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nanotimes News in Brief

11-01 :: December 2010 / January 2011

Barron said binding just the right amount of silica to P25 creates an effect at the molecular level called band bending.

“Because the silicone-oxygen bond is very strong, you can think of it as a dielectric,” he said. “If you put a dielectric next to a semiconductor, you bend the conduction and valence bands. And therefore, you shift the absorption of the ultraviolet (used to activate the catalyst).”

Bending the bands creates a path for electrons freed by the UV to go forth and react with water to cre- ate hydroxyl radicals, an oxidant responsible for contaminant degradation and the most significant reactive agent created by titanium dioxide. “If your conduction band bends to the degree that electrons find it easier to pop out and do something else, your process becomes more efficient,” Barron said.

Li saw great potential for enhanced P25. In deve- loped countries, photo reactors designed to take advantage of the new material in centralized treat- ment plants could more efficiently kill bacteria and inactivate viruses in water supplies while minimizing the formation of harmful disinfection byproducts, she said.

But the greatest impact may be in developing na- tions where water is typically disinfected through the

SODIS method, in which water is exposed to sunlight for its heat and ultraviolet radiation.

“In places where they don‘t have treatment plants or even electricity, the SODIS method is great, but it takes a very long time to make water safe to drink,” Li said. “Our goal is to incorporate this photocatalyst so that instead of taking six hours, it only takes 15 minutes.”

Barron wants to spread the good news. “Here‘s a way of taking what is already a very good environ- mental catalyst and making it better,” he said. “It works consistently, and we‘ve done batch after batch after batch of it now. The methodology in the paper is the one we routinely use. As soon as we buy P25, we treat it.”

Huma R. Jafry, Michael V. Liga, Qilin Li, and Andrew R. Barron: Simple Route to Enhanced Photocatalytic Activity of P25 Titanium Dioxide Nanoparticles by Silica Addition, In: Environmental Science & Technology ASAP, December 31, 2010, DOI:10.1021/es102749e: http://pubs.acs.org/doi/abs/10.1021/es102749e