Application of Scanning Probe Microscopy for New Physical Measurements and Studies of Surface Chemical Reactions of Materials at the Molecular Level

Abstract

Scanning probe microscopy (SPM) provides unique capabilities for surface visualization and measurements that reach atomic and molecular dimensions. My research focus is directed toward applying and developing new measurements for analytical and surface chemistry with SPM. Two distinct goals based on studies with atomic force microscopy (AFM) will be described within this dissertation. The primary goal was to develop and apply a new AFM imaging mode for ultrasensitive measurements of the superparamagnetic properties of proteins. Magnetic sample modulation (MSM)-AFM, has capabilities to investigate and map the magnetic response of nanomaterials with unprecedented spatial resolution. The second goal was to apply high resolution AFM to probe the scaling and magnitude of corrosion of copper surfaces as a function of selected chemical parameters. Characterization of the magnetic properties of nanomaterials using a new AFM imaging mode will be described in the first part of the dissertation. Ferritin is a model nanomaterial for SPM studies because of the superparamagnetic iron-oxide (Fe2O3) core and ultra small dimensions of the protein, as described in Chapter 3. Periodic arrays of ferritin architectures were fabricated on surfaces and used as test platforms for measurements with magnetic sample modulation (MSM), for mapping the magnetic domains of ferritin are described in Chapters 4 and 5. The new MSM approach combines contact mode AFM with electromagnetic modulation of samples to measure the vibration and motion of nanomaterials. Proof-of-concept results demonstrate the capabilities for selective mapping of individual ferritin molecules through vibration of the superparamagnetic iron cores. Corrosion by-products from copper plumbing that are released into tap water are known to impact water quality and are detrimental to consumer health. The second part of this dissertation (Chapter 6) presents results for surface changes caused by water chemistry parameters typical of domestic water supplies. In this study, AFM was used to characterize nanoscale changes in surface morphology caused by chemical treatments at the earliest onset of copper corrosion as a function of pH, solution concentration and immersion intervals of copper substrates. Conclusions and future directions for the work of this dissertation will be summarized in Chapter 7.