Understanding of the superior stability of Silicon- and oxygen-containing hydrogenated amorphous carbon in harsh environments

  • By Leena Aggarwal
  • 3 January 2018

Recently, Tevis D. B. Jacobs and colleagues have shown how silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) coating enhance the thermal stability in vacuum, but tremendously increases the thermo-oxidative stability and the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO). These findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.

Department of Chemistry
PhD, Chemistry, Harvard University

Raúl Hernández Sánchez's research group is interested in combining supramolecular, inorganic, and materials chemistry to synthesize functional systems that bridge the gap between nanoscale materials and molecular chemistry. Their research is focused on developing new synthetic methodologies to access well-defined nanometer-sized clusters where they can investigate surface structure-function relationships relevant in catalytic and magnetic materials. Other efforts in the Hernández Sánchez (HS) group are aimed at designing and synthesizing structural analogues of carbon nanotubes where exquisite control of the resulting framework allows for properties manipulation.

Students in the HS group will engage in synthetic chemistry and develop familiarity with a range of spectroscopic, electrochemical, crystallographic and magnetic techniques. While rooted in synthetic chemistry, research in the HS group will interface with materials, organic, theory, and physical chemistry.

Most Cited Publications
  1. "High total proton conductivity in large-grained yttrium-doped barium zirconate," Y Yamazaki, R Hernandez-Sanchez, SM Haile, Chemistry of Materials 21, 2755 (2009
  2.  "Cation non-stoichiometry in yttrium-doped barium zirconate: phase behavior, microstructure, and proton conductivity," Y Yamazaki, R Hernandez-Sanchez, SM Haile, Journal of Materials Chemistry 20, 8158 (2010)
  3. "Ligand Field Strength Mediates Electron Delocalization in Octahedral [(HL)2 Fe6 (L')m]n+ Clusters," Hernández Sánchez, R., Zheng, S.-L., Betley, T.A. Journal of the American Chemical Society 137(34), 11126-11143 (2015)
  4. "Synthesis of open-shell, bimetallic Mn/Fe trinuclear clusters," Powers, T.M., Gu, N.X., Fout, A.R., Hernández Sánchez, R., (...). Journal of the American Chemical Society 135(38), 14448-14458 (2013)
  5. "Single-Walled Carbon Nanotubes: Mimics of Biological Ion Channels," 
    Amiri, H., Shepard, K.L., Nuckolls, C., Hernández Sánchez, R. Nano Letters 17(2), 1204-1211 (2017)
Recent Publications
  1. "Defying strain in the synthesis of an electroactive bilayer helicene." Milton, Margarita, Nathaniel J. Schuster, Daniel W. Paley, Raúl Hernández Sánchez, Fay Ng, Michael L. Steigerwald, and Colin Nuckolls. Chemical Science (2018).
  2. "Thermally persistent high spin ground states in octahedral iron clusters." Hernández Sánchez, Raúl, and Theodore A. Betley. Journal of the American Chemical Society (2018).
  3. "Molecular Materials for Nonaqueous Flow Batteries with a High Coulombic Efficiency and Stable Cycling," Margarita Milton, Qian Cheng, Yuan Yang, Colin Nuckolls, Raúl Hernández Sánchez, Thomas J Sisto, Nano Letters, 17, 7859 (2017)
  4. "Towards Catalytic Ammonia Oxidation to Dinitrogen: A Synthetic Cycle Using a Simple Manganese Complex,"Megan Keener, Madeline Peterson, Raúl Hernández Sánchez, Victoria F Oswald, Guang Wu, Gabriel Menard, Chemistry-A European Journal 23, 11479 (2017)
  5. "Single-Walled Carbon Nanotubes: Mimics of Biological Ion Channels,"Hasti Amiri, Kenneth L Shepard, Colin Nuckolls, Raúl Hernández Sánchez, American Chemical Society, 17, 1204 (2017)

Asher Symposium: Adventures in Enhanced Spectroscopies: Resonance Raman, Surface Enhanced Raman, and Twisted Chiro-Optical Spectroscopies

Multiple speakers
Thursday, May 11, 2017 - 9:00am to 6:00pm

The Asher Symposium on Adventures in Enhanced Spectroscopies: Resonance Raman, Surface Enhanced Raman, and Twisted Chiro-Optical Spectroscopies will be held May 11, 2017-9:00am to 6:00pm. For more information, contact Sharon Mansfield, Assistant to Distinguished Professor Sanford A. Asher, Department of Chemistry at (412) 624-6295 or sharone@pitt.edu

Department of Chemistry, University of Pittsburgh
Ph.D., Physical Chemistry, University of Wisconsin-Madison, 2013

In the Laaser Lab, we are interested in developing a physical understanding of how changes at the molecular level translate to the macroscopic properties of responsive polymeric materials. For example, how does a change in charge spacing affect the interactions between charged polymers, and at what point do the polymers stop behaving like isolated chains in solution and start behaving like part of a bulk material? How do orientational changes in single polymer chains propagate through a material to achieve macroscopic ordering? And how do polymeric networks transduce force, to achieve things like mechanochemical responses?

We explore these questions by a number of optical and spectroscopic methods, such as light scattering and Raman and infrared spectroscopy, along with classical materials characterization methods like rheology and electron microscopy. Together, these methods allow us to develop new understanding of the structure and dynamic properties of responsive polymeric materials, and offer students the opportunity to gain broad experience in both physical chemistry and polymer science.

Most Cited Publications
  1. "Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy," Wei Xiong, Jennifer E. Laaser, Randy D. Mehlenbacher, and Martin T. Zanni, PNAS 108, 20902 (2011)
  2. "Time-Domain SFG Spectroscopy Using Mid-IR Pulse Shaping: Practical and Intrinsic Advantages," Jennifer E. Laaser, Wei Xiong, and Martin T. Zanni, J. Phys. Chem. B 115, 2536 (2011)
  3. "Transient 2D IR Spectroscopy of Charge Injection in Dye-Sensitized Nanocrystalline Thin Films," Wei Xiong, Jennifer E. Laaser, Peerasak Paoprasert, Ryan A. Franking, Robert J. Hamers, Padma Gopalanand Martin T. Zanni, J. Am. Chem. Soc. 131,18040 (2009)
  4. "Bridge-Dependent Interfacial Electron Transfer from Rhenium−Bipyridine Complexes to TiO2 Nanocrystalline Thin Films," Peerasak Paoprasert, Jennifer E. Laaser, Wei Xiong, Ryan A. Franking, Robert J. Hamers, Martin T. Zanni, J. R. Schmidt and Padma Gopalan, J. Phys. Chem. C 114, 9898 (2010)
  5. "Two-Dimensional Sum-Frequency Generation Reveals Structure and Dynamics of a Surface-Bound Peptide," Jennifer E. Laaser, David R. Skoff, Jia-Jung Ho, Yongho Joo, Arnaldo L. Serrano, Jay D. Steinkruger, Padma Gopalan, Samuel H. Gellman, and Martin T. Zanni, J. Am. Chem. Soc. 136, 95 (2014)
Recent Publications
  1. "19F Magnetic Resonance Imaging of Injectable Polymeric Implants with Multiresponsive Behavior." Sedlacek, Ondrej, Daniel Jirak, Andrea Galisova, Eliezer Jager, Jennifer E. Laaser, Timothy P. Lodge, Petr Stepanek, and Martin Hruby. Chemistry of Materials 30, no. 15 (2018): 4892-4896.
  2. "Composition-dependent dynamics in polyelectrolyte complex coacervates." Laaser, Jennifer, Frances Morin, and Jun Huang. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol. 255. 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC, 2018.
  3. "Charge Density-Dependent Phase Behavior and Rheology of Polyelectrolyte Complex Coacervates." Morin, Frances, and Jennifer Laaser. Bulletin of the American Physical Society (2018).
  4. "Charge density as a determinant of dynamics in polyelectrolyte complexes and coacervates." Laaser, Jennifer, Michael McGovern, Yaming Jiang, and Timothy Lodge. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol. 254. 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC, 2017.
  5. "Complexation of Linear DNA and Poly (styrenesulfonate) with Cationic Copolymer Micelles: Effect of Polyanion Flexibility." Jiang, Yaming, Dustin Sprouse, Jennifer E. Laaser, Yogesh Dhande, Theresa M. Reineke, and Timothy P. Lodge. The Journal of Physical Chemistry B 121, no. 27 (2017): 6708-6720.

Reflections on Nano and Femto Imaging

  • By Aude Marjolin
  • 12 February 2016

"Scanning near-field optical microscopy combined with pump–probe spectroscopy can resolve ultrafast dynamics at the nanoscale."

In this short article, Hrvoje Petek reflects on a new technique that combines the nanometre resolution of near-field microscopy with the femtosecond resolution of pump–probe spectroscopy. This technique has been developed by Markus Raschke and colleagues at the University of Colorado at Boulder and submitted in the present issue of Nature Nanotechnology.

Department of Chemistry and Biochemistry, Duquesne University
Ph.D., Chemistry, Texas A&M University, 1994

Undergraduate and graduate students in the van Stipdonk research group use ion trap mass spectrometry, spectroscopy and theory to study a variety of chemical processes in the gas-phase. As summarized below, our current research projects can be grouped into three general areas: (a) fundamental studies of peptide ion dissociation to support application of tandem mass spectrometry (tandem MS) to peptide and protein identification in proteomics; (b) studies of the intrinsic stability and reactivity of metal ion complexes important to biology, energy production and the environment, and (c) vibrational spectroscopy of gas-phase ions using wavelength-selective infrared multiple-photon photodissociation. Besides extensive use of mass spectrometry and tandem MS, work in our laboratory involves the synthesis of model molecules and peptides, including those with isotope labels, and use of density functional theory (DFT) to predict ion structures, energies and vibrational spectra. Our work on tandem MS and peptide dissociation has been funded by the National Science Foundation (NSF). Studies of intrinsic metal ion chemistry have been supported by the U.S. Department of Energy and the Idaho National Laboratory. Work on ion spectroscopy is supported in part by the NSF, the Institue for Molecules and Materials, Radboud University Nijmegen; and the Nederlandse Organisatie voor Wetenschappelijk Onderzoek. 

Selected Publications: 
  1. "Formation of [UVOF4] by collision-induced dissociation of a [UVIO2(O2)(O2C-CF3)2] precursor," Michael Van Stipdonk, Amanda Bubas, Irena Tatosian, Evan Perez, Nevo Polonsky, Luke Metzler, Arpad Somogyi, International Journal of Mass Spectrometry 424, 58 (2018)
  2. "Equatorial coordination of uranyl: Correlating ligand charge donation with the Oyl-U-Oyl asymmetric stretch frequency," John K Gibson, Wibe A de Jong, Michael J van Stipdonk, Jonathan Martens, Giel Berden, Jos Oomens, Journal of Organometallic Chemistry (2017)
  3. "Cleaving Off Uranyl Oxygens through Chelation: A Mechanistic Study in the Gas Phase," Rebecca J Abergel, Wibe A de Jong, Gauthier J-P Deblonde, Phuong D Dau, Ilya Captain, Teresa M Eaton, Jiwen Jian, Michael J van Stipdonk, Jonathan Martens, Giel Berden, Jos Oomens, John K Gibson, Inorg. Chem., 56, 12930 (2017)
  4. "Thermodynamics and Reaction Mechanisms of Decomposition of the Simplest Protonated Tripeptide, Triglycine: A Guided Ion Beam and Computational Study," Abhigya Mookherjee, Michael J. Van Stipdonk, P. B. Armentrout, J. Am. Soc. Mass Spectrom. 28, 739 (2017)
  5. "Revealing Disparate Chemistries of Protactinium and Uranium. Synthesis of the Molecular Uranium Tetroxide Anion, UO4–," Wibe A. de Jong, Phuong D. Dau, Richard E. Wilson, Joaquim Marcalo,  Michael J. Van Stipdonk, Theodore A. Corcovilos, Giel Berden, Jonathan Martens, Jos Oomens,and John K. Gibson, Inorg. Chem., 56, 3686 (2017)
Most Cited Publications
  1. "Sequence-Scrambling Fragmentation Pathways of Protonated Peptides," C Bleiholder, S Osburn, T D Williams, S Suhai, M Van Stipdonk, A G Harrison and B. Paizs, Journal of the American Chemical Society 130, 17774 (2008)
  2. "Vibrational spectroscopy of mass-selected [UO2 (ligand) n ]2+ complexes in the gas phase: Comparision with theory,"  Groenewold, G.S., Gianotto, A.K., Cossel, K.C., Van Stipdonk, M., (...). Journal of the American Chemical Society 128(14), 4802-4813 (2006)
  3. "Infrared Spectroscopy of Fragments of Protonated Peptides: Direct Evidence for Macrocyclic Structures of b5 Ions," U Erlekam, B J Bythell, D Scuderi, M Van Stipdonk, B Paizs, P Maître,  Journal of the American Chemical Society 131, 11503 (2009)
  4. "Vibrational characterization of simple peptides using cryogenic infrared photodissociation of H2-tagged, mass-selected ions," Michael Z. Kamrath, Etienne Garand, Peter A. Jordan, Christopher M. Leavitt, Arron B. Wolk, Michael J. Van Stipdonk, Scott J. Miller, Mark A. Johnson,  Journal of the American Chemical Society 133, no. 16 (2011): 6440-6448.
  5. "Spectroscopic Evidence for an Oxazolone Structure of the b2 Fragment Ion from Protonated Tri-Alanine," Oomens, J., Young, S., Molesworth, S., van Stipdonk, M. Journal of the American Society for Mass Spectrometry 20(2), 334-339 (2009)
Recent Publications
  1. Campuzano, Iain DG, Frank Sobott, and Michael J. van Stipdonk. "Editorial and Review: 30th ASMS Sanibel Conference on Mass Spectrometry—Computational Modelling in Mass Spectrometry and Ion Mobility: Methods for Ion Structure and Reactivity Determination." Journal of the American Society for Mass Spectrometry (2018): 1-4.
  2. Metzler, Luke J., Stephen Koehler, Árpád Somogyi, and Michael J. Van Stipdonk. "Formation of [Cu (CO2)(CH3OH)]+ and [Cu (N2)(CH3OH)]+ by Gas-phase Dissociation and Exchange Reactions." International Journal of Mass Spectrometry (2018).
  3. "Uranyl/12-crown‑4 Ether Complexes and Derivatives: Structural Characterization and Isomeric Differentiation," Jiwen Jian, Shu-Xian Hu, Wan-Lu Li, Michael J. van Stipdonk, Jonathan Martens, Giel Berden, Jos Oomens, Jun Li and John K. Gibson, Inorg. Chem. (2018).
  4. "Formation of [UVOF4] by collision-induced dissociation of a [UVIO2(O2)(O2C-CF3)2] precursor," Michael Van Stipdonk, Amanda Bubas, Irena Tatosian, Evan Perez, Nevo Polonsky, Luke Metzler, Arpad Somogyi, International Journal of Mass Spectrometry 424, 58 (2018)
  5. "Equatorial coordination of uranyl: Correlating ligand charge donation with the Oyl-U-Oyl asymmetric stretch frequency," John K Gibson, Wibe A de Jong, Michael J van Stipdonk, Jonathan Martens, Giel Berden, Jos Oomens, Journal of Organometallic Chemistry (2017)
  6. "Cleaving Off Uranyl Oxygens through Chelation: A Mechanistic Study in the Gas Phase," Rebecca J Abergel, Wibe A de Jong, Gauthier J-P Deblonde, Phuong D Dau, Ilya Captain, Teresa M Eaton, Jiwen Jian, Michael J van Stipdonk, Jonathan Martens, Giel Berden, Jos Oomens, John K Gibson, Inorg. Chem., 56, 12930 (2017)
Department of Physics and Astronomy, University of Pittsburgh
Ph.D., Chemistry, University of California Berkeley, 1985

Carrier dynamics in solid–state materials Fundamental electrical, magnetic, and optical properties of solid–state materials are determined  by the dynamical response of carriers to internal and external fields. The near–equilibrium properties of carriers in most materials are well  understood from classical studies of transport and optical conductivity. However, due to strong interactions of carriers among themselves and with the lattice, studies of nonequlibrium dynamics on femtosecond time scales (10 – 15 s) are just emerging. In our group, a particularly versatile and powerful technique, time–resolved two–photon photoemission (TR–2PP) spectroscopy, has been developed for studying the carrier excitation and relaxation processes in solid–state materials. With this technique we are investigating the quantum mechanical phase and carrier population relaxation times in metals, and for intrinsic and adsorbate induced surface states on metals. Of particular interest are the physical processes that induce e–h pair decoherence, since they impose limits on time scales for quantum control of carriers through the optical phase of the excitation light. The manipulation of the carrier phase with light may lead to applications such as ultrafast (>10 THz) switching and information processing, as well as, atomic manipulation of matter, and therefore, it is of great interest for advanced technologies in the 21st century. Ultrafast microscopy Understanding of the carrier dynamics under quantum confinement is a key to advancing nanoscale science and technology. Although with the existing scanning probe techniques we can potentially study dynamics of individual nanostructures, there is also a clear need for ultrafast imaging microscopic techniques in studies of dynamics in complex systems of nanostructures that could comprise ultrafast electronic or optical device. Photoemission electron microscopy (PEEM) is a well–developed surface science technique for imaging nanostructures on metal and semiconductor surfaces. In combination with femtosecond pump–probe excitation, we intend to develop time–resolved PEEM with potentially <1 fs, <20 nm, <100 meV carrier energy resolution. This technique will be applied to fundamental studies of carrier dynamics in individual nanostructures and coupled nanocomposite systems, in order to understand the fundamental physics of hot carriers in low dimensional systems and to develop advanced device concepts. Atomic manipulation with light Electronic excitation of clean or adsorbate covered metal surfaces can impulsively turn–on large mechanical forces that lead to mass transport parallel or perpendicular to the surface. When such forces are harnessed properly, they can be used for atomic manipulation or even atomic switching. Although there are now several examples of atomic manipulation with STM techniques, much less is known about how equivalent, but much larger scale manipulation could be accomplished with light. The recent observation and demonstration of quantum control of motion of Cs atoms above a Cu(111) surface by our group provides a proof–of–principle for the atomic manipulation of surfaces with light. Such studies are being extended to identify the factors that govern the electronic relaxation of adsorbates on metal surfaces, which can effectively quench the nuclear motion.

Most Cited Publications
  1. "Femtosecond time-resolved two-photon photoemission studies of electron dynamics in metals," H Petek, S Ogawa, Progress in Surface Science 56, 239 (1997)
  2. "Femtosecond imaging of surface plasmon dynamics in a nanostructured silver film," Atsushi Kubo, Ken Onda, Hrvoje Petek, Zhijun Sun, Yun S Jung, Hong Koo Kim, Nano Lett. 5, 1123 (2005)
  3. "Real-time observation of adsorbate atom motion above a metal surface," Hrvoje Petek, Miles J Weida, Hisashi Nagano, Susumu Ogawa, Science 288, 1402 (2000)
  4. "Wet electrons at the H2O/TiO2 (110) surface," Ken Onda, Bin Li, Jin Zhao, Kenneth D Jordan, Jinlong Yang, Hrvoje Petek, Science 308, 1154 (2005)
  5. "Atomlike, hllow-core-bound molecular orbitals of C60,"  Jin Zhao, Hrvoje Petek, and Min Feng, American Association for the Advancement of Science 320, 359-362 (2008)
Recent Publications
  1. "Excitation of two-photon photoemission where epsilon is near zero on Ag(111)," Marcel Reutzel, Andi Li, Branko Gumhalter, and Hrvoje Petekarxiv.org/abs/1809.02101v1
  2. "Ultrafast asymmetric Rosen-Zener-like coherent phonon responses observed in silicon," Yohei Watanabe, Ken-ichi Hino, Nobuya Maeshima, Hrvoje Petek and Muneaki Hase, arXiv:1808.08693v1 (2018)
  3. "Deconstruction of the electronic properties of a topological insulator with a two-dimensional noble metal-organic honeycomb-Kagome band structure," Hao Sun, Shijing Tan,  Min Feng, Jin Zhao, and Hrvoje Petek, J. Phys. Chem. (2018) 
  4. "Coherent two-dimensional multiphoton photoelectron spectroscopy of metal surfaces," Marcel Reutzel, Andi Li, Hrvoje Petek, arxiv.org/abs/1807.09164v1
  5. "Ultrafast Microscopy of Spin-Momentum Locked Surface Plasmon Polaritons," Yanan Dai, Maciej Dabrowski, Vartkess Ara Apkarian, and Hrvoje Petek, ACS Nano (2018).
  6. "Coherent electron transfer at the Ag/graphite heterojunction interface," Shijing Tan, Yanan Dai, Shengmin Zhang, Liming Liu, Jin Zhao, and Hrvoje Petek,  Phys. Rev. Lett. (2018).
  7. "Ultrafast Microscopy: Imaging Light with Photoelectrons on the Nano-Femto Scale," Maciej Dąbrowski, Yanan Dai, Hrvoje Petek, The Journal of Physical Chemistry Letters (2017).
  8. "Sub-picosecond acoustic pulses at buried GaP/Si interfaces,"Kunie Ishioka, Avinash Rustagi, Andreas Beyer, Wolfgang Stolz, Kerstin Volz, Ulrich Höfer, Hrvoje Petek, and  Christopher J. Stanton, Appl. Phys. Lett. 111, 062105 (2017)
Department of Chemistry, University of Pittsburgh
Ph.D., Physical Chemistry, University of California Berkeley, 2005

An urgent problem in protein science is to understand ion uptake and ion recognition (selectivity) by proteins and polypeptides. This impacts proteins ranging from ion channels to ion sensors to metalloregulatory proteins to metallo-enzymes. Why and how are these bio-nanostructures so exquisitely sensitive to particular ions? How do local changes in the binding pockets lead to global conformational change? These questions have major implications for biology, and they need an answer from physical chemistry. In a separate field, that of green chemistry, there is another pressing problem to understand structural and dynamical heterogeneity in ionic liquids. What does this proposed heterogeneity imply about the solvation properties of these new "designer solvents''? Can we measure it? Can we use it to tune the solvent's properties? Better understanding the chemical physics of these systems will aid the rational design of new solvents, which in turn will have industrial consequences. There is an underlying connection between these biophysical and chemical physics questions – to really probe the mechanisms in operation, one must be able to separate static and dynamic heterogeneity. The nonliear spectroscopies developed in the Garrett-Roe lab can do exactly this. Multidimensional infrared spectroscopy can reveal structural dynamics on timescales spanning femtosecond–microseconds, and make molecular movies as reported by vibrational frequencies. These techniques will clarify

  1. The mechanism of ion selectivity in selectivity filter of an archetypal biological ion channel (KcsA).
  2. The conformational dance of guest and host in the molecular recognition of ionophores such as valinomycin.
  3. The binding of calcium ions in a biological ion sensor, EF hand, in a time- and reside-resolved way. Calcium uptake is a key step of many cellular signalling processes and is unexplored on a submicrosecond timescale.
  4. The structural and dynamical heterogeneity of ionic liquids. These fluids are a fascinating arena to move towards a deeper understanding of complex fluids.

Each of these experiments requires a combination of experimental expertise in the non-linear spectroscopy as well as skill modelling stochastic dynamics on a complex free energy landscape.

Most Cited Publications
  1. "Electron Solvation in Two Dimensions," A. D. Miller, I. Bezel, K. J. Gaffney, S. Garrett-Roe, S. H. Liu, P. Szymanski, C. B. Harris, Science 297, 1163 (2002)
  2. "Time- and angle-resolved two-photon photoemission studies of electron localization and solvation at interfaces," P. Szymanski1, S. Garrett-Roe, C.B. Harris, Progress in Surface Science 78, 1 (2005)
  3. "Intermolecular zero-quantum coherence imaging of the human brain," Rahim R. Rizi, Sangdoo Ahn, David C. Alsop, Sean Garrett-Roe, Marlene Mescher, Wolfgang Richter, Mitchell D. Schnall, John S. Leigh, Warren S. Warren, Magnetic Resonance in Medicine 43, 627 (2000)
  4. "Purely absorptive three-dimensional infrared spectroscopy," Sean Garrett-Roe and Peter Hamm, J. Chem. Phys. 130, 164510 (2009)
  5. "Transient excitons at metal sufaces," Cui, X., Wang, C., Argondizzo, A., Garrett-Roe, S., Gumhalter, B., Petek, H., Nature Physics 10, no. 7 (2014)
Recent Publications
  1. "Modeling Carbon Dioxide Vibrational Frequencies in Ionic Liquids: III. Dynamics and Spectroscopy," Thomas Brinzer, Clyde A. Daly, Cecelia Allison, Sean Garrett-Roe, and Steven A. Corcelli, J. Phys. Chem. B (2018)
  2. "Hydrogen bond dynamics in protic ionic liquids: Ultrafast vibrational spectroscopy of SCN." Garrett-Roe, Sean. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol. 255. 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC, (2018).
  3. "POGIL activity clearinghouse: Helping authors to create, test, and distribute peer-reviewed POGIL activities." Garrett-Roe, Sean, Caryl Fish, Michael Garoutte, Melissa Reeves, Craig Teague, Robert Whitnell, Alexander Grushow, and Sally Hunnicutt. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol. 255. 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC, (2018).
  4. "Enthalpic Driving Force for the Selective Absorption of CO2 by an Ionic Liquid." Daly Jr, Clyde A., Thomas Brinzer, Cecelia Allison, Sean Garrett-Roe, and Steven A. Corcelli. The journal of physical chemistry letters 9, no. 6 (2018): 1393-1397.
  5. "Temperature and chain length dependence of ultrafast vibrational dynamics of thiocyanate in alkylimidazolium ionic liquids: A random walk on a rugged energy landscape", Thomas Brinzer, and Sean Garrett-RoeThe Journal of Chemical Physics 147, 194501 (2017).
Department of Chemistry, Carnegie Mellon University
Ph.D., Physical Chemistry, University of Chicago, 1989

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. 

Selected Publications: 
  • "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. PeteanuJ. 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)
Most Cited Publications
  1. "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.
  2. "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.
  3. "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.
  4. "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.
  5. "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.
Recent Publications
  1. "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).
  2. "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).
  3. "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).
  4. "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).
  5. "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).