Preparation of Subnanometer Au Particles

It is of interest to prepare subnanometer Au particles as they possess unusual catalytic properties¹. However, conventional preparation of colloidal Au particles usually resulted in particles of 5 nm or larger. We explored two different strategies to synthesize such particles.  In the first method we used “designer siloxane polymers” to control the particle growth.  The polymer possessed Si-H functionalities that could reduce the Au(I) precursor to Au(0) and amine groups that could protect the Au clusters from agglomeration.  Various parameters such as steric constrain, temperature of nucleation and particle growth as well as the proximity of the reductant to the amine protective groups were examined to determine the critical factors that control the size of the Au nanoparticles.  In the second method, nanocages were synthesized and the au particle size was constrained by the size of the cage interior.  Characterizations of the Au particles were performed using TEM, DLS and Uv-visible.