MIT researchers use super‑flexible ligands to create customizable nanoparticle materials

Researchers from MIT and the University of Delaware have developed a new method for assembling nanoparticles into designer materials, published in Nature Materials. The approach utilizes super-flexible connector molecules, or ligands, that intentionally deform based on their surrounding environment to regulate the packing of nanoparticle networks. By leveraging connector flexibility and electric charges, the team demonstrated how to tune the structure of these networks, creating new kinds of nanoparticle-based materials. This technique aims to overcome previous limitations in controlling the number and direction of links between particles, offering a more versatile pathway for applications in photonics, chemical catalysis, medicine, and agriculture.

Traditional methods for creating nanoparticle superlattices often relied on changing particle shapes or aligning rigid connector chains. However, these approaches limited the possible material structures and were difficult to scale because they required specific, bespoke synthesis methods that worked only under certain conditions. Rob Macfarlane, the Richard P. Simmons (1953) Professor in Metallurgy in MIT’s Department of Materials Science and Engineering, noted that the prevailing dogma for 20 years was that connector ligands needed to be rigid to prevent assembly failure. The new research challenges this view by demonstrating that extreme flexibility can be just as effective, allowing ligands to reorganize as particles come together.

In the new system, the nanoparticles feature flexible ligands with electrically charged tips, where positive and negative charges attract one another. This allows the bonds to be as flexible as desired, spontaneously moving toward configurations that maximize bond stability. Experiments led by MIT PhD candidate Nicholas Sbalbi showed that researchers could control the connections by altering nanoparticle sizes and ligand chain lengths. The amount of polymer flexibility dictates the number of bonds each particle forms, enabling the creation of lattices with fewer bonds per particle than previously possible using rigid connectors.

The team successfully assembled the nanoparticles into previously unseen crystal structures without needing to predesign specific connection points or particle shapes. Macfarlane explained that this method allows for less dense formations of nanoparticles, which opens up interesting applications that are limited by traditional dense packing. The researchers believe this establishes ligand flexibility as a new path for customizing material structures at scale, moving toward independent control over both the particle properties and the resulting assembly.

In addition to Macfarlane and Sbalbi, the paper includes contributions from University of Delaware doctoral student Stephen Kronenberger, MIT undergraduate Hana Shinzawa, Matthew Ye PhD ’26, and former University of Delaware professor Arthi Jayaraman. The research was supported in part by the National Science Foundation, the Department of Energy, the U.S. Army, and the U.S. Navy.