Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization

Control of interparticle interactions in terms of their direction and strength highly relies on the use of anisotropic ligand grafting on nanoparticle (NP) building blocks. We report a ligand deficiency exchange strategy to achieve site-specific polymer grafting of gold nanorods (AuNRs). Patchy AuNRs with controllable surface coverage can be obtained during ligand exchange with a hydrophobic polystyrene ligand and an amphiphilic surfactant while adjusting the ligand concentration (C_PS) and solvent condition (C_water in dimethylformamide). At a low grafting density of ≤0.08 chains/nm², dumbbell-like AuNRs with two polymer domains capped at the two ends can be synthesized through surface dewetting with a high purity of >94%. These site-specifically-modified AuNRs exhibit great colloidal stability in aqueous solution. Dumbbell-like AuNRs can further undergo supracolloidal polymerization upon thermal annealing to form one-dimensional plasmon chains of AuNRs. Such supracolloidal polymerization follows the temperature-solvent superposition principle as revealed by kinetic studies. Using the copolymerization of two AuNRs with different aspect ratios, we demonstrate the design of chain architectures by varying the reactivity of nanorod building blocks. Our results provide insights into the postsynthetic design of anisotropic NPs that potentially serve as units for polymer-guided supracolloidal self-assembly.