This US-Poland Marie Sklodowska-Curie Joint Fund research project between Dr. Jacek Michalik of the Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Warsaw, and Dr. Larry Kevan, Department of Chemistry, University of Houston, is on "Reactivity of Silver Clusters in Zeolites." The researchers will explore the reactivity of small silver clusters as an entry into the utilization of silver cluster species in heterogenous catalysis. The critical aspect of this study is to control the cluster size within narrow range. Many generation methods lead to a broad size distribution. One method to limit this is to produce the metal clusters within a molecular size cage or channel as one finds in molecular sieves called zeolites. In addition to ESR and associated optical spectroscopies (infared and diffuse reflectance), the researchers propose a pulse ESR method known as Electron Spin Echo Modulation (ESEM) as a major new tool in characterizing the reactivity of silver cluster species in zeolites. By analyzing the modulation signal associated with weak electron-nuclear dipolar interactions, it is possible to determine the coordination geometry of paramagnetic species with adsorbed molecules. In favorable cases this should provide the structure details, not readily obtainable by other techniques, such as the number of adsorbate molecules, their orientation as well as the changes of coordination geometry in the course of reaction. Thus, rather detailed structural information about reaction intermediates can be obtained by using a combination of ESR, ESEM, diffuse relectance and infrared spectroscopies which will improve our knowledge about the mechanism of heterogenous catalysis on metal clusters. This project in radiation chemistry fulfills the program objective of advancing scientific knowledge by enabling leading experts in Poland and the United States to combine complementary talents and pool resources in areas of strong mutual interest and competence.
