Special properties
Nanoparticles are composed of just tens to thousands of molecules, which give them vastly different properties from bulk materials built up by quintillions of the exact same molecules. For example, copper nanowires are transparent. Manufacturers utilize these special properties in products like sunscreen, tires, clothing and plasters. But their tiny size also poses a problem; they are very difficult to track, so it is still unknown to what extent they harm the environment.

Sharper contrast
Leiden physicist Aquiles Carattino and his colleagues have developed a new way to track conducting nanoparticles using fluorescence. They shine a laser on a particle using light of a particular wavelength, matching the particle’s so-called plasma resonance. Surprisingly, the particle will give off some light with an even higher energy than it received. This gives it a sharper contrast against the background.

Filter
To develop a new detection technique based on this phenomenon, Carattino used a filter to get rid of the surrounding background light. In this way, nanoparticles are easier to detect because scientists can scan for one specific, clear signal. It gives environmental researchers a method for tracking nanoparticles and investigating their effect on nature.