Technical University of West Berlin, Ph.D., 1985 Argonne National Laboratory, Post-Doctoral Fellow, 1987 California Institute of Technology, Research Fellow, 1989

Physical

Physical Chemistry: Photochemical generation and reactions of reducing macromolecular radicals in light-sensitive polymer systems, synthesis of nanometer-sized metal crystallites including kinetics and mechanism of the formation process in liquid and solid matrices, preparation of thermo and photoadaptive systems, degradation of toxic chemicals initiated via photolysis.

Overview

Photochemical generation and reactions of reducing radicals, synthesis of nanometer-sized metal crystallites including kinetics and mechanism of the formation process in liquid and solid matrices, degradation of toxic chemicals initiated via photolysis.

Interesting changes in the physical and chemical properties of metals and oxides take place upon restricting their dimensions to the nanometer size range. Research in our lab aims at exploring new strategies for the generation of such crystallites in solution and in solids. An attractive approach is to use photochemical reactions to form small metal particles since photons can serve as the energy source that transforms compounds present in the system into reactive intermediates able to induce redox processes. An example is the method developed in our lab that employs blends of sulphonated poly(ether etherketone), SPEEK as a sensitizer and PVA as a donor of H-atoms. Benzophenone (BP) groups of SPEEK undergo light-excitation to triplet states able to abstract H-atoms from PVA yielding strongly reducing and long-lived polymeric SPEEK• radicals.

Exposure of films and solutions of SPEEK/PVA blends to light yields nanometer-sized crystallites of a variety of metals. Analogous methods based on BP photochemistry enabled photogeneration of Cu, Ag Pd and Pt crystallites in hydrocarbons, which also served as electron donors. These colloids are being tested in terms of their ability to enhance heat transport and function as nanofluids.

Another area of research currently being pursued involves investigation of SPEEK/PVA films as protective (self-decontaminating) barriers against toxins. Shown in the Figure is a scheme representing the attack by photogenerated SPEEK• on an undesired compound (for instance, CCl4) adsorbed on the surface of an SPEEK/PVA film, which results in a reductive degradation of the toxin under illumination (top). Reaction of SPEEK• with oxygen forms H2O2 as a byproduct, which can degrade toxins in the dark (bottom scheme).

Clary, D. R.; Mills, G. “Photochemical Generation of Nanometer-Sized Cu Particles in Octane” J. Phys. Chem. C 2011, 115, 14656-14663.

Clary, D. R.; Mills, G. “Preparation and Thermal Properties of CuO Particles” J. Phys. Chem. C 2011, 115, 1767-1775.

Little, B. K.; Li, Y.; Cammarata, V.; Broughton, R.; Mills, G. “Metallization of Kevlar Fibers with Gold” ACS Appl. Mater. Interfaces 2011, 3, 1965-1973.

Korchev, A. S.; Konovalova, T.; Cammarata, V.; Kispert, L.; Slaten, B. L.; Mills, G., “Radical-Induced Generation of Small Silver Particles in SPEEK/PVA Polymer Films and Solutions: UV-Vis, EPR, and FT-IR Studies” Langmuir 2006, 22, 375.

Korchev, A. S.; Shulyak, T. S.; Slaten, B. L.; Gale, W. F.; Mills, G., “Sulfonated Poly(Ether Ether Ketone)/Poly(Vinyl Alcohol) Sensitizing System for Solution Photogeneration of Ag, Au and Cu Crystallites” J. Phys. Chem. B 2005, 109, 7733.

Korchev, A. S.; Sartin, M.; Mills, G.; Slaten, B. L.; Gale, W. F., Clusters and Nano-Assemblies: Physical and Biological Systems; Jena, Puru; Khanna, Shiv N.; Rao, Bijan K.; Eds, World Scientific Publishing Co.: Singapore, 2005; 371.

Korchev, A. S.; Bozak, M. J.; Slaten, B. L.; Mills, G., “Polymer-Initiated Photogeneration of Silver Nanoparticles in SPEEK/PVA Films: Direct Metal Photopatterning” J. Am. Chem. Soc. 2004, 126, 10.

Gaddy, G. A.; Locke, E. P.; Miller, M. E.; Broughton, R.; Albrecht-Schmitt, T. E.; Mills, G., “Photoinduced, Controlled Generation of Palladium Crystallite Structures in Polyimide Films” J. Phys. Chem. B. 2004, 108, 17378.