Phase diagrams of honeycomb and square nanocrystal superlattices from the nanocrystal's surface chemistry at the dispersion-air interface.

Abstract

In this work, we theoretically investigate the conditions favoring the interfacial self-assembly of PbSe nanocrystals (NCs) resulting in silicene-honeycomb superstructures. Using a coarse-grained molecular dynamics model, we study the NCs' self-assembly at the dispersion-air interface with respect to the input parameters regulating the various forces experienced by the NCs at the interface. From these results, we extrapolate detailed assembled-phase diagrams showing which ranges of the input parameters promote the formation of silicene-honeycomb superstructures and which regimes result in square geometries. Then, we use a sharp-interface numerical model to compute the energy landscape experienced by each NC at the dispersion-air interface with respect to the NC's surface chemistry. From such an energy landscape, we fit the parameters regulating the interface-adsorption forces experienced by the NCs at the interface. Combining these findings with the results presented in our assembled-phase diagrams, we find out which surface-chemistry properties of the NCs better promote the interfacial self-assembly in silicene-honeycomb superstructures, and we speculate on some experimental strategies to reach an improved control on the synthesis of PbSe silicene-honeycomb superstructures.