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Titanium Dioxide Nanocrystals: Simple Industrial Scale Manufacturing Process Revealed by Chinese Academy of Sciences Researchers

Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences (Changchun, Jilin Province, CN) secured U.S. Patent 7,709,540 for a method for preparing organic ligand-capped titanium dioxide (TiO2) nanocrystals. The titanium dioxide nanocrystals have particle diameters of 1-20 nm. The preparing process has the features of mild reaction conditions and is a simpler and easier method with a shorter preparation period, thereby facilitating the industrialization.
According to inventors Daocheng Pan, Nana Zhao, Qiang Wang, Xiangling Ji, Shichun Jiang and Lijia An,  the manufacturing method comprises the steps of using methyl titanate, ethyl titanate, n-propyl titanate, iso-propyl titanate, butyl titanate or titanium tetrachloride as a titanium source, and with capping by oleic acid or an organic capping agent, reacting the titanium source in an organic non-polar solvent with an aqueous alkaline substance solution in the interface at a temperature of 25 to 280 degree. C. for 0.5 to 240 hrs, thus producing a transparent sol containing titanium dioxide nanocrystals.   
FIG. 1A is a TEM image of oleic acid (OA)-capped TiO2 nanocrystals
 FIG. 2A is a TEM image of stearic acid (SA)-capped TiO2 nanocrystals
With the advantage of two-phase preparing method, a solution of titanium source in an organic non-polar solvent is reacted with an aqueous alkaline substance solution under an ambient pressure or a high pressure, titanium dioxide nanocrystals form nuclei and grow at the interface, while they are capped with the organic capping agent. The resultant titanium dioxide nanocrystals can be dispersed stably in an organic non-polar solvent.
On one hand, the defects of a traditional single phase preparing method such as high reaction temperature, long reaction time, and difficulties in preparing titanium dioxide nanocrystals with small sizes have been overcome, meanwhile the nano-particles prepared by the method of the present invention exhibit a narrow size distribution, and can be dispersed stably in an organic non-polar solvent. On the other hand, the sizes of titanium dioxide nanocrystals are controlled effectively.

The titanium dioxide nanocrystals prepared by the Chinese Academy of Sciences method have small particle diameters, narrow size distribution, and can be dispersed stably in a non-polar solvent. The manufacturing method solves the problem that titanium dioxide nanocrystals are difficult to processing during its application. The whole preparing process of the material has the features of mild reaction conditions and is a simpler and easier method, and has a short preparation period, and is suitable for mass production.