Microemulsions as Templates for New Materials

Project I: Metallic NanoparticlesProject II: High Surface Area Polymers

Dr. Cosima StubenrauchSchool of Chemical and Bioprocess Engineering,

UCD, Ireland

Dublin, 27th September 2007

emulsion „microemulsion“

~ 5 nm ~ 5 µm

J.H. Schulman, W. Stoeckenius, L.M. Prince, J. Chem. Phys., 1959, 63, 1677

oil

H2O

What is a Microemulsion?

thermodynamically stable

surfactant concentration < 1 % surfactant concentration > 10 %

thermodynamically unstable

H2O

oil

Structures of Microemulsions

bicontinuous µe ~ 10 - 50 nm

A ~ 150 - 30 m2/g

o/w-µe ~ 5 nm

A ~ 60 - 240 m2/g

w/o-µe ~ 5 nm

A ~ 60 - 240 m2/g

Goal: High Surface Area Material with Surface/Volume Ratio as large as possible via Templated Synthesis!

Dr. Cosima Stubenrauch, Dr. Reza Najjar, Miguel MagnoSchool of Chemical and Bioprocess Engineering, UCD, Ireland

Prof. Frank DiSalvoDepartment of Chemistry, Cornell University, Ithaca, NY

Prof. Vincenzo Turco Liveri, Dr. Cristina GiordanoUniversity of Palermo, Italy

Dr. Thomas Sottmann, Prof. Reinhard StreyInstitut für Physikalische Chemie, Universität zu Köln, Germany

Project I: Metallic Nanoparticles

oil + surfactant + aqueous phase

(1) NaBH4(2) H2PtCl6

Capek, Adv. Colloid Interface Sci., 2004, 110, 49; Uskokovic, Surf. Rev. Lett., 2005 , 12, 239.

1

~ 5 nm

1 2

t (exchange of reactants) t (fusion-fission)

2

~ 5 nm

initial droplet size ~ final nanoparticle size

Pt Pt

w/o-µe w/o-µe

Project I: Metallic Nanoparticles - Concept

Project I: Metallic Nanoparticles - Concept

wefb = water emulsification failure boundary= droplet formation

(2) add metal precursor (e.g. H2PtCl6) to base system and remeasure wefb

(1) add reducing agent (NaBH4) to base system and remeasure wefbStrategy

n-decane/AOT 0.85 0.90 0.95 1.00

0.05

0.10

H2O/NaCl

C4E0

1

2

_2

wefb

C. Stubenrauch, T. Wielpütz, T. Sottmann, C. Roychowdhury, F. J. DiSalvo, COLSUA, submitted

Project I: Metallic Nanoparticles - Goal

Intermetallic Pt/Bi and Pt/Pb Nanoparticles for Fuel Cells

DiSalvo et al., J. Electr. Soc. 2004, 151, A971

Challenges• time-consuming studies of phase diagrams• large difference in reduction potentials: [PtCl6]2-/[PtCl4]2- = +0.68V,

[PtCl4]2-/Pt = +0.76V, Bi3+/Bi = +0.22 V Pb2+/Pb = -0.13 V • reaction of NaBH4 with H2O

oil + surfactant + aqueous phase

(1) NaBH4 (2) H2PtCl6

1

~ 5 nm

2

~ 5 nm

w/o-µe w/o-µe

+ Bi(NO3)3

initial droplet size ~ final nanoparticle size

Bi/Pt Bi/Pt

+ Pb(NO3)2(2) H2PtCl6

or

Nanoparticle content of aqueous phases

aqueous phase (g)

n-decane(g)

SDS(g)

1-butanol

(g)

Water dropletdiameter (nm)

Pt H2PtCl6 0.2027 2.1852 0.1152 1.2662 11 ± 3

NaBH4/NaOH 0.2007 2.1856 0.1169 0.9409 11 ± 3

Bi Bi(NO3)3 0.1516 2.1856 0.1159 0.5579 11 ± 3

NaBH4/NaOH/NaNO3 0.1596 2.1869 0.1157 0.2754 11 ± 3

Pb Pb(NO3)2 0.1501 2.1878 0.1157 0.8671 11 ± 3

NaBH4/NaOH/NaNO3 0.1507 2.1889 0.1158 0.4792 11 ± 3

Pt/Pb H2PtCl6 / Pb(NO3)2 0.1515 2.1901 0.1159 0.8129 11 ± 3

NaBH4/NaOH/NaNO3 0.1507 2.1909 0.1152 0.4816 11 ± 3

Pt/Bi H2PtCl6 / Bi(NO3)3 0.1505 2.1901 0.1171 0.3319 11 ± 3

NaBH4/NaOH/NaNO3 0.1503 2.1858 0.1159 0.4861 11 ± 3

Compositions of microemulsions containing metal precursor and reducing agent;all microemulsions were titrated with 1-butanol to determine the webf;

Project I: Metallic Nanoparticles - Results

R. Najjar, C. Stubenrauch, JCIS, manuscript in preparation

b = 0.05, wA = 0.05, T = 21°C

Project I: Metallic Nanoparticles - Results

Inte

nsi

ty/ a

.u.

2θ / °

bismuth

Inte

nsi

ty/ a

.u.

2θ / °

Inte

nsi

ty/ a

.u.

2θ / °

bismuth

Inte

nsi

ty /

a.u

.

2 / °10 20 30 40 50 60 70 80 90

C. Stubenrauch, T. Wielpütz, T. Sottmann, C. Roychowdhury, F. J. DiSalvo, COLSUA, submitted

bismuthplatinum

2? / °

Inte

nsity

/ a.u

.

platinumplatinum

2? / °

Inte

nsity

/ a.u

.In

ten

sity

/ a.u

.

2 / °10 20 30 40 50 60 70 80 90

platinum

2? / °

Inte

nsity

/ a.u

.

platinumplatinum

2? / °

Inte

nsity

/ a.u

.In

ten

sity

/ a.u

.

2 / °10 20 30 40 50 60 70 80 90

R. Najjar, C. Stubenrauch, C. Giordano, V. Turco Liveri, preliminary results

210 20 30 40 50 60 70 80 90

Inte

nsi

ty / a

.u.

Quartz Substrate Pt:Bi = 1:1

Pt/Bi nanoparticles prepared in microemulsion

20 – 30 ° Glass Substrate

20 – 30 ° Glass Substrate

Project I: Metallic Nanoparticles - Techniques

Phase Diagrams of Microemulsions• 3 water basins and 1 cryostat; available group Dr. Stubenrauch

Characterization of Metallic Nanoparticles

• UV/VIS – completeness of reduction; available group Dr. Stubenrauch • XRD (X-ray diffraction) or WAXS (wide angle X-ray scattering) –

composition; available groups Dr. Carr, Dr. Dowling but currently “out of order”

• SAXS (small angle X-ray scattering) – size, size distribution and shape; SFI equipment call Dr. C. Stubenrauch 344,400 €

• Scanning Electron Microscope – size and shape; SFI equipment call Prof. D. MacElroy 1,325,998 €

Dr. Cosima Stubenrauch, Miguel MagnoSchool of Chemical and Bioprocess Engineering, UCD, Ireland

Dr. Iseult Lynch, Dr. Anna Salvati, Prof. Kenneth DawsonSchool of Chemistry and Chemical Biology, UCD, Ireland

Renate Tessendorf, Dr. Thomas Sottmann, Prof. Reinhard StreyInstitut für Physikalische Chemie, Universität zu Köln, Germany

Project II: High Surface Area Polymers

bicontinuous µeA ~ 150 - 30 m2/g

AIMporous polymer with A ~ 150 - 30 m2/g

Raj et al. Polymer 1995, 36, 2637Henzte et al. Top. Curr. Chem. 2003, 226, 197

RESULTporous polymer with A ~ 3 - 0.6 m2/g

REASONtstructural changes << tpolymerisation

SOLUTIONslow down / arrest structural changes

IT IS ALL A MATTER OF TIMESCALES!IT IS ALL A MATTER OF TIMESCALES!

Project II: High Surface Area Polymers - Concept

Stubenrauch, C., Tessendorf, R., Strey, R., L., Lynch, I., Dawson, K.A., Langmuir, 2007, 23, 7730

0.00 0.05 0.10 0.15 0.20 0.25 0.30

T /

°C

25

35

45

55

65

75

2

1

3

H2O - C12H26 - LutensolAO5

_2

H2O – n-dodecane – C13/15E5

= 0.5

Project II: High Surface Area Polymers - Concept

water- (oil-) soluble high surface area polymer

polymerisable aqueous (oil) phase

water (oil) oil (water)

organogel (hydrogel)

arrest

replace1 2

3 4

po

lymerise

remo

ve

Remeasure Phase Diagram after each compositional change!

Lynch, I., Dawson, K. A., Macromol. Chem. Phys. 2003, 204, 443 and references therein.

(1) High Surface Area p-NIPAm = Stimuli-Responsive Hydrogel

pharmazeutical applications: control of release rate for drug delivery (high surface area = small pore size = fast

response)

biomimetic material: functionalize the polymer with biologically active entities

Project II: High Surface Area Polymers – Goals

(2) Conjugated Polymers for PV Cells (SRC)

top electrode

transparent electrode„continuous“ TiO2 =electron acceptor

„continuous“ polymer =electron donator

Coakley et al. Chem. Mater. 2004, 16, 4533.

bicontinuous µeA ~ 150 - 30 m2/g

Stubenrauch, Tessendorf, Strey, Lynch, Dawson, Langmuir, 2007, 23, 7730

12-HOA – n-dodecane OH

O

OH

3. Organogel

2. Polymerisable Aqueous Phase

N-isopropylacrylamide, NIPAm, Monomer

N,N’-methylene bisacrylamide, BisAm, Crosslinker

H2O – n-dodecane – C13/15E5

(OCH2CH2)5OH

1. Base Microemulsion

Project II: High Surface Area Polymers – Results

0.00 0.05 0.10 0.15 0.20 0.25 0.30

T /

°C

15

25

35

45

55

65

LC

LC+12

1

LC+1

3

_2

2

NIPAm/BISAm/TEMED - C12H26 / 12-HSA - LutensolAO5

=0.029sol-gel transition

=0.0

HOA-12

HOA-12

mm

m

oil = 0.5

= 0.07

TEM, SANS polymerize

H2O/NIPAM – n-dodecane/12-HOA – C13/15E5

NMR Stubenrauch, C., Tessendorf, R., Strey, R., Lynch, I., Dawson, K.A., Langmuir, 2007, 23, 7730

Stubenrauch, C., Tessendorf, R., Strey, R., Belkoura, L.,Lynch, I., Salvati, A., Dawson, K.A.,Langmuir, in preparation

Project II: High Surface Area Polymers – Results

1. Gelled Microemulsion!2. Bicontinuous Structure!

3. Domain Size Template?4. Polymerisation? 5. Domain Size Polymer?

Project II: High Surface Area Polymers - Techniques

Phase Diagrams of Microemulsions• 3 water basins and 1 cryostat; available group Dr. Stubenrauch• Polarization Microscope with camera and hotstage; available group Dr. Stubenrauch

Characterization of Template (T) / High Surface Area Polymer (P)• Conductivities – bicontinuity of T; available group Dr. Stubenrauch• Surface Area and Pore Size Analyser; available group Prof. MacElroy• DOSY NMR – bicontinuity of T / P; available at UCD • SAXS (small angle X-ray scattering) – domain size and structure of T / P; SFI equipment call Dr. C. Stubenrauch 344,400 €• High Resolution Transmission Electron Microscope with Freeze Fracture and Freeze Etch System – domain size and structure of T / P