Incorporation strategy for organic dyes into gold nanoparticle supercrystals

Ordered arrays of plasmonic nanoparticles, supercrystals can lead to the formation of plasmon-polaritons. Coupling light emitters with plasmon polaritons might allow the formation of exciton-plasmon polaritons with properties tuneable by the supercrystal design. To construct such optically active materials, the inclusion of emitters is imperative. The addition of organic dyes without affecting the periodic order of the nanocrystals is difficult, as post-formation protocols might dissolve the supercrystals, and pre-formation addition might affect the self-assembly process. Here, we present an exemplary strategy to functionalize gold nanoparticles prior to self-assembly with a cyanine isothiocyanate dye that was obtained by a straightforward reaction of the amine functionalized dye with carbon disulfide. In the second step, the nanoparticles are functionalized with a thiol-terminated polystyrene, which stabilizes the nanoparticles and governs the self-assembly process. The dye can be integrated in a quantitative fashion, and the nanoparticles can be self-assembled into supercrystals. The strategy should be applicable in general for amine functionalized dyes, which is a common modification.