Preparation and covalent surface modifications of silica coated spherical and rod-shaped gold nanoparticles

The surface chemistry of silica-coated gold nanoparticles (Au NPs) was investigated by modifying these surfaces using alcohol-based reagents. Alcohol condensation reactions were facilitated by dielectric heating using a microwave reactor. The attachment of two alcohol-based reagents, a carboxylic acid functionalized alcohol and a chelating agent with a terminal alcohol functional group, was achieved on the surfaces of spherical gold nanoparticles and gold nanorods, respectively. A fluorescent probe was coupled to the carboxylic acid functionalized silica-coated Au NPs as a confirmation of the surface functionalization, and as a demonstration of an application for these nanoparticles. The silica-coated gold nanorods modified with a chelating species were evaluated for their ability to capture metal ions present in an aqueous solution. A wide range of surface chemistry for silica-based nanoparticles can be achieved using the methods presented herein to meet the requirements of their future applications.