The discovery could allow the development of highly adjustable materials whose structures change depending on the conditions to which they are exposed.
Researchers in Japan have discovered a new way to make gold nanoparticles dynamically reorganize in response to environmental changes, a discovery that could pave the way for smarter, more adaptable materials in electronics, sensing technologies and nanotechnology applications.
The study, led by scientists at Tohoku University and published in the Journal of the American Chemical Society, showed that small changes in the arrangement of organic molecules attached to gold nanoparticles can trigger drastic structural transformations throughout the nanoparticle layer.
According to the research team, gold nanoparticles exhibited unusual behaviorsimilar to that of a liquid, when positioned at the interface between air and water. Unlike dry environments, where the molecules attached to the nanoparticles remain relatively fixed unless exposed to very high temperatures, the air/water interface allowed the particles to move and reorganize much more freely.
“This work demonstrates how very small changes at the molecular level can lead to drastic structural transformations in nanoparticle systems”, said Kiyoshi Kanie, one of the main researchers, cited by The discovery could open new possibilities for the development of materials capable of automatically adapting to changes in their environment.
To carry out the study, the researchers created gold nanoparticles coated with two different types of organic molecules. One was a temperature-sensitive liquid crystal molecule known as a dendron, while the other was a simpler straight-chain ligand. The team then observed how the nanoparticle layers behaved as temperatures increased and the layers were mechanically compressed.
At room temperature, the nanoparticles formed isolated island-like structures. As temperatures rose, these structures gradually evolved into chain-like formationsbefore finally developing into extensive network-like patterns at around 40 °C. When the layer was compressed, the network structures returned to isolated islands.
Using advanced X-ray measurements at the DESY synchrotron facility in Hamburg, Germany, scientists have identified the mechanism that drives the transformations. The two types of surface molecules spontaneously redistributed across the nanoparticle surfaces in response to changes in temperature and pressure. This changed the apparent symmetry of particlescausing large-scale reorganization of the entire layer.
The researchers say the findings are significant because the optical, magnetic and electronic properties of nanoparticles depend strongly on how they are organized. Being able to reversibly control these arrangements could therefore enable the development of highly tunable materials with applications ranging from smart coatings and sensors to advanced electronic and photonic devices.
