Open Access
Smith, Rachel Katherine
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
September 20, 2005
Committee Members:
  • Paul S Weiss, Committee Chair
  • David Lawrence Allara, Committee Member
  • Thomas E Mallouk, Committee Member
  • Vincent Henry Crespi, Committee Member
  • scanning tunneling microscopy (STM)
  • nanotechnology
  • nanoparticles
  • monolayers (SAMs)
  • self-assembly
  • infrared spectroscopy (IR)
Self-assembly has emerged to reach towards future device scales of several or tens of nanometers, and will directly compete with or will complement existing `top down' fabrication schemes. Self-assembly techniques have created new materials from the `bottom up,' connecting the length scales of synthetic chemistry and microfabrication. Extensive knowledge of the chemical, physical, and electronic properties of the constituents of `bottom up' architectures is required to develop new materials rapidly. This thesis describes the development of precise, nanometer-scale assemblies derived from <i>n</i>-alkanethiolate self-assembled monolayers (SAMs): the phase behavior of multi-component SAMs containing internally subsituted <i>n</i>-alkanethiolates, the electronic spectra of atomically precise gold clusters and larger nanoparticles immobilized atop <i>n</i>-alkanethiolate SAMs via &#945;,&omega;-alkanedithiolate tethers, and the structure and order of single- and multi-component SAMs containing &#945;,&omega;-alkanedithiols. Replacement of methylene units of the <i>n</i>-alkanethiolate backbone with an amide bond buried near the sulfur headgroup begins to tune intermolecular interactions with precision in order to control the spatial distributions of the adsorbates on the surface. Solvent-solute interactions heavily contribute to determining film structure. The tunability of these interactions may be used to advantage when patterning molecules on surfaces; the strengths and types of these intermolecular interactions have a profound effect on the structure and quality of the structure of the nano-scale assembly. The electronic properties of undecagold clusters and larger gold nanoparticles were investigated using STM, using <i>n</i>-alkanethiolate SAMs as supports that electrically isolated the particles from the substrate. The particles were immobilized using &#945;,&omega;-alkanedithiolate tethers; significant spectral diffusion was observed across single and multiple particles and was closely coupled to the particle's chemical and physical environment. SAMs were created containing &#945;,&omega;-alkanedithiolates, both single-component SAMs as well as dithiols inserted into host <i>n</i>-alkanethiolate SAMs (supports for the gold particles, <i>vide supra</i>). The intramolecular competition for the thiol to the surface as well as the propensity for aggregation due to short-range van der Waals forces led to SAMs with a distribution of complex structures and reactivities. A combination of scanning probe and ensemble measurements characterized the properties of these films across multiple length scales, showing that the SAM order was highly dependent on film preparation conditions. The structure and function of these &#945;,&omega;-alkanedithiols cannot be substituted for their <i>n</i>-alkanethiol counterparts. The creation of nano-scale assemblies from self-assembly techniques is deceptively simple; the structural properties of these assemblies are highly dependent upon the preparation conditions, and special care must be taken to keep the environments of these nano-scale assemblies controlled with high precision.