Chemical Physics and Physical Chemistry

Physical Chemistry Seminar, Dr Shelley Claridge, Purdue

Thu, 2019-01-24 13:00 - 14:00
Speaker: 

Dr. Shelley Claridge

 

 

Standing, Lying, and Sitting: Transforming the Cell Membrane

to Interface with Synthetic Nanomaterials

Shelley A. Claridge1,2

1Department of Chemistry, Purdue University, West Lafayette, Indiana

2Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

 

A surprisingly broad array of problems in modern materials chemistry relate to creating interfaces with two distinct, well-structured chemical environments at near-molecular scales. For instance, positioning nm-wide metal and semiconductor features with a pitch of 5-7 nm in a nonconductive matrix represents a central requirement for next-generation nanoelectronic devices.  Controlling interfacial chemical structure at scales from 5-10 nm is difficult using conventional lithographic patterning techniques. At the same time, a 6-nm pattern forms the cross-section of biological cell membranes, with distinct chemical environments created by a bilayer of phospholipids. We find powerful functions of phospholipid chemistry are preserved when the molecules are instead assembled in striped phases, in which the alkyl tails lie flat on a surface and the headgroups form 1-nm-wide stripes with a pitch of ~6 nm. We will discuss the relationship between structure and function at these interfaces, and useful material properties that emerge from the unusual surface chemistry; these include assembly of inorganic nanocrystals and crystallization of functional organic molecules.

 

 

Shelley Claridge received undergraduate degrees in mathematics and biochemistry from Texas A&M University, and subsequently worked as a software engineer for six years prior to completing a Ph.D. at UC Berkeley with Paul Alivisatos and Jean Fréchet. After a postdoctoral fellowship with Paul Weiss at UCLA, she joined the faculty at Purdue University in 2013. Her research at Purdue has been recognized with Young Investigator awards from NSF, DARPA, 3M, and DuPont (one of 8 globally), and received emerging investigator recognitions from Journal of the American Chemical Society, Chemical Communications, Analytical Methods, and Analytical and Bioanalytical Chemistry.

 

Location: 

Carol Lynch Lecture Hall

Chemisty Compplex

Host: Fakharri / Murray

 

inquires rvargas@sas.upenn.edu

Physical Chemistry Seminar, Dr. Matthias Waegele, Boston College

Thu, 2019-04-18 13:00 - 14:00
Speaker: 

Dr. Matthias Waegele

Location: 

Carol Lynch Lecture Hall

Chemistry Complex

Host: Dr Gai

Title & Abstract: TBA

inquires rvargas@sas.upenn.edu

 

Physical Chemistry Semianr: Dr. Sara Mason, University of Iowa

Thu, 2019-03-14 13:00 - 14:00
Speaker: 
Dr. Sara Mason
Location: 
Lynch Lecture Hall Chemistry Complex

Host: Dr. Rappe

Title & Abstract:TBA

inquires rvargas@sas.upenn.edu

Physical Chemistry Seminar, Dr. Sanat Kumar, Columbia University

Thu, 2018-10-11 13:00 - 14:00
Speaker: 

Dr. Sanat Kumar

"Polymer-Grafted Nanoparticle Membranes with Controllable Free-Volume"

 

-Polymer based membranes play a key role in several industrially important gas separation technologies, e.g., removing CO2 from natural gas, with enormous economic and environmental impact. Baker advocates the development of novel membrane architectures since current, pure polymer membranes only offer limited systematic pathways for improvement. Here, we develop a novel hybrid membrane construct comprised entirely of nanoparticles grafted with polymers. These membranes are shown to have broadly tunable separation performance through variations in graft density and chain length. Computer simulations show that the optimal NP packing forces the grafted polymer layer to distort, yielding regions of measurably lower polymer density. Multiple experimental probes confirm that these materials have the predicted increase in “polymer free volume”, which explains their improved separation performance. These polymer-grafted NP materials thus represent a new template for rationally designing membranes with desirable separation abilities, coupled with improved aging characteristics in the glassy state and enhanced mechanical behavior.
Location: 
Carol Lynch Lecture Hall Chemistry Complex

Host: Dr. Fakhraai

 

inquires rvargas@sas.upenn.edu

 

Physical Chemistry Seminar, Dr. Paul Wennberg, Caltech

Thu, 2019-02-07 13:00 - 14:00
Location: 

Carol Lynch Lecture Hall

Chemistry Complex

Host: Dr. Lester

Title & Abstract TBA

Inquiries rvargas@sas.upenn.edu

Joseph S. Francisco

Photo: 
First Name: 
Joseph S.
Last Name: 
Francisco
Official Title: 
President’s Distinguished Professor
Additional Titles: 
Professor of Chemistry
Professor of Earth & Environmental Sciences
Contact Information
Email: 
frjoseph@sas.upenn.edu
Phone: 
215-573-3164
Education: 

B.S.: Chemistry, University of Texas at Austin, 1977

 

Ph.D.: Chemical Physics, Massachusetts Institute of Technology, 1983.

 

Research Fellow: University of Cambridge, 1983-1985

 

Provost Postdoctoral Fellow: Massachusetts Institute of Technology, 1985-1986

Research Interests: 

Research in our laboratory focuses on basic studies in spectroscopy, kinetics and photochemistry of novel transient species in the gas phase, in aerosol and at the ice-quasi liquid layer. These species play an important role in atmospheric processes. Yet questions dealing with how structures correlate to reactivity and photochemical mechanisms have not been addressed for these systems. These problems are addressed by research efforts in our laboratory. Specific research areas of interest are: 1) Spectroscopic determinations of electronic and vibrational transitions in free radicals; 2) Kinetics of individual gas-phase reaction steps involving free radicals in complex reaction mechanisms involved in the gas phase and at interfaces; 3) Characteristics of primary photo chemical processes that free radicals can undergo in the gas phase and at interfaces; 4) Atmospheric chemistry and dynamics at the air/water interface chemistry; and 5) Atmospheric chemistry and dynamics at the ice-quasi liquid layer.

 

 

Our goal is to use state-of-the-art molecular orbital methods to predict properties that can be used as a guide in the experimental search. We aim to predict spectroscopic properties for these novel species in the gas phase and at the air/water interface, that would facilitate their full experimental characterization. 

Selected Publications: 

M. Kumar, and J.S. Francisco, Mechanistic Insight into Ion-Pair Particle Formation from Methanesulfonic Acid-Amines Chemistry at the Air-Water Interface,  Proc. Natl. Acad. Sci. USA., 114, 12401-12406 (2017).

 

L. Artiglia, J. Edebeli,  F. Orlando, S. Chen, P. C. Arroyo, A. Gilgen, T. Bartels-Rausch, A. Kleibert, M. Vazdar, M. A. Garegnano, J.S. Francisco,  P.B. Shepson, I. Gladich, and M. Ammann, A Surface-Stabilized Ozonide Triggers Bromide Oxidation at the Aqueous Solution-Vapor Interface, Nature Communications8, 700 (2017).

 

C.Q. Zhu, J. Zhong, M. Kumar, J.S. Francisco, X.C. Zeng, New Mechanistic Pathways for Creigee-Water Chemistry at the Air/Water Interface,  J. Am. Chem. Soc., 138, 11164-11169 (2016).

 

R. Hoehn, M.A. Carignano, S. Kais,  J.S. Francisco, and  I. Gladich, Hydrogen Bonding and Orientation Effects on the Accommodation of Methylamine at the Air-Water Interface, J. Chem. Phys.144, 214701 (2016).

 

M. Kumar, A. Sinha, and J. S. Francisco, Role of Double Hydrogen Atom Transfer Reactions in Atmospheric Chemistry, Acc. Chem. Res., 49, 877- 833 (2016).

 

M. Kumar and J.S. Francisco, Red-Light Induced Decomposition of Organic Peroxy Radical: A New Source of the HO2Radical, Angew. Chem. Int. Ed.54, 15711-15714 (2015).

 

J.M. Anglada, M. Martins-Costa, M.F. Ruiz-Lopez, J.S. Francisco, Spectroscopic Signatures of Ozone at the Air/Water Interface and Photochemistry Implications, Proc. Natl. Acad. Sci. USA., 111, 11618-11623 (2014).

Physical Chemistry Seminar: Dr. Josh Vura- Weis, University of Illinois

Thu, 2019-01-17 13:00 - 14:00
Speaker: 

Dr. Josh Vura-Weis

Location: 

Carol Lynch Lecture Hall

Chemistry Complex

Host: Dr. Subotnik

Title & Abstract TBA

inquiries rvargas@sas.upenn.edu

Physical Chemistry Seminar: Dr. Sean Roberts, University of Texas-Austin

Thu, 2018-12-13 13:00 - 14:00
Speaker: 

Dr. Sean Roberts

 

Manipulating Energy and Spin for Photon Up- and Down-conversion The negligible spin-orbit coupling in many organic molecules creates opportunities to alter the energy of excited electrons by manipulating their spin. In particular, molecules with a large exchange splitting have garnered interest due to their potential to undergo singlet fission (SF), a process where a molecule in a high-energy spin-singlet state shares its energy with a neighbor, placing both in a low-energy spin-triplet state. When incorporated into photovoltaic and photocatalytic systems, SF can offset losses from carrier thermalization, which account for ~50% of the energy dissipated by these technologies. Likewise, compounds that undergo SF’s inverse, triplet fusion (TF), can be paired with infrared absorbers to create structures that upconvert infrared into visible light. In this presentation, I will review our group’s efforts to create organic:inorganic structures that use SF and TF for improved light harvesting and photon upconversion.

Location: 

Carol Lynch Lectrue Hall

Chemistry Complex

Host: Dr. Anna

inquiries rvargas@sas.upenn.edu

Physical Chemistry Seminar: Dr. Wei Xiong, UC San Diego

Thu, 2018-11-01 13:00 - 14:00
Speaker: 

Dr. Wei Xiong

 

Ultrafast Nonlinear IR Spectroscopy for Exotic Molecular Materials


In this seminar, I will discuss two developments in ultrafast nonlinear IR spectroscopy for exotic molecular materials: (1) 2D IR spectroscopy for molecular vibrational polaritons and (2) transient electric field induced VSFG spectroscopy for probing interfacial charge transfer. Both show the advantages of ultrafast nonlinear IR spectroscopic technique: to decipher hidden physics of exotic molecular materials. 

2D IR of Molecular Polaritons.1 Molecular vibrational polaritons, half-light, half-matter hybrid quasiparticles, are studied using ultrafast, coherent 2D IR spectroscopy. Molecular vibrational-polaritons are anticipated to produce new opportunities in the photonic and molecular phenomena. Many of these developments hinge on fundamental understanding of physical properties of molecular vibrational polaritons. Using 2D IR spectroscopy to study vibrational-polaritons, we obtained results that challenge and advance both polariton and spectroscopy fields. These results invoke new developments in theory for the spectroscopy, discover observation of new nonlinear optical effects and unexpected responses from hidden dark states. We expect these results to have significant implications in novel infrared photonic devices, lasing, molecular quantum simulation, as well as new chemistry by tailoring potential energy landscapes. 

Transient E-field induced VSFG for Direct Interfacial Charge Transfer.2 We describe direct electron-transfer at buried interfaces between an organic polymer semiconductor film and a gold substrate, by observing the transient electric-field-induced vibrational sum frequency generation (VSFG).  We observe dynamic responses (<150 fs) where electrons are directly transferred from the Fermi level of gold to the LUMO of organic semiconductor. Transient spectra further reveal that, although the interfaces are prepared without deliberate alignment control, a sub-ensemble of surface molecules can adopt conformations for direct electron transfer, supported by DFT calculations. This result will have implications for implementing novel direct electron transfer in energy materials.

References.

1.        Xiang, B. et al. Two-dimensional infrared spectroscopy of vibrational polaritons. Proc. Natl. Acad. Sci. 115, 4845–4850 (2018).

2.        Xiang, B., Li, Y., Pham, C. H., Paesani, F. & Xiong, W. Ultrafast Direct Electron Transfer at Organic Semiconductor and Metal Interfaces. Sci. Adv. 3, e1701508 (2017). 

 

 

Location: 

Carol Lynch Lecture Hall 

Chemistry Complex

Host: Dr. Saven

inquiries rvargas@sas.upenn.edu

Department of Chemistry

231 S. 34 Street, Philadelphia, PA 19104-6323

215.898.8317 voice | 215.573.2112 fax | web@chem.upenn.edu

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