Workshop: Light-Driven Processes for Bio-Inspired...

Workshop: Light-Driven Processes

for Bio-Inspired Materials

December 14-16, 2014 BioScience Research Collaborative

Funded by: 2013 John S. Dunn Collaborative Event Award

Rice University, Faculty Initiative Fund Gulf Coast Consortia

Dunn Award Collaborative Team: Christy Landes, Rice University Stephan Link, Rice University

Neal Waxham, University of Texas Health Science Center at Houston Richard Willson, University of Houston

www.gulfcoastconsortia.org

The Gulf Coast Consortia (GCC), located in Houston, is a dynamic, multi-institution

collaboration of basic and translational scientists, researchers, clinicians and students in the quantitative biomedical sciences who participate in joint training programs, utilize shared facilities and equipment, and exchange scientific knowledge. Working together, GCC member institutions provide a cutting edge collaborative training environment and research infrastructure, beyond the capability of any single institution. GCC training programs currently focus on biomedical informatics, computational cancer biology, molecular biophysics, neuroengineering and pharmacological sciences. GCC research consortia gather interested faculty around research foci within the quantitative biomedical sciences, and currently include bioinformatics, chemical genomics, magnetic resonance, protein crystallography, translational pain research, early disease detection, neuroengineering, and translational addiction sciences, in addition to regenerative medicine. Current members include Baylor College of Medicine, Rice University, University of Houston, The University of Texas Health Science Center at Houston, The University of Texas Medical Branch at Galveston and The University of Texas M. D. Anderson Cancer Center. John S. Dunn Collaborative Event Award This workshop is funded, in part, by a 2013 Event Award from the John S. Dunn Collaborative Research Award Program, administered by the Gulf Coast Consortia. Launched in 2009 as a 10-year program with generous support from the John S. Dunn Foundation, this seed grant program continues to build the Bioscience Research Collaborative (BRC) and the interdisciplinary environment of the Gulf Coast Consortia (GCC).

The purpose of this program is to foster excellent interdisciplinary and inter-institutional engagement in the quantitative life sciences by providing two types of seed grants: (1) Research: Up to $100,000 total to support research/preliminary work by new collaborative teams for two (2) years that is essential to be competitive for future funding (2) Event: Up to $8,000 for one (1) year to support events/activities designed to bring together new interdisciplinary communities.

Funds are awarded each year with one member of each team required to be part of the BioScience Research Collaborative-Associated Faculty. The next cycle of the program will be announced in early 2015. To learn more about the program, including eligibility criteria and previously funded projects, visit the website: http://gcc.rice.edu/Funding_Opportunities_Main.aspx

Rice University Faculty Initiatives Fund This workshop is funded, in part, by the Rice University's Faculty Initiatives Fund (FIF), an internal funding mechanism that awards competitive grants of between $5,000-$50,000 to Rice faculty. (In extenuating circumstances, grants of up to $75,000 can be considered.) These grants are intended to help faculty members develop adventurous projects that might enhance the university and that might lead to larger endeavors, research breakthroughs, external funding opportunities, or unusually creative works. Full-time and research faculty members at Rice are eligible to apply. Proposals may be submitted individually or by a group of faculty. Visit the website for more information: https://facultyinitiativesfund.rice.edu/

5:30 pm Welcome Reception BRC Event Space

7:00 pm Welcome Christy Landes, Rice University

7:15 pm Capturing color: cephalopod‐inspired plasmonic active

materials

Naomi Halas, Rice University

7:45 pm Exciton transport in carbon nanotube photovoltaics using 2D

White‐Light Spectroscopy: Design principles from light

harvesting proteins

Martin Zanni, University of Wisconsin

8:15 pm Linker Rectifiers for Covalent Attachment of Catalysts to

Semiconductor Surfaces

Victor Batista, Yale University

8:45 pm Improving the Photocurrent Generation of Thylakoid Bio‐solar

Cells

Shelley Minteer, University of Utah

9:15 pm Adjourn

8:00 am Breakfast BRC Lobby

BRC Auditorium

9:00 am Novel Plasmonic Nanomaterials and Instruments for

Biomedical Applications

Wei Shih, University of Houston

9:15 am Monitoring Charge Interactions through Changes in the

Plasmon Linewidth

Stephan Link, Rice University

9:30 am Super‐resolution imaging of hybrid organic‐plasmonic

nanostructures

Katherine Willets, University of Texas at

Austin

10:00 am Plasmonic nanoparticles for sensing applications Emilie Ringe, Rice University

10:15 am In Situ Three‐dimensional Super‐resolution Imaging of

Molecular Transport and Single Particle Catalysis

Ning Fang, Iowa State University

10:45 am Coffee Break

11:00 am Light Management in Extremely Thin Photoelectrode

Architectures for Solar‐Fuel Generation

Isabell Thomann, Rice University

11:15 am Tuning of Charge Separation at the Nanoscale for Energy

Applications

Clemens Burda, Case Western Reserve

University

11:45 pm Lunch BRC Event Space

BRC Auditorium

1:15 pm Organic Solar Cells: Current Progress and Challenges Thuc‐Quyen Nguyen, University of

California, Santa Barbara

1:45 pm Charge Separation and Photovoltaic Performance of All‐

Conjugated Block Copolymers

Rafael Verduzco, Rice University

Workshop: Light‐Driven Processes for Bio‐Inspired Materials and SystemsDecember 14‐16, 2014

BioScience Research Collaborative

Talk Session 1 ‐‐ Introduction to Interdisciplinary Vision of the Workshop BRC Auditorium

Sunday, December 14, 2014

Monday, December 15, 2014

Talk Session 2

Talk Session 3a

Session Chair: Neal Waxham, University of Texas Medical School at Houston

Session Chair: Christy Landes, Rice University

Session Chair: Anatoly Kolomeisky, Rice University

2:00 pm Metal Oxide Photocatalysts for Overall Solar Water Splitting:

Recent Advances and Challenges

Jiming Bao, University of Houston

2:15 pm Single‐molecule spectroscopic study of the counterion effect

at the polyelectrolyte aqueous interface

Y. Elaine Zhu, Notre Dame University

2:45 pm Computational Challenges in Broadband Mid‐Infrared

Imaging

David Mayerich, University of Houston

3:00 pm Mass Transport in Confined Environment Studied with Super

Resolution Optical Microscopy

Gufeng Wang, North Carolina State

University

3:30 pm Interfacial Molecular Foraging Daniel Schwartz, University of Colorado,

Boulder

4:00 pm Coffee Break

BRC Auditorium

4:15 pm Exploring Materials Structure and Mass Transport Dynamics

on Chemical Gradients by Single Molecule Tracking and

Spectroscopy

Daniel Higgins, Kansas State University

4:45 pm How To Understand Dynamics of Singlet Fission Process Anatoly Kolomeisky, Rice University

5:00 pm Seeing Single‐Molecule Dynamics at Interfaces with Optical

Microscopy

Jixin Chen, Ohio University

5:15 pm Influence of molecular connectivity and nearest neighbor

interaction on the charge transport properties of porphyrin

assemblies on Au surfaces

James D. Batteas, Texas A&M University

5:45 pm Quantifying Diffusion in Complex Media Neal Waxham, University of Texas Medical

School at Houston

6:00 pm Biomolecular synthesis of conducting polymers: Harnessing

the structural diversity of proteins to tune polymer properties

Christine Payne, Georgia Institute of

Technology

6:30 pm Poster Session and Reception BRC Event Space

8:00 am Breakfast BRC Classroom 280, lobby (2nd floor)

BRC Classroom 280 (2nd floor)

9:00 am Fabrication of Novel Titania Nanostructures for Energy

Applications

Anna Samia, Case Western Reserve

University

9:30 am Surface Enhanced Raman Spectroscopy (SERS) Of Core‐Shell

Structures With Different Shell Morphology

Laura Sagle, University of Cincinnati

10:00 am Electropolymerized Molecularly Imprinted Polymer (E‐MIP)

SPR based Sensors

Rigoberto Advincula, Case Western Reserve

University

10:30 am Coffee Break

10:45 am Single‐Molecule Methods to Quantify Adsorptive Separations Christy Landes, Rice University

11:15 am Quantum Plasmonics: Applications in Light Harvesting Peter Nordlander, Rice University

11:45 pm Biochemical applications of Surface‐Enhanced Raman

spectroscopy

Martin Moskovits, University of California,

Santa Barbara

12:15 pm

Session Chair: Emilie Ringe, Rice University

Lunch; Working Meeting to discuss possible future collaborations and/or center/collaborative proposals;

Closing Remarks

Tuesday, December 16

Talk Session 4

Session Chair: Stephan Link, Rice University

Talk Session 3b

Workshop: Light-Driven Processes for Bio-Inspired Materials

December 14-16, 2014 Speaker Abstracts

(in alphabetical order by speaker’s last name)

Electropolymerized Molecularly Imprinted Polymer (E-MIP) SPR based

Sensors

Rigoberto C. Advincula, Department of Macromolecular Science and

Engineering, Case Western Reserve University

The use of biomimetic artificial receptors based on polymers has gained much

attention in separation and sensing applications. We have specialized in the use

of electrochemically molecularly imprinted polymers (E-MIP) on surface

plasmon resonance (SPR) platforms to investigate high selectivity and

sensitivity in detecting endocrine disrupting chemicals (EDCs), drugs, nerve

agents. By utilizing electropolymerizable monomers and dendrimers, a very

high degree of interaction with the analyte is involved during the cross-linking

process. The result of optimized ratio, thickness, and washing steps enable the formation of these

effective sensing elements to achieve sensitivities up to picoMolar concentrations. These artificial

receptors can be tailor made to any number of analyte classes that have strong binding interaction with the

monomers in a pre-complex manner.

Metal Oxide Photocatalysts for Overall Solar Water Splitting:

Recent Advances and Challenges

Jiming Bao, Department of Electrical and Computer Engineering

University of Houston

Efficient solar water splitting through colloidal photocatalysts is

attractive both scientifically and technologically. Hundreds of

semiconductor photocatalysts have been identified or developed over

past several decades; however, very few of them can decompose pure

water without co-catalysts. In this talk, I will review recent emergence

of visible light photocatalysts for overall water slitting without co-

catalysts. I will show several approaches that have been used to make photocatalysts active for

overall water splitting; I will then discuss challenges of obtaining mechanistic understanding and

developing new photocatalysts.



Linker Rectifiers for Covalent Attachment of Catalysts to Semiconductor

Surfaces

Victor S. Batista, Department of Chemistry, Energy Sciences Institute, Yale

University

Linkers that favor

rectification of

interfacial electron

transfer are likely to

be required for

efficient photo-driven

catalysis of multi-

electron reactions at electrode surfaces. Design

principles are discussed, together with the

synthesis and characterization of a specific pair of

molecular frameworks, related by inversion of the

direction of an amide bond at the heart of the

molecule. The linkers have a terpyridyl group that

can covalently bind Mn as in a well-known water

oxidation catalyst and an acetylacetonate group

that allows attachment to TiO2 surfaces. The

appropriate choice of the sense of the amide

linkage yields directionality of interfacial electron

transfer, essential to enhance electron injection

and slow back-electron transfer. Support comes

from electron paramagnetic resonance, terahertz

spectroscopic, computational modeling

characterizing the asymmetry of electron transfer

properties, and conductance measurements based on the scanning tunneling microscope break-junction

(STM-BJ) technique.

Influence of molecular connectivity and nearest neighbor interactions on

the charge transport properties of porphyrin assemblies on Au surfaces James D. Batteas, Departments of Chemistry and Materials Science and

Engineering, Texas A&M University

The transport properties of a series of free-base and zinc coordinated tri-pyridyl

and tri-phenyl porphyrin thiols inserted into a dodecanethiol matrix on Au(111)

were investigated using scanning tunneling microscopy (STM). For single

molecules, the tunneling efficiency and I-V behvaiour was found to be

dominated by tunneling through the hydrocarbon tether used to bind the

molecules to the surface. However, when the porphyrin thiols were driven to

aggregate into islands on the surface (e.g. through pi-stacking), distinct changes in their charge transport

were observed, suggesting that molecular aggregation results in sufficiently reduced charge confinement

energy to facilitate a transition from a purely tunneling mechanism to a charge-hopping mechanism.

These results illustrate the impact of molecular aggregation and nearest neighbor interactions on charge

transport of molecular assemblies, and demonstrate the effectiveness of using such aggregates to achieve

single-electron transport characteristics from relatively simple, tunable subunits.

Figure 1: (Left) Schematic representation of the state

responsible for electron transport (LUMO) and alignment

relative to the Fermi level under equilibrium (V=0), positive

(V>0) and negative bias (V<0). (Right) Calculated I-V curves

for Mn-terpy-L1 (A) and Mn-terpy-L2 (B). The red and blue

lines represent the current under negative and positive bias,

respectively. Mn-terpy-L2 shows significant rectification.



Tuning of Charge Separation at the Nanoscale for Energy Applications Clemens Burda, Director, Center for Chemical Dynamics and Nanomaterials

Research, Department of Chemistry, Case Western Reserve University

Over the past decade, research in the group of Prof. Clemens Burda at Case

Western Reserve University has evolved around the design of nanostructured

materials with improved optical or electronic properties. Nanostructuring

materials can enhance specific properties in ceramics, semiconductors,

semimetals, as well as in metals. This has led to a bio-inspired design

approach for nanomaterials that targets the application in mind, and to

materials that have been used in a broad range of energy conversion

applications. This talk aims to give an overview of the physical chemistry involved in creating a

nanoscale charge separation system out of two simple semiconductor materials. The talk will discuss light

harvesting, hole and electron transfer photophysics,1 and the ultrafast carrier dynamics that is observed in

strongly coupled quasi-type-II charge separation centers.

1

C. Chuang and C. Burda*, Journal of Physical Chemistry Letters, 2012, 3 (14), 1921–1927.

Video: http://pubs.acs.org/page/jpclcd/burda.html

Seeing Single-Molecule Dynamics at Interfaces with Optical Microscopy

Jixin Chen, Department of Chemistry and Biochemistry, Ohio University

Single-molecule fluorescence microscopy allows us to do super-resolution

optical imaging and to measure molecular dynamics in many biological

systems. In this talk, Chen will share his experience in the application of a

super-resolution imaging technique in the measurement of single DNA-DNA

interaction, which is motivated by the clinical needs for DNA

sequencing/testing. He will also share his experience in applying single-

molecule Förster Energy Resonance Transfer (FRET) to study single DNA

hairpin folding dynamics.

http://pubs.acs.org/page/jpclcd/burda.html



In Situ Three-dimensional Super-resolution Imaging of Molecular

Transport and Single Particle Catalysis

Ning Fang, Department of Chemistry, Iowa State University and USDOE-

Ames Laboratory

Despite recent successes of super-resolution chemical imaging, the current

techniques still lack several critical abilities. On one hand, the axial

resolution, which is typically 2~3 times the corresponding lateral resolution,

is often insufficient to resolve the axial distribution of fluorescent

molecules in certain chemical systems, such as nanoparticles of up to

several hundred nanometers high used in the single particle catalysis

studies. On the other hand, it is becoming more and more important to

extend the applicability of super-resolution chemical imaging from relatively simple systems (e.g.,

functional flat surfaces) to more complex three-dimensional nanoscale and mesoscale materials.

To address these limitations, we are designing highly tunable complex structures with well-defined

geometry and manageable complexity for imaging under novel imaging techniques. One model platform,

which consists of metal nanoparticles sandwiched between an optically-transparent solid SiO2 core and a

mesoporous SiO2 shell with aligned pores, resembles the structures of many intensively-investigated

high-performance core-shell catalysts. The multilayer platform provides a uniquely well-defined structure

to study adsorption and diffusion at the single molecule level because a fluorescent product molecule is

generated on metal nanoparticles located at the surface of the core silica sphere, which provides an

unambiguous starting point (both in time and space) of the molecular transport out of a single reactive site.

Capturing color: cephalopod-inspired plasmonic active materials

Naomi J. Halas, Departments of Electrical & Computer Engineering, Physics

& Astronomy, Chemistry, and Bioengineering, Rice University

In nature, cephalopods (squids, octopus, and cuttlefish) are the unparalleled

masters of camouflage, capable of color-matching to their surroundings and

replicating the pattern of their local environment, even with three-dimensional

structure, in a matter of seconds. This most remarkable of capabilities is even

more amazing considering that these animals are color blind. So how are they

capable of the visual perception required for both pattern and color matching?

If has been hypothesized that a network of primitive color sensors lies within

their skin itself, whose active coloration elements also filter the input light,

allowing for extra-ocular color detection. With this organism’s capabilities as

our model, we have investigated highly compact methods for color detection and plasmon-based

approaches for active displays. Plasmonic nanostructures can serve both as coloration elements,

potentially capable of large area active, controllable coloration, and also as wavelength-dependent

photodetectors by harvesting the hot electrons generated by plasmon decay. Ultimately these nanoscale

components can be integrated into a single material that could observe its surroundings and modify its

color and pattern accordingly. (Funded by the Office of Naval Research)



Exploring Materials Structure and Mass Transport Dynamics on

Chemical Gradients by Single Molecule Tracking and Spectroscopy

Daniel A. Higgins, Department of Chemistry, Kansas State University

Gradients play important roles in a number of biological processes that

involve spontaneous, directed transport of ions, molecules, cells and even

whole organisms. For example, potential gradients drive the transport of ions

across cell membranes. Certain types of cells and small organisms will also

spontaneously follow chemical gradients in solution (chemotaxis) and on

surfaces (haptotaxis). Some have even evolved the ability to follow gradients

in light intensity (phototaxis). These processes provide strong motivation for

the development of chemical gradients that may be useful in the directed

transport of energy, chemical reagents, liquid droplets, etc. In collaboration

with the Collinson group (Chemistry, VCU), the Higgins group is working to prepare and characterize

thin film chemical gradients supported on solid substrates. Both dip coating and vapor phase deposition

methods are employed to prepare these gradients. Their macroscale properties are characterized primarily

by water contact angle measurements and spectroscopic ellipsometry. Their microscopic properties are

probed by Raman and IR microscopy and by atomic force microscopy. Efforts by the Higgins group

emphasize investigation of gradient properties on nanometer length scales by high-resolution (and super-

resolution) optical single molecule tracking and spectroscopic methods. This presentation will focus

primarily on the latter studies, where we have employed single molecule methods to investigate mass

transport and surface adsorption phenomena in and on gradient thin films and to assess their local polarity

(i.e., dielectric) properties.

How to Understand Dynamics of the Singlet Fission Process

Anatoly B. Kolomeisky, Departments of Chemistry, and Chemical

& Biomolecular Engineering, Rice University

Singlet fission (SF) is a complex electronic process in which one

singlet excited state splits into two triplets that ultimately produce

four charge carriers. It has been argued that SF might significantly

increase the efficiency of the solar cells. However, mechanisms of

this process remain not fully understood. We developed a simple

kinetic model that allows us to describe better dynamics of the

singlet fission. It is argued that the SF process is governed by the free-energy changes that underlie the

importance of both electronic energies and entropic contributions. The entropy drives SF in the systems

where electronic energies changes are unfavorable. A procedure to estimate the entropic contributions is

presented. Our theoretical method is applied for analyzing SF processes in a series of acene molecules

(tetracene, pentacene and hexacene). We explained experimentally observed 3 orders of magnitude

difference in the rate of SF in tetracene and pentacene and predicted that the rate in hexacene will be

slightly faster than in pentacene. Consistently with the experimental observation, the model predicts weak

temperature dependence of the multiexciton formation rate in tetracene as well as a reduced rate of this

step in solutions and isolated dimers. The approach was successfully extended to explain the role of local

structures and morphologies in the SF processes in other molecular systems.



Single-Molecule Methods to Quantify Adsorptive Separations

Christy Landes, Departments of Chemistry and Electrical & Computer

Engineering, Rice University

Adsorption and transport are the chemical and physical processes that

underlie separations occurring in a wide range of biological and synthetic

materials applications. Although separations technology accounts for

hundreds of billions of dollars (USD) in the global economy, the process is

not well-understood at the mechanistic level and instead is almost always

optimized empirically. One of the reasons is that access to the underlying

molecular phenomena has only been available recently via single-molecule

methods. There are still interesting challenges because adsorption, desorption,

and transport are all dynamic processes, whereas much of the advances in

super-resolution imaging have focused on imaging static materials. Our lab

has focused in recent years on developing and optimizing data analysis methods for quantifying the

dynamics of adsorption and transport in porous materials at nanometer-resolution spatial scales. Our

methods include maximizing information content in dynamic single-molecule data and developing

methods to detect change-points in binned data. My talk will outline these methods, and will address how

and when they can be applied to extract dynamic details in heterogeneous materials such as porous

membranes.

Monitoring Charge Interactions through Changes in the Plasmon

Linewidth Stephan Link, Departments of Chemistry and Electrical & Computer

Engineering, Laboratory for Nanophotonics, Rice University

We present an analysis of the electron transfer between single gold nanorods

and a monolayer of graphene under no electrical bias. Using single particle

dark-field scattering and photoluminescence spectroscopy to access the

homogenous linewidth, we observe broadening of the surface plasmon

resonance for gold nanorods on graphene compared to nanorods on a quartz

substrate. Because of the absence of spectral plasmon shifts, dielectric

interactions between the gold nanorods and graphene are not important and we assign the plasmon

damping to charge transfer between plasmon-generated hot electrons and the graphene that acts as an

efficient acceptor. A charge transfer interaction between plasmonic nanorods and self-assembled alkane-

thiol monolayers is observed in a similar approach. Our results are important for future applications of

light harvesting with metal nanoparticle plasmons and efficient hot electron acceptors as well as for

understanding hot electron transfer in plasmon-assisted chemical reactions.



Computational Challenges in Broadband Mid-Infrared Imaging

David Mayerich, Department of Electrical & Computer Engineering,

University of Houston

There is a powerful demand in biomedicine for techniques that can acquire

structural and chemical information from a sample, particularly using fast and

non-invasive imaging methods. One promising example is mid-infrared

spectroscopic imaging, which measures the interactions between an incident

electromagnetic (EM) field and a sample. The measured absorption

characteristics are then used to determine the chemical composition at each

point in the sample. However, these EM interactions cause the structural and

chemical features to become tightly coupled. Separating these components requires inverting the

broadband light scattering process, which is computationally intensive and difficult to both model and

visualize.

In this talk, I will discuss the state of the art in this field, with a particular emphasis on current

computational challenges. I will describe methods that we have developed for modeling and visualizing

electromagnetic fields. These include both theoretical methods used for designing new imaging

instruments, and practical methods that can aid in clinical diagnosis. For example, we have recently

shown that molecular pathology can be conducted accurately and at low cost using these methods.

Improving the Photocurrent Generation of Thylakoid Bio-solar Cells

Shelley D. Minteer, Departments of Chemistry and Materials Science &

Engineering, University of Utah

Previously, our group has developed thylakoid bio-solar cells which are

capable of direct solar energy conversion to electricity. However, the current

output of these cells was quite small compared to mediated

bioelectrochemical systems. Several methods have been implemented to

improve the performance. Incorporation of fluorescent carbon quantum dots

leads to an increase in photocurrent generation. The conductive quantum dots

allow for greater transfer of electrons. Additionally, the quantum dots absorb

at wavelengths not useful for photosynthesis but emit light at wavelengths at

which the photosystems of the thylakoids absorb. This makes it possible for the electrodes to use more of

the light spectrum.

A second method involved the intercalation of conjugated oligoelectrolytes into the thylakoid

membrane. These molecules allow for greater electron transfer through the membrane which decreases

the resistance in the thylakoid bio-solar cell. Additionally, the photocurrent produced by the thylakoid

electrodes increased as well.



Biochemical Applications of Surface-Enhanced Raman Spectroscopy

Martin Moskovits, Departments of Chemistry & Biochemistry and Mechanical

Engineering, University of California, Santa Barbara

Surface-Enhanced Raman Spectroscopy (SERS), especially when combined with

such sample handling techniques as microfluidics, can be used in multiple

biochemical and biomedical sensing and imaging applications. SERS analogs to

fluorescent biotags can be synthesized with brightness and uniformity comparable

to that of fluorescent tags, but with the advantage that (on account of the narrow

bandwidths of Raman) the spectra of 6 or more tags can be deconvoluted from a single SERS spectrum,

that, additionally, is excited by a single near IR laser, making multiplexed cell tagging routine. SERS

substrates can also be fabricated for biomolecule sensing by binary capture, essentially creating a SERS-

based ELISA assay; but one that reports quantitative results in minutes rather than hours. Combining

SERS with microfluidics can also yield a sensor capable of detecting illicit drugs and therapeutic agents

in body fluids, for use in an enforcement environment, or to determine an individual’s response to a

pharmaceutical substance, determining baselines and absorption and clearance rates of substances for

assaying a patient’s individualized response to a therapeutic agent, in a personalized medicine context.

Some examples of such applications will be presented.

Organic Solar Cells: Current Progress and Challenges

Thuc-Quyen Nguyen, Center for Polymers and Organic Solids and

Department of Chemistry & Biochemistry, University of California, Santa

Barbara

According to a recent report by the US Department of Energy, “world

demand for energy is projected to more than double by 2050 and to more

than triple by the end of the century.” Thus, the development of alternative

energy sources is now recognized by government, society and the global

community as an urgent need. Organic solar cells potentially can offer low

cost, large area, flexible, light-weight, clean, and quiet alternative energy

sources for indoor and outdoor applications. In this talk, I will give an

overview of the current progress and challenges in organic solar cells. Then,

I will discuss recent progress at UCSB on molecular donor materials for application in solution processed

bulk heterojunction solar cells. Molecular donors offer potential advantages over conjugated polymer

systems in terms of their ease of synthesis and purification; making them more affordable to produce on

large scales. Additionally, small molecules do not suffer from molecular weight dependence and

polydispersity, and thus large batch-to-batch variation as their polymer counterparts. The molecular

design is based on donor/acceptor/donor or acceptor/donor/acceptor using common building blocks such

as oligothiophenes, dithieno silole (DTS), pyridal thiadiazole (PT), diketopyrrolopyrrole (DPP), etc.

Functional groups attached to the conjugated core can be used to tune the energy level, bandgap,

solubility, molecular packing, the film morphology, charge mobility, and hence, device performance. A

series of compounds has been synthesized to establish structure-function-property relationships. A

combination of techniques is employed to characterize material properties including steady-state

spectroscopy, AFM, photoconductive atomic force microscopy, TEM, XRD, UPS, etc. Furthermore, these

donor materials in combination with the widely-used acceptor PC70BM can be used to form the active

layer in organic solar cells with power conversion efficiencies up to 9% under simulated AM 1.5 solar

irradiation. The results from these studies provide design guidelines for new generation of molecular-

based materials for applications in organic solar cells.

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Speaker Abstracts

Quantum Plasmonics: Applications in Light Harvesting Peter Nordlander, Department of Physics, Rice University The “plasmon hybridization”concept,[1] shows that the plasmon resonances in complex metallic nanostructures interact and hybridize in an analogous manner as atomic wavefunctions in molecules. The insight gained from this concept provides an important conceptual foundation for the development of new plasmonic structures that can serve as substrates for surface enhanced spectroscopies, chemical and biosensing, and subwavelength plasmonic waveguiding and other

applications. The talk is comprised of basic overview material for a general audience interspersed with a few more specialized “hot topics” such quantum plasmonics,[2] graphene and molecular plasmonics,[3] hot carrier generation,[4] and active plasmonic nanoantennas for enhanced light harvesting and photocatalysis.[4] [1] N.J. Halas et al., Adv. Mat. 24(2012)4842 [2] R. Esteban et al., PRL 110(2013)263901, Opt. Express 21(2013)27306 [3] Z.Y. Fang et al., NL 4(2013)299, A. Manjavacas et al., ACS Nano 7(2013)3635 [4] A. Manjavacas et al., ACS Nano 8(2014)7630 [5] S. Mukherjee et al., NL 13(2013)240; JACS 136(2014)64; Adv. Mat. 26(2014)6467

Biomolecular synthesis of conducting polymers: Harnessing the structural diversity of proteins to tune polymer properties Christine K. Payne, School of Chemistry and Biochemistry, Georgia Tech Conducting polymers have important applications in solar energy conversion, solid-state lighting, hydrogen storage, and regenerative medicine. Conductivity is typically tuned through post-process doping. Results from the Payne Lab show that conductivity can instead be controlled through the proper choice of oxidant in a single-step aqueous reaction. We have demonstrated the first use of iron-containing proteins, rather than enzymes, as oxidants for the synthesis of PEDOT:PSS. We show that both catalase and denatured catalase, which lacks enzymatic activity, result in polymerization. This observation suggested that a much broader array of iron-containing

proteins, without enzymatic activity, could be used for the biosynthesis of conducting polymers. This was tested using an iron-containing protein, transferrin, and apotransferrin, which lacks iron. Only transferrin results in polymerization. These results demonstrate that the biological synthesis of PEDOT:PSS requires an iron-containing protein to serve as a source of iron; enzymatic activity is not necessary. We then demonstrate that conductivity can be increased using iron-containing biomolecules as oxidants and that conductivity is a function of protein structure. We find that hemoglobin-polymerized PEDOT:PSS is 105 times more conductive than catalase-polymerized PEDOT:PSS. Hemoglobin-polymerized PEDOT:PSS possesses bipolarons, while catalase polymerized PEDOT:PSS is dominated by polarons. This difference is due to different active oxidants. Free iron in solution dominates the catalase polymerization and leads to polarons, while heme B dominates the hemoglobin polymerization and leads to bipolarons. When free iron is removed from the hemoglobin polymerization with an iron chelator, bipolarons dominate and the conductivity is further enhanced to 19.5 S cm-1 in a single-step aqueous reaction.

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Speaker Abstracts

Plasmonic nanoparticles for sensing applications Emilie Ringe, Departments of Materials Science & Nanoengineering and Chemistry, Rice University Interest in nanotechnology is driven by unprecedented means to tailor physical behavior via structure and composition. Most properties, including optical, catalytic, and electronic, can be fine tuned through choice of composition, size, and shape of nanoparticles. Characterization and modeling of such structure-function relationships are crucial to the development of novel applications such as biological sensors and plasmonic devices. This talk covers how nanoparticles can be tuned and characterized to obtain optical properties optimized for

sensing and detection. Specifically, we will review how shape affects plasmonic functions such as plamon energy,

spatial distribution, decay, and refractive index sensitivity. Recent technical advances on opticl processed, both electron and photon-based, will be covered, with a special focus high throughput single particle optical scattering approaches and monochromated electron-energy loss spectroscopy and electron tomography.

Surface Enhanced Raman Spectroscopy (SERS) Of Core-Shell Structures With Different Shell Morphology Laura Sagle, University of Cincinnati, Department of Chemistry, University of Cincinnati

Core-shell structures with plasmonic materials have been utilized towards energy storage devices, catalysis and optical spectroscopy. Herein, we have constructed Au@Au core shell structures with 60 nm spherical gold cores and gold shells of both smooth and spiky morphology. SERS enhancement was evaluated through incorporation of Raman-active

reporters both in between the core and the shell as well as on the surface of these structures. Interestingly, at 785 nm excitation, the structures containing a spiky shell show increased SERS signal when compared to the smooth shell structures for dye molecules residing in between the core and the shell. Finite difference time domain (FDTD) calculations show this is a near field effect with the increased field intensities at the tips of the spiky shell penetrating into the region between the core and shell. In addition, both experimental data and FDTD calculations indicate the SERS enhancement for dye molecules placed on the surface of the spiky shell structures is greater than that observed for gold nanostars. Currently, this work is being extended to create biocompatible core shell structures using liposomes as a scaffold. These structures exhibit SERS enhancement for biomolecules placed between the encapsulated cores and liposome-based shells.



Plasmonic nanoparticles for sensing applications

Emilie Ringe, Departments of Materials Science & Nanoengineering

and Chemistry, Rice University

Interest in nanotechnology is driven by unprecedented means to tailor

physical behavior via structure and composition. Most properties,

including optical, catalytic, and electronic, can be fine tuned through

choice of composition, size, and shape of nanoparticles.

Characterization and modeling of such structure-function relationships

are crucial to the development of novel applications such as biological

sensors and plasmonic devices. This talk covers how nanoparticles can

be tuned and characterized to obtain optical properties optimized for

sensing and detection.

Specifically, we will review how shape affects plasmonic functions such as plamon energy,

spatial distribution, decay, and refractive index sensitivity. Recent technical advances on opticl processed,

both electron and photon-based, will be covered, with a special focus high throughput single particle

optical scattering approaches and monochromated electron-energy loss spectroscopy and electron

tomography.

Bionanomaterials And Nanofabrication For Improved Localized

Surface Plasmon Resonance Biosensing

Laura Sagle, University of Cincinnati, Department of Chemistry,

University of Cincinnati

Biosensing utilizing Localized Surface Plasmon Resonance (LSPR) offers

relatively inexpensive, label-free, facile detection that is amenable to on-

chip devices. However, several challenges remain, such as: sensitivity to

small molecule binding, specificity in complex biological solutions, and

integration into on-chip devices. This presentation will highlight recent

advances in LSPR-based biosensing devices in the Sagle group to

overcome these limitations. Protein-nanoparticle devices which monitor and are selective towards small

molecules in solution are presented. These devices make use of protein conformational changes which

mediate the plasmonic coupling between nanoparticles. The resulting changes in the LSPR frequency are

significantly less susceptible to biofouling. Moreover, the specificity stems from the protein itself, and is

not limited by surface chemistry. Ultimately, our goal is to put such plasmonic devices on a surface to

allow for microfluidic, on-chip fabrication. In order to improve protein-surface compatibility,

nanofabrication techniques designed to optimize biomolecular orientation and binding capabilities on a

surface are also presented.



Fabrication of Novel Titania Nanostructures for Energy Applications Anna Cristina S. Samia, Director of the Women in Chemistry@CWRU

Program Department of Chemistry, Case Western Reserve University

Dr. Samia’s research interests center around the fabrication and study of

intermetallic and metal oxide nanostructures with emphasis on chemical

design to achieve desired properties and function. One main area of

application is in the field of catalysis and energy conversion. Inspired by

nature’s design, we have been working on fabricating titania nanostructures

with bamboo-like morphologies as a platform for developing hybrid

materials that have efficient properties for solar energy conversion. This

talk aims to provide a general overview of our synthesis approach that enable us to prepare highly ordered

titania nanotubes with tunable bamboo-like morphologies. Moreover, we will present our studies on the

optoelectronic characterization and fabrication of solar cells from this class of materials.

Interfacial Molecular Foraging

Daniel K. Schwartz, Department of Chemical and Biological Engineering,

University of Colorado Boulder

Interactions between molecules and surfaces lead to complex and highly-

varied interfacial behavior, where heterogeneity may arise from spatial

variation of the surface/interface itself, from structural configurations (i.e.

conformation, orientation, aggregation state, etc.), or temporally, through

inhomogeneous dynamic behavior. As an example of temporal heterogeneity,

we have used high-throughput single-molecule tracking methods to study the

interfacial transport of small molecules, polymers, and biomolecules. We

universally observe intermittent motion, with periods of confined Brownian motion punctuated by long

(Levy) flights. The motion is described within the context of a continuous time random walk (CTRW)

model, with power-law distributions of both waiting times and flight distances. The specific CTRW

parameters describing a particular system are sensitive to molecular characteristics including molecular

weight, and surface properties such as chemical and topographical heterogeneity.

CTRW-based search processes are widely predicted to exhibit improved efficiency compared

with Brownian searches, and many biological systems have evolved intermittent search strategies. To

directly measure the search efficiency and dynamics associated with intermittent interfacial molecular

transport, we used single-molecule Förster resonance energy transfer (FRET) to observe the dynamic

behavior of donor-labeled ssDNA at the interface between aqueous solution and solid surfaces

(hydrophilic or hydrophobic) decorated with complementary acceptor-labeled ssDNA. Molecules from

solution adsorbed nonspecifically to the surface, where a two-dimensional search was performed with a

chance of hybridization. The search process was dramatically more successful on hydrophobic surfaces,

and successful searches were also faster on hydrophobic surfaces. Notably, on both types of surface,

searches were an order of magnitude faster than expected from simple two-dimensional Brownian motion,

and consistent with a more efficient search process associated with CTRW transport.



Novel Plasmonic Nanomaterials and Instruments for Biomedical

Applications

Wei-Chuan Shih, Departments of Electrical & Computer and Biomedical

Engineering, University of Houston

I will present our work in developing and understanding novel porous

plasmonic nanoparticles fabricated by the combination of top-down

lithography and bottom-up atomic dealloying. They feature both shorter-

ranged (5-15 nm) internal localized surface plasmon in its 3D porous structures,

as well as longer-ranged (100-1000 nm) external surface plasmon across its

monolithic sub-micron disk architecture. The unique 3-dimensional structural

hierarchy produces distributed hot-spots in a volumetric fashion with compatible large surface area. I will

then describe several potential applications such as sensing, imaging, photothermal light harvesting,

molecular delivery and therapy. I will also touch base on high-throughput hyperspectral laser microscopy,

which is instrumental to nanomaterial characterizing. They also have the potential for minimally invasive

disease diagnosis and margin detection.

Light Management in Extremely Thin Photoelectrode Architectures

for Solar-Fuel Generation

Isabell Thomann, Department of Electrical and Computer Engineering,

Rice University

Concepts from metamaterials, plasmonics and nanophotonics are expected

to aid the design of future solar energy conversion devices. Here, I will

describe how we use these concepts to create advanced photoelectrode

architectures for biologically-inspired solar-to-chemical-fuel conversion

reactions, including water splitting and CO2 reduction. We focus on light

management in extremely thin absorber structures to achieve broadband, omnidirectional solar absorption

while carefully choosing materials systems that allow for efficient charge separation and catalytic activity.

Such thin-film absorber photoelectrodes hold promise for achieving enhanced charge carrier extraction,

increased photovoltages and the possibility to exploit hot carriers for purposes of driving chemical

reactions.

I will discuss our analytical models and three-dimensional electromagnetic simulations that we

employ to engineer light absorption in two-dimensional materials and plasmonic metal nanostructures,

and describe our progress towards the experimental realization and characterization of such structures.

Complementing these materials and device design efforts, we are developing an experimental

characterization toolbox, including photoelectrochemical and spectroscopic techniques.

http://rcqm.rice.edu/researchers/isabell-thomann/



Charge Separation and Photovoltaic Performance of All-Conjugated Block

Copolymers

Rafael Verduzco, Department of Chemical and Biomolecular Engineering, Rice

University

All-conjugated block copolymers bring together hole- and electron-conductive

polymers and can be used in the active layer of solution-processed photovoltaic

devices. Recent studies have demonstrated the potential of all-conjugated donor-

acceptor block copolymer for organic photovoltaics (OPVs), but it remains unclear

how molecular structure, morphology, and electronic properties of conjugated block

copolymers influence performance. Here, we study the role of chemical linker

between donor and acceptor polymers on photovoltaic performance and optoelectronic properties. Two

poly(3-hexylthiophene)-poly(2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl-(9,9-

dioctylfluorene)) (P3HT-PTBTF) donor-acceptor block copolymers which differ only in the chemistry of

linking group are studied through device measurements, grazing-incidence X-ray analysis, and steady-

state and time-resolved absorbance and photoluminescence measurements. Device studies show that

power conversion efficiencies decrease by a factor of 40, from 2.2 % to 0.05 %, by changing the linking

group. X-ray analysis shows that the morphology is virtually identical in both samples, as expected.

Ultrafast transient absorption measurements reveal charge separation in block copolymers which contain

a wide bandap monomer at the donor-acceptor interface, but charge separation is suppressed when donor

and acceptor blocks are directly linked without this spacer present. This demonstrates that the chemistry

of the linking group can influence the electronic properties of the donor-acceptor interface and kinetics

for charge separation and recombination. For both samples studies, we find that the rate of charge

recombination in these systems is faster than in polymer-polymer and polymer-fullerene blends,

suggesting further improvement possible through optimization of the linking group. This work

demonstrates that the linking group chemistry influences charge separation in all-conjugated block

copolymer systems, and also suggests that all-conjugated block copolymers can be used as model systems

for the donor-acceptor interface in bulk heterojunction blends.

Mass Transport in Confined Environment Studied with Super Resolution

Optical Microscopy

Gufeng Wang, Department of Chemistry, North Carolina State University

Macromolecules and small nanoparticles tend to behave in unusual ways at

solid-liquid interfaces. Especially of interests are nanoconfined environments, in

which molecules are confined by interfaces within a length scale of nanometers.

Understanding microscopic molecular behavior in nanoconfined environments is

an important step for many energy-relevant applications. It also matches one of

the workshop theme topics “what are the forces driving nano-confined charge

and mass transport?” Current techniques lack sufficient spatial or temporal

resolution, leading to unresolved issues about the magnitude, length scale, and mechanism of the

abnormal molecular behavior in nanoconfined environments. We are interested in developing new

techniques to solve these questions. Two types of super-resolution techniques: stimulated emission

depletion (STED) microscopy, and 3D single molecule tracking, are used to study microscopic molecular

and nanoparticle movements in cylindrical nanopores. Our single particle study shows a macroscopically

slow but microscopically active picture for observed slow diffusion in bulk measurements. It sheds new

light toward understanding abnormal mass transport in confined environments.



Quantifying Diffusion in Complex Media

M. Neal Waxham, Department of Neurobiology and Anatomy, University of

Texas Medical School at Houston

Cell signaling involves an intricate series of protein-protein binding events

whose interactions are further complicated by the densely packed and

heterogeneous cytoplasm. Unless existing in preformed complexes, the first

step in biological recognition is the random walk of interacting partners and

analysis of such diffusion can be quantified using fluorescence correlation

spectroscopy (FCS). Application of FCS to quantify the transport of signaling

molecules in living cells reveals complex diffusion whose underlying physical

mechanisms are not clear. To address this complexity, we studied diffusion of

different sized tracer molecules in synthetic systems proposed to recapitulate

various aspects of the crowded environment found inside cells. Concentrated mixtures of different sized

dextrans and ficolls (glucose polymers) were used as a proxy to represent levels of macromolecular

crowding of relatively inert (non-interacting) mobile molecules. In addition, silica based sol-gels were

used to mimic immobile barriers to diffusive tracers. In addition to the need for well-controlled physical

environments, appropriate methods are required to properly analyze the autocorrelation function from

FCS data to deduce the physical meaning of complex diffusion. A number of fitting models including

single- and multi-component, anomalous, and maximum-entropy were employed and the strengths and

weaknesses of these fitting routines were revealed. As an extension of these procedures, a modified

autocorrelation function was developed to examine variations in diffusion at different timescales. We

found in simulated data a transient anomalous subdiffusion between two freely diffusing regimes that was

evident in experiments examining binding interactions of diffusive tracers with actin gels.

Super-resolution imaging of hybrid organic-plasmonic nanostructures

Katherine A. (Kallie) Willets, Department of Chemistry, University of Texas

at Austin

Noble metal nanoparticles have attracted significant attention due to their

ability to support localized surface plasmons, which generate local

electromagnetic field enhancements, produce strong environmentally-sensitive

nanoparticle color, lead to localized heating, and even produce energetically

excited (or hot) electrons. In order to impart additional function to these

materials, hybrid nanostructures, in which organic or inorganic materials are

covalently attached to the nanoparticle surface, have been synthesized,

allowing plasmonic nanoparticles to be used in biosensing, drug delivery, and photonic applications. One

challenge is knowing the nature of the assembly of these molecules onto the surface of the nanoparticles,

which is complicated by their small size and lack of contrast in traditional surface characterization

techniques, such as electron microscopy. This talk will describe super-resolution optical imaging of

fluorescently-labeled molecules covalently attached to the surface of gold nanorods, highlighting some of

the unique challenges of performing super-resolution imaging on plasmonic nanostructures, as well as

providing insight into local binding heterogeneity.



Exciton transport in carbon nanotube photovoltaics using 2D White-Light

Spectroscopy: Design principles from light harvesting proteins

Martin T. Zanni, Department of Chemistry, University of Wisconsin-Madison

Semiconducting carbon nanotubes are an exciting new material for solar cells

and other electronics. Mesoscale films can now be made and incorporated into

devices in which the semiconducting tubes are the photoactive layer,

analogous to organic dyes in a dye-sensitized solar cell. We are studying the

photophysics of these films in order to understand their exciton transport

properties. However, obtaining a comprehensive picture of the rates, pathways,

and bottlenecks is challenging because, like many solar cell materials, they

absorb across a very broad region of the spectrum. The standard approach to study such a wide frequency

range is to use a tunable pump pulse to sequentially excite each electronic transition, one after the other.

We have instead developed a method that continuously interrogates the spectral range spanning 500-1400

nm, by using a technical we call two-dimensional white light (2D WL) spectroscopy. The spectra resolve

energy transfer between all possible combinations of excitonic states in the chirality-selected nanotubes,

thereby providing an instantaneous and comprehensive snapshot of the dynamical pathways. We observe

exciton hopping, exciton dissociation, and anti-correlated energy levels. Physics like these are related to

light harvesting and transport proteins, which suggest ways of modifying the nanotube films to better

transport and direct energy flow.

Single-molecule spectroscopic study of the counterion effect at the

polyelectrolyte aqueous interface

Y. Elaine Zhu, Department of Chemical and Biomolecular Engineering,

University of Notre Dame

The electrostatic environment near a charged polymer chain is critical to the

structure and functions of these polymers, including both synthetic and

biological ones, in aqueous media. To quantitatively evaluate the impact of

surrounding ions on the conformations of polyelectrolytes in solution,

fluorescence measurements with single molecule sensitivity by using

fluorescence correlation spectroscopy (FCS) are conducted to determine not

only the polymer hydrodynamic size but also the local pH in the immediate

vicinity of a polyelectrolyte chain. Weak polyelectrolyte, poly(2-vinyl pyridine) (P2VP) end labeled with

a pH-sensitive dye in dilute aqueous solutions is investigated in this work with the focus on the effect of

different counterions. By tuning solution pH, the critical pH at which the coil-to-globule conformational

transition occurs is determined from the change in the measured hydrodynamic size of P2VP chain. The

local pH near the dye, inferred from its fluorescence brightness, is found to be considerably different from

the bulk pH. Adding different counterions can all lead to increasing the protonation degree on the P2VP

chain. Yet the surface electric potential of P2VP decreases with increasing the concentrations of divalent

ions and multivalent nanocluster macroions, suggesting the enhanced counterion condensation at the

polyelectrolyte aqueous interface by multivalent ions.

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Poster Abstracts

POSTER SESSION Poster No.

Optical Properties of Nanoporous Gold Plasmonic Nanoparticles: Absorption and Scattering Applications Arnob M P, Shih W-C

1

Active Plasmonic Control of Bimetallic Nanoparticles and Dimers via Electrochemical Redox Tuning Byers CP, Yorulmaz M, Hoener BS, Huang D, Hoggard A, Chang WS, Link S,

Landes CF

2

Low Absorption Losses of Strongly Coupled Surface Plasmons in Nanoparticle Assemblies Chang W.-S., Willingham B. A., Slaughter L.S., Khanal B.P.,Vigderman L., Zubarev E.R. and Link S.

3

Exploring the conformational landscape of the NMDA receptor via single molecule FRET David Cooper, Drew Dolino, Henriette Jaurich, Bo Shuang, Swarna Ramaswamy, Jixin Chen, Vasanthi Jayaraman, Christy F. Landes

4

Preventing the Aggregation of Colloidal Gold Nanoparticles with a Protein Monolayer Dominguez-Medina S, Blankenburg J, Olson J, Landes CF, Link S

5

Au Nanoparticle Spectroelectrochemical Response Modified by Electrolyte Anion and Particle Morphology Benjamin S. Hoener, Chad P. Byers, Wei-Shun Chang, Mustafa Yorulmaz, Stephan Link, and Christy F. Landes

6

Super-Resolution Spatial and Diffusion Properties Obtained Simultaneously By Correlation-Based Analysis in Hard and Soft Porous Materials Kisley L, Brunetti R, Tauzin LJ, Shuang B, Yi X, Weiss S, Landes CF

7

Mechanistic Insights into Protein Ion-exchange Adsorptive Separations using Single-molecule, Super-resolution Imaging Poongavanam M, Kisley L, Chen J, Mansur AP, Kourentzi K, Chen W-H, Dhamane S, Dominguez-Medina S, Kulla E, Landes CF, Willson RC

8

Laser-assisted Dealloying Lithography Li J, Shih WC

9

Role of Chemical Spacer at Molecular Level for Charge Separation in All-conjugated Block Copolymers Solar Cells Jorge W. Mok, Yen-Hao Lin, Kevin G. Yager, Seth B. Darling,± Youngmin Lee‖, Enrique Gomez‖, David Gosztola, Richard Schaller, and Rafael Verduzco

10

Aluminum Plasmonic Pixels Olson, J., Manjavacas, A., Liu, L., Foerster, B., Chang, W.-S., King, N., Knight, M., Halas, N., Nordlander, P., Link, S.

11

Single Particle Circular Dichroism Spectroscopy of Nanomaterials Smith, K. W., Wang, L. Y., Chang, W. S., Link S.

12

Optical Imaging Strategies In Complex Environments Using Rod-Like Plasmonic Nanoparticles Stender, Anthony S., Wang, G., and Fang, N.

13

Mechanical Coupling of Au/Ti Bimetallic Nanostructures on Glass Substrates Su M-N, Chang W-S, Wen F, Chakroborty D, Zhang Y, Sader JE, Nordlander PJ, Halas NJ and Link S

14

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Poster Abstracts

Microfluidic Label-Free Monitoring of DNA Hybridization Ji Qi, Jianbo Zeng, Fusheng Zhao, Yu-Lung Sung, Shih W-C

15

pH Switchable, Charge Dependent Transport in a Weak Polyelectrolyte Multilayer Tauzin LJ, Shuang B, Kisley L, Mansur AP, Chen J, Leon A, Advincula RC, Landes CF

16

Molecule Identification in High Molecule Density with Rod-Shaped Rotating Point Spread Function Wenxiao W, Shuang B, Landes CF

17

Single-Particle Absorption Spectroscopy of Plasmonic Nanostructures Yorulmaz M, Nizzero S, Chang WS, Wang LY, Link S

18

Morphological control and plasmonic tuning of nanoporous gold disks by surface modifications Zeng J, Zhao F, Shih WC

19

Monolithic NPG nanoparticles with large surface area, tunable plasmonics, and high-density internal hot-spots Zhao F, Zeng J, Shih WC

20

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Poster Abstracts #1

Optical Properties of Nanoporous Gold Plasmonic Nanoparticles: Absorption and Scattering Applications Arnob M P1, Shih W-C1, 2 1. Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston 2. Department of Biomedical Engineering, Cullen College of Engineering, University of Houston Corresponding Author: Arnob M P, Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston, 4800 Calhoun Rd, Engineering Bldg. 2, Room # W332, Houston, TX 77204-4005, USA, E-mail: [email protected] Maxwell-Garnett effective medium theory (MGT) and Finite Difference Time Domain (FDTD) method have been employed to calculate the optical properties of disk shaped nanoporous gold nanoparticles (NPG nanoparticle or NPG Disk). The MGT estimates the effective optical constants for NPG nanoparticle which are then used to calculate its optical properties using FDTD method. The calculated optical properties for NPG nanoparticles clearly reflect the well-known dependence on particle dimensions. A systematic quantitative study of the various trends is presented. The MGT modeling provides an interesting observation about the porosity development in NPG nanoparticles. With increasing particle diameter, porosity or air volume fraction follows a decreasing trend. Localized surface plasmon resonance (LSPR) for NPG nanoparticles can be tuned from 600 to 1300 nm by changing the particle diameter from 100 to 500 nm respectively. While enlarging particle diameter results in LSPR red shifting, increasing particle thickness causes blue shift in the LSPR peak wavelength. The calculation of relative scattering contribution to the extinction facilitates the selection of NPG nanoparticles for scattering and absorption applications. For scattering applications, 400 nm diameter and 75 nm thick NPG nanoparticles should provide the optimum results, while nanoparticles with 100 nm diameter and 25 nm thickness is the proper choice for absorption applications. Wei-Chuan Shih acknowledges the National Science Foundation (NSF) CAREER Award (CBET-1151154), National Aeronautics and Space Administration (NASA) Early Career Faculty Grant (NNX12AQ44G) and a grant from Gulf of Mexico Research Initiative (GoMRI-030).

mailto:[email protected]


Active Plasmonic Control of Bimetallic Nanoparticles and Dimers via Electrochemical Redox Tuning Byers CP1, Yorulmaz M1, Hoener BS1, Huang D1, Hoggard A1, Chang WS1, Link S12

, Landes CF12

1. Dept. of Chemistry, Rice Quantum Institute, Laboratory for Nanophotonics, Rice University, Houston, Texas, USA 2. Dept. of Electrical and Computer Engineering, Rice University, Houston, Texas, USA Corresponding Author: Landes CF, Department of Chemistry, School of Natural Science, Rice University, 6100 Main St, Houston, TX, USA 77005. Email: [email protected] The plasmonic properties of metallic nanostructures have broad tunability through their morphology, composition, and structure, but active and reversible in-situ modification of these properties has proven difficult. Active control of nanoparticle plasmons would allow greater technological application in color and intensity modification, i.e. smart surfaces and displays. We approach this challenge with electrochemical redox tuning of bimetallic nanoparticles and assembled structures. Our method allows us to deposit silver salts on the surface of gold nanostructures and selectively grow silver metal on the surface of these structures. By controlling the oxidation state of the silver metal, we demonstrate the repeatable redox tuning of single nanoparticles, capacitively coupled nanoparticle dimers, and conductively coupled dimers, as verified by single nanoparticle spectroelectrochemistry techniques. Through redox tuning, we repeatedly and reversibly tuned the coupling mechanism from capacitive coupling to conductive coupling, as verified by the presence of the charge transfer plasmon. Our methodology and results will be of value for extreme plasmon modulation, experimental tests of charge transfer plasmonics, and nanoscopic plasmonic switches. C.F.L. thanks the Robert A. Welch Foundation [Grant C-1787], the National Science Foundation [Grants CBET-1134417 and CHE-1151647], and the National Institutes of Health [Grant GM94246-01A1. S.L. acknowledges support from the Robert A. Welch Foundation [Grant C-1664], and the Office of Naval Research [Grant N00014-10-1-0989]. C.P.B. acknowledges support from the National Science Foundation through a Graduate Research Fellowship [0940902].


Low Absorption Losses of Strongly Coupled Surface Plasmons in Nanoparticle Assemblies. Chang W.-S.1, Willingham B. A.1, Slaughter L.S.1, Khanal B.P.1,Vigderman L.1, Zubarev E.R.1 and Link S.1,2,*

1Department of Chemistry and 2Department of Electrical and Computer Engineering, Rice University, Houston, TX, USA Corresponding Author: Link S, Department of Chemistry and Department of Electrical and Computer Engineering, Rice University. 6100 Main Street, MS-60, Houston TX 77005. Email: [email protected] Coupled surface plasmons in one-dimensional assemblies of metal nanoparticles have attracted significant attention because strong interparticle interactions lead to large electromagnetic field enhancements that can be exploited for localizing and amplifying electromagnetic radiation in nanoscale structures. Ohmic loss, i.e. absorption by the metal, however, limits the performance of any application due to nonradiative surface plasmon relaxation. While absorption losses have been studied theoretically, they have not been quantified experimentally for strongly coupled surface plasmons. Here, we report on the ohmic loss in one-dimensional assemblies of gold nanoparticles with small interparticle separations of only a few nanometers and hence strong plasmon coupling. Both the absorption and scattering cross sections of coupled surface plasmons were determined and compared to electrodynamic simulations. A lower absorption and higher scattering cross section for coupled surface plasmons compared to surface plasmons of isolated nanoparticles suggest that coupled surface plasmons suffer smaller ohmic losses and therefore act as better antennas. These experimental results provide important insight for the design of plasmonic devices. This research is financially supported by the Robert A. Welch Foundation (Grant C-1664, C-1703), NSF (CHE-0955286, DMR-0547399, DMR-1105878), ONR (N00014-10-1-0989), and 3M for a Nontenured Faculty Grant.



Exploring the conformational landscape of the NMDA receptor via single molecule FRET David Cooper,1 Drew Dolino,3 Henriette Jaurich,1 Bo Shuang,1 Swarna Ramaswamy,3 Jixin Chen,1 Vasanthi Jayaraman,3 Christy F. Landes1,2

1Department of Chemistry, Rice University, Houston, TX, USA 2Department of Electrical and Computer Engineering, Rice University, Houston, TX, USA 3Department of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, TX, USA The N-methyl-D-aspartate receptor (NMDAr) is member of the glutamate receptor family of proteins and is responsible for slow excitatory transmission. Activation of the receptor is thought to be controlled by conformational changes in the ligand binding domain (LBD). In order to probe the conformational landscape we measured the distance of the cleft closure using single molecule Förster resonance energy transfer (FRET) spectroscopy using the isolated LBD of the glycine bound subunit of the receptor. We developed an algorithm to assess both the number of states and their FRET efficiencies from the measured data. Multiple states were identified that were associated with the closed and open states of the cleft indicating a more complex pathway for the opening mechanism of the channel. The transitions among different states were observed to progress state-to-state reversibly. We found that the NMDAr proceeds primarily from one adjacent FRET state to the next under equilibrium conditions. We also studied the conformational dynamics of the system after introducing high concentrations of denaturant and found that the equilibrium of the system could be reversibly moved towards the lower FRET efficiencies. Grant Acknowledgments This work is supported by the Welch Foundation (Grant C-1787), National Science Foundation (Grants CBET-1134417 and CHE-1151647), and the National Institutes of Health (Grant GM94246-01A1).


Preventing the Aggregation of Colloidal Gold Nanoparticles with a Protein Monolayer Dominguez-Medina S,1 Blankenburg J,1 Olson J,1 Landes CF,1,2 Link S1,2 1. Department of Chemistry, Rice University, Houston, Texas, USA 2. Department of Electrical and Computer Engineering, Rice University, Houston, Texas, USA Corresponding author: Stephan Link, Dept. of Chemistry, Rice University, Houston, Texas, USA 6100 Main St MS-60 Houston, Texas, USA E-mail: [email protected] Citrate-stabilized gold nanoparticles aggregate and precipitate below the NaCl concentration of many bodily fluids and blood plasma. Our experiments indicate that this is due to complexation of the citrate anions with Na+ cations in solution. We find that monolayer adsorption of bovine serum albumin -the most abundant protein in cow blood and a side product of the cattle industry- completely prevents the aggregation of colloidal gold nanoparticles under harsh environmental conditions where the NaCl concentration is well beyond the isotonic point. Furthermore, we explore the mechanism of the formation of this albumin corona and find that monolayer protein adsorption is most likely ruled by hydrophobic interactions. As for many nanotechnology-based biomedical and environmental applications, particle aggregation and sedimentation are undesirable and could substantially increase the risk of toxicological side effects; the formation of the BSA corona presented here provides a low-cost biocompatible strategy for nanoparticle stabilization and transport in biological fluids. SL acknowledges support from the Robert A. Welch Foundation [Grant C-1664] and the Cancer Prevention and Research Institute of Texas [CPRIT RP110355]. CFL thanks the Robert A. Welch Foundation [Grant C-1787], the National Science Foundation [Grants CBET-1134417 and CHE-1151647], and the National Institutes of Health [Grant GM94246-01A1]. JO acknowledges support from the National Science Foundation through a Graduate Research Fellowship [0940902]. We thank Dr. Wei-Shun Chang for insightful discussions.


Au Nanoparticle Spectroelectrochemical Response Modified by Electrolyte Anion and Particle Morphology Benjamin S. Hoener,1 Chad P. Byers,1 Wei-Shun Chang,1 Mustafa Yorulmaz,1 Stephan Link1,2, and Christy F. Landes1,2

1Department of Chemistry, Rice University, Houston, TX, United States 2Department of Electrical and Computer Engineering, Rice University, Houston, TX, United States The scattering spectrum of 50 nm gold colloids and 25 x 86 gold nanorods deposited on an indium tin oxide (ITO) electrode was measured in a spectroelectrochemical cell using dark-field microscopy. The charge density of the gold nanoparticles was modified by cycling the potential of the ITO working electrode. A charge density-modified Drude dielectric function and Mie Theory predict a linear relationship between charge density and plasmon resonance energy under non-Faradaic conditions. A qualitatively linear decrease in plasmon resonance energy was observed in gold nanorods and spheres when the potential of the ITO working electrode was increased from -.4V to +.4 V at 10 mV/s using NaCl and Na2SO4 electrolyte, but the magnitude of the shift was much larger in gold nanorods. However, the full-width half-max increase as potential increased was much greater in NaCl than Na2SO4, which could be due to differences in anion damping. These relationships were reversible and repeatable over multiple cycles. S.L. acknowledges support from the Robert A. Welch Foundation [Grant C-1664] and the Office of Naval Research [Grant N00014-10-1-0989]. C.F.L. thanks the Robert A. Welch Foundation [Grant C-1787], the National Science Foundation [Grants CBET-1134417 and CHE-1151647], and the National Institutes of Health [Grant GM94246-01A1]. C.P.B. acknowledges support from the National Science Foundation through a Graduate Research Fellowship [0940902].


Super-Resolution Spatial and Diffusion Properties Obtained Simultaneously By Correlation-Based Analysis in Hard and Soft Porous Materials Kisley L,1 Brunetti R,2 Tauzin LJ,1 Shuang B,1 Yi X,3 Weiss S,3,4 Landes CF1,5 1 Department of Chemistry, Rice University, Houston, TX 77251 2 Department of Physics, Scripps College, Claremont, CA 91711 3 Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095 4 Department of Physicology and the California NanoSystem Institute, University of California Los Angeles, Los Angeles, CA 90095 5 Department of Electrical and Computer Engineering, Rice University, Houston, TX 77251 Corresponding author: Kisley L, Department of Chemistry, Rice University, 6100 Main Street, MS 60, Houston, TX 77251, Email: [email protected] Porous materials such as hydrogels, engineered co-block polymers, and the cellular cytosol have nanoscale features that determine their uses and properties, but characterizing their structure by current techniques is challenging due to non-native imaging conditions and high computational requirements. Here, we introduce a new super-resolution optical imaging technique inspired both by super-resolution optical fluctuation imaging (SOFI) and fluorescence correlation spectroscopy (FCS) that simultaneously characterizes both the porous structure on the nanometer scale and transport properties within the pores. Correlation analysis of the fluctuations from diffusing photoluminescent probes within the porous space of the sample improves the resolution of the diffraction limited point spread function that is convolved with the porous area traversed, while the correlation curve shape and decay quantifies the diffusion dynamics. We demonstrate by simulation that more accurate quantitative features of the structure can be revealed by the auto- and cross-correlation analysis compared to the diffraction limited average image and Brownian diffusion dynamics can be accurately recovered. We apply our technique experimentally to mesoporous silica, a model 1D hard porous material, and agarose, a model porous 2D hydrogel material, under high-throughput experimental conditions to distinguish different structures. The quantitative pore sizes obtained from an image of 1% agarose agrees with accepted literature values compared to diffraction limited imaging and single particle tracking. These results demonstrate that our technique is a novel to qualitatively image and quantitatively analyze diffusion and pore sizes that could be applied to soft environments, such hydrogels, polymers, and membranes, in addition to hard materials, such as zeolites.

Acknowledgements: Landes, CF acknowledges the Welch Foundation (Grant C-1787), the National Science Foundation (NSF; Grants CBET-1134417 and CHE-1151647), and the National Institutes of Health (NIH; Grant GM94246-01A1). Kisley, L acknowledges the NSF Graduate Research Fellowship (Grant 0940902). Brunetti, R acknowledges the NSF Research Experience for Undergraduates at the Rice Quantum Institute (Award Number 1156542). Weiss, S acknowledges Willard Chair funds.


Mechanistic Insights into Protein Ion-exchange Adsorptive Separations using Single-molecule, Super-resolution Imaging Poongavanam M1, Kisley L3, Chen J3, Mansur AP3, Kourentzi K2, Chen W-H2, Dhamane S1, Dominguez-Medina S3, Kulla E3, Landes CF3, Willson RC1,2 1Department of Biology and Biochemistry, University of Houston, Houston, TX 77004 2Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77004 3Department of Chemistry, Rice University, Houston, TX 77025 Corresponding author: Willson RC, Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Rd, Houston, TX 77004 In this work we are employing single-molecule methods to study the complex mechanistic details involved in protein chromatography. Using a single-molecule, super-resolution imaging technique called motion-blur Points Accumulation for Imaging in Nanoscale Topography (mbPAINT), we present the direct mapping and kinetic characterization of individual functional sites on thin-film agarose ion-exchange matrices. By extracting single-protein adsorption and desorption kinetics at individual ligands, direct experimental evidence in support of the stochastic theory of chromatography is obtained. Simulated elution profiles calculated from the molecular-scale data suggest that, if it were possible to engineer uniform optimal interactions into ion-exchange systems, separation efficiencies could be improved by as much as a factor of five. Using the single molecule approach, we also investigated the influence of ionic strength on the heterogeneity of protein ion-exchange functional adsorption sites, and therefore the heterogeneity of elution profiles. We observed that the number of functional adsorption sites was smaller at high ionic strength and these sites had reduced desorption kinetic heterogeneity. The results suggest the reduction of heterogeneity is due to both electrostatic screening between the protein and ligand and tuning of steric availability within the agarose support. Overall, we have shown that single molecule super-resolution imaging can aid in improving our understanding of ion-exchange adsorptive separations and the results of such studies could be used to improve adsorbent properties. This research was funded in part by grants from NSF (CBET-1134417 and CHE-1151647 (CFL); CBET-1133965 (RCW)) and the Welch Foundation (C-1787 (CFL); E-1264 (RCW)).


Laser-assisted Dealloying Lithography Li J1, Shih WC1 1 Department of Electrical and Computer Engineering, University of Houston Corresponding author: Shih WC, Dept. of Electrical and Computer Engineering, University of Houston 4800 Calhoun Rd. Houston, TX, 77204, E-mail: [email protected] Abstract Nanoporous gold (NPG) is a porous material of high interest due to its unique properties such as high surface area to volume ratio, continuous porous nanostructure, high electrical conductivity and thiol-gold surface chemistry. The desire to utilize NPG in various applications as well as fundamental studies demand the development of novel fabrication and synthesis techniques. NPG could be fabricated by the corrosion process, known as dealloying, when the less noble constituent of an alloy is selectively removed in a strong corrosive solution while the noble constituent forms an open pore network structure with bicontinuous pores. Pre- and post-modifications of NPG film structure has been demonstrated in prior research where the process of dealloying and patterning are separated standalone procedures. Elevated temperature promotes chemical reactions in general, thus increasing the dealloying rate. Nitric acid, when diluted to a certain extent, could not induce the dealloying of alloy film due to insufficient energy level to break Ag-Au atom bonding. When it is heated to higher temperatures, the heat-elevated energy level of nitric acid overcomes the Ag-Au atom bonding and induces the dealloying of Ag-Au alloy. Compared to alloy composition, corrosion medium, voltage in electrolyte, etc., temperature is seldomly used as a parameter in controlling the morphology of the nanoporous materials. However, temperature provides a means of selectivity if it could be localized, which inspired the combination of laser and dealloying in this work. When a focused laser beam irradiates on the alloy immersed in diluted nitric acid, only the irradiated area could be heated and dealloyed while the rest of the alloy remains intact. In this work, we present a novel method for micropatterning NPG film to implement patterning and dealloying simultaneously. W.C.S. acknowledges NSF CAREER Award (CBET-1151154), NASA Early CAREER Faculty Grant (NNX12AQ44G), and Gulf of Mexico Research Initiative (GoMRI-030).



Role of Chemical Spacer at Molecular Level for Charge Separation in All-conjugated Block Copolymers Solar Cells Jorge W. Mok†, Yen-Hao Lin†, Kevin G. Yager⊥, Seth B. Darling,§,± Youngmin Lee‖‖, Enrique Gomez‖‖, David Gosztola§, Richard Schaller§,‖, and Rafael Verduzco†,‡,✻

†Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States ⊥Center for Functional Nanomaterials, Brookhaven National Laboratory, New York 11973, United States §Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States ±Institute for Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States ‖‖Department of Chemical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States ‖Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States ‡Department of Material Science and Nanoengineering, Rice University, Houston, Texas 77005, United States ✻Corresponding Author: [email protected] Recent studies have demonstrated the potential of all-conjugated donor-acceptor block copolymer for organic photovoltaics, but it remains unclear how molecular structure, morphology, and electronic properties of conjugated block copolymers influence performance. Here, we study the role of chemical linker between donor and acceptor polymers on photovoltaic performance and optoelectronic properties. Two poly(3-hexylthiophene)-poly(2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl-(9,9-dioctylfluorene)) (P3HT-PTBTF) donor-acceptor block copolymers which differ only in the chemistry of linking group are studied through device measurements, grazing-incidence X-ray analysis, and steady-state and time-resolved absorbance and photoluminescence measurements. Device studies show that power conversion efficiencies decrease by a factor of 40, from 2.2 % to 0.05 %, by changing the linking group. X-ray analysis shows that the morphology is virtually identical in both samples, as expected. Ultrafast transient absorption measurements reveal charge separation in block copolymers which contain a wide bandgap monomer at the donor-acceptor interface, but charge separation is suppressed when donor and acceptor blocks are directly linked without this spacer present. This demonstrates that the chemistry of the linking group can influence the electronic properties of the donor-acceptor interface and kinetics for charge separation and recombination. For both samples studies, we find that the rate of charge recombination in these systems is faster than in polymer-polymer and polymer-fullerene blends, suggesting further improvement possible through optimization of the linking group. This work demonstrates that the linking group chemistry influences charge separation in all-conjugated block copolymer systems, and also suggests that all-conjugated block copolymers can be used as model systems for the donor-acceptor interface in bulk heterojunction blends. Acknowledgments JWM, YHL, and RV acknowledge the support of the National Science Foundation CAREER award (DMR – 1264703). Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.


Aluminum Plasmonic Pixels Olson, J.1,2, Manjavacas, A.2,3, Liu, L.2,3, Foerster, B.1,2, Chang, W.-S.1,2, King, N.2,3, Knight, M.2,4, Halas, N.1,2,3,4, Nordlander, P.2,3,4, Link, S1,2,4. 1. Department of Chemistry, Rice University, Houston TX 77005 2. Department of Physics and Astronomy, Rice University, Houston TX 77005 3. Department of Electrical and Computer Engineering, Rice University, Houston TX 77005 4. Laboratory for Nanophotonics, Rice University, Houston TX 77005 Corresponding author: Jana Olson Rice University Department of Chemistry MS-60 6100 Main Street Houston TX 77005 Email: [email protected] Full-color displays are typically fabricated using a combination of chromatic materials of various types, introduced into an addressable pixel-based electronic device. Here we show that brightly colored, highly vivid pixels, directly suitable for RGB displays, can be fabricated using periodic areas of Al nanorods in each pixel. Both nanorod length and spacing are critically important in achieving strong and spectrally distinct scattering signatures across the visible spectrum. This use of a low-cost, abundant metal for achieving full-spectrum coloration is compatible with complementary metal-oxide semiconductor manufacturing methods and directly applicable to current liquid crystal display technology. This work was funded by Robert A. Welch Foundation Grants C-1220, C-1222, and C-1664 and Office of Naval Research Grant N00014-10-0989. A.M. acknowledges financial support from the Welch foundation through the J. Evans Attwell-Welch Postdoctoral Fellowship Program of the Smalley Institute of Rice University (Grant L-C-004). J.O. acknowledges support from the National Science Foundation through Graduate Research Fellowship 0940902.


Single Particle Circular Dichroism Spectroscopy of Nanomaterials Smith, K. W.1, Wang, L. Y.1, Chang, W. S1., Link S1. 1. Department of Chemistry, Rice University, Houston, TX Corresponding author: Smith, K. W. Department of Chemistry, Rice University, Houston, TX, USA Email: [email protected] Circular dichroism (CD) spectroscopy measures the difference in coupling of a material with left-handed and right-handed circularly polarized light. CD has been used extensively in small molecule and protein characterization and more recently to examine the optical activity of chiral nanostructures. We report to the best of our knowledge the first demonstration of far-field CD measurements of individual nanostructures through the use of dark field scattering microscopy. We calculate necessary correction factors for the ellipticity in our incident light by measuring achiral single Au nanorods of random orientations. We demonstrate the effectiveness of our method through the measurement of twisted nanowires composed of CdTe nanoparticles whose chirality was verified through scanning electron microscopy images. Additionally, we present the CD of chiral twisted gold nanorod dimers which show varied behavior within the sample, demonstrating the usefulness of single particle measurements on heterogeneous self-assembled nanomaterials.


Optical Imaging Strategies In Complex Environments Using Rod-Like Plasmonic Nanoparticles Stender, Anthony S.,1 Wang, G.,2 and Fang, N.3 1. Department of Materials Science, Rice University, Houston, TX, USA 2. Department of Chemistry, North Carolina State University, Raleigh, NC, USA 3. Department of Chemistry & Ames Laboratory, Iowa State University, Ames, IA, USA Corresponding Author: Stender, A.S., Dept. of Materials Science, Rice University, 6100 Main Street, MS-325, Houston, TX 77005 USA, E-mail: [email protected] Plasmonic nanoparticles with anisotropic shapes are commonly used for optical imaging in complex biological environments, particularly when real-time imaging is required over extended periods of time. Anisotropic nanoparticles display orientation-dependent extinction, such that they can reveal the motion and orientation of any molecular motor to which they are attached. However, concerns about imaging heterogeneous nanoparticles in complex systems persist, since structurally characterizing each nanoparticle prior to deployment is impossible. Such difficulties are centered around three topics: variability in particle size and shape, distinguishing single particles from aggregates, and selecting the ideal imaging method. Here, we will show results that address each of these three aspects of single particle imaging and explain how they apply to imaging in complex media.

Gold nanorods and nano-dumbbells were studied under dark field and differential interference contrast (DIC) microscopy. Aggregates of the two types of nanoparticles were also investigated. DIC microscopy was found to be superior to dark field in distinguishing between single particles and non-interacting particles separated by a distance less than the diffraction limit. The two aforementioned types of optical microscopy performed equally well at identifying nanorod dimers. However, because DIC microscopy relies on image generation via interferometry, it produces a more complicated spectrum at non-resonant wavelengths. A comparison of single dumbbells and nanorods revealed that the two types of particles have similar optical behavior, although the intensity, line-width, and energy of the single dumbbell’s plasmonic bands were found to be highly dependent on the amount of overgrowth. Simulations revealed that dumbbells are a transition point between nanorods and spheres (see Figure below). Furthermore, because of the shape of dumbbell particles, they tend to interlock like puzzle pieces, thus leading to an assortment of aggregate geometries and optical behaviors.

Figure: Simulated results for absorption, using light polarized along the longitudinal axis (A) and transverse axis (B) of

seven nanoparticle shapes, each with a length of 91 nm. TEM inset: Image of a single dumbbell particle with a length of 91 nm that was studied as a part of this research. Funding Sources: This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Basic Energy Sciences, Office of Science, U.S. Department of Energy through Ames Laboratory. Ames Laboratory is operated by the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358. This work was also supported in part by the Mary K. and Velmer A. Fassel Fellowship from Iowa State University.



Mechanical Coupling of Au/Ti Bimetallic Nanostructures on Glass Substrates Su M-N1, Chang W-S1, Wen F1, Chakroborty D4, Zhang Y2, Sader JE4, Nordlander PJ1,2,3, Halas NJ1,2,3 and Link S1,2,3 1. Department of Chemistry, Rice University Houston 2. Department of Physics, Rice University Houston 3. Department of Electric and Computer Engineering, Laboratory for Nanophotonics, Rice University Houston 4. Department of Mathmatics and Statistics, The University of Melbourne, Victoria 3010, Australia Corresponding author: Link S, Dept. of Chemistry, Dept. of Physics, Dept. of Electric and Computer Engineering, Laboratory for Nanophotonics, Rice University Houston TX 77005 E-mail: [email protected]

Top-down lithography facilitates precise control over the physical dimensions of nano-objects. This control is critical for various applications utilizing the mechanical properties of nanomaterials. Unlike chemically prepared nanostructures that are deposited onto a substrate, lithographically fabricated nanostructures made of gold require an adhesion layer between the gold and the substrate. However, very little is known about how the substrate and adhesion layer affect the mechanical properties of the nanostructure. In this study, we fabricated Au nanodisks on glass substrates with varying thicknesses of the Ti adhesion layer, and probed the acoustic vibration of the nanostructure using single-particle transient absorption spectroscopy. A nanodisk breathing mode was observed parallel to the substrate surface. With increasing Ti thickness we observed an increase of the acoustic vibration frequency originating from the strength of the binding between the substrate and nanodisk. A clear transition from non-binding to strong binding was observed with increasing Ti thickness confirmed by FEM simulation. Additionally, the breathing mode frequency of the nanodisks scaled linearly with the volume percent of Ti, suggesting that this could be a non-invasive optical method to determine the Ti content in Ti/Au bimetallic nanostructures. These results provide detailed understanding of the mechanical properties of lithographically fabricated structures. This work is supported by the Robert A. Welch Foundation (Grants C-1220, C-1222, and C-1664), NSF (CHE-0955286), and the Army (MURI W911NF-12-1-0407).


Microfluidic Label-Free Monitoring of DNA Hybridization Ji Qi1, Jianbo Zeng1, Fusheng Zhao1, Yu-Lung Sung2, Shih W-C1, 2 1. Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston 2. Department of Biomedical Engineering, Cullen College of Engineering, University of Houston Corresponding Author: Yu-Lung Sung, Department of Electrical and Computer Engineering, Cullen College of Engineering, University of Houston, 4800 Calhoun Rd, Engineering Bldg. 2, Room # W332, Houston, TX 77204-4005, USA, E-mail: [email protected] Surface-enhanced Raman scattering (SERS) is an attractive approach for label-free multiplexed DNA/RNA detection because of its single-molecule sensitivity, molecular specificity, and freedom from quenching and photo-bleaching. We present a SERS-based label-free approach capable of in situ monitoring of the same immobilized short-single-strand DNA (ssDNA) molecules and their individual hybridization events over more than an hour. To achieve such performance, we have successfully implemented molecular sentinel immobilized on nanoporous gold disks inside a microfluidic channel. The microfluidic environment prevents sample desiccation, permits small sample volumes, and agile fluid manipulation. We were able to detect the onset of hybridization events within ~10 min after introducing 20 pM target ssDNA molecules. Given the single-molecular sensitivity, robust SER signals, and simple detection system, this approach could find potential applications in time-lapsed monitoring of DNA interactions and point-of-care applications. Wei-Chuan Shih acknowledges the National Science Foundation (NSF) CAREER Award (CBET-1151154), National Aeronautics and Space Administration (NASA) Early Career Faculty Grant (NNX12AQ44G) and a grant from Gulf of Mexico Research Initiative (GoMRI-030).


pH Switchable, Charge Dependent Transport in a Weak Polyelectrolyte Multilayer Tauzin LJ1, Shuang B1, Kisley L1, Mansur AP1, Chen J1, Leon A2, Advincula RC2, Landes CF1 1. Department of Chemistry, William Marsh Rice University, Houston, Texas 2. Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio Corresponding Author: Landes, C, Department of Chemistry, Rice University, 6100 Main St. MS 60, Houston, Texas, 77005. Multilayers composed of weak polyelectrolytes (PEMs) exhibit tunable properties making them ideal for use in applications such as drug uptake and selective delivery, separations, and water purification. In order to optimize devices for these applications, an understanding of mass and charge transport in PEMs is required. We have directly measured the interaction of monovalent ions with a multilayer of poly(acrylic acid) and poly(allylamine hydrochloride) and found it to be multimodal, pH tunable and charge dependent. Fluorescence microscopy and single molecule tracking were used to determine the presence of two primary transport modes: 1) adsorption, characterized by periods of immobilization in a subresolution region, and 2) diffusion trajectories characteristic of hopping (D ~ 10-9 cm2/s) likely due to intermittent surface interactions. Radius of gyration evolution analysis was used along with simulated trajectories to demonstrate the coexistence of the two transport modes in the same single molecule trajectories. For both anionic and cationic probe molecules, the hopping transport mode could be reversibly switched on and off by changing the solution pH. These results confirm the previously suggested hopping mechanism for the interaction of charged molecules with PEMs and offer insight into the role of electrostatics and nanoscale tunability of transport in weak polyelectrolyte multilayers. This work was funded by the National Science Foundation (CBET-1134417, CHE-1151647, and 1333651), the National Institutes of Health (GM94246-01A1), and the Welch Foundation (C-1787).


Molecule Identification in High Molecule Density with Rod-Shaped Rotating Point Spread Function Wenxiao W1, Shuang B2, Landes CF2 1. Department of Electrical and Computer Engineering, William Marsh Rice University, Houston, Texas 2. Department of Chemistry, William Marsh Rice University, Houston, Texas Corresponding Author: Landes, C, Department of Chemistry, Rice University, 6100 Main St. MS 60, Houston, Texas, 77005. Extracting Information to reconstruct the super resolution images at high molecule density is usually challenging for traditional molecule identification method. Although some approaches, such as DAOSTORM and CSSTORM, can achieve 2D molecule localization at high molecule density, problems still remain in terms of 3D super resolution. In this work a sparse reconstruction algorithm is applied to 3D rotating point spread function (PSF) microscopy data to localize the molecule. A new PSF, rod-shaped rotating PSF is proposed and it is more flexible when combined with the sparse reconstruction algorithm. The molecule recall rate by combining the sparse reconstruction algorithm with rod-shaped PSF can reach 0.78 with molecule density to be 2 emitters /µm2, which is ten times of the molecule density that is limited by the traditional method. This work was funded by the National Science Foundation (NSF) (Grants CBET-1134417 and CHE-1151647), the Welch Foundation (Grant C-1787) and the National Institute of Health (Grant GM94246-01A1).


Single-Particle Absorption Spectroscopy of Plasmonic Nanostructures Yorulmaz M1, Nizzero S1,2, Chang WS1, Wang LY1, Link S1,3 1. Department of Chemistry, Rice University, Houston, Texas 77005, United States 2. Applied Physics Graduate Program, Rice University, Houston, Texas 77005, United States 3. Department of Electrical and Computer Engineering, Laboratory for Nanophotonics, Rice University, Houston, Texas 77005, United States Corresponding author: Link S, Department of Chemistry, Department of Electrical and Computer Engineering, Laboratory for Nanophotonics, Rice University, Houston, Texas 77005, United States, E-mail: [email protected] Plasmonic nanoparticles exhibit interesting radiative and non-radiative properties upon their interaction with light. These properties have been exploited for a variety of intriguing applications such as optical probing and sensing, field enhancement, and localized heating. Single-particle methods have been utilized to understand these properties providing the advantage of having an access into distribution of variables, which otherwise is averaged out in an ensemble of particles. While the radiative properties are well-characterized using fluorescence and scattering spectroscopy, studying the non-radiative properties remains a challenge. Photothermal microscopy is a very sensitive technique that can be used to detect the heat generated by a single nano-object, or even a single chromophore. However, these measurements are limited to a single excitation wavelength, and method to measure the pure absorption as a function of wavelength for an individual nano-object has not yet been established. Here, we introduce the evolution of photothermal imaging toward absorption spectroscopy. In order to achieve that, we incorporate photothermal microscopy with a supercontinuum laser source and a correction procedure which accounts for the effects of chromatic aberration and wavelength dependent excitation efficiency on the measured absorption spectrum. The single-particle absorption spectroscopy we develop can benefit applications of individual plasmonic nanostructures in photonics and optoelectronic devices. We acknowledge financial support from the Robert A. Welch Foundation (C-1664, C-1222), the Office of Naval Research (N00014-10-1-0989), the Army Research Office (MURI W911NF-12-1-0407), and a DURIP equipment grant (N00014-12-1·0727). M. Y. acknowledges financial support from the Richard E. Smalley Institute at Rice University through a Carl&Lillian Illig Postdoctoral Fellowship. We thank Anneli Hoggard for help with the preparation of indexed substrates.



Morphological control and plasmonic tuning of nanoporous gold disks by surface modifications Zeng J1, Zhao F,1 Shih WC1,2

1Department of Electrical and Computer Engineering, University of Houston, Houston, TX, USA 2Department of Biomedical Engineering, University of Houston, Houston, TX, USA Corresponding Author: Shih WC, Department of Electrical and Computer Engineering, Department of Biomedical Engineering, University of Houston, 4800 Calhoun Road, Houston, TX 77204, USA, Email: [email protected] Abstract We report a surface modification protocol to control nanoporous gold (NPG) disk morphology and tune its plasmonic resonance. Enlarged pore size up to ~20 nm within 60 s dealloying time has been achieved by adsorbing halides onto alloy surfaces in between two dealloying steps. In addition, plasmonic resonance has been significantly redshifted for up to ~258 nm by the surface modification. Furthermore, we show that by tuning the pore sizes, small or large gold nanoparticles could be loaded into the porous structure or attached at the surface of NPG disks to form nanoporous gold nanocomposites. The strong plasmonic coupling not only originates from the interaction between nanoporous gold nanoparticles and small gold nanoparticles, but also between small gold nanoparticles. The plasmonic resonance can be easily tuned in both visible and NIR spectral ranges by changing the diameter of attached gold nanoparticle sizes. The nanoporous gold nanocomposites can significantly enhance the performance of surface-enhanced Raman scattering (SERS) due to the strong plasmonic coupling. Acknowledgements Shih WC acknowledges the National Science Foundation (NSF) CAREER Award (CBET-1151154), National Aeronautics and Space Administration (NASA) Early Career Faculty Grant (NNX12AQ44G) and a grant from Gulf of Mexico Research Initiative (GoMRI-030).



Monolithic NPG nanoparticles with large surface area, tunable plasmonics, and high-density internal hot-spots Zhao F1, Zeng J1, Shih WC1 1 Department of Electrical and Computer Engineering, University of Houston Corresponding author: Shih WC, Dept. of Electrical and Computer Engineering, University of Houston 4800 Calhoun Rd. Houston, TX, 77204, E-mail: [email protected] Abstract Plasmonic metal nanostructures have shown great potential in sensing, photovoltaics, imaging and biomedicine, principally due to the enhancement of local electric field by light-excited surface plasmons, i.e., collective oscillation of conduction band electrons. Thin films of nanoporous gold have received a great deal of interest due to the unique 3-dimensional bicontinuous nanostructures with high specific surface area. However, in the form of semi-infinite thin films, nanoporous gold exhibits weak plasmonic extinction and little tunability in the plasmon resonance, because the pore size is much smaller than the wavelength of light. Here we show that by making nanoporous gold in the form of disks of subwavelength diameter and sub-100 nm thickness, these limitations can be overcome. Nanoporous gold disks not only possess large specific surface area but also high-density, internal plasmonic “hot-spots” with impressive electric field enhancement, which greatly promotes plasmon–matter interactions as evidenced by spectral shifts in the surface plasmon resonance. In addition, the plasmonic resonance of nanoporous gold disks can be easily tuned from 900 to 1850 nm by changing the disk diameter from 300 to 700 nm. Furthermore, nanoporous gold disks can be fabricated as either bound on a surface or as non-aggregating colloidal suspension with high stability. W.C.S. acknowledges the National Science Foundation (NSF) CAREER Award (CBET-1151154), National Aeronautics and Space Administration (NASA) Early Career Faculty Grant (NNX12AQ44G) and a grant from the Gulf of Mexico Research Initiative (GoMRI-030)


Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Participant List

Workshop Participant Contact Information

Last Name First Name Institutional Affiliation Email Advincula Rigoberto Case Western Reserve University [email protected] Arnob Masud Parvez University of Houston [email protected] Bao Jiming University of Houston [email protected] Basu Tiyash Rice University [email protected] Batista Victor Yale University [email protected] Batteas James Texas A&M University [email protected] Bhatnagar Parijat Baylor College of Medicine [email protected] Burda Clemens Case Western Reserve University [email protected] Byers Chad Rice University [email protected] Cai Dong University of Houston [email protected] Cai Yiyu Rice University [email protected] Chang Wei-Shun Rice University [email protected] Chatterjee Sudeshna Rice University [email protected] Chen Jixin Ohio University [email protected] Chen Sishan Rice University [email protected] Cooper David Rice University [email protected] Dhamane Sagar University of Houston [email protected] Dominguez-Medina Sergio Rice University [email protected] Fang Ning Iowa State University [email protected] Halas Naomi Rice University [email protected] Higgins Daniel Kansas State University [email protected] Hoener Benjamin Rice University [email protected] Hoggard Anneli Rice University [email protected] Huang Da Rice University [email protected] Indrasekara Swarnapali Rice University [email protected] Kisley Lydia Rice University [email protected] Kolomeisky Anatoly Rice University [email protected] Kourentzi Katerina University of Houston [email protected] Kumar Anjli Rice University [email protected] Landes Christy Rice University [email protected] Lee T. Randall University of Houston [email protected] Li Jingting University of Houston [email protected] Li Qilin Rice University [email protected] Li Chien-Hung University of Houston [email protected] Link Stephan Rice University [email protected] Mayerich David University of Houston [email protected] Minteer Shelley University of Utah [email protected]

Workshop: Light-Driven Processes for Bio-Inspired Materials December 14-16, 2014 Participant List

Mok Jorge Rice University [email protected]

Moskovits Martin University of California, Santa Barbara [email protected]

Nguyen Thuc-Quyen University of California, Santa Barbara [email protected]

Nizzero Sara Rice University [email protected] Nordlander Peter Rice University [email protected] Olson Jana Rice University [email protected] Patil Ujwal University of Houston [email protected] Payne Christine Georgia Tech [email protected] Requejo Roque Katherinne Isabel Rice University [email protected] Ringe Emilie Rice University [email protected] Sagle Laura University of Cincinnati [email protected] Samia Anna Case Western Reserve University [email protected]

Schwartz Daniel University of Colorado Boulder [email protected] Shahsavari Rouzbeh Rice University [email protected] Shakiba Amin University of Houston [email protected] Shen Hao Rice University [email protected] Shih Wei University of Houston [email protected] Smith Kyle Rice University [email protected] Stender Anthony Rice University [email protected] Su Man-Nung Rice University [email protected] Sung Yulung University of Houston [email protected] Tauzin Lawrence Rice University [email protected] Thomann Isabell Rice University [email protected] Thompson Melissa Gulf Coast Consortia [email protected] Verduzco Rafael Rice University [email protected] Villarreal Eduardo Rice University [email protected] Wang Lin-Yung Rice University [email protected] Wang Gufeng North Carolina State University [email protected] Wang Wenxiao Rice University [email protected] Waxham Neal UT Medical School at Houston [email protected] Willets Katherine University of Texas at Austin [email protected] Yorulmaz Mustafa Rice University [email protected] Yu Cunjiang University of Houston [email protected] Zanni Martin University of Wisconsin [email protected] Zeng Jianbo University of Houston [email protected] Zhang Yifei Rice University [email protected] Zhao Fusheng University of Houston [email protected] Zhu Y. Elaine University of Notre Dame [email protected]

Workshop: Light-Driven Processes for Bio-Inspired...

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