Chemistry 620
Welcome to Photons 'R Us!

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Last Announcements page update: 02/11/08
The class will read four papers in detail. The papers listed below have been selected by the class for discussion in Spring 2008. The summary questions provide guidelines for the written critiques students submit each as problem sets.
Papers Selected for Class Discussion (access via UDelLib Electronic Journals)
Paper I

Klimov, V.I. and D.W. McBranch, Femtosecond high-sensitivity, chirp-free transient absorption spectroscopy using kilohertz lasers. Optics Letters, 23(4), 277-279 (1998).
Paper II

Sanchez, E.J., L. Novotny, and X.S. Xie, Near-field fluorescence microscopy based on two-photon excitation with metal tips. Physical Review Letters, 82(20), 4014-4017, (1999).
Paper III

Campagnola, P. J., Wei, M. D., Lewis, A., Loew, L. M., High-resolution nonlinear optical imaging of live cells by second harmonic generation. Biophys. J., 77(6), 3341-3349 (1999).
Paper IV

Kukura, P.; Yoon, S.; Mathies, R.A. Femtosecond stimulated Raman spectroscopy, Anal. Chem., 78 (17): 5952-5959 (2006).
Papers Under Consideration for Study
Several of the papers listed below have been read by the class in the past. Students are encouraged to submit papers they are interested in studying by adding the citation to the paper ballot they turn in with their homework portfolios on 4/10/08.
Electronic Absorption Measurements Klimov, V.I. and D.W. McBranch, Femtosecond high-sensitivity, chirp-free transient absorption spectroscopy using kilohertz lasers. Optics Letters, 23(4), 277-279 (1998).

From the abstract: A simple method is demonstrated for high-sensitivity, chirp-free measurements of femtosecond (fs) transient absorption over the entire bandwidth of a white-light continuum probe.

B. Kraabel, V. I. Klimov, R. Kohlman, S. Xu, H-L. Wang, and D. W. McBranch, Unified picture of the photoexcitations in phenylene-based conjugated polymers: Universal spectral and dynamical features in subpicosecond transient absorption. Phys. Rev. B , 61, 8501-8516 (2000).

From the abstract: Using subpicosecond transient absorption spectroscopy, we investigate the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer.

Ellingson, R.J., Beard, M. C., Johnson, J. C. et al., Highly efficient multiple exciton generation in colloidal PbSe and PbS quantum dots. Nano Letters, 5(5) 865-871 (2005).

From the abstract: We report ultra-efficient multiple exciton generation (MEG) for single photon absorption in colloidal PbSe and PbS quantum dots (QDs). We employ transient absorption spectroscopy and present measurement data acquired for both intraband as well as interband probe energies. Quantum yields of 300% indicate the creation, on average, of three excitons per absorbed photon for PbSe QDs at photon energies that are four times the QD energy gap.
Fluorescence Measurements

K.G. Heinze, A. Koltermann, P. Schwille. Simultaneous two-photon excitation of distinct labels for dual-color fluorescence crosscorrelation analysis, Proc. Nat. Acad. Sci. USA, 97(19), 10377-10382 (2000).

From the abstract: In this work, we demonstrate that two-photon excitation combined with dual-color fluorescence correlation spectroscopy can be the key to simplifying simultaneous investigations of multiple fluorescent species significantly on a single-molecule scale. ... The concept of dual-color two-photon fluorescence crosscorrelation analysis is introduced and experimentally demonstrated with an established assay probing the selective cleavage of dual-labeled DNA substrates by restriction endonuclease EcoRI.

Sanchez, E.J., L. Novotny, and X.S. Xie, Near-field fluorescence microscopy based on two-photon excitation with metal tips. Physical Review Letters, 82(20), 4014-4017, (1999).

From the abstract: We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with femtosecond laser pulses of proper polarization. ... The spatial resolution is shown to be better than that of the conventional aperture.

Eigen, M. and R. Rigler, Sorting Single Molecules - Application To Diagnostics And Evolutionary Biotechnology. Proc. Nat. Acad. Sci. USA, 91(13), 5740-5747, (1994).

From the abstract: A method is described for detection and identification of single molecules in solution. The method is based on fluorescence correlation spectroscopy, which records spatio-temporal correlations among fluctuating light signals, coupled with devices for trapping single molecules in an electric field.

Vibrational Absorption Measurments Rammelsberg, R., Hessling, B., Chorongiewski, H., Gerwert, K.
Molecular reaction mechanisms of proteins monitored by nanosecond step-scan FT-IR difference spectroscopy. Appl. Spectrosc., 51(4), 558-562 (1997).

From the abstract: Step-scan FT-IR difference spectroscopy with 100-ns time resolution is applied to the membrane protein bacteriorhodopsin. The experimetal setup and data acquisition are described in great detail.

Leeson, D. T., Gai, F., Rodriguez, H. M. et al., Protein folding and unfolding on a complex energy landscape. Proc. Nat. Acad. Sci. USA, 97(6), 2527-2532 (2000).

From the abstract: Herein, we introduce a new type of kinetics experiment that shows how different unfolding pathways can be selected by varying the initial reaction conditions. The relaxation kinetics of the major cold shock protein of Escherichia coli (CspA) in response to a laser-induced temperature jump are exponential for small temperature jumps, indicative of folding through a two-state mechanism.

Campagnola, P. J., Wei, M. D., Lewis, A., Loew, L. M., High-resolution nonlinear optical imaging of live cells by second harmonic generation. Biophys. J., 77(6), 3341-3349 (1999).

From the abstract: By adapting a laser scanning microscope with a titanium sapphire femtosecond pulsed laser and transmission optics, we are able to produce live cell images based on the nonlinear optical phenomenon of second harmonic generation (SHG). Second harmonic imaging (SHIM) is an ideal method for probing membranes of living cells because it offers the high resolution of nonlinear optical microscopy with the potential for near-total avoidance of photobleaching and phototoxicity.
Raman Scattering Measurements Qin L., Zou, S., Xue C., Atkinson, A., Schatz G.C, Mirkin, C.A. “Designing, fabricating, and imaging Raman hot spots” Proc. Nat. Acad. Sci. USA, 103(36), 13300-13303 (2006).

From the abstract: ... disk thickness and interparticle gap are precisely controlled from 5 nm to many micrometers. Confocal Raman microscopy demonstrates that disk thickness and gap play a crucial role in determining surface-enhanced Raman scattering intensities.

D.P. Cherney, J.C. Conboy, J.M. Harris*, Optical-Trapping Raman Microscopy Detection of Single Unilamellar Lipid Vesicles. Anal. Chem. 75, 6621-6628 (2003).

From the abstract: Raman spectra of individual unilamellar phospholipid vesicles ( 0.6 ím in size) have been acquired by optical trapping confocal Raman microscopy over the 900-3200 cm-1 region. Raman scattering from the phospholipid bilayer of a single, trapped liposome could be detected, along with molecular species trapped within the vesicle.

Kukura, P.; Yoon, S.; Mathies, R.A. Femtosecond stimulated Raman spectroscopy, Anal. Chem., 78 (17): 5952-5959 (2006).

From the introduction: Despite [many] advances, limitations exist that prevent these methods from exploiting the full potential of Raman scattering. We asked: Can an analytical resonance Raman technique be developed that can produce high-S/N spectra that are immune to background fluorescence, with short data-acquisition times?
 
 
All of the papers listed are available via the UD Library Electronic Journals page.