Design, Control, and Measurement of Molecular and Supramolecular Assemblies
- Author(s): Pathem, Bala Krishna
- Advisor(s): Weiss, Paul S
- et al.
Molecular switches and motors respond structurally, electronically, optically, and/or mechanically to external stimuli, testing and potentially enabling extreme miniaturization of optoelectronic devices, nanoelectromechanical systems, and medical devices. Assembling
motors and switches on surfaces makes it possible both to measure the properties of individual molecules as they relate to their environment, and to couple function between assembled molecules. We designed molecules with precise functionality and assembled them on solid substrates either as isolated single molecules, linear one-dimensional chains, or as two dimensional islands in order to measure and to test the fundamental limits and cooperative function of the assemblies. We established that proximate functional molecules interact with each other to drive unprecedented cooperative motion at the nanoscale. In conjunction with theory, we establish the mechanism by which the molecules perform this nanoscale action. We modify the environments in which these assemblies are adsorbed to tune their dipole-dipole interactions via self- and directed assembly. We establish the role of the tethers that decouple the functional molecules from the underlying conductive substrates. By varying the composition of the tether we understood that the molecular function varies inversely with the conductance of the tether. In order to circumvent problems with steric hindrance in molecular assemblies, novel functional molecules were designed and tested at single-molecule and at ensemble scales. This thesis details the effects of parameters such as the molecular environment, intermolecular interactions, and internal functional groups of molecular switches on their nanoscale actuation.