This project is in the general area of analytical and surface chemistry and in the subfield of chemical sensors. During the tenure of this three-year continuing grant, Professor Bright and his students will build upon results derived from previous studies supported under NSF grant CHE-8921517 and employ excited state fluorescence decay kinetics to study the immobilization of active antibody fragments and their interaction with a soluble antigen. The overall goal of this research is directed toward improving our understanding of biological and synthetic chemical recognition elements (receptors) immobilized at an interface. %%% This research will yield fundamental information on the thermodynamics and dynamics of surface-immobilized receptors (artificial and biochemical) thereby providing valuable insights to guide the development of interfaces suitable for chemical sensing in complex milieu and enable the rational design of a variety of technologically important receptor-based sensing devices.