Characterization of Dynamic Surface Processes by Atomic Force Microscopy
Surfaces are actively involved in numerous biological systems as well as catalytic reactions. The control of matters at surfaces is also of uttermost importance with the advent of nanotechnology. A thorough knowledge of surface processes would not only help to describe the mechanism of different reactions or interactions at surfaces but also lead to rational design of surfaces for construction of functional systems. Among the various surface characterization techniques, Atomic Force Microscopy (AFM) offers outstanding spatial resolution which enables investigation of surface processes at single molecular level and establishment of microscopic models. In this dissertation, AFM is used to study different surface processes, with a focus on the dynamics of surface reactions (Chapter 2) and the dynamic change of surface properties (Chapter 3 & 4). In Chapter 2, the AFM is configured in a certain way to improve the temporal resolution, and the electrochemical etching of gold within a nanoshaved self-assembled monolayer is investigated. Novel kinetic information is obtained which also demonstrates the potential of electrochemical etching in the fabrication of high-resolution nanoplasmonic structures. In Chapter 3 and 4, self-assembled monolayers that contain electroactive species are used to construct dynamic surfaces that can alternate their charge states upon control of applied potential. The nanoscale dynamic surface patterns are fabricated by AFM at nanometer scale and the characterization of the different surface charge states by AFM is explored in Chapter 3. In Chapter 4, AFM is used to probe the adhesion of polyelectrolyte on the dynamic surface, which serves as a model system for studying electrostatic interaction between charged substances in biological systems. Microscopic picture of the interface is described based on the information obtained from Dynamic Force Spectroscopy (DFS). Background information for Chapter 2,3,4 is introduced in Chapter 1.