A general approach to directing assembly behavior of gold colloids by co-polymer molecules, and tracking and imaging solution nanostructures of the polymer molecules

For the first time the templating function of block polymers, which have been widely used in templated synthesis of mesoporous silica and metal oxides, was successfully used to direct assembly of gold (Au) colloids. The Au colloids were prepared by reduction of a Au precursor (HAuCl₄) by ethanol in the presence of lysine and Pluronic P123 molecules. The lysine molecules are able to cap the Au colloids and form H-bond with the Pluronic P123 molecules, thus the self-assembly behaviors of the polymer molecules can drive that of the Au colloids. A number of nanostructures of the polymer including linear, spherical and lamellar aggregates coated with Au colloids were observed depending on the P123/Au ratio, reaction temperature and time, etc. These different nanostructures finally evolved into a spherical structure and could be harvested by centrifuge. On the other hand, the self-assembling behaviors of the polymer molecules could be influenced by the loaded Au colloids and their nanophases became much more visible by TEM and UV-vis absorbance measurement due to the loading of the Au colloids on them. It is believed this new approach can be applied to the controlled assembly of some other metal nanoparticles and lead to new applications for them.