"We had already reported that [magnesium oxide] nanoparticles were biocidal, but this is the first publication that shows what happens to a bacterium when it is touched by the particles," said Kenneth Klabunde of Kansas State University. "These nanoparticle powders won't be as messy or as corrosive as other biocides."

The magnesium oxide nanoparticles can destroy a bacterium in about five minutes. The bacterium ends up visible as a "misshapen mess" in the microscope, with dark splotches where nanoparticles have broken through its lining. The researchers used three types of microscope in their study.

The nanoparticles have an electrical charge opposite to that of the bacteria - so they are attracted towards them - and have sharp-edged surfaces that can penetrate tough outer shells, such as those that protect anthrax spores. What's more, the particles are bases, which soften the exteriors of the bacteria and chemically damage them by "stealing" electrons in the same way that chlorine does.

Most biocides are either gases, which are corrosive and can be blown away by the wind, or liquids, which are messy and tend to ruin electronics. Nanoparticles are solid, however, and can be put in air filtration units or sprayed like a powder. The particles don't penetrate gas masks or affect human skin, although they can cause health problems if a large amount is inhaled.

Klabunde founded NanoScale Materials, a spin-out from Kansas State University, in 1995. The company plans to build a factory to mass produce magnesium oxide nanoparticles, which it will market under the name FASTACT. NanoScale Materials hopes to sell the product to "police departments, firefighters and other first responders".

Although the first FASTACT nanoparticles will be magnesium oxides, NanoScale Materials says that other metal oxides will follow.