This is a proposal for a theoretical study, by combined numerical simulations and analytical techniques, of the electrostatics of the interface of a polar liquid in contact with a solute of a nanometer dimension. Intellectual Merit. Electrostatics of dielectrics and polar liquids are reasonably well understood on the scale of macroscopic experiments and on the microscopic scale where numerical simulations have produced a very detailed picture of the energetics and the electrostatic potential distribution. What happens on the scale of nanometers and, beyond that on the meso-scale, is mostly unknown. The common approach to study this length-scale, vastly important to a great number of presently hot problems, is to extend the experience learned from either micro- or macro-scales, with an often resulting conflict of ideas. Our results from the last grant period suggest that neither microscopic nor macroscopic pictures apply to the nanometer liquid interface. The understanding of what makes this scale so distinct from the previous experience will be gained by combining extensive numerical simulations with the development of new theoretical tools and formalisms. The proposed research includes two components. First, we will numerically study electrostatics of cavities in force-field fluids focusing on the distribution of the potential and potential fluctuations inside the cavities and how these properties scale with the cavity size. A formal model of electrostatics in cavities will be developed. Second, we will study the electrostatics of redox proteins. We will address the problem of the parameters affecting the activation barrier for protein electron transport and general electrostatics of the protein/water interface. The two projects will then be combined to develop a model of electrostatics of patchy polar/nonpolar interfaces often encountered in biological and nanoscience applications. Broader Impact. Interfacial electrostatics affects many problems of fundamental significance and many practical applications. The distribution and fluctuations of the electrostatic potential inside proteins is of general interest for bioenergetics in problem ranging from equilibrium redox potential to electron and energy transport. Many of these questions are currently very hard to approach experimentally. This theoretical research will make contact with experiment and will develop new theoretical tools to understand solvation and energetics of proteins. The project will also provide some fundamental prescriptions to guide the development of artificial photosynthesis. The new mechanisms of electron transport proposed in this research offers the opportunity of activationless hopping transport with a much higher energetic efficiency than has been previously anticipated. In addition, the distribution of the interfacial electrostatic potential at the nano-scale liquid interface is critical for the transport and capture of charge carriers by nanoparticles employed as active components in solar energy harvesting. The combination of simulation techniques, formal models, and interpretation of experiment proposed in this project will provide an excellent interdisciplinary training ground for graduate students and postdoctoral research associates. Some aspects of the project may be appropriate for undergraduate research. Four graduate students and a postdoctoral associate have been trained during the last grant period. Research will be combined with outreach activities to help training high-school teachers and create demonstration modules to inspire interest in science in local schools.
|Effective start/end date||8/1/09 → 7/31/13|
- National Science Foundation (NSF): $405,000.00