Controllable Synthesis and Catalytic Performance of Gold Nanoparticles with Cucurbit[]urils ( = ⁻).

A series of gold nanoparticles (AuNPs) was prepared in situ with different cucurbit[]urils (CB[]s) in an alkaline aqueous solution. The nanoparticle sizes can be well controlled by CB[]s ( = , , , ) with different ring sizes. The packing densities of CB[⁻] and free surface area on AuNPs were determined. A direct relationship was found between the ring size and packing density of CB[]s with respect to the AuNP-catalyzed reduction of 4-nitrophenol in the presence of NaBH₄. The larger particle size and higher surface coverage of bigger CB[]-capped AuNPs significantly decreased the catalytic activity. Furthermore, this work could lead to new applications that utilize AuNPs under an overlayer of CB[]s for catalysis, sensing, and drug delivery.