Synthesis and Characterization of Orthogonally Self-Assembled Nanoparticle Heterodimers

Abstract

This project involved the synthesis of novel bifunctional linear linker molecules that were used to bind gold and platinum nanoparticles using orthogonal self-assembly. These heterodimers were created as a model for the possibility of using similar bimetallic structures as molecular electronic components.

The binding affinities of the terminal thiol and isonitrile functional groups on planar surfaces and nanoparticles were analyzed using surface and transmission Fourier-transform infrared spectroscopy. It was found, qualitatively, that the binding affinity of the binding groups differed significantly depending on whether the functional group was binding to a planar surface or a nanoparticle.

The linking of two nanoparticles to form a heterodimer was also studied using transmission electron microscopy (TEM) and size-exclusion chromatography (SEC). While unable to provide quantitative results on heterodimer formation, TEM provided a straight-forward, though limited, method for demonstrating that some heterodimer formation did occur. The main limiting factor of TEM was the relative size difference of the particles in the heterodimer. SEC provided a more quantitative view of the heterodimer sample, but this technique introduced many variables that control the separation of nanoparticles and heterodimers. Results from the SEC experiments support the formation of heterodimers, but many of the variables inherent to the technique must be overcome for it to become a viable technique for routine analysis of nanoparticle arrays.