Tuesday, December 29, 2009

Cleaner Air and Water Possible with Improved Photocatalytic Nano-Crystalline TiO2 Thin Films Developed by Chinese University of Hong Kong Researchers


In U.S. Patent  7,638,555Chinese University of Hong Kong (CUHK) (Hong Kong, CN) inventors Professor Chai-Mei Jimmy Yu and Jun Lin reveal photocatalytic nano-crystalline titanium dioxide (TiO2) thin films with improved catalytic activity and their manufacturing methods.  The TiO2 thin films can be used for killing bacteria and viruses in an environment under ultraviolet irradiation. The TiO2 thin films have higher photocatalytic activity, and can particularly be used to photocatalytically degrade organic pollutants in the air by killing bacteria and viruses.

Compared with the prior art, the invention has many advantages in that the TiO2 thin film can be formed onto all kinds of substrates in various shapes without any specific manufacturing apparatus. The TiO2 thin film can be readily doped with other components by coating essential components for the TiO2 thin film together with the other components. The TiO2 particle's size in the thin film can be controlled by changing the molar ratio between the surfactant and water in the reverse micelle solution. The phase constitutions can be controlled by the thermal treatment of the thin film.  The thin film has a larger specific area and a higher activity of killing bacteria and viruses due to its nano-structure.

The manufacturing method includes:


a) providing a reverse micelle solution containing highly-dispersed water nano-droplets, which is made from an organic continuous phase, a non-ionic surfactant and water;

b) adding an alkyl titanate to the reverse micelle solution and subjecting titanium alkoxide to being hydrolyzed in said nano-droplets of the reverse micelle solution to form a TiO2-containing solution;

c) forming a wet film onto a substrate dipped into the TiO2-containing solution by a dip coating technique; and

d) drying the wet film and calcining the dried film.


FIG. 4 is a scanning electron microscope image of a TiO2 thin film on stainless steel calcined at 500.degree. C. for 3 hours which exhibit improved photocatalytic activity made by CUHK process.


 Image Source: U.S. Patent  7,638,555, Figure 4.

Researchers at the CUHK have successfully developed state-of-the-art photocatalytic oxidation technology with the support of the Innovation and Technology Fund, and transferred the new invention to industry. NanoPCO ™ technology has been commercialized and licensed to EnvironmentalCare Ltd., a company selling environmental protection products for use in high-end water treatment and air purification systems. 

The first application of this new technology, developed by Prof. Jimmy Yu Chai-mei of the Department of Chemistry, leads to a very safe and attractive water treatment system which has been proven to be more effective than conventional UV irradiation. It can be used to treat drinking water, industrial or agricultural waste water, and sea water. Currently water treatment systems employing NanoPCO ™ technology have been installed in many Hong Kong seafood restaurants. 


The second license introduces a new approach for cleaning up air which overcomes the poor solar efficiency of traditional photocatalysts, making commercialization possible. This air purification system can be installed at hospitals, offices, schools, restaurants, and homes.

The Chinese University of Hong Kong
Technology Licensing Office
Rm 328, Pi Ch'iu Building Shatin, N.T. Hong Kong SAR
Tel: (852) 2609 8885 Fax: (852) 2603 5451

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