This award is to support a cooperative research between Dr. Eric Bakker, Department of Chemistry, Auburn University, Auburn, Alabama and Dr. Mohammed Abbas, Department of Applied Chemistry, National Research Center, Cairo, Egypt. They plan to explore the covalent immobilization of active sensing reagents for the detection of anions, especially porphyrins, phthalocyanines, metallophthalocyanines and their derivatives, onto a variety of polymeric materials used for the fabrication of electrochemical and optical sensors. Target polymers include acrylates and methacrylates as well as polypyrrole, polyaniline or polythiophene. The covalent attachment of active sensing ingredients will allow one to fabricate ultraminiaturized, yet durable sensing systems where the leaching of active components is no longer limiting the lifetime of these devices. In recent years, ion-selective electrodes have experienced a paradigm shift by the discovery that they may reach extremely low detection limits, often in the low parts per trillion-concentration range of total ion concentration measured. Research in improving the materials chemistry aspects is required for better chemical control of ion diffusion properties and the minimization of component leaching into the contacting aqueous solution. This research lays the groundwork for numerous current directions in the field of ion-selective electrodes and miniature optical sensors. The covalent attachment of active sensing ingredients will transform both fields from using traditionally doped systems to all-polymeric materials with unique properties. Ultraminiaturized sensing systems based on this technology will only be truly practically useful if this transition can be accomplished. The research will eventually help answer important questions: how will drastically lowered diffusion coefficients influence the sensor response, especially in zero-current potentiometry? What are the ultimate size limits of such sensors, considering the theoretical necessity of maintaining permselectivity for proper functioning? Will sensing systems with covalently attached ionophores lead to drastically low detection limits because transmembrane ion fluxes can be largely eliminated?
Broader impacts: The collaborative research between the Egyptian and U.S. research groups will foster the scientific relationship between the two countries. From a broader scientific standpoint, this research has a strong impact on the health care and environmental analysis fields, where chemical sensors are currently used at the rate of over 1 billion measurements per year. A significant enhancement of the underlying chemistry and the possibility for the creation of durable ultraminiaturzed sensing systems on the basis of this research will result in important breakthrough in analysis techniques at the single cell level, in physiological samples, in bioanalysis, and in the monitoring of environmental samples.
