An interdisciplinary collaboration of physicists, chemists, and materials scientists lead by the University of the Basque Country (UPV-EHU) and the Donostia International Physics Centre has invented a new ultrasensitive molecular sensing technique to monitor a nuclear decay reaction. With it, the collaboration could solve a decadeslong mystery about the nature of neutrino particles and address some of the fundamental questions about our universe.

Neutrinos are subatomic particles that have no electrical charge and extremely small mass — some even think they could have no mass. Most particles of matter have a corresponding antiparticle, which has the same mass but opposite physical charges, but scientists have been puzzling for decades over whether neutrinos could be their own antiparticles.

One way to answer this question is by studying a process called “neutrinoless double beta decay.” In this rare type of nuclear decay, two neutrons from the nucleus of an atom turn into protons, emitting two electrons in the process. This can occur spontaneously in a particular isotope of xenon atoms (136-Xe), which undergo decay into barium ions. However, the process is so rare that observing it is very difficult and until now, scientists had not found a viable method of detecting individual barium ions.

In their results, published recently in Nature, the authors report a “tagging” method that could be used to detect barium ions that originate from this decay. They have designed a fluorescent molecule that can capture the barium ions to form a supramolecular complex. These molecules usually emit green light when excited with ultraviolet illumination, but the emission turns blue if the complexes have captured barium ions.

What is remarkable about this work is its truly interdisciplinary nature. It harnesses the expertise of synthetic chemists and materials scientists to develop an experimental technique that will be applied in a completely different field: particle physics. The success of this collaboration, involving researchers from nine different research institutes, shows how interdisciplinary science often leads to innovative and impactful solutions, as well as the value in bringing in new perspectives to our work.