Microscopic Probing of Silica Surfaces

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Professor Mary Wirth of the University of Delaware is supported by the Analytical and Surface Chemistry Program to utilize the combined techniques of single molecule spectroscopy and atomic force microscopy (AFM) to probe adsorption processes and kinetics of materials central to separation technology. In particular, studies focus on the adsorption of peptides as a prerequisite for studying protein adsorption. The probe dye molecule DiI is used to spectroscopically report on the physical and chemical nature of adsorption sites on silica gel. AFM is used to measure nanoscale roughness and to relate possible connections between roughness and chemical adsorption. The work addresses why topography promotes active silanols. It also addresses whether smoothing can reduce active silanols sufficiently to impact peptide and protein separations. Modern liquid chromatography is approximately a two billion dollar per year worldwide industry, and is crucial to pharmaceutical, biotechnology and many other industries. Developing efficient and reliable techniques for peptide and protein separation is of basic interest for proteomics, and in this sense, for further developments in diagnosis and treatment of disease. There remain unresolved issues, with one of the most problematic being the undesirable loss of resolution due to residual silanols on the silica phases used to separate compounds in mixtures. This work attempts to explain the fundamental issues about the residual silanols, eventually enabling improved separations.