研究领域

Physical Chemistry

The research activities of my group involve the application of lasers to the study of equilibrium and dynamic properties of molecules at liquid and solid interfaces. To probe the very thin region (~10Å) that constitutes an interface, we use the interface selective techniques of second harmonic and sum frequency generation. Our picosecond and femtosecond lasers provide the high power needed for nonlinear spectroscopy, and the time resolution to study very fast molecular changes and motions. We have developed new methods to (1) measure the absolute orientation of molecules at liquid interfaces, (2) obtain the energetics of adsorption of neutral and charged molecules to the interface, (3) study chemical equilibria and pH at interfaces that we find are markedly different from their bulk values; and a polarity scale for liquid interfaces‹the motions and unexpected orientational phase transitions of long chain amphiphiles at the air/water interface‹using the new method of second harmonic fluctuation spectroscopy, and most recently vibrational spectroscopy, at interfaces, which greatly extends the power to probe chemical and physical phenomena at interfaces. Using a pump/probe technique, with second harmonic generation as the probe method, has enabled us to observe dynamics at interfaces of excited state cis-trans isomerization, intermolecular energy transfer, solvation dynamics, and rotational molecular motions, which generally differ significantly from their bulk counterparts. We have recently shown that second harmonic spectroscopy can be used to selectively probe the surfaces of centrosymmetric microscopic particles of submicron to micron diameters. Among the surfaces of microscopic particles studied so far are polymer beads in aqueous solution, oil droplet/aqueous emulsions, semiconductor colloids, naturally occurring clay particles, and phospholipid liposomes. The information obtained includes the absolute population of solutes adsorbed to the particle surface, the free energy of adsorption, the electrostatic potential and charge density of charged microscopic particles, and the observation in real time of the transport of organic molecules across a liposome bilayer. This new application of second harmonic and sum frequency spectroscopy provides a new and promising method to selectively study the interfaces of microscopic structures.

近期论文

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"Dynamics of excited state electron transfer t a liquid interface using time-resolved sum frequency generation" Y. Rao, M. Xu, S. Jockusch, N.J. Turro, K.B. Eisenthal, Chem. Phys. Lett. 544, 1-6 (2012). "Binding and cleavage of DNA with the restriction enzyme EcoR1 using time-resolved second harmonic generation" B. Doughty, S.W. Kazer, K.B. Eisenthal, Proceedings of the National Academy of Sciences of the United States of America 108, 50, 19979-19984 (2011). "Observations of Interfacial Population and Organization of Surfactants with Sum-Frequency Generation and Surface Tension" Y. Rao, X. Li, X. Lei, S. Jockusch, M.W. George, N.J. Turro, K.B. Eisenthal, Journal of Physical Chemistry C 115, 24, 12064-12067 (2011). "Molecular Orientational Distribution at Interfaces Using Second Harmonic Generation" Y. Rao, S.Y. Hong, N.J. Turro, K.B. Eisenthal, Journal of Physical Chemistry C 115, 23, 11678-11683 (2011). "Competitive Adsorption at the Air-Water Interface: A Second Harmonic Generation Study" K. Sahu, K.B. Eisenthal, V.F. McNeill, Journal of Physical Chemistry C 115, 19, 9701-9705 (2011). "Probing the Colloidal Gold Nanoparticle/Aqueous Interface with Second Harmonic Generation" L.H. Haber, S.J.J. Kwok, M. Semeraro, K.B. Eisenthal, Chemical Physics Letters 507, 1-3, 11-14 (2011). "Effect of Salt on the Adsorption Affinity of an Aromatic Carbonyl Molecule to the Air-Aqueous Interface: Insight for Aqueous Environmental Interfaces" K. Sahu, V.F. McNeill, K.B. Eisenthal, Journal of Physical Chemistry C 114, 42, 18258-18262 (2010). "Solvation Dynamics at the Air/Water Interface with Time-Resolved Sum-Frequency Generation" Y. Rao, N.J. Turro, K.B. Eisenthal, Journal of Physical Chemistry C 114, 41, 17703-17708 (2010). "Ultrafast Intermolecular Energy Transfer in Heavy Water" L. Piatkowski, K.B. Eisenthal, H.J. Bakker, Physical Chemistry Chemical Physics 11, 40, 9033-9038 (2009). "Water Structure at Air/Acetonitrile Aqueous Solution Interface" Y. Rao, N.J. Turro, K.B. Eisenthal, Journal of Physical Chemistry C 113, 32, 14384-14389 (2009). "Organic Ions at the Air/Water Interface" Y. Rao, M. Subir, E.A. McArthur, N.J. Turro, K.B. Eisenthal, Chemical Physics Letters 477, 4-6, 241-244 (2009). "In-Plane Molecular Rotational Dynamics at a Negatively Charged Surfactant/Aqueous Interface" X.Shang, K.Nguyen, Y.Rao, K.B.Eisenthal, Journal of Physical Chemistry C 112, 51, 20375-20381, (2008). "Second Harmonic Studies of Ions Crossing Liposome Membranes in Real Time" J. Liu, M. Subir, K. Nguyen, K.B. Eisenthal, Journal of Physical Chemistry B 112, 48, 15263-15266 (2008). "Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation" M. Subir, J. Liu, K.B. Eisenthal, Journal of Physical Chemistry C 112, 40, 15809-15812 (2008). "Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation" Y. Rao, D. Song, N.J. Turro, K.B. Eisenthal Journal of Physical Chemistry B 112, 43, 13572-13576 (2008). "Second harmonic generation in neurons: electro-optic mechanism of membrane potential sensitivity" J.Jiang, K.B.Eisenthal and R.Yuste, Biophysical Journal,93,5,L26 (2007). "Sodium channels amplify spine potentials" R.Araya, V.Nikolenko, K.B.Eisenthal and R.Yuste ,Proceedings of the National Academy of Sciences of the United States of America, 104,30,12347-12352 (2007). "Ultrafast excited-state electron transfer at an organic liquid/aqueous interface" E. A. McArthur and K. B. Eisenthal,Journal of the American Chemical Society,128,4,1068-1069 (2006). "Absolute orientation of molecules at interfaces" Y. Rao, M. Comstock and K. B. Eisenthal,Journal of Physical Chemistry B,110,4,1727-1732 (2006). "Imaging membrane potential in dendritic spines" M. Nuriya, J. Jiang, B. Nemet, K. B. Eisenthal and R. Yuste,Proceedings of the National Academy of Sciences of the United States of America,103,3,786-790 (2006). "Molecular rotation at negatively charged surfactant/aqueous interfaces" K. T. Nguyen, X. M. Shang and K. B. Eisenthal,Journal of Physical Chemistry B,110,40,19788-19792 (2006). "The spine neck filters membrane potentials" R. Araya, J. Jiang, K. B. Eisenthal and R. Yuste,Proceedings of the National Academy of Sciences of the United States of America,103,47,17961-17966 (2006). "Second harmonic spectroscopy of aqueous nano- and microparticle interfaces" K. B. Eisenthal,Chemical Reviews,106,4,1462-1477 (2006). "Dendritic spines linearize the summation of excitatory potentials" R. Araya, K. B. Eisenthal and R. Yuste,Proceedings of the National Academy of Sciences of the United States of America,103,49,18799-18804 (2006). "Antibiotic assisted molecular ion transport across a membrane in real time" J. Liu, X. M. Shang, R. Pompano and K. B. Eisenthal,Faraday Discussions,129,291-299 (2005). "Role of water in electron-initiated processes and radical chemistry: Issues and scientific advances" B. C. Garrett, D. A. Dixon, D. M. Camaioni, D. M. Chipman, M. A. Johnson, C. D. Jonah, G. A. Kimmel, J. H. Miller, T. N. Rescigno, P. J. Rossky, S. S. Xantheas, S. D. Colson, A. H. Laufer, D. Ray, P. F. Barbara, D. M. Bartels, K. H. Becker, H. Bowen, S. E. Bradforth, I. Carmichael, J. V. Coe, L. R. Corrales, J. P. Cowin, M. Dupuis, K. B. Eisenthal, J. A. Franz, M. S. Gutowski, K. D. Jordan, B. D. Kay, J. A. LaVerne, S. V. Lymar, T. E. Madey, C. W. McCurdy, D. Meisel, S. Mukamel, A. R. Nilsson, T. M. Orlando, N. G. Petrik, S. M. Pimblott, J. R. Rustad, G. K. Schenter, S. J. Singer, A. Tokmakoff, L. S. Wang, C. Wittig and T. S. Zwier,Chemical Reviews,105,1,355-389 (2005). "Electrostatic surface charge at aqueous/alpha-Al2O3 single-crystal interfaces as probed by optical second-harmonic generation" J. P. Fitts, X. M. Shang, G. W. Flynn, T. F. Heinz and K. B. Eisenthal,Journal of Physical Chemistry B,109,16,7981-7986 (2005).