Stamp-sized, sun-powered device purifies water in minutes
People in many parts of the world cleanse water by leaving it in plastic bottle for long hours under the sun to let UV rays kill microbes. Since, this is a very time consuming process (UV rays, that form only 4 percent of the sun’s total energy, can take up to a couple of days to purify water), engineers at the Stanford University and SLAC National Laboratory have noticed the problem and have developed a small device that works on the energy of the sun to kill 99.99 percent germs in water in only 20 minutes.
The postage stamp-sized device, which developers say is like “a rectangle of black glass” is very easy to use. Simply drop the device into a water container and leave it in the sun; with sunlight falling on the device it triggers formation of hydrogen peroxide and additional disinfecting chemicals to kill 99.99 percent bacteria in just 20 minutes. Once bacteria is dead, the chemicals quickly dissipate leaving behind clean, drinkable water.
According research reported in Nature Nanotechnology, the water purifying device comprises a layer of molybdenum disulfide measuring a few atoms thick. Molybdenum disulfide is an industrial lubricant. When layer of Molybdenum disulfide hit with sunlight, electronic begin to fly out of it. The electrons and holes they make create chemical reaction, and coper layer in the device acts as a catalyst to activate a reaction necessary to produce hydrogen peroxide.
According to the research team, their experimental device can kill only three type of bacteria for now, and cannot remove chemical pollutants from water. The team is hopeful of delivering a device that will be able to clean chemically polluted water with large variation of bacteria.