Modelling Janus Nanoparticles

Janus particles are compartmentalised objects with different, usually even opposite, chemical make-ups on their two hemispheres, which make them a unique class of materials at the meso- and nanoscale. The name is reminiscent of Janus the ancient Roman god with two heads looking in opposite directions, simultaneously forward to the future and backward to the past.First made by Casagrande and Veyssie (Compt Rend Ac Sci 306:1423, 1988) of one hydrophilic and one hydrophobic hemisphere, raised to an international attention as “new animals with a polar and an apolar face” by de Gennes in his Nobel lecture, Janus particles are acquiring more and more importance because of their wide range of technological applications. Thanks to their toposelective and functionalised coating, they are utilised as surfactants, drug-delivers and catalysts. The flexibility proper of soft matter has been thought to be applied to bimetallic nanoalloys where the Janus motif represents a layered segregation effect leading to two different chemical regions in the cluster. Janus nanoalloys have been proposed in magneto-optical applications, such as structural colourations on textile, and as flip-flop switchers in the presence/absence of a magnetic field.The numerical modelling of Janus particles is a useful tool to understand and drive their synthesis and preparation. In this chapter, the attention is focused, but not limited, on the modelling of the growth of bi-comparmentalised nanoalloys, where the cases of gold–platinum (AgPt) and silver–cobalt (AgCo) are presented as paradigmatic examples.