Chemists discover the spontaneous formation of nanoparticles in charged microdroplets

A team of chemists from the Indian Institute of Technology in Madras, working with a pair of colleagues from the Jawaharlal Nehru Center for Advanced Scientific Research in India, discovered that mineral particles sometimes disintegrate spontaneously when immersed in charged microdroplets, leading to the formation of nanoparticles.

In his study published in the journal Sciencethe group performed experiments with minerals and an electrospray device. R. Graham Cooks and Dylan T. Holden of Purdue University published a Perspective article in the same issue of the journal in which they reported this work.

Previous research has shown that natural processes often produce nanoparticles, and many types of such nanoparticles exist in nature. However, little is known about how they are formed. In this new endeavor, the research team suspected that some of it might be due to minerals being immersed in charged liquid particles. To find out whether this might be the case, they designed an experiment to replicate such natural processes.

Scientists note that charged microdroplets abound in the natural world and can be found in clouds and sea spray. To create their own charged microdroplets, they used an electrospray device.

When filled with water and electrically charged, it can produce a mist of charged droplets. In their experiments, the research team added mineral particles to the water before placing it in the spray device. They then captured samples of charged microdroplets and other materials found in the fog. They found many cases of spontaneous expulsion of nanoparticles from microdroplets into the surrounding air.

The researchers found that shortly after the droplet was formed, a double electric field was generated on its surface, creating a reactive sphere. The droplets then split when the Coulomb energy in the droplet exceeded its surface tension, followed by the ejection of the mineral nanoparticle in the form of a microdroplet.