2D materials: Solar purification

Nat.Nanotech.http://doi.org/bp75(2016)

Films made from few-layered vertically aligned sheets of the popular 2D material molybdenum disulfide (MoS₂) topped with a 5-nm-thick layer of copper can act as a highly effective solar-based water purifier, according to scientists in California. Chong Liu and co-workers from Stanford University report that the films act as a photocatalyst, harvesting visible light to generate electron–hole pairs that react with water to produce bacteria-killing reactive oxygen species. Experimental tests indicate that water disinfection takes just a few minutes, with 99.999% of bacteria in water being inactivated in 20 min when 1.6 mg l⁻¹ of the material is added to a water sample that is then exposed to visible light. Unlike other light-based purification schemes, the approach can work with visible rather than ultraviolet light. This is made possible by increasing the bandgap of MoS₂ from 1.3 eV (bulk material) to 1.55 eV (few-layered MoS₂).