Making steam without first boiling up the water? Now it may only seem impossible. Scientists from Rice University say they have achieved such feature by using metallic nanoparticles which are capable of absorbing huge amounts of incident light.
Absorbed light heats the particles very quickly so that their temperature causes to form a small “cloud” of water vapor around them. Meanwhile, the water doesn’t start to boil, but the vapor escapes it successfully. This invention could be used not only to generate steam, but also to treat some forms of cancer:
Naomi Halas, D.Sc., Peter Nordlander, Ph.D., and colleagues note in the report that metallic nanoparticles (so small that 1,000 would fit across the width of a human hair) absorb large amounts of light, resulting in a dramatic rise in their temperature. They are with Rice University. That ability to generate heat has fostered interest among scientists in using nanoparticles in a range of applications. These include photothermal treatment of certain forms of cancer, laser-induced drug release and nanoparticle-enhanced bioimaging.
Scientists in the past also explored the use of nanoparticles in solar energy applications. However, that research focused mainly on using nanoparticles to improve the ability of fluids to conduct heat. Until now, scientists had not reported on the use of nanoparticles, mixed into fluids, to capture sunlight, heat up and change the fluid into steam or other vapor.
The new report explains that nanoparticles illuminated by light can quickly rise to temperatures above 212 degrees Fahrenheit, the boiling point of water. Steam forms around the surface of each nanoparticle, billons of which can be placed in water or other fluids. Eventually, the vapor escapes from the particle, forming nanobubbles that float to the top of the surface and escape as water vapor or steam, vapors of ethanol in the case of distillation of alcohol for beverages or fuel, or other vapors.
Read more at: PhysOrg