Design, synthesis and testing of fullerene-functionalized devices and machines
Tour, James M.
Doctor of Philosophy
Herein is described the design, synthesis and testing of molecules that contain fullerenes as essential parts. In chapter 1, a series of multiple fullerene terminated oligo( p -phenylene ethynylene) (OPE) hybrid compounds was synthesized through a newly developed in situ ethynylation method. Electronic and optical interactions between the fullerenes and the OPE backbones were investigated by UV/Vis spectroscopy, cyclic voltammetry (CV), and differential optical Kerr effect (DOKE) experiment. Enhanced nonlinear optical (NLO) performance of some of the fullerene-OPE hybrids is presumably due to the occurrence of periconjugation and/or charge transfer effects between the fullerene and OPE moieties in the excited state. This result indicates that the use of such fullerene-derivatized conjugated oligomers aids the quest for NLO devices. In chapter 2, fullerene-wheeled single molecular nanomachines, namely nanocars and nanotrucks, are presented. These nanovehicles are composed of spherical fullerene wheels, freely rotating alkynyl axles, and a molecular chassis. The use of spherical wheels based on C 60 and freely rotating axles based on alkynes permits directed nanoscale rolling of the molecular structure on gold surfaces. The rolling motion observed by scanning tunneling microscope (STM) resembles the same motion performed by macroscopic entities in which rolling occurs perpendicular to the axles. This study underscores the ability to control directionality of motion in molecular-sized nanostructures through precise molecular design and synthesis. Chapter 3 describes that the seemingly simple and widely employed approach to self-assembly of fullerene-derivatives on gold surfaces can be complicated due to multilayer formation and head-to-tail assemblies resulting from the strong fullerene-fullerene and fullerene-gold interactions. These anomalies were not examined in detail in previous studies on fullerene self-assembled monolayers (SAMs) but were clearly detected in the present work using surface characterization techniques including ellipsometry, CV, and X-ray photoelectron spectroscopy (XPS). This study specifically addresses the need to properly characterize and control fullerene-thiol assemblies on gold before evaluating subsequent device performances. Finally, chapter 4 describes the synthesis and testing of a motorized nanocar. Kinetics studies in solution show that the motor indeed rotates upon irradiation with 365 nm light, and the fullerene-free carborane wheel system is an essential design feature for motor operation.