Herein, a new strategy is proposed for achieving dynamic chiral controls in self-assembly systems of plasmonic nanorods based on temperature-modulation. Via enlarging Au{100} side facets of Au nanorod (AuNR) building block and changing surface ligand from often-used cetyltrimethylammonium bromide (CTAB) to cetylpyridinium chloride (CPC), inversion of chiroptical signal in side-by-side (SS) oligomers is realized. Under the guide of chiral cysteine (Cys), Au{100} side facet-linked SS rods twist in the opposite direction compared with Au{110} side facet-linked counterparts. At high CPC concentration, by controlling the incubation temperature of chiral Cys, the dominant twist mode can be regulated. Finite-difference time-domain (FDTD) simulations indicate the key role of the twisting dihedral angle of the oligomers in driving chiral signal inversion. At low CPC concentration, a temperature-sensitive chiral switching is observed owing to the conformation change of the CPC ligand layer. The temperature-modulated chiral responses are based on the interactions of chiral molecules, achiral surface ligands, and exposed facets of the building block. The rich dynamic tunability of chiroptical responses of plasmonic assemblies may find applications in stimulus-responsive nanodevices.

Generation of circular dichroism (CD) beyond the UV region is of great interest in developing chiral sensors and chiroptical devices. Herein, we demonstrate a simple and versatile method for fabrication of plasmonic oligomers with strong CD response in the visible and near IR spectral range. The oligomers were fabricated by triggering the side-by-side assembly of cysteine-modified gold nanorods. The modified nanorods themselves did not exhibit obvious plasmonic CD signals; however, the oligomers show strong CD bands around the plasmon resonance wavelength. The sign of the CD band was dictated by the chirality of the absorbed cysteine molecules. By adjusting the size of the oligomers, the concentration of chiral molecules, and/or the aspect ratio of the nanorods, the CD intensity and spectral range were readily tunable. Theoretical calculations suggested that CD of the oligomers originated from a slight twist of adjacent nanorods within the oligomer. Therefore, we propose that the adsorbed chiral molecules are able to manipulate the twist angles between the nanorods and thus modulate the CD response of the oligomers.