Polyelectrolytes and Nanoparticles: Synthesis and Mediation · ACS-PRF Summer School on...

ACS-PRF Summer School on Nanoparticles 2004

R.C. Advincula/ University of Houston

Polyelectrolytes and Nanoparticles: Synthesis and Mediation

Rigoberto C. AdvinculaRigoberto C. Advincula

Department of Chemistry

University of HoustonUniversity of HoustonHouston, TX 77204

E-mail: [email protected] www.chem.uh.edu



Nanoscience or Nanotechnology ?

- self-assembly- quantum effects- molecular building blocks- surface science- Self-assembly or directed

assembly



Nanostructured Materials

Molecular and Macromolecular Design and Engineering at the nanoscale

-Design, synthesis, characterization-application

Organic and PolymerMaterials

- Surfactants, polymers, dendrimers, molecular organic crystals, films,

micelles, nanoparticles-Functional materials (optical,

electrical, spectroscopic)-Isotropic and “soft”

Inorganic Materials- crystals, quantum dots,films,

nanotubes, nanoparticles- Functional materials (optical,

electrical, spectroscopic)-Anisotropic or long

range order and “hard”

Hybrid materials/Nanocomposites

- Interfacial Phenomena

- Ultrathin Films

- Crystal Eng. - Solid state- High Vacuum

-FundamentalScience

-Technology



Convergence of Materials in Interfacial and Colloidal Phenomena

500 nm

100nm

• Quantum dot nanoparticles• Colloidal particles• Organic nanoparticles• Polyelectrolytes, surfactants• Hybrid organic-inorganic• nanocomposites



Innovative Surface Sensitive Analytical Techniques

θ0

He-Ne Laser (632.8 nm)

Polarizer

Lenses

CCD cameraElectrochemicalinstrumentation

Electrochemical cell

Microcontact Printed SAM (ODT) Polypyrrole

Au

Electropolymerization

• Scanning probe microscopy• Time-resolved and frequency resolved

spectroscopy• Evanescent wave techniques• Light scattering methods• Surface sensitive acoustic methods



Patterning Methods and Devices

ODT

Gold

Stamp

Schematic representation of microcontact printing

PDMS Stamp

ODTsolution

Ink

ODT

Driedunder niotrogen

Micropatterned ODT SAM

ODT SAM

SiliconSubstrateGate

molecularlyassembledoligothiophenesemiconductor

source drain

source drain

BOTTOM CONTACT

TOP CONTACT

SiO2

• Lithographic and nonlithographic methods• Photolithography and soft-lithography• Semiconductor devices• Display and nonlinear optical devices



Nanoparticles

1. Silver: catalysis, photographic processes

2. CdS: optoelectronics,photoluminescence

3. Gold: optoelectronics, electronics, biosensors

4. Silica: insulator, catalyst support, membrane, filling material

5. Palladium: catalysis6. TiO2: photoelectrochemistry7. Metal oxide: Mg, Ca, Mn, Fe, Co, Ni,

Cu: magnetic properties8. Polymer: conducting composite,

drug delivery

ISynthesis

(Stable and well-defined nanoreactor)

ISynthesis

(Stable and well-defined nanoreactor)

Nanoparticles with1. Size and shape uniformity2. Stability

1. Unique properties2. Ordered deposition3. Selective decoration

Nanoparticles with1. Size and shape uniformity2. Stability

1. Unique properties2. Ordered deposition3. Selective decoration



Synthesis of Nanoparticles: the Concept of Nanoreactors

Cationicpolyelectrolytes

Amphiphilicblock copolymers

(PS-b-P2VP)Dendrimers(PAMAM)

Self-assembledmonolayers

(n-Alkanethiols)

• “Stable Nanoreactor” for the control of size and shape of nanoparticles

• Strategies for the gold nanoparticle preparation

Nanoparticles as colloidal systems of a solid-state material -dimensions in between molecules and a bulk solid-state material.

Strategies for the synthesis of nanoparticles: surfactant or polymeric amphiphiles (block copolymers) micelles as a “nanoreactor” for nanoparticle synthesis.

Mechanism - Metal ions trapped inside the particles exposed to precipitating or reducing agents to start nanoparticle growth: the number of metal ions initially trapped inside the particle determine growth.

Key step: Control over the diffusion of reagents into the micelle.

Design: The possibility of attaching coordinating ligands to the polymer in order to stabilize both precursors and nanoparticles within.

Nanoparticles and nanostructured Films; Fendler, J. H., Ed.; Wiley-VCH; Weinheim, 1998.



Synthesis of Nanoparticles in General

a cb

Schematic representation of the concurrent process during reduction reaction inside block copolymer micelles.

a) Reduction is initiated by the entry of the reducing agent into the core of the micelles loaded by precursor salt.

b) Destabilized micelles exchange block copolymer and may coagulate.

C) “Empty” micelles are formed besides block copolymer stabilized gold particles.

H: reduction agent; O: precursor salt; crystal.

Wavelength (nm)

400 450 500 550 600 650 700

Abs

orba

nce

0.0

0.1

0.2

0.3

0.4

0.5

P4VP (NaBH4)PAMAM Dendrimer (UV)PS-b-P2VP (Hydrazine)

__200 nm

Star block copolymer

(PS-b-P2VP)N:Au=10:1



Mechanism:

• Reduction:

HAuCl4reduction

• Reducing agent (Organic or inorganic reducing agent, UV irradiation, electrochemistry, etc)

• The relative rate of Nucleation and Growth of Nanoparticles- Manage the particle size

• Nucleation

Where Rc is radius of initial particle, γ is interfacial tension, and C/Co is the degree of supersaturation.

• Growth- Ostwald-ripening process: One particle per domain

AuCl-

Cl-

Cl-

Cl-

)Ln(C/CR

oC

γ∝



PS-b-P2VP Micelles Containing Gold nanoparticles: Aggregation

M. Moller et al., Macromolecules, 2000, 33, 4791.

PS(300)-b-P[2VP Au0.5(300)]

A dried filmC=0.01mg/ml solution(a) Directly after deduction (b) 30 min after reduction



Organic Ultrathin Film Multilayer Assemblies

• How different is this from spin-coating?

• Nanostructured multilayer architecture

• control molecular orientation and organization on the nanoscale

• precisely tunes the macroscopic properties of the organic and polymer thin films

• Applications in microelectronics, electro-optics, sensors, and biotechnology

• To be explored? Organic and polymer multilayers by vapor deposition and thermal evaporation methods

Chemisorption

Organicand Polymeric

Ultrathin Multilayer films

Langmuir-Blodgett (LB) Film

Layer-by-Layer(LbL) Film

SiO

OSiO

SiO

OSiO



Nanostructured Layer-by-layer Self-assembly from Solution

• Electrostatic (coulombic forces)• Interfacial phenomena • Solution properties:

concentration,pH salts,temperature

• Surface sensitive techniques

-

- - -

------

----- ++

+

+++

++

----

----

+ ++++`

++

+

++

++

+

+++

++

--

--+ ++++`

++

+

++

+

+++

++

---

------

-----

Deposition Process

Equilibrium of Deposition



Structure – Fuzzy Nanoassemblies?

1 2 3 4 5 6 7 8 9 10 Layer Number

subs

trat

e

Rel

ativ

e C

ompo

sitio

n0.0

0.2

0.4

0.6

0.8

1.0

- Neutron reflectometryBragg peaks appear (NR-3 ~6)((A/B)m(A/Bd))n, m = 1, 2, 3

- Interpenetration- Stratification

Decher, G. Science 1997, 277, 1232.

(A/Bd)n



A Variety of Materials for the LbL Technique

N Cl

SO3Na

C O

OH

CH2

NH3

N coN

H

CH2CH2NH2

Cl

n n

n

n

n n

Poly(diallyldimethylammonium chloride) (PDADMAC)

Poly(allyamine hydrochloride) (PAH)

Poly(styrene sulfonated) (PSS)

Poly(ethyleneimine) (PEI)

Poly(acrylic acid) (PAA)

bolaamphiphiles, phthalocyanine, Azobenzene dyes, cyanine dyes

Small organic materials

Charged nanoobjects; Silica, metal oxides, semiconductor nanoparticles (CdS, TiO2, CdSe, CdTe), metal colloids (Au, Pt), charged latex spheres, microcrystallites, metallo-supramolecular complexesclay platelets; Montmorillonte, hectorite, saponitea-zirconium phosphate, graphite oxide, MoS2

Inorganic materials

proteins, virus, lipids, albumin, DNA, polypeptides, enzymes, avidin, bacteriorhodopsinPolysaccharides; chitosan, dextan sulfate, cellulose sulfate

Bio-organic materials

conjugated polymer; poly(phenylene vinylene) precursor, poly(p-phenylene), polyaniline, sulfonated polyaniline, polythiophenes dendrimers, liquid crystalline polyelectrolytes, diazo-resins, azo-polymers

PolyelectrolytesTypical polyelectrolytes



New Applications and Devices from LBL films

Ultrathin Film Electrochromic Devices

Electrochemical Photovoltaic Devices

Modification of PLED and OLED Devices

Field Effect Transistor Devices

Anti-reflective Coatings

Corrosion Resistance Films

Solid-State Polyelectrolyte materials

Nanoporous and Ion-permselective Membranes

Electro-resistive and Piezoelectric Thin FilmsNonlinear Optical Thin Film Materials

Chemical and Gas-sensor Devices

http://www.chem.fsu.edu/multilayers/multilayerpatents.htm



POLYELECTROLYTES and NANOPARTICLES

• Mediate synthesis of nanoparticles: precursor approach• Adsorption of nanoparticles to polyelectrolytes and vice

versa: fundamental studies in adsorption kinetics, flocculation, electrical double layer, etc.

• Active and passive media: separation of nanoparticles, synthesis of nanoparticles, interaction of nanoparticles (stabilization)

• Preparation of thin films containing nanoparticles: flat substrates and colloidal particles with nanoparticles

• Coating of Colloidal Particles with Polyelectrolyetes and Nanoparticles: subject of a future review

• Tethering of polyelectrolytes to nanoparticles: DNA and proteins.

• Nanocomposite preparation



Nanoparticles and colloidal stability

• Particles in colloid (A) uncharged particles are free to collide and agglomerate and (B) charged particles repel each other

• Steric stabilization of particles by (A) entropic effects and (B) osmotic effects

• Droplet of a colloid suspension dried slowly, the particles aggregate at the rim of the droplet because of attractive capillary forces.



Interfacial Behavior of Polyelectrolyte Nanoparticle Systems

• The stability of a colloidal system is primarily determined by the electrostatic and van der Waals interaction present in the system.

• The co-adsorption of nanoparticles to polyelectrolytes causes extensive swelling of polyelectrolyte surface layers

• Surface force measurements: The electrostatic repulsive forces are reinforced by the presence of particles while attractive binding forces are decreased (separation)

• Nanoparticle adsorption is slow due to complex formation, retarded diffusion, and barrier effects.

• Ionic strength, concentration, and adsorption history dependent.• Importance in flocculation and multilayer thin films.



Polyelectrolyte Nanoparticle Composites: LBL assembly



Topic 1: Collective and Individual Plasmon Resonance in Nanoparticle LBL films by Spin-assisted assembly

• Nanoscale films with Au nanoparticles (NPs) and polyelectrolyte LBL were prepared by spin-assembly.

• Plasmon resonance peaks from isolated NPs and interparticle interactions were analyzed from the UV-vis spectra.

• Collective plasmon resonance observed on films with sufficient density: intralayer coupling (620 nm), and interlayer, interparticle resonance observed at 800 nm

• Environment of NP’s in polyelectrolyte critical for sensing.

• Au/PAH-PSS structure deposited on PEI surface• Topographic AFM image and height histogram• UV-vis of solutions for small and large nanoparticle• Tsukruk et. al. Langmuir 2004, 20, 882



Interlayer and intralyer interaction in Au nanoparticles

• UV-visible extinction spectrum of the Au (PAH-PSS) film with 22% Au NP surface density with three major absorption bands

• UV-vis absorption with different NP densities.

• Variation of plasmon resonance peak positions and their intensity ratio

• Tsukruk et. al. Langmuir 2004, 20, 882



Topic 2: Enhanced Luminescence of Quantum Dots on Gold colloids in Polyelectrolyte LbL Media

• Enhancement of PL of the CdSe core-shell QD on gold colloids as a function of distance between metal and QD. LBL polyelectrolytewas uses as spacer layer with distance dependent enhancement and quenching.

• PL intensity versus the number of polyelectrolyte layers betweenthe QD and the gold colloids. Excitation at 550 nm.

• SPR enhancement of the PL• Absorption spectra of Au colloidal film on glass. • Differential AFM image of AU colloidal film on glass.• Artemyev et. al. Nanoletters 20002, 12, 1449



Topic 3: DC Transport in Nanocrystal assemblies

• Follow the film conductivity:function of the number of layers• Linear increase in conductance with increasing layers• Probe both in-layer and cross-layer charge transport• Conductor to insulator transition



Effect of the linker on the conductivity of the assemblies



Topic 4: Electrostatically assembled Fluorescent Thin Films of Rare-earth doped Lanthanum Phosphate Nanoparticles

• LbL films of rare earth (QDs) base on (Ce, Tb, Eu, Dy, etc.) on flat substrates and PS microspheres.

• PL spectra of PS sphere coated with one layer of a mixture of Ce/Tb doped and Ce/Dy doped nanoparticles. 273 nm excitation.

• Plot of PL intensity vs. composition of the mixture of green andyellow NP.

• TEM image of the LaPO4 NPs (green) dried from an aqueous solution illustrating high monodispersity. The close packing is due to the high concentration of NP.

• Caruso et. al. Chem. of Mater. 2002, 14, 4509



Topic 5: Ultrathin Cross-linked Nanoparticle Membranes

• Chemical cross-linking of the ligands attached to the nanoparticles as an effective route to “freeze” interfaces. Vinylbenzene ligand and AIBN initiator from solution

• Nm thick membranes prevent convection but allow diffusion of small molecules across the interface- liquid/liquid interface.

• Fluorescence confocal microscopy on a nanoparticle assembly where an air bubble was introduced by a micropipet showing (a) preferential segregation of the CdSe at the interface at oil/water and water/oil.

• Nanoparticle sheets (free standing)• Organic dye (red solution) becoming entrapped

and then diffusing across a membrane of cross-linked nanoparticles.

• Emrick et. al. JACS 2003, 125, 12690



Topic 6: Grafted Block Copolymer Brushes: Synthesis of Nanoparticles

• Polyelectrolyte brushes of PS and PAA tethered to a Si/SiOx surface using the grafting from strategy. Silver or Pd ions were complexed. NPs were formed after addition of reducing agent and high temperature treatment.

• Analyzed by AFM, FT-IR and XPS. • Boyes et. al. Macromolecules 2003, 36, 9539



Topic 7: Complexation Approach to Hybrid Nanocomposite Materials

• In-situ synthesis of nanoparticle on the surface of microspheres by employing ion exchange of counterions in the electrical double layer of latex beads

• The use of a three layer hybrid core shell particle as structural units of the nanocomposite material.

• TEM micrographs of PMMA-PMASS beads covered with CdS and Ag NP’s obtained under different magnification. (A) periodic array, (B) fragment (C) high resolution image of CdS particle.

• Kumacheva, J. Am. Chem. Soc. 2002, 124, 14512



Topic 8: Catalysis: Selective Hydrogenation by Pd Nanoparticles Embedded in Polyelectrolyte Multilayers

• Catalytic properties of nanoparticles embedded in polyelectrolyte films. High surface area by limiting aggregation of NPs (stabilization) and also impart catalytic selectivity (decreases unwanted isomerization) by restricting access to active sites.

• TEM image of 3.5 bilayers in copper grid

• Bruening et. al. JACS 2004, 126, 2658



Topic 9: Nanorainbows: Graded Semiconductor Films from Quantum Dots

• LBL deposition of 1-D graded semiconducting films. Possibilities for photodetectors, bipolar transistors, waveguides, etc.

• CdTe dispersion of different sizes allow for the preparation of graded films.

• AFM image of the PDDA/CdTe films with polymer and NPs as last layers

• PL spectra of different sizes• Cross-sectional confocal microscopy

image of the graded LBL film of CdTe NPs made of 10 bilayers of green, yellow, orange, and red NPs. 220 nm thickness.

• Kotov et. al. JACS 2001, 123, 7738



Topic 10: Lateral Patterning of CdTe Nanocrystal Films by the Electric Field Directed LBL Assembly Method

• Electric field directed LBL assembly (AFDLA) was used to patter 2 different types of CdTe nanocrystals on ITO. Pixel array of CdTe with different colors for EL device.

• Use of bias voltage to control amount of deposition of NP and polyelectrolyte (PDDA): monitored by QCM

• Large contrast was observed.• PL spectra of different sizes• Gao et. al. Langmuir 2002, 18, 4098



Patterning and EL Device Behavior

• PL and EL spectra of PDDA/CdTe with different sizes. EL spectra at 5V bias.

• Lateral structures of the CdTe (green) and CdTe (red).

• Large contrast was observed.• PL spectra of different sizes• Gao et. al. Langmuir 2002, 18, 4098



ADVINCULA GROUP

• Project 1. Synthesis of Nanoparticles using Star Block copolymers

• Project 2. REDOX Formation of Au Nanoparticles in LBL Films



The Concept of Block Copolymers as Nanoreactors

Cationicpolyelectrolytes

Amphiphilicblock copolymers

(PS-b-P2VP)Dendrimers(PAMAM)

Self-assembledmonolayers

(n-Alkanethiols)

• “Stable Nanoreactor” for the control of size and shape of nanoparticles

• Strategies for the gold nanoparticle preparation

Nanoparticles as colloidal systems of a solid-state material -dimensions in between molecules and a bulk solid-state material.

Strategies for the synthesis of nanoparticles: surfactant or polymeric amphiphiles (block copolymers) micelles as a “nanoreactor” for nanoparticle synthesis.

Mechanism - Metal ions trapped inside the particles exposed to precipitating or reducing agents to start nanoparticle growth: the number of metal ions initially trapped inside the particle determine growth.

Key step: Control over the diffusion of reagents into the micelle.

Design: The possibility of attaching coordinating ligands to the polymer in order to stabilize both precursors and nanoparticles within.



Synthesis of Nanoparticles in General

a cb

Schematic representation of the concurrent process during reduction reaction inside block copolymer micelles.

a) Reduction is initiated by the entry of the reducing agent into the core of the micelles loaded by precursor salt.

b) Destabilized micelles exchange block copolymer and may coagulate.

C) “Empty” micelles are formed besides block copolymer stabilized gold particles.

H: reduction agent; O: precursor salt; crystal.

Wavelength (nm)

400 450 500 550 600 650 700

Abs

orba

nce

0.0

0.1

0.2

0.3

0.4

0.5

P4VP (NaBH4)PAMAM Dendrimer (UV)PS-b-P2VP (Hydrazine)

__200 nm


(PS-b-P2VP)N:Au=10:1



Project 1: Reduction of Au in Star Copolymers

N

n m

PS P2VP

1. Synthesis of PS-b-P2VP

2. Synthesis of Star Block Copolymer

PS-b-P2VP + Coupling Agent(EGDMA)

(Ethylene glycol dimethacrylate)H2C=C(CH3)CO-OCH2CH2O-COC(CH3)=CH2

N + HAuCl4NH+ AuCl4

-4HAuCl4 + 3N2H4 --> 4Au + 3N2 + 16 HCl

1. Polyionic block 2. Reduction with Hydrazine

Polyionic star block copolymer Reduction, Nucleation and Growth

Youk, J, H.; Yang, J.; Locklin, J.; Park, M.K.; Mays, J.; Advincula, R.” Controlled Preparation of Gold Nanoparticles using Well-defined Star Block Copolymers” ACS-Polymer Preprints, 2001 42, 2, 358.

- Synthesis by anionic polymerization, complete characterization necessary

-Stability in solution compared to micelles

- Control of diffusion of salts and reducing agent in organic solvents

Youk, J. H.; Park, M.-K.; Locklin, J.; Advincula, R.; Yang, J.; Mays, J.; “Preparation of Aggregation Stable Gold Nanoparticles Using Star-Block Copolymers”, Langmuir 2002; 18(7); 2455-2458.



Characterization of Star Block Copolymer: GPC

1.46155,100106,200Star Block Copolymer

1.2241.20033.800PS-b-P2VP

1.2535,30025,100PS

PDIMwMnPolymer

Star block copolymer: After fractionation with THFPS: 65.1 wt%, P2VP:34.9wt%

Retention time (min)

20 25 30 35

PS

PS-b-P2VP




UV-vis spectroscopy

Wavelength (nm)

400 450 500 550 600 650 700

Abs

orba

nce

0.0

0.5

1.0

1.5

2.0

2.5

Au:N = 1:10 Au:N = 3:10 Au:N = 5:10

• Absorption band at 525 nm for all samples: Surface plasmon resonance of Au nanocrystals)

• Increase of absorbance intensity with increasing the size of gold nanoparticles

Langmuir. R. Advincula, M.K. Park, J.Youk; J. Locklin, J. Yang; J. Mays “The Preparation of Aggregation Stable Gold Nanoparticles using Star Block Copolymers”- ASAP article-web



TEM

N:Au=10:1Avg. Size: d=4.1 nm



TEM

N:Au=10:3

Avg. Size: d=5.5 nm



TEM

N:Au=10:5

Avg. Size: d=6.7 nm



UV-vis Spectroscopy (After several Months)

Wavelength (nm)

400 450 500 550 600 650 700

Abs

orba

nce

0.0

0.5

1.0

1.5

2.0

2.5

N:Au=10:1N:Au=10:3N:Au=10:5

• Peak position shifted from 525 nm to 530 nm for N:Au=10:3 and 10:5 after 1 month

• Shift to longer wavelength :Increase of the average size of gold nanoparticles

• Increase of absorbance intensity for N:Au=10:3 and 10:5 with time due to the additional reduction process



TEM (After several months)






Project 2a.Project 2a. Nanoparticle formation from Poleylectrolyte Nanoparticle formation from Poleylectrolyte Complexes of SexithiophenesComplexes of Sexithiophenes

HAuCl4

Fast

Slow

PSS+ATTComplex

Wavelength (nm)

250 350 450 550 650

Abs

orba

nce

0

1

2

3

0.19/10.38/10.95/11.91/13.82/15.73/1TT+PSSSolution

250 350 450 550 6500.0

0.1

0.2

0.3

0.4

0.50.19/10.38/10.95/1

TT/HAuCl4

• Suggestion of Mayer and Mark (Eur. Polym. J., 1998, 34, 103)

1. Polymer containing sulfur would have the high affinity to gold surfaces

2. Polymer possessing reducing groups could be very suitable

• PSS increased the solubility of terthiophene amphiphile

S S

S

N+

CH - CH2m

Na+SO3-

CH - CH2m

SO3-

S SS

N+PolyelectrolyteComplex (PEC)

Poly(sodium styrenesulfonate) (PSS)

Amidatedterthiophene

(ATT)

+

Youk, J, H.; Locklin, J.; Xia, C.; Park, M.K. and Advincula, R.”Langmuir 2001 17(15); 4681-4683.



Coupling of Terthiophenes to form Sexithiophenes simultaneous with nanoparticle formation

-

--

-

-

-

--

-

- -

CH - CH2

CH - CH2

N+

(CH 2)6

S

S

CH - CH2

N+

(CH 2)6

S

S

S S

S

S

S

N+

(CH 2)6

l m

n

+.

SO 3- SO 3

-

SO 3-

• Sexithiophene bolaform amphiphile formation

• Mechanism (electrochemical or oxidative) needs to be determined

• Stabilization of gold particles is very important

• Characterization of complexes is very important

• New materials combining metallic, semi-conductor and organic materials: interesting electrical and optical properties.

Wavelength (nm)

250 300 350 400 450 500 550 600 650

Abs

orba

nce

0.0

0.5

1.0

1.5

PSS + ATT + HAuCl4PSS+ ATT + FeCl3PSS + AST

AST

SS

SN

SS

SS

SS

NN

SS

SN +



TEM Characterization

0.38/1 0.95/1 5.73/1

300 nm

- As the terthiophene concentration increases, the size of nanoparticles increases

- Nanoparticle partially stabilized: inhomogeneous growth and aggregation

- Increase in size, loss of spectroscopic properties associated with nanoparticle

Youk, J, H.; Locklin, J.; Xia, C.; Park, M.K. and Advincula, R.” Preparation of Gold Nanoparticles from a Polyelectrolyte Complex Solution ofTerthiophene Amphiphiles” Langmuir 2001 17(15); 4681-4683.



Project 2b. LBL Films as Nanoreactor Hosts for Nanoparticle Synthesis

Preparation of Gold Nanoparticles with PSS: Preparation of Gold Nanoparticles with PSS: WaterWater--soluble Terthiophene Complexsoluble Terthiophene Complex

(Youk et al. Langmuir 2001, 17, 4681.)(Youk et al. Langmuir 2001, 17, 4681.)

• REDOX reaction occurs between the terthiophenemoeity and the Au precursor with formation of AuNanoparticles and sexithiophene• Au nanoparticle partially stabilized by the PE complexresulting in irregular growth and aggregation



Growth of PVP-3T and PAA films



Gold Nanoparticle Formation in LBL Multilayer Films

• Red-shift in absorbance of the 3T moiety from 368 to 396 nm attributed to coupling of the terthiophene units to form sexithiophene with simultaneous formation of Au nanoparticles (surface plasmon peak = 580 nm)

• Position of the Au SP band and presence of broad absorption tail around 700 nm indicate aggregation and/or particles that deviate from a spherical geometry

Before After

J. Phys. Chem. B 1999, 103, 7441.Adv. Mater. 1998, 10, 133.



TEM Imaging

TEM image of a 3 bilayer PVP3T/PAA film containing Au nanoparticles after ~ 50 hrs at

60 ˚C/95% humidity. Scale bar = 200 nm.

TEM image depicting dendritic nanostructures formed with the PVP3T/PAA thin film.



Conclusions

• Nanoparticle (NP) synthesis and colloidal dispersions are essential nanomaterials: high surface area and qunatum size effects ( PL and plasmons)

• Polyelectrolytes can be used to mediate synthesis of NPs from precursors or as media for film assembly of nanoparticles

• Interaction of NPs and nanoparticles follows classical colloidal phenomena

• Advantages in stability and processing

• Synthesis and assembly of nanoparticles in films and colloids: active and passive role of polyelectrolytes

• Film preparation results in a variety of functions and phenomena observed: sensor, devices, optical materials, etc.



AcknowledgmentAcknowledgment

Students: Chuanjun Xia, Mi-kyoung Park, Xiaowu Fan, Jason Locklin, Derek Patton, Tim Fulghum, Suxiang Deng, Prasad Taranekar, Post-Docs: Dr. Seiji Inaoka, Dr. Ji Ho Youk, Dr. Shuangxi Wang, Dr. Qing-Ye Zhou, Dr. Ken Onishi,Dr. Akira Baba, Dr. Mitchell Millan.Collaborations: Wolfgang Knoll (MPI-P), Futao Kaneko ( Niigata University), Hiroaki Usui (TUAT)Zhenan Bao (Stanford University), Jimmy Mays (UT/ORNL)

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Polyelectrolytes and Nanoparticles: Synthesis and Mediation · ACS-PRF Summer School on...

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