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The Association of Chemical Engineering Graduate Students Presents the
2011 Chemical Engineering
Graduate Student Symposium
Monday, September 26
Johnson Hall 102
The Association of Chemical Engineering Graduate Students Presents the
2011 Chemical Engineering
Graduate Student Symposium
Monday, September 26
Johnson Hall 102
The Association of Chemical Engineering Graduate Students Presents the
2011 Chemical Engineering
Graduate Student Symposium
1
Welcome to the 2011 Graduate Student Symposium!
Hosted by the Association of Chemical Engineering Graduate Students (ACES)
ACES would like to welcome you to this year’s Chemical Engineering Graduate Student Symposium. We
have a great schedule of talks and poster presentations lined up showcasing the latest research in
biotechnology, energy, and molecular engineering. We hope that you have a stimulating day of learning
and engaging with the graduate students pursuing these exciting fields.
ACES at the University of Washington is a student-run organization with a commitment to providing
opportunities for graduate students to participate in professional development and outreach beyond
what is typically encountered during graduate studies. We believe that such extracurricular involvement
is crucial to student development and to a well-rounded graduate education.
The Graduate Student Symposium is held as a means for students to share their research with
colleagues, faculty and representatives from industry; and to showcase to the local community the
exciting work being done at the UW. The Symposium also serves as a forum in which students can
practice their presentation skills and gain valuable feedback from people outside of academics in their
field..
Thank you for attending! We are very excited to have guests from industry joining us this year and are
hoping to gain even more participation in years to come. We hope that you will share your positive
experiences with colleagues and return to participate next year. If you would like more information
about ACES events or would like to sponsor any future events, please contact
[email protected]. We would love your feedback on our organization and this event. Look
for future events and updates at http://depts.washington.edu/acesche.
Enjoy the day!
- The ACES Professional Development Committee
2
Table of Contents
Campus Map…………………………………………………………………………………………………………………………...3
Symposium Agenda………………………………………………………………………………………………………….….….4
Keynote: Tough Plastics by Molecular Design, Frank S. Bates……………………………………………….…5
Oral Presentation Abstracts………………………………………………………………………………………………….…6
Poster Presentation Summary……………………………………………………………………………………………….16
Poster Presentation Abstracts……………………………………………………………………………………………….18
Acknowledgements……………………………………………………………………………………………………………….28
Parking and Campus Map
3
Agenda
8:30am Coffee and Breakfast (Johnson Hall Lobby, outside of Room 102)
9:00am Dean O’Donnell Welcome Remarks
9:20am Eric Karp A trend in the Strength of Bonding of Oxygen-Containing
Intermediates on Pt(111) Surfaces, and its Implications in
Energy-Related Catalysis
9:40am TJ McDonald Kinetic and Thermodynamic Study of Nanoscale Engineered
LaxSr1-xCoO3-d Thin Film Electrodes through Linear and Nonlinear
Electrochemical Techniques
10:00am Prasad Bhosale Acoustic Spectroscopy and Electroacoustics of Gel Trapped
Colloids
10:20am Jeff Richards Structure and Properties of Porous Poly(3-hexylthiophene) Gel
Particles in Aqueous Dispersion
10:40am Break
11:00am Dr. Frank Bates Tough Plastic by Molecular Design
12:00pm Lunch (Mary Gates Hall Commons)
1:30pm Sathana Kitayaporn Orchestrated Structure Evolution: Co-deposition of Ni-Cu alloy
1:50pm Kurt Spies Hydrogen Generation by Electrocatalyic Reforming of Ethylene
Glycol on a Pt Electrode
2:10pm Brent Nannenga Improved Expression Vector for the Efficient Production of
Membrane Proteins
2:30pm Brandon Coyle A Robust Platform for 2D Crystallization of Membrane Proteins
through Nanotemplating and Directed Assembly
2:50pm Michael Robinson 3D Chemical Imaging of Single Cells
3:10pm Andrew Keefe Poly(Zwitterionic) Protein Conjugates: Relieving PEGylation
3:30-5:00pm Graduate Student Poster Competition (Johnson Hall Lobby)
4
Keynote Address
Tough Plastics by Molecular Design
Frank S. Bates
Regents Professor and Department Head
Chemical Engineering and Materials Science
University of Minnesota
https://www.cems.umn.edu/about/people/faculty.php?id=20164
Monday, September 26, 2011
11:00am - 12:00pm
Johnson 102
Perhaps the most ubiquitous requirement for commercial polymer products is mechanical integrity.
Conventional approaches to imparting toughness to solid polymers include the addition of rubber
particles to glassy plastics such as polystyrene or increasing the amorphous content in semicrystalline
materials like polyethylene. Both methods necessitate balancing tradeoffs between toughness and other
important properties such as clarity and stiffness. Block copolymers provide a unique opportunity to
design tough plastics without sacrificing other desirable material features. A plethora of morphologies
can be developed with one-, two-, or three-dimensional order and with morphological dimensions
between 5 and 50 nm in scale. These compounds find applications as neat (undiluted) materials or as
additives to reactive monomers or bulk homopolymers. This presentation will address two categories of
brittle plastics that benefit from block copolymer modification: poly(cyclohexylethylene) a new optically
pristine plastic now under commercial development, and thermosetting epoxy, a high volume
commodity material that finds myriad applications across innumerable technological disciplines. Optimal
results require a combination of molecular (architectural) and morphological design, which rely on a
fundamental understanding of the principles that govern block copolymer self-assembly.
5
Oral Presentation Abstracts
9:20am
A trend in the strength of bonding of oxygen-containing intermediates on Pt(111) surfaces, and its
implications in energy-related catalysis
Speaker: Eric Karp
Principal Investigator: Charles Campbell
The bond energies of methoxy and hydroxyl on the Pt(111) surface were measured using single crystal
adsorption calorimetry (SCAC). These values resulted in a trend between the metal-ligand bond
energies and their corresponding hydrogen-ligand bond energies in the gas phase. The measured bond
energies for Pt--OCH3, Pt--OD and the resulting trend, allows for the prediction of other oxygen
containing adsorbed intermediates that we could not measure. This trend will be discussed along with
its application in predicting the stability of other catalytic intermediates and the energetic feasibility of
proposed catalytic pathways.
6
9:40am
Kinetic and Thermodynamic study of Nanoscale Engineered LaxSr1-xCoO3-d Thin Film Electrodes
Through Linear and Nonlinear Electrochemical Techniques
Speaker: T.J. McDonald
Principal Investigator: Stu Adler
Many advanced technologies are constrained by limitations of oxygen transport (within solids) and the
Oxygen Reduction Reaction (ORR). Applications such as Solid Oxide Fuel Cells (SOFCs), Solid Oxide
Electrolyzer Cells (SOECS), gas sensors, and air separation membranes would benefit from optimization
of these processes.
Non Linear Electrochemical Impedance Spectroscopy (NLEIS) can be used to study the processes
governing the electrochemical behavior of mixed conducting, solid oxide fuel cell electrodes. The NLEIS
technique uses a moderate amplitude sinusoidal current input, and analyzes the non-linear harmonic
voltage responses. NLEIS differs from the widely used Electrochemical Impedance Spectroscopy (EIS) in
its ability to probe non-linearities; providing access to mechanism-specific information. Understanding
the mechanisms and relative importance of reactions, ionic transport, and material thermodynamics is
the first step in engineering high efficiency materials
O2 reduction kinetics on heteroepitaxial thin films of LaxSr1-xCoO3-δ, were investigated using NLEIS.
Testing was done on films with two different dopant amounts (x =6, x = 8), on both heteroepitaxial films
as well as semi amorphous films, over a range of temperatures and partial pressure of oxygen, and over
a range of film thicknesses (25 - 90 nm). The nonlinear harmonics were compared to a previously
proposed rate limiting kinetic mechanism [1], for a larger dense thin film of La0.6Sr0.4CoO3-δ. Additionally,
thermodynamic properties of the current thin film were compared to bulk material and the previously
studied dense films; yielding significant differences in thermodynamic behavior.
The thermodynamic behavior, of the current thin films, was obtained from both the non-linear
harmonics (NLEIS data) and from the capacitances (EIS data). Values obtained were in close agreement
(analysis of EIS data was based on a thermodynamic model put forth by Mizusaki et al and Lankhorst et
al) [2,3]. Reasons for the discrepancies between bulk and thin film materials, as well as a materials
characterization of the thin films, will be discussed.
[1] J. R. Wilson, M. Sase, T. Kawada, and S.B. Adler, Electrochemical and Solid State Letters, 10 (5), B81-
B86 (2007).
[2] J. Mizusaki, Y. Mima, S. Yamauchi, K. Fueki, H. Tagawa, Journal of Solid State Chemistry, 80 (1), 102-
111 (1989).
[3] M. H. R. Lankhorst et al. Journal of Solid State Chemistry, 133 (2), 555-567 (1997).
7
10:00am
Acoustic Spectroscopy and Electroacoustic of Gel Trapped Colloids
Speaker: Prasad Bhosale
Principal Investigator: John Berg
Gel trapped particles have wide spread applications in food and pharmaceutical industries. However,
techniques for characterizing gel-trapped particles size distribution and electrical properties remain
rather limited, especially for dense or opaque systems. Conventional light scattering or centrifugation
techniques are developed for Newtonian mediums and require special conditions such as, the use of
transparent gels (matching refractive index of polymer and liquid) and low particle concentration to
characterize particles. The technique of acoustic spectroscopy and electroacoustics offers some
significant advantages over conventional techniques for the characterization of dense colloidal
dispersions in that it does not require the systems be highly dilute and transparent. Another advantage
of the acoustic methods may derive from the fact that in applications, the relative motion between any
particle and the medium is very small compared to particle diameter. It may thus be suited, within
limits, to the study of dispersions in polymer gels, without the additional limitation of conventional
methods to transparent media.
The present work seeks to probe experimentally the limits of the acoustic spectroscopy for the
determination of gel trapped particle size distributions and examine the electroacoustics of particles
dispersed in polymer gels with the particle size less than or greater than the gel mesh size. The particle
size distribution (PSD) was successfully measured by acoustic spectroscopy theory for dispersions in
Newtonian media provided that the hydrodynamic particle diameter was less than the hydrodynamic
mesh size of the gel (mesh size/particle size >1.5). In electroacoustic measurements when the particles
are smaller than the gel mesh size, their acoustic vibration is resisted by only the background water
medium, and the measured dynamic electrophoretic mobility, μd, is the same as that in water. For the
case of particles larger than the gel mesh size, μd, the measured mobility μd remains constant as mesh
size is decreased, i.e., storage modulus G’ characterizing cross linking density increased, up to a critical
value of 300 Pa, beyond which it decreases steeply. The degree of trapping, as varied by either
decreasing mesh size at a constant particle size, or increasing particle size at a constant mesh size, did
not alter the mobility below the critical value G’ (300 Pa).
8
10:20am
Structure and Properties of Porous Poly(3-hexylthiophene) Gel Particles in Aqueous Dispersion
Speaker: Jeff Richards
Principal Investigator: Danilo Pozzo
The demand for thin-film solar cells has increased significantly because modules can be inexpensively
produced using scalable roll-to-roll processing techniques. We have developed aqueous dispersions of
colloidal poly(3-hexylthiophene) (P3HT) gel particles that can serve as solution-processable inks for
active layer materials in polymer solar cells. Bulk P3HT organogels have been emulsified into water to
produce sub-micron gel particles that are stabilized with surfactant. The emulsification process produces
stable dispersions of porous P3HT particles that maintain a high crystallinity, high porosity and the
networked structure of the original organogel. The optical characteristics, structure and stability of the
resulting gel particles have been thoroughly assessed using spectroscopy, neutron scattering, DLS and
electron microscopy. It is shown that the P3HT particles retain the crystallinity and high degree of
intrachain order with no evidence of doping. Simple processing is demonstrated via spray-coating of the
dispersions. Thin-films have been prepared and their structure and properties have been characterized.
The use of gel particle dispersions opens up a new avenue to produce thin-films for polymer solar cells
and organic electronic applications while minimizing the need for post-processing.
9
1:30pm
Orchestrated Structure Evolution: Co-deposition of Ni-Cu alloy
Speaker: Sathana Kitayaporn
Principal Investigator: Daniel T. Schwartz
Orchestrated structure evolution (OSE) is a method that combines the molecules, algorithms, and self-
propagating growth processes (bottom-up) with tool-directed patterning (top-down) to minimize cost
and reduce the build time for a nanopatterned substrate while providing flexibility and high quality
nanomanufactured products[1, 2]. The OSE process starts by patterning “seeds” with a reconfigurable
tool such as dip-pen nanolithography (DPN), electron-beam lithography (EBL) or electrochemical printing
(EcP)[3-5]. Seeds are nucleation initiators (proteins, seed crystals, catalyst, nanoelectrodes, etc.) that
can be patterned to initiate growth that propagates into the final patterned thin film.
We expand the OSE concept by investigating the interaction of seed configuration and patterning on the
composition of binary nickel/copper alloy. A Greens function mass transfer model is used to compute
the incorporation of copper into each growing seed. Nickel is added to the seed at a charge-transfer
limited rate. Simulations of the growth rate and composition of an OSE thin film is compared with
experiments that use EBL to pattern seeds on an electrode. We show that the composition of an alloy
thin film depends on the seed configuration as well as the pattern shape. Areas with high local mass
transfer, such as isolated small seeds or high aspect ratio regions of a pattern produce high Cu alloy. The
ability to use seed configuration to control local composition in a thin film is explored. We show that
OSE provides a new degree of design to the creation of patterned thin films.
Acknowledgments
This work is supported by the National Science Foundation grant CMMI-0709131. Portions of the work
were performed at the University of Washington node of the National Nanotechnology Infrastructure
Network (NNIN).
[1] K. Sathana, J.H. Hoo, K.F. Bohringer, F. Baneyx, D.T. Schwartz, Nanotechnology, 21 (2010) 195306.
[2] A. Shaghayegh, et al., Nanotechnology, 22 (2011) 165303.
[3] B.D. Gates, Q. Xu, M. Stewart, D. Ryan, C.G. Willson, G.M. Whitesides, Chemical Reviews, 105 (2005)
1171-1196.
[4] D.S. Ginger, H. Zhang, C.A. Mirkin, Angewandte Chemie International Edition, 43 (2004) 30-45.
[5] S. Roy, J. Phys. D-Appl. Phys., 40 (2007) R413-R426.
10
1:50pm
Hydrogen Generation by Electrocatalyic Reforming of Ethylene Glycol on a Pt Electrode
Speaker: Kurt A. Spies
Principal Investigator: Eric M. Stuve
Biofuels continue to receive national attention motivated by concerns about a finite energy supply,
geopolitical issues surrounding petroleum imports, and the environmental impact of fossil fuels.
Biomass is an abundant resource, but is not easily converted to a usable transportation fuel. The
aqueous phase reforming (APR) process [1] shows promise for converting compounds derived from
biomass into hydrogen and alkanes at moderate temperatures (225°C) in an aqueous phase. However,
hydrogen selectivity in APR is a concern, especially as carbon chain length of the feed molecules increase
[2]. An alternative and complementary process for reforming carbohydrates is electrocatalytic reforming
which involves electrooxidation of a carbohydrate or prototypical carbohydrate and reduction to
produce hydrogen at the cathode. In this work we use ethylene glycol as a prototypical carbohydrate, as
it is the simplest sugar-like molecule. The reactions of study are:
C2H6O2+2H2O ↔ 2CO2+10H++10e
- (1)
2H++2e
- ↔H2 (2)
Protons formed at the anode reduce and form gaseous hydrogen at the cathode. The formation of
hydrogen away from the reacting mixture simplifies hydrogen removal and purification, providing an
extra benefit of electrocatalytic reforming. Successful electrocatalytic reforming rests largely on
effective electrooxidation, which typically is hampered by formation of poisons at the anode [3], The
objective of this work is to examine electrooxidation at elevated temperature in aqueous phase to
determine whether desorption of poisons at high temperature permit effective electrooxidation. We
have developed a reactor that utilizes proton exchange membrane fuel cell architecture while operating
at up to 120°C and up to 30 atm with a liquid phase reactant. The reaction is monitored
electrochemically by cyclic voltammetry and step potential measurements and reaction products are
measured by gas and liquid phase chromatography.
Results for ethylene glycol oxidation up to 120°C including effective activation energy, tafel kinetics, and
concomitant hydrogen production will be presented and the prospects of electrocatalytic reforming
explored. Further work to explore aqueous phase electrooxidation of ethylene glycol above 120°C will
be discussed, along with ongoing work on high temperature ionomer materials for an improved
electrolyte membrane.
[1] G. Huber and J. A. Dumesic Catal. Today, 111, 119,(2006).
[2] R. Cortright, R. Davda, and J. A. Dumesic, Nat., 418,964, (2002).
[3] H. Wang, Z. Jusys, and R. J. Behm Electrochim Acta,54, 6484 (2009).
11
2:10pm
Improved Expression Vector for the Efficient Production of Membrane Proteins
Speaker: Brent L. Nannenga (rising 5th
year student)
Principal Investigator: François Baneyx
Membrane proteins (MPs) account for 20-30% of the genomes sequenced and are important
pharmacological and therapeutic targets, as well as having uses in the emerging field of
nanobiotechnology. To date, this potential remains largely untapped because MPs are extremely
difficult to produce, and because little is known about their structure and function. In order to advance
the study and application of these important proteins, robust strategies facilitating the production of
functional MPs at high levels are necessary. Here, I will describe the isolation, characterization, and use
of a novel expression vector for improved MP production in E. coli. When used in conjunction with
expression strains that have been engineered for MP expression, this improved expression vector can
the increase the yields of properly folded overexpressed MPs by as much as 4-fold.
12
2:30pm
A Robust Platform for 2D Crystallization of Membrane Proteins through Nanotemplating and Directed
Assembly
Speaker: Brandon Coyle (4th
year student)
Principal Investigator: François Baneyx
In spite of the tremendous relevance to cell biology and medicine, roughly 300 membrane protein (MP)
structures have been solved to date. While X-ray crystallography and NMR spectroscopy are increasingly
adept at the task, no generic sample preparation protocols exist. As such, crystallization trials are
optimized on a case-by-case basis. Relying on 2D rather than 3D crystals, electron crystallography offers
an attractive alternative. Advantages include: (i) smaller protein amounts mitigate MP overexpression
difficulties; (ii) direct assay of MP function enables rigorous structure-function correlation; and (iii) 2D
crystals are robust. However, obtaining a complete protein structure requires hundreds of crystals. To
date, 2D crystal production is the major bottleneck to electron crystallography MP structure
determination. The talk will focus on the first steps of a bold and holistic approach to fabricate tailored
nanoscale templates that drive the facile 2D crystallization of a broad range of MP’s fitted with
inorganic-binding tags.
The research is supported by
NSF-MRSEC Program through the University of Washington GEMSEC (DMR 0520567).
13
2:50pm
3D Chemical Imaging of Single Cells
Speaker: Michael Robinson
Principal Investigator: David G. Castner
Using a dual beam approach, we have successfully an intracellular lipid domain, possibly the the nuclear
membrane, of a biological single cell (fibroblast 3T3). We were able to visualize this in a full 3D image
stack by correcting the data in the z-direction using in-house software and reducing the opacity of the
outer lipid layer, as seen in below. This lays the groundwork necessary for future experiments that seek
to localize, in three dimensions, metabolites, drugs or nanoparticles that have accumulated inside of a
cell. Three dimensional is essential for accurately describing where these components are inside of a
cell. The pixel shift is necessary to compensate for imaging non-flat surfaces and allows the ability to
determine exactly where in z a component is located. This correction was first described in [1].
Combined AFM and ToF-SIMS experiments have shown that the sputter rate through these cells is
constant, a necessity for the correction to work properly. The sputter rate was calculated to be about
10 nm per 1.25 x1013
ions/cm2 of C60
++.
The intensity of many important cellular structures (lipids, etc) quickly degrade during bombardment
with C60, reducing the quality and sensitivity of depth profile and 3D datasets. These can be dramatically
improved by increasing the intensity throughout acquisition. We have found that by decreasing the salt
chloride concentration, these signals display higher counts, which agrees with similar results in protein
films [2]. Cells that were plunge frozen in liquid ethane and freeze dried have been compared with cells
fixed with 4% paraformaldehyde followed by light or heavy rinses, as well as those analyzed frozen
hydrated to determine which yielded the highest intensities of organic peaks throughout a depth profile.
The lowest intensities were detected from the freeze dried cells, which also exhibited the highest
chloride intensity. The the largest organic and lowest chloride intensities came from fixed, heavily rinsed
cells. The effect of frozen hydrated analysis as it applies to the increase in ionization of organic peaks in
single cells is still being studied, but preliminary data indicates that the behavior may be similar to that
described in protein films in [3]: little to no increase in yields in lower mass molecular fragments, but a
larger increase in ionization in higher molecular weight fragments.
[1] Breitenstein, D, et al. Angewandte Chemie, Int. Ed. 46(28), 2007, 5332-5335.
[2] Piwowar, A., et al. Anal. Chem, 81(3), 2009, 1040-1048
[3] Piwowar, A., et al. Anal. Chem., 82 (19), 2010, 8291–8299
14
3:10pm
Poly(Zwitterionic) Protein Conjugates: Relieving PEGylation
Speaker: Andrew Keefe
Principal Investigator: Shaoyi Jiang
Maintaining both the stability and bioactivity of therapeutic proteins has been one of the most difficult
tasks in biotechnology. The current PEGylation technique maintains stability of proteins at the expense
of their binding affinity. Here, we report a new concept in protein-polymer conjugation based on
zwitterionic polymers such as poly(carboxybetaine) (pCB) to resolve this fundamental issue. Our results
show that pCB-protein conjugates not only have increased stability, but retain or improve binding
affinity due to enhanced protein-substrate hydrophobic-hydrophobic interactions. In contrast,
conjugates possessing poly(ethylene glycol) (PEG) have increased stability, but with significantly lower
affinities due to steric hindrance between the substrate and the active site. This chemistry opens a new
avenue to develop protein therapeutics by not having to compromise between stability and affinity.
15
Poster Presentation Title Summary
CcrR, a TetR-family transcriptional regulator, activates the transcription of a key gene of EMC pathway
in Methylobacterium extorquens AM1
Bo Hu, Mary Lidstrom
A Comparative Study on the Enhanced Sampling of Small Peptides
Michael Deighan, Jim Pfaendtner
The Effect of Biomaterial Surface Chemistry on the Development and Functions of Dendritic Cells
Christina Yacoob, Hong Shen
Engineering Proteins for 2D Self Assembly
James Matthaei , François Baneyx
High-Performance Multilayered Blue Phosphorescent Organic Light-Emitting Diodes achieved by
Sequential Solution-Processing Method
Taeshik Earmme, Eilaf Ahmed, Samson A. Jenekhe
Improving the Expression of Functional Membrane Proteins in Escherichia coli
Brent L. Nannenga, François Baneyx
Interfacial Structure of Nanoparticle Stabilized Emulsions
Kjersta Larson-Smith and Danilo C Pozzo
Investigating the Candida rugosa lipase activation mechanism using multiscale simulation
Patrick Burney, Jim Pfaendtner
Low-Cost Solar Cells from Nanocrystal Inks: The Importance of Size
Cori Bucherl, Andrew Collord, Hugh W. Hillhouse
Measurement of PDMS/Water Partition Coefficients of Trace Organics Contaminants Using Raman
Spectroscopy
Ikechukwu C. Nwaneshiudu, Qiuming Yu, Daniel T. Schwartz
Nanoscale Mobility Characterization In Organic Systems
Lakshmi Suhasini Kocherlakota, Renee Overny
Numerical Simulations of Intracellular Temperature Distribution During Nanoshell Enabled
Photothermal Therapy (No abstract)
Hai Nguyen, Hong Shen
16
Photophysics and Ambipolar Field-Effect Charge Transport in Heterojunction Thin Films of Polymer
Semiconductors
Felix Sunjoo Kim, Eilaf Ahmed, Selvam Subramaniyan, Samson A. Jenekhe
Simulation, Design, and Characterization of Microeddy Hydrodynamic Tweezers
Tyler House, Daniel T. Schwartz
Structural analysis of protein complexes with sodium alkyl sulfates (No abstract)
Monica Ospinal-Jimenez, Danilo Pozzo
Structural and Rheological Investigation of Fully Hydrated Fibrin Gels: an In-Situ Neutron Scattering
Study of Structural Transitions under Shear Deformation
Kathleen Weigandt, Lionel Porcar, Danilo Pozzo
Structure-Property Relationships in Conjugated Polymer Networks
Greg Newbloom, Kathleen Weigandt, Danilo Pozzo
Synthesis of Iron Pyrite (FeS2) Semiconducting Nanocrystals: Polymer-Assisted Hydrothermal and Hot
Injection Methods
John Bae, Leize, Qiuming Yu
Toward High-Efficiency Solar Cells: Double Gyroid Devices
Robert McCarthy, Hugh W. Hillhouse
Toward High-Efficiency Solar Cells: The Double Gyroid Nanostructure
Steven Gaik, Hugh W. Hillhouse
Understanding the effect of Gelation Conditions on the Self-Assembly of Conjugated Polymers
Pablo DeLa Iglesia, Danilo Pozzo
Using Diblock Copolymer Approach to Improving Performance of Organic Photovoltaic Cells
Guoqiang Ren, Samson Jenekhe
17
Poster Presentation Abstracts
CcrR, a TetR-family transcriptional regulator, activates the transcription of a key gene of EMC pathway
in Methylobacterium extorquens AM1
Bo Hu, Mary Lidstrom
M. extorquens AM1 has been considered a promising biotechnological platform due to the relatively
inexpensive substrates and high flux through intermediates of biotechnology interest that are involved
in the C1 and C2 assimilation. In this study, a TetR-type activator, CcrR, has been shown to regulate the
expression of crotonyl-CoA reductase/carboxylase, a key enzyme of the ethylmalonyl CoA pathway
involved in assimilation of C1 and C2 compounds in Methylobacterium extorquens AM1. The ccrR
mutant is impaired in its ability to grow on C1 and C2 compounds, correlating with the reduced activity
of crotonyl-CoA reductase/carboxylase. Promoter fusion assays have demonstrated that the expression
of the promoter involved in ccr expression (the katA-ccr promoter) decreased as much as 50% in the
absence of CcrR compared to that in wild type M. extorquens AM1. The results of gel mobility shift
assays confirmed that CcrR binds to the region upstream of the katA-ccr promoter. A palindrome
sequence upstream of katA at position -334 to -321 with respect to the translational start site was found
to be the binding site and mutations in this region eliminated gel retardation with CcrR. This work is not
only the first step in understanding the regulation mechanism of the EMC pathway, but also sets the
stage for identifying additional regulatory elements, information that will be key to manipulating the
EMC pathway for biotechnological applications.
--------------------------------------
A Comparative Study on the Enhanced Sampling of Small Peptides
Michael Deighan, Jim Pfaendtner
Molecular dynamics (MD) provides a useful way to investigate the underlying thermodynamics and
kinetics of a system that are difficult to resolve by experiment alone. However, MD as it stands is
insufficient when the subject of interest involves large-scale conformational changes (e.g., soft-matter
systems such as proteins or polymers). These events tend to occur on the order of microseconds or
longer, a timescale far beyond the range of MD. In response to this, numerous enhanced sampling
algorithms have been developed to effectively explore conformational space in a reasonable amount of
time. Two common classes of methods for overcoming energy barriers are: 1) those that manipulate a
system’s energy by adding an external bias (e.g., umbrella sampling or metadynamics) and 2) those that
periodically expose a system to temperatures above the melting point (e.g., parallel tempering).
The work we present focuses on the convergence of conformational sampling and thermodynamic
energy landscapes of an explicitly solvated 20-residue tryptophan-cage protein (Trp-cage). Three types
of simulations are compared: classical parallel tempering (PT) [1], parallel tempering and well-tempered
metadynamics (PT-WTM) [2], and a new method that uses metadynamics within the well-tempered
ensemble of Bonomi and Parrinello [3]. This new method allows for a broad temperature range to be
18
sampled using many fewer replicas than PT or PT-WTM. Not only does this approach significantly reduce
computational cost – compared to the aforementioned methods – but it also enables the possibility of
scaling to systems larger than what was previously considered practical for PT simulations.
[1] Sugita & Okamoto, Chem. Phys. Let. 314, 141-151 (1999)
[2] Barducci et al., Biophys. Jour. 98, L44 (2010)
[3] Bonomi & Parrinello, Phys. Rev. Let. 104, 190601 (2010)
--------------------------------------
The Effect of Biomaterial Surface Chemistry on the Development and Functions of Dendritic Cells
Christina Yacoob, Hong Shen
Immunogenic responses can be induced when biomaterials are implanted in the body. Dendritic cells
(DCs), key antigen presenting cells, play a major role in initiating immune reactions and link innate and
adaptive immunity. In this study, the effects of biomaterial surface chemistry on DC phenotypes and
functions were examined using self-assembled monolayer (SAM)-functionalized substrates. Chemical
groups, including OH, SO3Na, COOH, and CH3 present in alkanethiols, were chosen to mimic the surface
chemistry present on typical biomaterial surfaces. Contact angles of each substrate were consistent with
the literature values. The presence of each chemical group was confirmed by FT-IR. The topology of each
substrate was examined by AFM.
DCs on the OH-terminated SAM displayed a higher level of maturation compared to that of other
functionalized groups. DCs on OH and SO3Na-terminated SAMs showed elevated levels of the pro-
inflammatory cytokine interleukin-6 (IL-6). Though the production of regulatory cytokine interleukin-10
(IL-10) by DCs on SAMs was nominal, DCs on CH3-terminated SAMs exhibited a significant higher level.
Our results demonstrate that the hydrophobicity of biomaterials may play a role in DC maturation
towards either tolerogenic or immunogenic phenotypes, although overall, these monolayers are
relatively inert.
--------------------------------------
Engineering Proteins for 2D Self Assembly
James Matthaei , Frank Dimaio, Yongdong Liu, David Baker, François Baneyx
Self-assembly is of great importance to nanotechnology because it is one the most effective strategies to
fabricate highly ordered nanostructures[1]. It is also a hallmark of many biological systems. For
example, Surface layer (S-layer) proteins, self-assemble into crystalline 2-D arrays of oblique, square and
hexagonal symmetry with pore sizes ranging from 2 to 8nm. S-layers have been used for applications
ranging from ultrafiltration membranes, to attachment layers for biosensor design, to templates for the
synthesis of ordered metal and metal oxide nanoarrays[2,3]. They however have limitations including
the lack of structural information, the fact that many genes encoding S-layers have not been cloned,
difficulties in expressing or isolating large amounts of protein, the co-existence of multiple pores with
different sizes and shapes, a characteristic sheet size in the µm range, and an intrinsic curvature in the
array. Here, we report on the computational design and
does not suffer from these limitations and self
single ≈3nm pore upon addition of calcium
[1] Whitesides, G.M. and B. Grzybowski,
2421.
[2] Sleytr, U.B., et al., S-Layers as a basic building block in a molecular construction kit.
2007. 274(2): p. 323-334.
[3] Allred, D.B., et al., Three-dimensional architecture of inorganic nanoarrays
a surface-layer protein mask. Nano Letters, 2008.
High-Performance Multilayered Blue Phosphorescent Organic Light
Sequential Solution-Processing Method
Taeshik Earmme, Eilaf Ahmed, Samson A. Jenekhe
Phosphorescent organic light-emitting diodes (PhOLEDs) have been extensively investigated over the
recent years for high-performance and various applications in the display technology. However, cu
high-performance PhOLEDs have largely been focused on thermal evaporation processes of small
molecules to obtain multilayered device structures, which directly affect the fabrication cost and also
not suitable for large area devices. Here we report h
sequential solution-processed layers, enabled by new series of solution
different sizes and shapes, a characteristic sheet size in the µm range, and an intrinsic curvature in the
report on the computational design and construction of an artificial S
does not suffer from these limitations and self-assembles into a hexagonal 2D crystalline array
≈3nm pore upon addition of calcium ions.
hitesides, G.M. and B. Grzybowski, Self-assembly at all scales. Science, 2002. 295
Layers as a basic building block in a molecular construction kit.
dimensional architecture of inorganic nanoarrays electrodeposited through
Nano Letters, 2008. 8(5): p. 1434-1438.
--------------------------------------
Performance Multilayered Blue Phosphorescent Organic Light-Emitting Diodes achieved by
ing Method
Taeshik Earmme, Eilaf Ahmed, Samson A. Jenekhe
emitting diodes (PhOLEDs) have been extensively investigated over the
performance and various applications in the display technology. However, cu
performance PhOLEDs have largely been focused on thermal evaporation processes of small
molecules to obtain multilayered device structures, which directly affect the fabrication cost and also
not suitable for large area devices. Here we report high-performance blue PhOLEDs achieved by three
processed layers, enabled by new series of solution-processable n
19
different sizes and shapes, a characteristic sheet size in the µm range, and an intrinsic curvature in the
l S-layer protein that
assembles into a hexagonal 2D crystalline array with
295(5564): p. 2418-
Layers as a basic building block in a molecular construction kit. Febs Journal,
electrodeposited through
Emitting Diodes achieved by
emitting diodes (PhOLEDs) have been extensively investigated over the
performance and various applications in the display technology. However, current
performance PhOLEDs have largely been focused on thermal evaporation processes of small
molecules to obtain multilayered device structures, which directly affect the fabrication cost and also
performance blue PhOLEDs achieved by three
processable n-type organic
20
semiconductors based on starburst dendritic oligoquinolines are synthesized and developed as electron-
transport and hole-blocking materials for PhOLEDs. Using solution-processable electron-transport layers
(ETLs), we observe a large improvement of the device performance compared to vacuum deposited ETL.
By virtue of the high electron mobility and a deep HOMO energy level, dendritic oligoquinolines serves
as an efficient electron-transport layer (ETL) and a good hole-blocking layer (HBL). The unique
oligoquinoline ETL surface formed by solution-processing enables the high quality ETL/Al interface
formation, resulting in efficient electron-injection/transport into the devices. We expect the solution-
processing approach demonstrated here for high performance blue PhOLEDs to be also applicable to
different colors of OLEDs / PhOLEDs as well as other solution-processed multilayered organic electronic
devices.
--------------------------------------
Improving the Expression of Functional Membrane Proteins in Escherichia coli
Brent L. Nannenga, François Baneyx
Membrane proteins (MPs) account for 20-30% of the genomes sequenced to date and hold great
potential as therapeutic targets, as well as for practical applications in bionanotechnology that range
from selective nanochannels to solar energy harvesting. This potential remains largely untapped
because MPs are difficult to express and little is known about their structure and function. Here we
describe folding engineering strategies that improve the yields of functional MPs in E. coli by 3-to-7 fold.
--------------------------------------
Interfacial Structure of Nanoparticle Stabilized Emulsions
Kjersta Larson-Smith and Danilo C Pozzo
Particle-stabilized emulsions (Pickering emulsions) are formed when oil is mechanically dispersed into
water in the presence of finely ground solid particles. Pickering emulsions of micron sized particles are
known to be sterically stabilized by close-packed microparticles that form an elastic shell. However,
emulsions with nanoparticles are less stable because the particles are only loosely bound to the
interface. The energy barrier necessary for particles to detach from the oil-water interface scales with
the particle radius squared, therefore nanoparticle adsorption is much more sensitive to solvent
conditions and thermal fluctuations. Small-Angle Neutron Scattering (SANS) and Small-Angle X-ray
Scattering (SAXS) are used to examine nanoparticle adsorption at a hexadecane-water interface in situ.
We show the highest particle adsorption occurs in emulsions with moderate ionic strength due to a
reduced electrostatic repulsion and low pH because of neutralized oil and particle surface charges.
--------------------------------------
21
Investigating the Candida rugosa lipase activation mechanism using multiscale simulation
Patrick Burney, Jim Pfaendtner
Lipase enzymes are a common component of most pathways for metabolizing lipids. They catalyze the
breakdown of large lipid structures by means of hydrolyzing ester bonds. Their importance in this role
explains why human lipases have been implicated in a variety of health conditions, including heart
disease and diabetes. Industrial utilization of lipases (purified from various microorganisms) has
predominantly been for food production and in detergents, yet in the past decade for the production of
biodiesel and other sustainable fuels from plant-derived substrates.
Despite their importance in both technological application and human health, little is known about the
dynamics of lipases at the atomic level. Previous experimental investigations have shown a common
structural motif among lipases is a flap-like domain that protects the active site from the solvent until in
the enzyme contacts a solvent-lipid interface. The C. rugosa lipase (CRL) structure has been resolved for
both the flap-open and flap-closed states. The two states have almost identical structure, except for the
26 amino-acid flap, which differs by 17 Angstrom between the open and closed states. This similarity has
led to the conclusion that the flap-opening mechanism is a hinge-like motion. Given the importance of
this conformational change in regulating lipase activity, the molecular details of the flap mechanism are
essential knowledge for engineering improved lipases. However, direct observation of this process is
difficult or impossible via experiment alone. Therefore, we have used molecular and coarse-grained
simulations to investigate the behavior of CRL in explicit water. The major challenge of using classical
MD in investigating conformational rearrangement and rare events (e.g., flap opening/closing) lies in
sufficient sampling. As we demonstrate, even microsecond-long simulations of the all-atom (AA) system
cannot provide enough sampling to calculate the equilibrium probability distribution of this process. We
use the AA simulation trajectories to develop coarse-grain (CG) models based on the recently developed
ED-CG [1] method. The ED-CG models help identify dynamically similar domains within the open and
closed states. Finally, we use the metadynamics [2] algorithm to calculate the free-energy landscape
and identify key structural transitions in the opening and closing process.
[1] Z. Zhang, L. Lu, W.G. Noid, V. Krishna, J. Pfaendtner, and G.A. Voth (2008). “A Systematic
Methodology for Defining Course-Grained Sites in Large Biomolecules.”Biophysical Journal 95: 5073-
5083.
[2] A. Laio and M. Parrinello (2002). "Escaping free-energy minima." PNAS 99(20): 12562-12566.
--------------------------------------
Low-Cost Solar Cells from Nanocrystal Inks: The Importance of Size
Cori Bucherl, Andrew Collord, Hugh W. Hillhouse
Nanocrystal inks, namely CuInGaS2 and Cu2ZnSnS4, offer a promising, low-cost, environmentally benign,
and scalable method for solar photovoltaic production. Here, we present plans for determining the
impact of nanocrystal size on final device performance. To that end, we also present the potential of
mathematical simulations to predict growth of nanocrystals in solution and provide control parameters
22
that can be utilized during syntheses to control the size and size distribution of the nanocrystal product.
Identifying optimal nanocrystal sizes and controlling the reaction to produce those sizes with narrow
distributions would maximize reaction yield, minimize incorporation of surface impurities into films, and
allow for optimal packing density for more highly uniform annealed continuous crystalline domains.
--------------------------------------
Measurement of PDMS/Water Partition Coefficients of Trace Organics Contaminants Using Raman
Spectroscopy
Ikechukwu C. Nwaneshiudu, Qiuming Yu, Daniel T. Schwartz
An optical method was developed to quantify the partitioning of trace organics into
polydimethylsiloxane (PDMS) matrices. The use of PDMS in research areas such as microfluidics and
solid phase micro-extraction (SPME) techniques has made it a polymer of interest in many disciplines.
Previous work utilized PDMS in a coupled SPME/Raman platform to detect trace BTEX (benzene,
toluene, ethylbenzene, xylene) fuel components, which are extracted from contaminated water and pre-
concentrated into the PDMS polymer matrix[5]
. Here we demonstrate the use of SPME/Raman to
estimate PDMS/organic partition coefficients (KPDMS/WATER). Partition coefficients for benzene and toluene
where obtained by comparing linear correlations of organic and aqueous experiments at the linear
dynamic range (LDR). The obtained values were in good agreement with those obtained using
conventional quantitative SPME techniques. We extend the method to analyze organics with unknown
partition coefficients.
--------------------------------------
Nanoscale Mobility Characterization In Organic Systems
Lakshmi Suhasini Kocherlakota, Renee Overny
Nanoscale information about the molecular mobilities and relaxation modes are critical parameters in
the molecular design of condensed organic materials. Intrinsic Friction Analysis (IFA), a spectroscopic
analysis method based on scanning force microscopy has been successfully employed by our group to
investigate intra-molecular and molecular mobilities in complex organic thin film materials like
amorphous organic non-linear optical (NLO) materials and complex organic polymeric systems.
Specifically the thermal active (α-, β-, γ-) relaxation modes in polystyrene (PS), which involve both the
enthalpic and entropic contributions are presented as a representative complex amorphous polymeric
systems. Relaxation energies deduced from self-assembling glassy chromophores are also discussed
which are relevant for understanding the interactions between self-assembling molecules in molecular
design requirements.
--------------------------------------
23
Photophysics and Ambipolar Field-Effect Charge Transport in Heterojunction Thin Films of Polymer
Semiconductors
Felix Sunjoo Kim, Eilaf Ahmed, Selvam Subramaniyan, Samson A. Jenekhe
We report photophysical and ambipolar charge transport properties in thin films of polymer/polymer
heterojunction. Unique solubility of constituent polymer semiconductors in different solvents enabled
us to form layered heterojunctions by sequential spin-coating of unipolar p- and n-type polymer
semiconductors, and to make bulk heterojunctions from a blend of the polymer semiconductors.
Absorption spectra of the polymer/polymer heterojunctions are simple superposition of those of their
parent homopolymers. The thin film transistors show typical ambipolar charge transport characteristics
with clear current modulation and saturation, enabling construction of complementary circuits based on
the transistors.
--------------------------------------
Pyrite FeS2 Nanocrystals for Use in Polymer:Inorganic Hybrid Solar Cells
Beau Richardson, Qiuming Yu
Pyrite FeS2 is a promising candidate for thin film photovoltaics as it is an abundant and environmentally
benign material with low procurement costs and has a similar energy band gap and higher absorption
coefficient than silicon, which is most commonly used in solar cells. In this work, organic-inorganic
hybrid solar cells are fabricated by deploying phase pure pyrite FeS2 nanocrystals (NC’s) with diameters
of 10-20 nm as an electron acceptor material in a bulk heterojunction with poly(3-hexylthiophene)
(P3HT). Extended red light absorption is observed when combining FeS2 NC’s into the active layer.
Ligand exchange is used to replace octadecylamine with less-insulating ligands on the NC surface to
enhance the short-circuit currents (Jsc) of these devices. In addition, various parameters of the
fabrication technique are currently being optimized to improve active layer morphology.
--------------------------------------
Simulation, Design, and Characterization of Microeddy Hydrodynamic Tweezers
Tyler House, Daniel T. Schwartz
Hydrodynamic tweezers are a category of steady streaming micro-scale flows where particles can be
trapped near engineered flow obstructions. Particle trapping is set by the particle size, the obstruction
size and arrangement, and the frequency of the oscillating flow that drives steady streaming. Here we
explore the behavior of neutrally-buoyant particles using a simple model that balances Stokesian drag
with the time-averaged drift force induced by the kinematics of motion in this flow. We show a complex
behavior for the trapping force vs. shear stress, with certain frequencies showing bifurcated trapping at
either a high or low shear stress state.
24
--------------------------------------
Structural and Rheological Investigation of Fully Hydrated Fibrin Gels: an In-Situ Neutron Scattering
Study of Structural Transitions under Shear Deformation
Kathleen Weigandt, Lionel Porcar, Danilo Pozzo
Fibrin is a protein that self-assembles into a bifurcating nanofibrous network forming the primary
structural component of a blood clot. Developing relationships between the mechanical and structural
properties of fibrin clots is critical to the diagnosis and treatment of various clotting conditions. Using
small angle neutron scattering (SANS) and rheological techniques we seamlessly characterize the
structural and mechanical properties of fully hydrated fibrin gels. Like many other biopolymers, fibrin
gels are highly elastic and stiffen when deformed. Though several theoretical models exist that describe
the strain-hardening of semi-flexible biopolymer gels, the origin of this phenomenon is, as of yet, not
fully understood. SANS is used to directly probe the structural properties of fibrin as the gel is deformed.
The results of this study indicate that as fibrin is strained it undergoes critical mechanical
transformations that are directly linked to the underlying structure of the gel.
--------------------------------------
Structure-Property Relationships in Conjugated Polymer Networks
Greg Newbloom, Kathleen Weigandt, Danilo Pozzo
Conjugated polymer semiconductors, such as polythiophenes (PTs), represent a novel approach towards
low-cost, easy-to-manufacture organic photovoltaic devices. Many of these polymers, such as poly(3-
hexylthiophene) (P3HT), are known to form fibrillar structures when solvent quality is reduced. At high
concentrations, P3HT will self-assemble and form semiconducting elastic networks of interconnected
fibers. The interconnectivity of these networks lead to a continuous, 3-dimensional path for charge
transport which is ideal for the bulk heterojunction structure of organic photovoltaic devices. This poster
will describe our recent systematic evaluation of these networks over multiple length scales (0.1 –
10,000 nm) using small angle neutron scattering. The complementary characterization of the mechanical
(rheology), optical and electrical properties of the organogels allows us to also formulate structure-
property relationships for this new class of materials.
--------------------------------------
Synthesis of Iron Pyrite (FeS2) Semiconducting Nanocrystals for Use in Polymer: Inorganic Hybrid Solar
Cells
John Bae, Beau Richardson, Leize Zhu, Qiuming Yu
Pyrite FeS2 is a promising candidate for thin film photovoltaics as it is an abundant and environmentally
benign material with low procurement costs and has a similar energy band gap and higher absorption
coefficient than silicon, which is most commonly used in solar cells. In this work, a hydrothermal
synthetic method with polymer is used (specifically polyvinyl alcohol and polyvinyl pyrrolidone) in order
25
to produce crystals with cubic or octahedral morphology. The hot injection method is also used to
achieve spherical nanocrystals between 10-20 nm in diameter. Organic-inorganic hybrid solar cells are
fabricated by deploying these phase pure pyrite FeS2 nanocrystals (NC’s) as an electron acceptor
material in a bulk heterojunction with poly(3-hexylthiophene) (P3HT). Extended red light absorption is
observed when combining FeS2 NC’s into the active layer. Ligand exchange is used to replace insulating
molecules on the NC surface with more favorable ones to enhance the short-circuit currents (Jsc) of
these devices. In addition, various parameters of the fabrication technique are currently being
optimized to improve active layer morphology.
--------------------------------------
Toward High-Efficiency Solar Cells: Double Gyroid Devices
Robert McCarthy, Hugh W. Hillhouse
This effort aims to produce double gyroid (DG) nanowire solar cells (approximately 5 nm in diameter)
that are highly efficient due to the phenomenon of multiple exciton generation (MEG). Many DG
semiconductor films have been deposited, characterized, and made into Schottky solar cells. Only very
low photocurrents have been measured so far, and recent modeling efforts suggest that interface
recombination losses may offset the efficiency gains from MEG.
--------------------------------------
Toward High-Efficiency Solar Cells: The Double Gyroid Nanostructure
Steven Gaik, Hugh W. Hillhouse
This work addresses the low efficiency of conventional photovoltaic devices by developing a
nanostructured film that can be used to create solar cells with intrinsically higher energy conversion
efficiencies. Solar cells employing this film technology would have improved efficiencies due to the use
of unconventional device physics
--------------------------------------
Understanding the effect of Gelation Conditions on the Self-Assembly of Conjugated Polymers
Pablo DeLa Iglesia, Danilo Pozzo
Polymeric solar cells (PSCs) are a very attractive renewable energy alternative due to their low costs,
compared to silicon-based solar cells, and the possibility to mass-produce them with printing
technology. Still, a large liability for PSCs is their low efficiency to transport charges after exciton
dissociation. Polymer crystallization allows for an increase of conjugation length and more efficient
charge transport. In concentrated samples of conjugated polymers, crystallization is often manifested as
macroscopic gelation. We have recently postulated that the interconnected fiber network of these gels
could represent an ideal structure for solar cells because it combines the high charge mobility of
crystalline polymers with a continuous path for charge transport. In order to fully optimize the structure
26
of these networks, it is first essential to understand the effects of temperature, concentration,
molecular weight and solvent on the crystallization of different conjugated polymers. We are using
conjugated polymers with different molecular characteristics to survey how crystallization conditions
affect the resulting fiber network structures so that we can engineer optimized networks to maximize
charge carrier mobility. For this particular study we will be using poly(9,9-dioctyl-fluorene) (PFO) to
compare its crystallization and gelation with our previous work on poly(3-hexylthiophene)(P3HT). The
differences in the gel nanostructure and on gelation time hint towards a fundamental difference in
crystal nucleation for both polymers. Identifying trends on the effects of solubility conditions on
crystallization of two very different conjugated polymers (i.e. PFO and P3HT) will allow us to relate
molecular characteristics of the polymer and gelation conditions to the resulting structure. This will
enable fundamental descriptions to be formulated that can be extended to other conjugated polymers
of interest for organic electronic applications.
--------------------------------------
Using Diblock Copolymer Approach to Improving Performance of Organic Photovoltaic Cells
Guoqiang Ren, Samson Jenekhe
The photovoltaic properties, charge transport, and morphology of a series of diblock conjugated
copolymers, poly(3-butylthiophene)-b-poly(3-octylthiophene) (P3BT-b-P3OT), were investigated as a
function of block composition. Bulk heterojunction solar cells comprising blends of P3BT-b-P3OT and
[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) were found to have power conversion efficiencies as
high as 3.0%, which represents factors of 1.6−9 enhancements compared to those of the homopolymers
made under similar conditions. Imaging of P3BT-b-P3OT/PC71BM blends by atomic force microscopy and
transmission electron microscopy revealed interpenetrating network with 11−18 nm crystalline polymer
domains. The zero-field space charge limited current mobility of holes ((1−3) × 10−4
cm2 V
−1 s
−1) was
similarly enhanced in the diblock copolymer solar cells compared to the homopolymers. These results
demonstrate that block conjugated copolymers offer a promising approach to advanced materials for
polymer solar cells and that the block composition is an attractive means to optimize the materials.
27
Acknowledgments
Thank you again to all of our guests from industry for participating and especially for assisting with
judging presentations!
Thank you to all of the graduate students who volunteered to organize and set up the Symposium, dealt
with logistics, and ensured that today was successful. The Professional Development Committee
couldn’t have done it without you!
We would also like to thank the Chemical Engineering Department Faculty and Staff for all of the
support they have given us.
Congratulations to the presentation winners! Utilize your winnings wisely!
Finally, mark your calendars for the 2012 Graduate Student Symposium, tentatively scheduled for
Monday, September 24, 2012. If you or your company would be interested in the opportunity to
support this event or any other ACES event, please contact [email protected].
Thanks for coming!
