H(2)O were formed in addition to molecules with monodentate geometry of interatomic bonds. In molecules with a bidentate mononuclear structure, the interatomic distance of Ti-O is commensurate with the average length of the Ti-O -bond in the octahedra of the anatase phase. Therefore, titanium-borate molecules of the second type act as a promoter of the formation of the TiO2 anatase phase.