Noncovalent Self-Assembly of Silver and Gold Nanocrystal Aggregates in Solution

This paper describes the programmed assembly in solution of Ag and Au nanocrystals. The approach adopted utilizes Ag and Au nanocrystals whose surfaces have been modified by the chemisorption of mixtures of 1-dodecanethiol with N, N ‘-2,6-pyridinediylbis(mercapto undecamide) ( II ) and with 1,2-mercaptododecyl-1-uracil ( III ), respectively. It is established that these nanocrystals recognize and selectively bind each other by the formation of an array of three complementary hydrogen bonds in a nonpolar solvent. This is among the first examples of the programmed assembly in solution of mixed-metal nanocrystal aggregates. In addition, this aggregation of mixed-metal nanocrystal dispersions is shown to be accompanied by a significant change in the optical spectrum over time. Binding is followed at the molecular level by 1 H NMR spectroscopy and at the macroscopic level by dynamic light scattering, UV-vis spectroscopy, and TEM.