Research Topics

 

Experimental Methods

 

 

Fayer Lab Research Overview

 

 

The Fayer Group is interested in the problem the dynamics, structure, and intermolecular interactions in complex molecular systems. Of particular interest are liquid systems that have mesoscopic structure, that is, an organization of the molecules that occurs over distance scales that extend well beyond the normal first and second solvation shells, which always found in liquids. We develop and apply experimental methods that allow us to examine fast molecular processes that are occurring under thermal equilibrium conditions. A vast amount of chemistry occurs at or near room temperature in the ground electronic state of molecules. From synthetic organic chemistry to biological chemistry, chemical processes occur on fast time scales. Although the rate of an overall process may be slow, key events on the molecular level are fast. For example, in a second order reaction, the rate of the reaction can be controlled by the diffusion of the species into contact, but the actual reactive event occurs on a very fast time scale that involves structural fluctuations to bring the system to the transition state. Proton transfer through a fuel cell membrane is slow, but the essential steps to move a proton depend on water hydrogen bond rearrangements, that are exceedingly fast. We are developing and applying new experimental and theoretical approaches to the study of important chemical processes and the nature of molecular systems that are governed by fast dynamics.
 

Why do we want to study fast molecular dynamics? On Earth, an enormous fraction of molecular processes in chemistry, biology, and materials science occur at or near the room temperature. These processes are driven by the thermal energy contained in the systems. They occur in the ground electronic state rather than through promotion to a high energy state by the absorption of light. While there are important chemical systems that are driven by the absorption of light, for example, the initial step in photosynthesis, most chemistry occurs through the dynamics induced by ambient thermal energy. But why should we be interested in fast molecular dynamics? Molecules are small. Therefore, the intrinsic time scale for molecular motions is very fast, on the order of picoseconds (ps), 10-12 seconds. Fundamental steps in molecular processes occur on very fast time scales. Slow processes, which are frequently observed in chemistry and biology, occur through sequences of very fast steps. Furthermore, as mentioned above, most chemistry and biology are driven thermally, that is by the heat that is present in systems at ambient temperatures. Therefore, understanding fast molecular dynamics under thermal equilibrium conditions is central to understanding the nature of the world around us.
 

We are studying a range of interrelated problems that involve complex systems of molecules. We are using ultrafast infrared methods including two dimensional vibrational echoes, polarization selective pump probe experiments, and heterodyne detected transient grating experiments, ultrafast to slow optical heterodyne detected optical Kerr effect experiments, as well as very fast fluorescence measurements. We are investigating room temperature ionic liquids (RTILs), how water influences them, and how water behaves in a sea of ions. We are also studying the influence on RTILs of lithium cations and other solutes. We are studying the dynamics of water in nanoscopic systems such as water nanopools in reverse micelles, water nanochannels in Nafion fuel cell membranes, water in planar systems, particularly at the surfaces of membranes and proteins, and we are studying the effect of charged solutes (salts) on water dynamics. We are examining the fast dynamics inside of membranes, and how they are influenced by additions such as cholesterol. We are studying dynamics and interaction in supercooled liquids, and liquid crystals. We are also investigating how nanoscopic environment influence important chemical processes, such a proton transfer in nanoscopic water environments like fuel cell membranes.
 

The following is a list of very recent review and feature articles that summarize some of our work.

 

 

Recent Reviews


353. “Ultrafast 2D IR Vibrational Echo Spectroscopy,” Junrong Zheng, Kyungwon Kwak, and M. D. Fayer Acc. of Chem. Res. 40, 75-83 (2007).

357. “Probing Dynamics of Complex Molecular Systems with Ultrafast 2D IR Vibrational Echo Spectroscopy,” Ilya J. Finkelstein, Junrong Zheng, Haruto Ishikawa, Seongheun Kim, Kyungwon Kwak, and M. D. Fayer Phys. Chem. Chem. Phys., 9, 1533-1549, (2007).

361. “Ultrafast 2D-IR Vibrational Echo Spectroscopy: A Probe of Molecular Dynamics,” Sungnam Park, Kyungwon Kwak, and M. D. Fayer Laser Phys. Lett. 4, 704-718 (2007).

369. “Water Dynamics and Proton Transfer in Nafion Fuel Cell Membranes,” David E. Moilanen, D.B. Spry, and M. D. Fayer Langmuir 24, 3690-3698 (2007).

370. “Water Dynamics – The Effects of Ions and Nanoconfinement,” Sungnam Park, David E. Moilanen, and M. D. Fayer J. Phys. Chem. B 112, 5279-5290 (2008).


379. “Dynamics of Liquids, Molecules, and Proteins Measured with Ultrafast 2D IR Vibrational Echo Chemical Exchange Spectroscopy,” M. D. Fayer Ann. Rev. P. Chem. 60, 21-38 (2008).

384. “Water Dynamics in Salt Solutions Studied with Ultrafast 2D IR Vibrational Echo Spectroscopy,” M. D. Fayer, David E. Moilanen, Daryl Wong, Daniel E. Rosenfeld, Emily E. Fenn, and Sungnam Park Acc. of Chem. Res. 42, 1210-1219 (2009).

390. “Analysis of Water in Confined Geometries and at Interfaces,” M. D. Fayer and Nancy E. Levinger Ann. Rev. Analytical Chem. 3, 89-107 (2010).

403. “Dynamics of Water Interacting with Interfaces, Molecules, and Ions,” M. D. Fayer Acc. of Chem. Res. 45, 3-14 (2012).

411. “Water in a Crowd,” M. D. Fayer, Physiology 26, 381-392 (2011).

413. “Protein Dynamics Studied with Ultrafast Two-Dimensional Infrared Vibrational Echo Spectroscopy,” Megan C. Thielges and M. D. Fayer Acc. Chem. Research 45, 1866-1874 (2012).
 

 

 

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