Daniel Kelly

Daniel Kelly

Surface chemistry has come under renewed interest due to advances in nanotechnology and enhanced detection methods. Most nanomaterials boast very large surface areas, leading to unique surface chemistry that is not necessarily fully understood. Surfaces have been traditionally difficult to study due to the small number of atoms that constitute a surface relative to the bulk material; this leads to small amounts of signal for detecting these few surface atoms as well as removing interfering signal from bulk atoms. New surface-selective detection methods have allowed further study of surfaces, expanding their use in designing new, functional nanomaterials.

Dr. Kelly’s research is two-fold; it attempts to unravel connections between surfaces and the Hofmeister Series, and then to use this knowledge for directed design of nanoscale chemical surfaces.

The Hofmeister Effect, the salting-in or salting-out of proteins from solution, is currently believed to be based upon the interactions of the ions with the protein surface. Theoretical calculations support this assumption, but direct experimental evidence has been difficult to obtain. Dr. Kelly uses an advanced electrochemical method known as electrokinetic streaming current to study the charge at solution/solid interfaces. Using liquid microjets with diameters of less than 40 µm, the current generated by laminar flow of water past the surface is dependant upon the amount of charge at that surface. By using very small concentrations of ions, the relationship between size, charge, and surface adsorption can be measured by comparing the streaming currents measured.

Additionally, Dr. Kelly’s work involves the chemical modification of nanostructures to unlock new chemical possibilities. Porous alumina is a nanoporous thin film (10-1000 nm pore diameters) that has been used since the 1950s, making it one of the earliest nanomaterials. A drawback to the use of porous alumina is the chemical nature of the aluminum oxide surface and the non-continuous range of pore-sizes available for the thin films. Most surface modifications available for porous alumina are wither too imprecise in the coating thickness or too expensive for industrial mass-production.

Dr. Kelly has developed a controlled sol-gel technique that utilizes the pores themselves to control the surface chemistry of coating porous alumina. This coating is then ready to undergo further chemical modification, unlocking new chemical environments by changing the ionic charge, hydrophobicity, or even attaching catalysts to the pore surface. This approach allows the limited porous alumina to create nanoscale environments involving materials that would not be easily made into a nanoporous film. Dr. Kelly looks to expand the practical uses of porous alumina and create new materials that can purge organic contaminants from water, selectively cleave proteins for further biochemical study, or improve upon existing reverse-osmosis materials.