In Situ Modification of the Surface of Gold Colloidal Particles. Preparation of Cyclodextrin-Based Rotaxanes Supported on Gold Nanospheres

A new method for the surface derivatization of gold colloidal particles is reported. The method is based on the aqueous solubilization of aliphatic thiols by α-cyclodextrin, which effectively binds to the aliphatic chains and carries the hydrophobic thiol molecules to the surface of the gold particles, where they undergo chemisorption. This method can be used to prepare gold colloidal particles (diameter > 10 nm) modified with long chain alkanethiolates. If the alkanethiol contains a bulky terminal group, such as ferrocene, the α-cyclodextrin host is trapped after surface attachment, yielding cyclodextrin-based rotaxanes supported on the gold nanospheres.