Synthesis and characterization of functionalized gold nanoparticles and their rational arrangement on DNA scaffolds

Functionalized metal nanoparticles have received an enormous amount of attention for their use as catalysts/catalyst supports, biological taggants, sensors, and as building blocks of nanoelectronic devices. In order for these materials to be useful in any of the above applications, a method for synthesizing the nanoparticles and reliably patterning and interconnecting them is necessary. Presented here is a method for the synthesis and characterization of functionalized gold nanoparticles that are shown to form extended, well-ordered, low-dimensional assemblies along a DNA template. These types of assemblies will undoubtedly prove highly useful in the fabrication of nanoparticle-based devices.; The synthetic procedure presented herein begins with the synthesis of a common precursor particle, Au₁₀₁(PPh₃)₂₁Cl ₅. This particle is analogous to the phosphine-stabilized particles first synthesized by Schmid (originally formulated as Au₅₅(PPh ₃)₁₂Cl₆) in its small size (d_core < 2 nm) and narrow size dispersity (∼30%) as well as its ability to undergo ligand exchange with functionalized thiols. Our synthesis of this new precursor eliminates the harsh reagents (e.g. diborane gas) used in the traditional procedure and provides a scalable reaction capable of producing gram quantities of the purified nanoparticle product.; This phosphine-stabilized precursor nanoparticle can be functionalized using a biphasic ligand exchange reaction to yield thiol-stabilized nanoparticles that are capable of interacting with a DNA structural template. Specifically, thiocholine (N,N,N-trimethylaminoethanethiol iodide) is used to both impart water-solubility to the nanoparticle (a necessary requirement for biopolymer templating) and to provide a terminal ammonium headgroup in the stabilizing ligand shell that is capable of electrostatically binding to the negatively charged phosphate backbone of DNA.; The structures formed using these nanoparticles and λ-DNA ( Hind III enzyme digest) provide some of the first examples of well-ordered, extended, low-dimensional nanoparticle assemblies in which the nanoparticles are observed to be close-packed along the DNA strand. Further, this is one of the first examples in which the individual nanoparticles attached to the DNA template were clearly visualized using transmission electron microscopy allowing for more in depth characterization of the assemblies and a higher level of control over the assembly process.; This dissertation includes both previously published and unpublished co-authored material.