We measure several fundamental electronic properties of molecules such as charge transfer and electronic delocalization using a technique known as Stark spectroscopy. Stark spectroscopy involves applying large electric fields to molecules in films or matrices and analyzing the effects of the field perturbation on the absorption or emission spectrum. We have recently focused on the properties of MEH-PPV and other molecules used to make to organic light emitting diodes (OLED's). Stark spectroscopy reveals the mechanism by which a large applied electric field, such as those present in OLEDs, produces undesirable emission quenching and suggests strategies for minimizing this loss of device efficiency through modifications of the polymer structure.
Emission properties of Single Molecules and Aggregates
Recent years has seen a huge growth in the use of organic conjugated oligomers and polymers in the design of light emitting diodes (OLEDs) and photovoltaic cells. When these molecules are placed in thin films to fabricate devices, they typically form aggregates. These confer several desirable properties for device function such as protection from oxidative damage and enhanced charge transport. However, they also typically shift the wavelength of emission to lower energies and often significantly reduce its intensity. Our group is using microscopy and spectroscopy to investigate the relationships between molecular structure and the brightness and photo-stability of molecules in the solid state, both in isolation (i.e. as single molecules) and as aggregates. We are also developing methods to image aggregation in films at high resolution and to follow the nucleation of aggregates in the solution phase.
- "Effects of Solvent Properties on the Spectroscopy and Dynamics of Alkoxy-Substituted PPV Oligomer Aggregates," Woong Young So, Jiyun Hong, Janice J. Kim, Gizelle A. Sherwood, Kelly Chacon-Madrid, James H. Werner, Andrew P. Shreve, and Linda A. Peteanu, J. Phys. Chem. B 116 10504 (2012)
- "Wavelength Dependence of the Fluorescence Quenching Efficiency of Nearby Dyes by Gold Nanoclusters and Nanoparticles: The Roles of Spectral Overlap and Particle Size," Chowdhury, Sanchari; Wu, Zhikun; Jaquins-Gerstl, Andrea; Liu, Shengpeng; Dembska, Anna; Armitage, Bruce A.; Jin, Rongchao; Peteanu, Linda A., J. Phys. Chem. C 115, 20105 (2011)
- "Visualizing Core-Shell Structure in Substituted PPV Oligomer Aggregates Using Fluorescence Lifetime Imaging Microscopy (FLIM)," Peteanu, Linda A.; Sherwood, Gizelle A.; Werner, James H.; Shreve, Andrew P.; Smith, Timothy M.; Wildeman, Jurjen, J. Phys. Chem. C 115 15607 (2011)
- "Fluorescent DNA Nanotags Featuring Covalently Attached Intercalating Dyes: Synthesis, Antibody Conjugation, and Intracellular Imaging," Stadler, Andrea L.; Delos Santos, Junriz O.; Stensrud, Elizabeth S.; Dembska, Anna; Silva, Gloria L.; Liu, Shengpeng; Shank, Nathaniel I.; Kunttas-Tatli, E.; Sobers, Courtney J.; Gramlich, Philipp M. E.; Carell, Thomas; Peteanu, Linda A.; McCartney, Brooke M.; Armitage, Bruce A., Bioconjugate Chem. 22, 1491 (2011)
- "pH-Responsive Fluorescent Molecular Bottlebrushes Prepared by Atom Transfer Radical Polymerization," Nese, Alper; Lebedeva, Natalia V.; Peteanu, Linda; Sheiko, Sergei, S.; Matyjaszewski, Krzysztof, Macromolecules 44 5905 (2011)
- "Vibrationally coherent photochemistry in the femtosecond primary event of vision," Wang, Qing, Robert W. Schoenlein, Linda A. Peteanu, Richard A. Mathies, and Charles V. Shank, Science 266, no. 5184 (1994): 422-424.
- "Biodegradable nanogels prepared by atom transfer radical polymerization as potential drug delivery carriers: synthesis, biodegradation, in vitro release, and bioconjugation," Oh, Jung Kwon, Daniel J. Siegwart, Hyung-il Lee, Gizelle Sherwood, Linda Peteanu, Jeffrey O. Hollinger, Kazunori Kataoka, and Krzysztof Matyjaszewski, Journal of the American Chemical Society 129, no. 18 (2007): 5939-5945.
- "Light‐induced reversible formation of polymeric micelles," Lee, Hyung‐il, Wei Wu, Jung Kwon Oh, Laura Mueller, Gizelle Sherwood, Linda Peteanu, Tomasz Kowalewski, and Krzysztof Matyjaszewski, Angewandte Chemie 119, no. 14 (2007): 2505-2509.
- "Direct observation of fast proton transfer: femtosecond photophysics of 3-hydroxyflavone," Schwartz, Benjamin J., Linda A. Peteanu, and Charles B. Harris, The Journal of Physical Chemistry 96, no. 9 (1992): 3591-3598.
- "The electronic spectrum of the amino acid tryptophan in the gas phase," Rizzo, Thomas R., Young D. Park, Linda A. Peteanu, and Donald H. Levy, The Journal of Chemical Physics 84, no. 5 (1986): 2534-2541.
- "Mechanism of Ligand-Controlled Emmision in Silicon Nanoparticles." So, W.Y., Li, Q., Legaspi, C.M., (...), Jin, R., Peteanu, L.A. ACS Nano 12(7). (2018).
- "Rigidity and Polarity Effects on the Electronic Properties of Two Deep Blue Delayed Fluorescence Emitters." Legaspi, C.M., Stubbs, R.E., Wahadoszaman, M., (...), Zheng, Q., Rothberg, L.J. Journal of Physical Chemistry C 122(22). (2018).
- "Eliminating Spurious Zero-Efficiency FRET States in Diffusion-Based Single-Molecule Confocal Microscopy." Dey, S.K., Pettersson, J.R., Topacio, A.Z., Das, S.R., Peteanu, L.A. Journal of Physical Chemistry Letters 9(9). (2018).
- "Detection of Ultralow Concentrations of Non-emissive Conjugated Polymer Aggregates via Fluorescence Correlation Spectroscopy." Wu, E.C., Stubbs, R.E., Peteanu, L.A., (...), McCullough, R.D., Wildeman, J. Journal of Physical Chemistry B 121(21). (2017).
- "Theoretical Investigations on the Roles of Intramolecular Structure Distortion versus Irregular Intermolecular Packing in Optical Spectra of 6T Nanoparticles." Li, W., Peng, Q., Ma, H., (...), Peteanu, L.A., Shuai, Z. Chemistry of Materials 29(6). (2017).