Host-Guest Directed Assembly of Gold Nanoparticle Arrays

The formation of a three-dimensional assembly of gold nanoparticles driven by host-guest interactions is described. Assembly is achieved via host-guest interactions between cyclodextrin-modified gold nanoparticles which associate with the adamantane unit of a redox active metal complex [Os(CAIPA)(3)](ClO4)(2), where CAIPA is 2-(4-carboxyphcilyl)imidazo[4,5-f][1,10]-phenanthroline-1-adamantylamine. The electrochemical properties of thin films formed on glassy carbon electrodes have been probed using cyclic voltammetry. In aqueous LiCIO4, the homogeneous charge transport diffusion coefficient, D-CT, is (8.4+/-0.4) x 10(-9) cm(2) s(-1) for both oxidation and reduction of the osmium complexes. Significantly, this charge transport rate is significantly larger than that obtained for a solid deposit of [Os(CA IPA)(3)](ClO4)(2) alone where D-CT is 2.3 x 10(-10) cm(2) s(-1). The higher D-CT value observed for the nanoparticle arrays suggests that the incorporated nanoparticles facilitate electron transfer between the bound osmium centers.