A twist to the self-assembly of nanoparticles

Arthur C. Newton, Jan Groenewold, Willem K. Kegel, and Peter G. Bolhuis: Rotational diffusion affects the dynamical self-assembly pathways of patchy particles. PNAS Early Edition, published online 30 Nov. 2015, DOI: 10.1073/pnas.1513210112

In an article published on 30 November 2015 in the Proceedings of the National Academy of Sciences (PNAS), Arthur Newton, Peter Bolhuis (both at the University of Amsterdam), and Jan Groenewold and Willem Kegel (at the Debye Institute, Utrecht) describe how decoupling of translational and rotational diffusion of macromolecules or nanoparticles may provide a design principle for new functional materials.

In the simulations, the researchers investigated the effect of releasing the Stokes-Einstein coupling between rotational and translational diffusion, an effect that has been observed in highly crowded systems. Even for two particles already a strong effect on the association route emerges. The effect is even more relevant for systems with multiple particles, where several metastable intermediate states are possible. In a simulation of cluster formation of four particles, varying the rotational diffusion significantly shifts the preference for the selfassembly routes. The researchers were able to generalize this finding to clusters of any size.

PNAS november 2015
Change of assembly mechanism when reducing rotational diffusion. Each circle depicts a metastable state. The black dots indicate where the particles can ‘stick’ to each other. One particle is colored orange in order to clarify the contrast. The thickness

The researchers argue that their results provide new opportunities for a better control of the bottom-up synthesis of functional materials. For example, it should be possible to design particles of which the rotation can be controlled with magnetic or electric fields.