Facile preparation of partially functionalized gold nanoparticles via a surfactant-assisted solid phase approach

Herein, we report a versatile solid phase synthesis approach for partial functionalization of gold nanoparticles (AuNPs) via the assistance of surfactant. Hexadecyl trimethyl ammonium bromide (CTAB) is used as the bifunctional ligand to link the solid substrate and the AuNPs. This brings at least two advantages comparing to other bifunctional ligands: first, the thickness of the CTAB bilayer is flexible. During the "catch" process, the bilayer bound on different sites of the AuNPs could shrink or extend to a total thickness difference of ~2.5 nm, which protects a spherical cap of the AuNPs with the height of ~2.5 nm from chemical modification; second, after chemical modification, the "release" of the AuNPs from the substrate is quite simple. Not any second ligand, but only sonication is enough to release the AuNPs. As a result, the proposed approach produces partially functionalized AuNPs with a large surface area (80-95%) covered with unreactive ligands, while keeps the other small spatially limited region of the surface unmodified. This small unmodified surface can be directly used for further chemistry. Finally, the partially modified AuNPs is demonstrated for a one-step synthesis of AuNP dimers.