lee, charles - organic materials chemistry - spring review 2012

Integrity Service Excellence

DISTRIBUTION A: Approved for public release; distribution is unlimited

Organic Materials

Chemistry

Charles Lee

Program Manager

AFOSR/RSA

Air Force Research Laboratory

09 MAR 2012

2 DISTRIBUTION A: Approved for public release; distribution is unlimited

2012 AFOSR SPRING REVIEW

NAME: Charles Lee

BRIEF DESCRIPTION OF PORTFOLIO:

To exploit the uniqueness of organic/polymeric materials

technologies for enabling future capabilities currently unavailable by

discovering and improving their unique properties and processing

characteristics

LIST SUB-AREAS IN PORTFOLIO:

Photonic Polymers/Organics

Electronic Polymers/Organics

Novel Properties Polymers/Organics

NanoTechnology


Research Objective and Challenges

To exploit the uniqueness of organic/polymeric materials technologies

for enabling future capabilities currently unavailable by discovering

and improving their unique properties and processing characteristics

Challenges:

- Discover New Properties

- Control Properties

- Balance Secondary Properties

Approach:

–Molecular Engineering

–Processing Control

–Structure Property Relationship

• Program Focused on developing New and Controlled Properties

• Not applications specific, but often use applications to guide the

properties focuses


Other Organizations That Fund Related Work

• Other Basic Research Organization in this area:

– ONR, ARO, NSF, NIH, DOE

• Other Non-Basic Research Organizations:

– AFRL/TDs, ARL, NRL, DARPA, NRO, DTRA

– DOE, JEIDDO, NIST

• Interactions with Other Agencies

– Federal Interagency Chemistry Representatives Meeting

– Tri-Service Laser Protection Information Exchange Meeting

– Joint AFOSR-ONR Organic Photovoltaic Program Review

– Tri-Service 6.1 MetaMaterials Review


Organic Lasers Achieve CW Lasing Stephen Forrest, U of Michigan

Intensity

Time

Step Optical

Pump

Lasing

Turn-off

Why does Organic Semiconductor Laser lasing only last <100ns?

Initial conditions after pulse (<10ns)

Negligible Triplet density

Gain=Loss

Lasing begins

Later (>100ns)

Triplets build up, along with triplet losses

Gain ↓ due to S-T quenching

Loss ↑ due to T absorption

Giebink, N. C.; Forrest, S. R. Phys. Rev. B 2009, 79, 073302

Lehnhardt, M.; Riedl, T.; Weimann, T.; Kowalsky, W. Phys. Rev. B 2010, 81, 165206

Conclusion:

To reach CW lasing threshold, the triplet state density must reach a steady

state.


Triplet Management Decreases Saturation Density

Host:

Alq3

Emitter:

DCM2

Host

Alq3

Guest

DCM2

S

T=1.8eV

T

manager

ADN

T=1.7eV

S

T=2.0eV

S

Manager

: ADN

Emission

400 500 600 7000.0

0.2

0.4

0.6

0.8

1.0

DCM2Alq3

PL (

norm

aliz

ed)

Wavelength (nm)

ADN

1.5 1.8 2.1 2.4

ADN

Alq3

Inte

nsity (

arb

. u

nit)

Energy (eV)

DCM2

Triplet State

measurement


Exceeding the CW threshold

Conditions 2.4kW/cm2, 10Hz/18μs

Consistent with theory

Single pulse 100 μs lasing

time Degradation limited

Implications: Higher intensity and higher

efficiency OLEDs

Significant step toward

electrically pumped lasing

“Continuous-wave threshold exists for organic semiconductor lasers”, Y. Zhang and S. R. Forrest, Phys.

Rev. B, 84, 241301 (2011).

“Enhanced efficiency in high-brightness fluorescent organic light emitting diodes through triplet

management”, Y. Zhang, et al., Appl. Phys. Lett., 99, 223303 (2011).


A Bottom-up Pathway to Chiral Metamaterials

Paras Prasad, U of Buffalo

effn Pushing toward values ≥1 will enable chiral

optical metamaterials

Synthesize new chiral conjugated polymers with high intrinsic

optical activity at visible wavelengths (molecular-scale chirality)

Control the supramolecular organization of these chiral polymers

to maximize chirality in thin film nanocomposites (supramolecular

chirality)

Create nanocomposites with inorganic components that enhance

chirality

Metallic nanocrystals (gold, silver) for plasmonic enhancement

Semiconductor nanocrystals (quantum dots) for excitonic

enhancement

Pattern nanocomposites to create chiral nanostructures (meso-

scale chirality)


First demonstration of plasmonic enhancement of chirality

in a polymeric thin film doped with gold NPs.

B BO

O O

O

NS

N

Br Br

NS

N

n

Polymerization

Poly(fluorene-alt-benzothiadiazole) (PFBT) film with dispersed Au NPs

300 400 500 600 700 800-2000

-1500

-1000

-500

0

500

1000

CD

(md

eg)

Wavelength(nm)

PFBT

PFBT- AuNPs(8nm), 1/1

effn

0.02

“Chiral Poly(fluorene-alt-benzothiadiazole) (PFBT) and Nanocomposites with Gold Nanoparticles: Plasmonically and Structurally Enhanced Chirality,” Heong Sub Oh, Sha Liu, HongSub Jee, Alexander Baev, Mark T. Swihart, and Paras N. Prasad, Journal of the American Chemical Society, 2010, 132, 17346–17348. (cited 13 times within 1 year of online publication)

First demonstration of plasmonic enhancement of chirality in

a polymeric thin film doped with gold NPs


B BO

O O

O

NS

N

Br Br

NS

N

n

Polymerization

First demonstration of excitonic enhancement of chirality

First demonstration of excitonic enhancement of chirality

in a polymeric thin film doped with quantum dots.

Polyfluorene film (PFBT) with dispersed CdTe/ZnS quantum dots

A: Pure PFBT B: PFBT with CdTe/ZnS

effn ~ 0.03

Manuscript in preparation


Glass Substrate

Cross-linked

Exposed Region

Post-bake, 95 °C

Glass Substrate

Develop in PGMEA

Glass Substrate

Rinse with propanol

and dry with nitrogen

Glass Substrate

Cross-linked PFBT/SU8

nanocomposite

PFBT aggregates left behind

Process flow for PFBT/SU8

Photopatterning

Glass Substrate Glass Substrate

PFBT/SU8 film Spin-coat

PFBT/SU8

solution Pre-bake, 95 °C

Glass Substrate

PFBT/SU8 film

Shadow mask

UV light


First demonstration of chirality enhancement by doping a chiral polymer in an

achiral photoresist matrix with subsequent photopatterning.

Photopatterning of Chiral Polymers

Polyfluorene PFBT co-dissolved with SU-8, cast into a film and photopatterned with UV light

“Dramatic Structural Enhancement of Chirality in Photopatternable Nanocomposites of Chiral Poly(fluorene-alt-benzothiadiazole) (PFBT) in Achiral SU-8 Photoresist,” Heong Sub Oh, Hongsub Jee, Alexander Baev, Mark T. Swihart and Paras N. Prasad, submitted to ACS Nano.

0.017


Exquisite Control of Molecules to Direct Chemical Reactions

Alex Jen, U of Washington

Self-assembly of Inert Molecules to Confine

Environment

Self-assembly of Photoactive Molecules to

Control Orientation

Photon-

STM

Stochastic switching

Increased conductance of excited state

Decreased conductance of photoproduct

Kim, Houk, Ma, Jen, Weiss, Science 2011, 331, 1312. Highlighted by Chem. & Eng. News March 14, 2011.


Molecular Design for Regio-selective Reaction on Surface

In solution: a) Diels-Alder reaction [4+2] b) Photocycloaddition [4+4]

rarely happens because of geometric constraints

+

+

PEA Photoreaction

(9-phenylethynylanthracene)

On surface: a) Creating defect sites of a

alkanethiolate SAM b) Tethering two MPEA molecules next

to each other on Au surface c) Poising in the correct orientation to

force photocycloaddition

9-(4-mercaptophenylethynyl)

anthracene (MPEA)

S H S S

9-phenylethynylanthracene

disulfide

S H

Kim, Houk, Ma, Jen, Weiss, Science 2011, 331, 1312. Highlighted by Chem. & Eng. News March 14, 2011.


Self Assembly Monolayer with Confined MPEA

• Tunable number and size of defect

sites dependent on concentration of

n-dodecanethiol in ethanol and time

of vapor annealing

• Disulfide molecules assured adjacent

placement of molecules


Study of Single Molecule Switching Dynamics in Confined Environment

Arrow sites: increased conductance

of molecular excited state

Box sites: Decreased conductance of

molecular photoproduct

a)

b)


Electricity Generation with Body heat Choongho Yu, TA&M

First demonstration of electricity generation from polymeric materials

Flexible TE polymers

Connected to

a multimeter

Cut by

scissors

Voltage –Time response

Voltage

Time


Fabrication of polymer Nanocomposites

Pour the mixture

into a plastic container

and dry at room temp.

Dry further in an oven or

dessicator to remove

micro voids and moisture

Mix CNTs and aqueous

stabilizer solution (e.g.,

PEDOT:PSS)

Disperse CNTs by

sonication and then (if

necessary) add polymer

emulsions (e.g., PVAc)

with sonication


Controlling Junctions & Surfaces and Material Morphology

Modifying junctions and surfaces

Heat

transport

Electron transport (by hopping)

Scattering

Nanotube

Junction

Nanoparticle

Vibrational

Spectra

mismatch

Frequency

Material B Material A

Ph

on

on

de

nsit

y o

f s

tate

s

Phonon

transport

across junction

can be

suppressed.

It is feasible to dramatically

change:

- Electrical conductivity

- Thermopower

- Thermal conductivity

for desired objectives.


Electrical Transport Increase without Changing Thermal Power

Yu et al. ACS Nano, 5, 7885 (2011). Used p-HipCo SWCNTs

(high CNT concentrations)

Power

Factor


Double-Wall Nanotubes

Carbon nanotube wt%

0 20 40 60 80 100

Ele

ctr

ical conductivity, (

S/m

)

0

5.0x104

105

1.5x105

2.0x105

2.5x105

Therm

opow

er,

S (

V/K

)

0

10

20

30

40

50

60

70

S

CNT wt%

0 20 40 60 80 100S

2

W/m

-K2

)0

200

400

600

800

800 %

improvement in

Power Factor

over SWNT

Double-wall carbon nanotube wt%

DWNT + PEDOT:PSS only composites


Layer by Layer Removal of Graphene: single-atomic-layer-resolution lithography

Dimiev, A.; Kosynkin, D. V.; Sinitskii, A.; Slesarev, A.; Sun,

Z.; Tour, J. M. “Layer-by-Layer Removal of Graphene for

Device Patterning,” Science 2011, 331, 1168-1172.


Layer-by-layer removal and patterning of GO

The method works with the four different types of graphene and graphene-

like materials: -graphene oxide,

-chemically converted graphene,

-chemical vapor–deposited graphene (CVDG),

-and micromechanically cleaved (“clear-tape”) graphene


Graphene nanoribbons heat circuit as de-icing coating for phased array antennas and radomes

Yu Zhu; Wei Lu and James M. Tour*

Department of Chemistry and Smalley Institute, Rice University, Houston, TX 77005

The MWCNTs are split by the potassium metal vapor

treatment and retain the resiliently rigid mechanical

properties of the parent nanotubes. The produced

graphene nanoribbons are highly conductive (800

S/cm) and dispersible in solvents such as

chlorosulfonic acid and othordichlorobenzene. ACS

Nano 2011, ASAP.

A thin graphene nanoribbon film is practically transparent for RF

electromagnetic waves.

With the layer thicknesses around 100 nm ,the film is suitable for a de-icing

cover to replace conventional heat circuits for phased array antennas and

radomes.

Quenched with styrene

2 um

Quenched with isoprene

4 um


Large Area De-icing coating for Antenna and Radome

De-icing test under -20°C conditions

Collaboration with Lockheed Martin

•Thickness of heating layer is not more than 100 nm

•Transparency for RF radar signals of any polarization

•10 grams of graphene nanoribbons per 10 m x 10 m antenna

aperture/face. Cost is $10 in nanoribbon starting material

Spray coated GRN film on flexible

polymer substrate


Growth of Graphene from any Carbon Source

J. Tour, Rice University Impurities remain on top of foil

1000°C

Ruan, G.; Sun, Z.; Peng, Z.; Tour, J. M. “Growth of Graphene from Food, Insects,

and Waste,” ACS Nano 2011, 5, 7601–7607.


Graphene from Girl Scout Cookies

Google “graphene girl scout cookie”= 51,000 hits.

The YouTube video has 40,000 hits too.

Converted to a single sheet of graphene, one box of Girl Scout Cookies can be

worth $15 billion, and would cover nearly 30 football fields


Upconversion with Terrestrial Solar Photons


Upconversion-Powered Water Splitting Photoelectrochemistry

F. Castellano, Bowling Green U

Chem. Commun. 2012, 48, 209-211.

The first example of water-splitting photoelectrochemistry being

operated solely under the influence of upconverted photons.


Upconversion Visualized in a PEC Cell

Photograph of the cell in action, pumped

by long-pass filtered lamp light delivered

via fiber optics to the outside of the

PhotoElectroChemical (PEC) cell

Shuttered current/time response of a

WO3 photoanode biased to +0.9 V vs

Ag/AgCl in 1.0 M H2SO4


Recognitions

Metamaterials and plasmonics for rf photonics

Rf Antenna

Rf waveguide

EO modulator

Optical Fiber Optical Fiber

Signal out Signal out

New Hybrid Antenna

Rf Input

On Going Transition:

EO Polymer is one of the key technologies for its development in AFRL


Flexible Photodetector

Summary

• Program Focused on developing New and Controlled

Properties

• Not applications specific, but often use applications to guide

the properties focuses

• Scientific Challenges

- Discover New Properties

- Control Properties

- Balance Secondary Properties

• General Approaches

- Molecular Design

- Processing Control

- Establish Structure Properties Relationship

lee, charles - organic materials chemistry - spring review 2012

Technology

public release distribution

unique properties

controlled properties

research objective

organic lasers

organic materialschemistry09

future capabilities

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