Chemists discover that microdroplets spontaneously produce hydrogen peroxide

Water is everywhere on Earth, but maybe that gives it more space to hide its secrets. Stanford researchers report his latest surprise on August 26 Proceedings of the National Academy of Sciencesis that microscopic water droplets spontaneously produce hydrogen peroxide.

This discovery could pave the way for greener ways to produce the molecule, a bleaching agent and a common disinfectant, said Richard Zare, natural science professor Marguerite Blake Wilbur and professor of chemistry at the Stanford School of Humanities and Sciences.

"Water is one of the most commonly found materials.It has been studied for years and one would think that there was nothing more to learn about this molecule, but here's another surprise, "said Zare, a member of Stanford Bio-X.

The discovery was made by chance as Zare and his lab investigated a new, more efficient way to create gold nanostructures in tiny droplets of water called microdroplets. To create these structures, the team added an additional molecule called reducing agent. As a control test, Zare suggested to see if they could create gold nanostructures without the reducing agent. Theoretically, this should have been impossible, but it still worked – alluding to a still unknown feature of microdroplet chemistry.

The team eventually found these results in the presence of a molecule called hydroxyl, a hydrogen atom coupled to an oxygen atom, which can also serve as a reducing agent. This equally unexpected result led Katherine Walker, then a graduate student in Zare's lab, to question whether hydrogen peroxide – a molecule with two atoms of hydrogen and oxygen – was also present.

To find out, Zare, Walker, lead scientist Jae Kyoo Lee and his colleagues performed a series of tests, the simplest of which was to spray micro-droplets of seemingly pure water onto a treated surface so as to turn into blue in the presence of hydrogen peroxide. blue did it. Additional tests have confirmed that water droplets spontaneously form hydrogen peroxide, that smaller microdroplets produce higher concentrations of the molecule and that hydrogen peroxide is not present. not lost when microdroplets recombine in bulk water.

The researchers dismissed a number of possible explanations before arriving at what they consider to be the most likely explanation for the presence of hydrogen peroxide. They suggest that a strong electric field near the surface of the micro droplets in the air causes the binding of hydroxyl molecules to hydrogen peroxide.

Although the results look like a basic scientific curiosity, Zare said, they could have important practical consequences. Hydrogen Peroxide is a major commercial and industrial chemical, manufactured most often through an environmentally friendly process. The new discovery could help make these methods greener, Zare explained, and could help disinfect surfaces in a simpler way: just spray micro-droplets of water on a table or the floor to clean them .

"I think this could be one of the most important things I've ever done," Zare said.