Controlling the Orientation of MOF Multishells on Single Nanogold Dumbbells for Tailoring Plasmonic Band Shifts and Promoting Molecular Sieving

The orientation of the ZIF-8 multishell on a single nanogold dumbbell (SNGD) was controlled during the nucleation–growth–crystallization process. The combination of regiospecific selection of active sites and a weak ligand modulator can affect the formation of ZIF-8 during nucleation–growth–crystallization via dynamically controllable adsorption–desorption. Thus, two important factors, the concentration and linear chain length of the modulator, can adjust the specific orientation of the ZIF-8 multishell, leading to the generation of the overlapped and staggered structures of SNGD@ZIF-8. On the one hand, the nucleation–growth of the ZIF-8 layer can cause an initial longitudinal localized surface plasmon band (LSPR) red-shift of the SNGD, accompanied by an increase in the thickness of ZIF-8; however, the subsequent blue-shifting degree is dependent on the structure of the ZIF-8 multishell on the SNGD during the crystallization process. On the other hand, the orientation of the ZIF-8 multishell on the SNGD can affect the compactness of the skeleton, which determines the stability and molecular sieving functions. Furthermore, the present investigations reveal that the SNGD@ZIF-8 multishell nanocrystals with overlapping cubic structures exhibit excellent chemical stability and molecule sieving performance as compared to the staggered flowerlike SNGD@ZIF-8 multishell nanocrystals. The tailorable LSPR properties and molecular sieving-induced surface-enhanced Raman scattering (SERS) discrimination functions of the SNGD@ZIF-8 multishell nanocrystals can be expected for applications in plasmonic rulers and SERS discrimination.