Experimental and Theoretical Investigations of Electrostatic Interactions and Ordering in Highly Charged Colloidal Assemblies

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"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." The Analytical and Surface Chemistry (ASC) program of the Division of Chemistry supports the research program of Professor Sanford A. Asher and Professor Rob Coalson of the University of Pittsburgh. Prof. Asher's group is experimentally investigating and the Coalson group is theoretically investigating how electrostatic interactions determine the self assembly and structural ordering of Crystalline Colloidal Arrays (CCA) which form photonic crystal materials. The project will investigate the nature of electrostatic interactions in highly concentrated, low salt suspensions of highly charged, monodisperse colloidal particles. The experimental part of the project aims at unveiling the form of the fundamental electrostatic interactions by direct measurements of electrostatic interactions using Colloidal Probe Atomic Force Microscopy on concentrated, highly charged colloidal particle dispersions. This work examines the charge induced self-assembly of these particles into an fcc CCA array by monitoring light diffraction from the CCA. These experimental results will be rationalized by theoretical calculations that model colloidal particle interactions in high concentration, highly charged particle dispersions. This project will lead to a fundamental understanding of electrostatic interactions in strongly interacting colloids and macromolecules. These interactions are ubiquitous in biological and material systems. Moreover, an increased understanding will enable advances in nanoscience and nanotechnology, especially in the bottom-up fabrication of photonic crystal materials through charge induced self-assembly. The graduate students and postdoctoral researchers who work on this project will be trained to become innovative researchers and leaders in academic science, government research laboratories and in industry. Through this research project, Prof. Asher and Prof. Coalson will provide research training for undergraduate students as well as enrichment opportunities for students of all levels in the greater Pittsburgh community.