Surface Modification of Gold Nanoprisms and Their Self-Assembly with Nanospheres

Controlled surface modification of gold particles is of central importance for the preparation of functional nano-objects, which can be used both in fundamental research and in advanced photonic or nanomedicine applications. In this study, the surface modification of gold nanoprisms using different thiols, namely cysteamine, (16-mercaptohexadecyl)trimethylammonium bromide (MTAB), and alpha-methoxy-omega-mercapto polyethylene glycol (mPEG-SH (5000 Da)) is investigated. The aim is to prepare binary surface-modified thiol/PEG patchy gold nanoprisms, where the tips/edges and the face regions of the particles are covered by different thiol moieties. By investigating the time evolution of the prisms' extinction spectra at different capping ligand concentration levels, the conditions to prepare such "patchy" particles are identified. While significantly faster adsorption kinetics are observed for MTAB compared to cysteamine, both molecule types can be used to prepare binary surface-modified thiol/PEG particles. Prisms modified with only MTAB or PEG and subsequently assembled with negatively charged spheres show that MTAB forms hetero-aggregates with the spheres, while PEG prevents particle attachment. For thiol (cysteamine or MTAB)/PEG binary surface-modified prisms, it is found that the efficiency of sphere attachment at the tip/side region during self-assembly is rather low, most likely due to the presence of PEG.