These are optical microscopy images of gold nanoparticle islands that are nucleating and growing over time on the liquid-air interface of a drying drop. The ~6 nm gold nanoparticles are ligated with dodecanethiol and dissolved in toluene. They impinge on and stick to the liquid-air interface where they self-assemble to form highly crystalline monolayer domains, similar to atomic epitaxy. The first frame shows the interface before nucleation and growth. The second frame and onward shows nanoparticle islands growing on the interface (note that optical microscopy cannot resolve the monomers nor the island nuclei). In the final frame, islands coalesce to form a single continuous monolayer that eventually covers the entire surface of the drop. We are adapting atomic epitaxial growth models to model the nanoparticle self-assembly process and better understand the forces and dynamics that govern assembly. We will present results from this project at the APS March Meeting. Each frame is ~175 µm in width. (credit: C. P. Joshi, Y. Krukov, J. G. Amar, T. P. Bigioni)

Image courtesy: Chakra Joshi, Terry Bigioni