temperature dependent STM studies of organic molecules at the solution/solid interface including new instrumental development.

摘要

Scanning tunneling microscopy (STM) has been widely used to investigate surface structures and electronic properties of adsorbed species on surfaces and also for observing chemical reactions on surfaces. The technique can be used in various environments including the solution-solid interface -- a particularly exciting environment to study. It exemplifies important biological environments and is compatible with chemical equilibrium involving materials transport to and from the surface. In solution-solid studies, one can change the solvent in order to tune molecule-solvent and substrate-solvent interactions, thereby changing the ordering and structure of the adsorbed species. Temperature dependent studies of the solution-solid interface can elucidate the kinetics and thermodynamics of surface reactions/structures as well as provide a pathway to new structures on the surface.;In this dissertation temperature dependent STM studies of conjugated organic molecules at the solution-solid interface are reported. These studies demonstrate the existence of three surface structure of coronene molecules at the heptanoic acid-Au(111) interface. It is shown that by changing the supernatant coronene concentration three surface structures are attainable. In order to extend temperature and pressure dependent studies, a new STM for solution solid interface studies was conceived, constructed, and tested. With this new design, studies of the solution solid interface with volatile solvents at elevated temperatures become possible.;This dissertation also explores the competitive two component adsorption of coronene and cobalt octaethylporphyrin (CoOEP) at the phenyloctane solution-Au(111) interface. It has been shown that by systematically changing the concentration of the supernatant solution a new bimolecular surface structure can be seen on the surface. It is shown that the structure is kinetically but not thermodynamically stable on the surface at 22 ?C and above.