Assembly of Nanoparticles into "Colloidal Molecules": Toward Complex and yet Defined Colloids with Exciting Perspectives in Advances in Colloid Science

Plüisch, C.S.; Wittemann, A.

Abstract: In line with atoms being the elementary units of molecules and crystals, colloidalparticles can be used as building blocks for organized materials. A major benefit indoing so is that joining colloids in a defined manner comes along with structuring. Inview of opening avenues to more complex structural motifs, significantefforts must begeared to colloids with specific shapes and symmetries. A straightforward strategy isjoining equal‐sized spherical particles into stable clusters. Such clusters are called“colloidal molecules” because they may exhibitconfigurations resemblingpretty muchthose of molecules. Their preparation can be based on the agglomeration of particlesdispersed in an emulsion. The particles adsorb on the emulsion droplets and coagulatein a defined way during the evaporation of the droplet phase. Using this methodoriginally applied to microscale particles, one can produce clusters with submicron‐sized global dimensions. Variable parameters such as radii and concentration of clusterconstituents provide the framework needed to obtain “colloidal molecules” that differ in size, shape, and physical properties. This opens up exciting perspectives for tailor‐made colloids as building units for hierarchically organized materials. Moreover, newphysical properties such as plasmonic “hotspots” may emerge from packing particlesinto assemblies of specificconfigurations.