UI researchers develop photocatalyst that works in dark

Researchers at the University have developed the newest generation of a photocatalytic disinfectant that can work with visible light and even in the dark.

Jian Ku Shang, a professor of materials science and engineering, led the research team.

“A catalyst is a substance that helps speed up chemical reactions. A photocatalyst is a catalyst that works with light. When you shine a light on the substance it generates electrons,” Shang said.

Previous catalysts have had to use high-energy photons, such as ultraviolet light. This new catalyst works with lower energy photons and can be generated by visible light, both natural and artificial.

When visible light shines on the substance it activates the photocatalyst, which speeds up the reaction, Shang said. This generates a special type of antibacterial substance, Hydroxyl radical, which is a form of oxygen and hydrogen.

“It (hydroxyl radical) is the same agent the human body produces whenever the body is infected with a bacterial infection,” Shang said.

While most catalysts require light activation to work, this catalyst continues to kill bacteria in the dark. It can continue to work up to 20 hours after its last exposure to light. This new development was made possible by “catalytic memory,” a method discovered about a year ago.

“You can produce a catalyst that remembers it had been activated before,” Shang said, “So even when the light is switched off, the catalyst can still stay active and kill bacteria and viruses.”

Catalytic memory works by using palladium nanoparticles to trap electrons while light is shining on the catalyst. These electrons are then stored in the nanoparticles. When the light is switched off, the nanoparticles discharge the electrons a little bit at a time, Shang said.

“The nanoparticles function like a tiny little battery. It gets charged when the light is on the photocatalyst, and when the light is off, the nanoparticles start to discharge the energy,” Shang said.

This project has been ongoing since 2001, said Jim Economy, professor of materials science and engineering. This development has the potential to expand, Economy said.

“He (Shang) has the enthusiasm and energy to make this technology happen. I suspect that if given half a chance, Shang will make this system suitable for a number of critical needs,” Economy said.

Photocatalysts have several applications.

“One application we are looking at very closely now is the disinfection of waste water,” Shang said.

Catalysts are useful in cleaning up the environment. The photocatalyst can help in the photo-oxidation of polluted water. Shang is interested in using this development to disinfect polluted bodies of water, especially in cities.

“For large cities, at this point, because there aren’t viable technologies to clean the water, the water is simply released to rivers without disinfection,” Shang said.

The University has a few options when it comes to commercializing this product.

The University can get a patented commercial license, which would allow other companies to use this development in their products. The other option is to start a new company and apply this method to a specific application, Shang said.

However, there are some obstacles when it comes to getting the product on the market.

“Perhaps the biggest obstacle is getting support from venture capitalists who are willing to allow Shang the funding to develop the technology in a timely way,” Economy said.

The photocatalyst is in its seventh version, and Shang said the product is far from finished.

“Research is never finished,” Shang said. “We are still doing research and developing new variations of these materials.”