Collaborative Research: Understanding the Design Principles of Modular Nanopores for Highly Efficient Chemical Sensing

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This project is funded by the Chemical Measurement and Imaging Program of the Chemistry Division. Professor Takashi Ito of Kansas State University, and Professor Amar Flood, and Dr. Yi Yi, both from Indiana University - Bloomington seek to design cylindrical nanoscale pores (pores 10-40 nanometers in diameter and 30-100 nanometers in length; there are 25,400,000 nanometers in one inch) for efficient chemical separations and detection. Chloride ion is used as the model target. This work examines how chloride can be chemically recognized by the nanopore geometry and physical environment. It is hypothesized that selectivity, specificity, and strength of chemical recognition can be enhanced by adjusting the environment and charge inside the nanopores. The control of the nanopore physical interior for chemical recognition can be a versatile, basic principle for designing highly efficient separations for various species, including those of environmental interest such as chemicals in fertilizers. A direct societal impact of improved anion sensing is improvement in water purification and analysis. Microscale anion sensors for measurements within the body are also being pursued. These research achievements are integrated with educational activities by developing a new hands-on polymer lab course that includes both polymer synthesis and characterization. Systematic investigations explore polymer-based cylindrical nanopores (10-40 nm in pore diameter; 30-100 nm in pore length) to assess the effects of nanopore physical environment on chemical recognition and redox-involved charge transport. Nanopores decorated with surface alkyne groups are covalently modified with various azide-tagged anion receptors and redox moieties. The fundamental understanding of the nanopore design principles present an approach to rationally fabricate monolithic nanoporous membranes and films for efficient chemical separations and detection. The research focuses on the fabrication and characterization of alkyne-decorated nanoporous scaffolds with controlled pore orientation and dimensions. This is followed by understanding of the effects of nanopore's physical environment on anion recognition and charge transport. The third area of research is the redox-controlled anion sensing. The anion recognition and electrochemical properties of modular nanopores are assessed using spectroscopic and electrochemical techniques. The investigators have complementary expertise for this interdisciplinary project: electrochemistry and spectroscopy on nanostructured films (Ito), design, synthesis and characterization of anion receptors with "click" reactions (Flood), and block copolymer synthesis (Yi). Results obtained in this project provide fundamental knowledge required to design better chemical sensing media of inorganic ions which are of special importance in water quality control and biosciences.