Nanotechnology & the Sun Used to Disinfect Water

     (CN) — Access to clean water is a major issue in many developing nations, which rely on time-consuming or energy-intensive processes to treat the water and make it safe for humans to drink. But a new technique may bypass those problems, giving poorer nations and communities a shot at avoiding the health issues from drinking contaminated water.
     In a paper published Monday in the journal Nature Nanotechnology, researchers present a nanostructured device about half the size of a postage stamp that disinfects water more efficiently than existing techniques.
     Current strategies for disinfecting water include boiling — which consumes fuel — or by putting it in a plastic bottle so ultraviolet rays can kill the microbes. The latter method typically requires six to 48 hours, which limits the amount of water that can be disinfected.
     “Our device looks like a little rectangle of black glass. We just dropped it into the water and put everything under the sun, and the sun did all the work,” Chong Liu, lead author of the report, said.
     Sunlight falling on the device triggers the formation of hydrogen peroxide and other disinfecting chemicals. The experiments showed that the device can kill more than 99.999 percent of bacteria in only 20 minutes.
     The team uses molybdenum disulfide as a photocatalyst, which, when hit by incoming light, leads to electrons leaving their normal position, leaving the electrons and the “holes” they leave behind excited to take part in chemical reactions.
     While molybdenum disulfide is an industrial lubricant, it begins to act like a photocatalyst and it abandons many of its commercial functions.
     Molybdenum disulfide is also cheap and simple to make, which is important for widespread use in developing nations. It also absorbs a broader range of
     The device looks like a fingerprint when examined with an electron microscope, with many closely spaced lines that researchers call “nanoflakes” of molybdenum disulfide. To the naked eye, the device resembles the walls of a labyrinth atop a rectangle of glass.
     The technique is not foolproof, however, since it does not remove chemical pollutants from water and has only been tested on three strains of bacteria. But the researchers say there is no reason to think it would not kill other strains and types of microbes like viruses.
     “It’s very exciting to see that by just designing a material you can achieve a good performance. It really works,” said Liu. “Our intention is to solve environmental pollution problems so people can live better.”

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