WATER - Using Light to Disinfect Water

New light-activated catalyst keeps on working even after the lights go out.
a light-activated catalyst  (of fibers of titanium oxide--a common material used as a white pigment--doped with nitrogen to make it absorb visible light) disinfects water even in the dark. Palladium nanoparticles on the surface of a nitrogen-doped titanium oxide help to extend the catalyst's disinfection power up to 24 hours.
an international research team has developed a photocatalyst that promises quick, effective water disinfection using sunlight or artificial light. What's more, the photocatalyst keeps working after the light is turned off, disinfecting water even in the dark.
It has long been known that irradiating water with high-intensity ultraviolet light kills bacteria.
a photocatalyst that gets activated by UV light and generates reactive chemical compounds that break down microbes into carbon dioxide and water.
The new photocatalyst improves on that by using visible (400 and 550 nanometers), rather than UV, light.
http://www.technologyreview.com/biomedicine/24415/?mod=more