Large-scale self-assembly and stretch-induced plasmonic properties of core-shell metal nanoparticle superlattice sheets

We report on a facile interfacial self-assembly approach to fabricate large-scale metal nanoparticle superlattice sheets from nonspherical core-shell nanoparticles, which exhibited reversible plasmonic responses to repeated mechanical stretching. Monodisperse Au@Ag nanocubes (NCs) and Au@Ag nanocuboids (NBs) could be induced to self-assembly at the hexane/water interface, forming uniform superlattices up to at least 13 cm2 and giving rise to mirror-like reflection. Such large-area mirror-like superlattice sheets exhibited reversible plasmonic responses to external mechanical strains. Under stretching, the dominant plasmonic resonance peak for both NB and NC superlattice sheets shifted to blue, following a power-law function of the applied strain. Interestingly, the power-law exponent (or the decay rate) showed a strong shape dependence, where a faster rate was observed for NB superlattice sheets than that for NC superlattice sheets.