Physical and Analytical Chemistry, Chemical Physics and Biology
Margaret Jorgenson Memorial Fellowship, 1997
National Science Foundation CAREER Award, 2005
Postdoctoral Fellow, University of Pennsylvania
Joined UCI faculty in 2002
Detailed knowledge of molecular structures and dynamics in condense phases is essential to a complete and predictive understanding of chemical, biological, and materials processes. Our research program is directed to determine how molecular structures change in time, at equilibrium and during reactions. Topics of current interest include: structure and dynamics of peptides, proteins, liquids, and interfaces; carrier dynamics in solar cell materials; and nanoplasmonics. These endeavors lead us to devise new techniques in nonlinear spectroscopy and microscopy that can provide detailed information on the time dependence of nuclear and electronic motions.Ultrafast two-dimensional infrared (2D IR) spectroscopy and its applications in biomolecular structure determination and condensed matter dynamics.
We are exploiting new experimental techniques that are vibrational analogues of multidimensional NMR. The extension beyond a single dimension gives these techniques the ability to disentangle structural information from complex spectra where the couplings, correlations, and relative angular orientations between structural units are revealed as "cross peaks". Moreover, the picosecond time resolution of 2D IR makes it an ideal structural probe for short-lived intermediates in chemical or biological processes once initiated by external triggers. The necessary science of multidimensional multicolor IR spectroscopy is being developed in our laboratory. Experimental results are compared to computer simulations to bring out atomic level understanding of the processes in question.
We are applying 2D IR to the study of complex systems such as peptides, proteins, liquids, membranes, and their composite interfaces. Structural distributions, evolutions, and their environmental dependence are investigated. Dynamics of vibrational relaxation, molecular reorientation, intermode vibrational energy transfer, and chemical exchange are studied. Strategic incorporation of isotope labels and vibrational markers are used to zoom into atomic moieties of particular interest. Current topics include peptide-membrane interactions, amyloid peptide aggregation, and enzyme catalysis. Sum-frequency generation (SFG) spectroscopy and microscopy and their applications in surface chemistry, polymer physics, and nanoplasmonics.
We are developing SFG spectroscopic and microscopic techniques that can reveal structure and dynamics in noncentrosymmetric systems, such as surfaces, interfaces, and biological tissues. By combining these techniques with surface plasmon enhancement of novel nanostructures, we will push the detection limit towards study of trace molecules at interfaces. We are building a femtosecond SFG microscope that is capable of time-resolving nonlinear response as well as multiplex detection in the frequency domain with submicron spatial resolution. Applications include catalysis, photon-driven devices, and biological systems. Nonlinear scattering-type scanning near-field optical microscopy (s-SNOM) and its applications in nanoplasmonics and carrier dynamics.
We are pushing our temporal and spatial resolution to the femtosecond-nanometer range with a new s-SNOM instrument that is capable of near-field imaging, nano FTIR, and pump-probe nanoscopy. We are applying s-SNOM to near-field mapping of plasmonic nanostructures and carrier dynamics in solar cell materials.Research Opportunities:Graduate, Undergraduate, and Postdoctoral Research positions available
"General noise suppression scheme with reference detection in heterodyne nonlinear spectroscopy," Y. Feng, I. Vinogradov, and N.-H. Ge, Opt. Express
, 25, 26262 [link]
"Structure of Penta-alanine Investigated by Two-Dimensional Infrared Spectroscopy and Molecular Dynamics Simulation," Y. Feng, J. Huang, S. Kim, J. H. Shim, A. MacKerell, and N.-H. Ge, J. Phys. Chem. B
, 120, 5325 [link] [e-print without subscription]
"Polarization-Sensitive Sum-Frequency Generation Microscopy of Collagen Fibers," Y. Han, J. Hsu, N.-H. Ge, and E. O. Potma, J. Phys. Chem. B
, 119, 3356 [link] [e-print without subscription]
N Isotope Dependence of the Amide-I/II 2D IR Cross Peaks for the Fully Extended Peptides," H. Maekawa, G. Ballano, F. Formaggio, C. Toniolo, and N.-H. Ge, J. Phys. Chem. C
, 118, 29448 [link] [e-print without subscription]
"Mapping Molecular Orientation with Phase Sensitive Vibrationally Resonant Sum-Frequency Generation Microscopy," Y. Han, V. Raghunathan, R.-R. Feng, H. Maekawa, C.-Y. Chung, Y. Feng, E. Potma, and N.-H. Ge, J. Phys. Chem. B
, 117, 6149. [link] [e-print without subscription]
"Vibrational Correlation between Conjugated Carbonyl and Diazo Modes Studied by Single and Dual Frequency Two-Dimensional Infrared Spectroscopy," H. Maekawa, S. Sul, and N.-H. Ge, Chem. Phys.
, 422, 22. Special issue honoring Professor Robin Hochstrasser. [link]
"Picosecond Rotational Interconversion Adjacent to a C=O Bond Studied by Two-Dimensional Infrared Spectroscopy," H. Maekawa and N.-H. Ge, J. Phys. Chem. B
, 116, 11292 [link] [e-print without subscription]
"Rapid Vibrational Imaging with Sum Frequency Generation Microscopy," V. Raghunathan, Y. Han, O. Korth, N.-H. Ge, and E. O. Potma, Opt. Lett.
, 36, 3891. [link]
"Stapling of a 310-Helix with Click Chemistry," Ø. Jacobsen, H. Maekawa, N.-H. Ge, C. H. Gorbitz, P. Rongved, O. P. Ottersen, M. Amiry-Moghaddam, and J. Klaveness, J. Org. Chem.
, 76, 1228. [link] [e-reprint without subscription]
"Linear and Two-Dimensional Infrared Spectroscopic Study of the Amide-I and II Modes in Fully Extended Peptide Chains," H. Maekawa, G. Ballano, C. Toniolo, and N.-H. Ge, J. Phys. Chem. B
, 115, 5168. [link] [e-reprint without subscription]
“Comparative Study of Electrostatic Models for the Amide-I and -II Modes: Linear and Two-Dimensional Infrared Spectra,” H. Maekawa and N.-H. Ge, J. Phys. Chem. B
, 114, 1434. [link] [e-reprint without subscription]
“Interactions of Tyrosine in Leu-Enkephalin at a Membrane-Water Interface: an Ultrafast Two-Dimensional Infrared Study Combined with Density Functional Calculations and Molecular Dynamics Simulations,” S. Sul, Y. Feng, U. Le, D. J. Tobias, and N.-H. Ge, J. Phys. Chem. B
, 114, 1180. [link] [e-reprint without subscription]
"Toward Detecting the Formation of a Single Helical Turn by 2D IR Cross-Peaks between the Amide-I and -II modes," H. Maekawa, M. De Poli, A. Moretto, C. Toniolo, and N.-H. Ge, J. Phys. Chem. B. 2009
, 113, 11775. [link] [e-reprint without subscription]
"Sensitivity of 2D IR Spectra to Peptide Helicity: a Concerted Experimental and Simulation Study of an Octapeptide," N. Sengupta, H. Maekawa, W. Zhuang, S. Mukamel, D. J. Tobias and N.-H. Ge, J. Phys. Chem. B. 2009
, 113, 12037. [link] [e-reprint without subscription]
"Couplings between Peptide Linkages across a 310
-Helical Hydrogen Bond Revealed by Two-Dimensional Infrared Spectroscopy," H. Maekawa, M. De Poli, C. Toniolo, and N.-H. Ge, J. Am. Chem. Soc. 2009
, 131, 2042. [link] [e-reprint without subscription]
"Chain Length Dependence of Two-Dimensional Infrared Spectral Pattern Characteristic to 310-Helix Peptides," Maekawa, F. Formaggio, C. Toniolo, and N.-H. Ge, in Ultrafast Phenomena XVI (eds: P Corkum, S.De Silvestri, KA Nelson, E Riedle, RW Schoenlein), Spring-Verlag, p. 415 (2009)
"Onset of 310
-Helical Secondary Structure in Aib Oligopeptides Probed by Coherent 2D IR Spectroscopy," H. Maekawa, F. Formaggio, C. Toniolo, and N.-H. Ge, J. Am. Chem. Soc. 2008
, 130, 6556. [link] [e-reprint without subscription]
"Two-Dimensional Infrared Spectral Signatures of 310
- and alpha-Helical Peptides," H. Maekawa, C. Toniolo, A. Moretto, Q. Broxterman, and N.-H. Ge, J. Phys. Chem. B 2007
, 111, 3222. [link] [e-reprint without subscription]
“Conformations of N-Acetyl-L-Prolinamide by Two-Dimensional Infrared Spectroscopy,” Sul S, Karaiskaj D, Jiang Y, and Ge N-H, J. Phys. Chem. B 2006
, 110, 19891. [link] [e-reprint without subscription]
“Different Spectral Signatures of Octapeptide 310
- and alpha-Helices Revealed by Two-Dimensional Infrared Spectroscopy,” Maekawa H, Toniolo C, Moretto A, Broxterman Q, and Ge N-H, J. Phys. Chem. B 2006
, 5834. [link] [e-reprint without subscription]
"Resolving Conformations of Acetylproline-NH2 by coherent two-dimensional infrared spectroscopy," in Ultrafast Phenomena XIV , Karaiskaj D, Sul S, Jiang Y, Ge N-H (eds: T Kobayashi, T Okada, T Kobayashi, KA Nelson, S.De Silvestri), Spring-Verlag, p. 545 (2005)
"Local Structure and Dynamics of Liquid Acetone by Heterodyned 2D IR Spectroscopy." in Ultrafast Phenomena XIII
, Ge N-H, Zanni MT, Hochstrasser RM (eds.: MM Murnane, NF Scherer, RJD Miller, AM Weiner), Spring-Verlag, pp. 592-594 (2003
"Femtosecond Two-Dimensional Infrared Spectroscopy: IR-COSY and THIRSTY." Ge N-H, Hochstrasser RM, PhysChemComm 2002
"Effects of Vibrational Frequency Correlations on Two-Dimensional Infrared Spectra." Ge N-H, Zanni, MT, Hochstrasser RM, J. Phys. Chem. A 2002
"2D IR Spectroscopy Can Be Designed to Eliminate the Diagonal Peaks and Exhibit Only the Cross Peaks Needed for Structure Determination." Zanni MT, Ge N-H, Kim YS, Hochstrasser RM, Proc. Natl. Acad. Sci. USA 2001, 98, 11265.
"Femtosecond Studies of Electron Dynamics at Interfaces." Ge N-H, Wong CM, Harris CB, Acc. Chem. Res. 2000
"Femtosecond Dynamics of Electron Localization at Interfaces." Ge N-H, Wong CM, Lingle RL, McNeill JD, Gaffney KJ, Harris CB, Science 1998
"Dynamics and Spatial Distribution of Electrons in Quantum Wells at Interfaces Determined by Femtosecond Photoemission Spectroscopy," McNeill JD, Lingle RL, Ge N-H, Wong CM, Harris CB, Phys. Rev. Lett. 1997, 79, 4645.
"Femtosecond Dynamics of Electrons on Surfaces and at Interfaces." Harris CB, Ge N-H, Lingle RL, McNeill JD, Wong CM, Annu. Rev. Phys. Chem. 1997, 48, 711.
“Femtosecond Studies of Electron Tunneling at Metal-Dielectric Interfaces,” Lingle RL, Ge N-H, Jordan RE, McNeill JD, and Harris CB, Chem. Phys. 1996, 205, 191.
American Chemical Society
American Physical Society
Optical Society of America
American Association of Advanced Science