This device uses visible sunlight to disinfect water

Using the sun to disinfect water is nothing new; UV rays start killing bacteria after six hours, although the process can take up to 48 hours. It’s time-consuming, but often an only option in developing countries. Researchers at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University's Institute for Materials and Energy Science created a device to speed up that process. Their findings were published in Nature Nanotechnology earlier this week. The device, which is smaller than a postage stamp, not only uses UV rays but also the visible part of the solar spectrum to disinfect water.

The device is made of glass and invisible layers of molybdenum disulfide. That compound becomes a photocatalyst that produces...