Optically Active AuNR@Ag Core-Shell Nanoparticles and Hierarchical Assembly via DNA-Mediated Surface Chemistry

To manipulate the chiroptical activity of plasmonic metal nanoparticles (MNPs) and control their hierarchical self-assembly are of great fundamental and technological significance; however, they remain a big challenge. Here, we in situ fabricated anisotropic bimetallic AuNR@Ag core-shell nanoparticles (AuNR@Ag NPs) capped with designed DNA molecules and systematically studied the plasmonic chiroptical properties of the individual AuNR@Ag NPs and their assemblies. The AuNR@Ag NPs were facilely prepared by employing DNA-capped Au nanorods (AuNRs) as seeds to grow Ag shells, and it was found that the as-prepared AuNR@Ag NP surfaces were encoded by the original DNA molecules through an in situ DNA "desorption and re-adsorption" dynamic process during shell overgrowth. This observation is distinctly different from the previous results that DNA molecules were embedded in the Ag shell. Interestingly, with this in situ DNA-mediated surface chemistry, plasmonic chiroptical activities were observed from individual AuNR@Ag NPs, and the chiroptical responses were conveniently manipulated over a broad optical window by simply modifying the shape anisotropy of the building blocks. Furthermore, the DNA molecules capped on the AuNR@Ag NP surface facilitate the hierarchical assembly of homogeneous and heterogeneous nanostructures with distinct chiral optical responses.