MIT researchers and collaborators have created previously unseen nanoparticle crystal structures using flexible molecular connectors. The approach turns away from the conventional strategy of using rigid links to control how particles join, instead allowing the connectors to bend and adjust as the particles assemble.
The connectors, known as ligands, attach to nanoparticle surfaces. In the team’s system, flexible polymer chains carry positive or negative charges at their ends. Attraction between opposite charges helps link the particles, while the chains’ flexibility affects how many neighboring particles each one can connect with.
Experiments showed that changing the nanoparticle sizes and the lengths of the polymer chains could alter those connections and the resulting structures. By limiting the number of links between particles, the researchers produced more open crystal arrangements rather than the densely packed patterns that commonly form.
The findings challenge an approach that has guided nanoparticle assembly for about 20 years: making connectors rigid to hold particles in carefully controlled orientations. The team’s results suggest that flexibility can itself help determine a material’s structure, without requiring scientists to predefine the direction of every connection.
The work, led by researchers at MIT with collaborators from the University of Delaware, is described in a paper slated to appear in Nature Materials. The researchers say the method could support the development of materials with tailored properties and may be relevant to applications including electronics, medicine, energy, photonics, and chemical catalysis. Further development would be needed to translate the approach into commercial technologies.
Sources: ScienceDaily.