Nanoparticles that efficiently absorb light energy and convert it into heat can act as miniature steam generators in a liquid.

Naomi Halas, Peter Nordlander and their colleagues at Rice University in Houston, Texas, used lenses to focus sunlight on carbon or gold–silica nanoparticles suspended in water. Within a few seconds, steam at a temperature well above 100 °C was generated around the particle surfaces and bubbled away, whereas the bulk of the water heated up only gradually.

This method of using sunlight to generate high-temperature steam could be used to sterilize waste or surgical instruments without the need to boil a large volume of fluid, the authors suggest. The same effect may improve distillation: sunlight focused on nanoparticles in an ethanol–water mixture produced vapours richer in ethanol than conventional thermal distillation.

ACS Nano http://dx.doi.org/10.1021/nn304948h (2012)