NIRT: Controlling Interfacial Activity of Nanoparticles: Robust Routes to Nanoparticle-NIRT: Controlling Interfacial Activity of Nanoparticles: Robust Routes to Nanoparticle-based Capsules, Membranes, and Electronic Materials (CBET 0609107)based Capsules, Membranes, and Electronic Materials (CBET 0609107)

Todd Emrick and Thomas P Russell, Polymer Science & Engineering Department, University of Massachusetts AmherstTodd Emrick and Thomas P Russell, Polymer Science & Engineering Department, University of Massachusetts AmherstAnthony Dinsmore and Narayanan Menon, Physics Department, University of Massachusetts AmherstAnthony Dinsmore and Narayanan Menon, Physics Department, University of Massachusetts Amherst

Benny D. Freeman, Chemical Engineering Department, University of Texas at Austin Benny D. Freeman, Chemical Engineering Department, University of Texas at Austin

Objectives: Harness the interfacial activity of nanoparticles, and the reactivity of functionalized ligands,for the preparation of robust, self-assembled structures , devices, and membranes

Materials for nano-composite films

Responsive Nanocomposites: using ligands to direct nanoparticles to polymer domains and interfacial boundaries

Thermalannealing

Idealized schematic of responsive nanocomposite

Effect on mechanical properties??

50 nm100 nm

25% OH terminated:NPs segregate to PS-PVP interface

50% OH terminated:NPs distributed within PVP domain

OH

OH HO

Lamellar morphology (solvent annealed films) with avg. 2.4 nm Au NPs

avg. 4.5 nm diameter Au NPs

Nanoparticle ripening + entropic penalty =

reorganization

170 deg C

Diblock copolymer host: polystyrene-poly(4-vinylpyridine)

Self-assembled nanorods and bionanorods using fluid interfaces

Hydrophilic segment Hydrophobic segment

* S

O

O

O O S O O *

100-X

O

O

SO

OO-Y+

S+Y-O

O

OX

Hydrophilic segment Hydrophobic segment

* S

O

O

O O S O O *

100-X

O

O

SO

OO-Y+

S+Y-O

O

OX

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

5

10

15

20

25

30

0 5 10 15 20 25 30

Wat

er P

erm

eab

ility

(L

.um

/(m

2.h

.bar

))

pH

t (days)

BPS-35N BPS-32K

BPS-32K/0.5%Au

94

95

96

97

98

99

100

5

10

15

20

25

30

0 5 10 15 20 25 30

Sa

lt R

eje

cti

on

(%

)

pH

t (days)

BPS-35N

BPS-32KBPS-32K/0.5%Au

PFDPFD

Low Concentration

PFDPFD

PFD

High Concentration

PFD

PFDPFD

High Concentration

PFDPFD

Washing

H2Ointerior

Oilphase

NanoparticleAssembly

20µm

Fluorescence confocal imagesof quantum dots on water droplets in a continuous oil phase

TOPO-covered CdSe quantum dots

122

/

/

/

/

/

/

/

/

2

/2

WO

WP

WO

OP

WO

WP

WO

OPWO R

z

R

zRzE

RzEWO

OPWP

/

//at min

z/R

E(z)/kT

Oil

Water

Emin

Pieranski, P. Phys. Rev. Lett 45, 569 (1980)

WP /

OP /

WO /

Interfacial assembly of nanoparticles: droplets and sheets

TCB

Water

20 m80 m

Droplet resizingthrough track-etch

membranes Confocal images

reduction in droplet size from

200 m to 10 m and less

Lin, Y., Skaff, H., Emrick, T., Dinsmore, A. D. & Russell, T. P., Science 299, 226-229.

2////

2

min/ lEngery Wel lInterfacia OPWPWOWO

OP

REEE

Interfacial energy well:

The structure and orientation of nanorods at the liquid-liquid interface can be manipulated by varying nanorod concentration in the bulk. At low TMV concentration, the rods orient parallel to the interface, which maximizes interfacial stabilizaiton. At high TMV concentrations, the rods orient normal to the interface, both mediating the interfacial interactions and neutralizing inter-rod electrostatic repulsion.

For charged nanorods like TMV, repulsive forces dominate the oil-water interfaces, which is strongly affected by the ionic strength, but not the pH, of the bulk solution in the range of pH = 6~8. Removal of the buffer solution leads to cleavage of the TMV nanorods at the oil/water interface.

25 µm

400 nm0.2 mg/ml

25 µm

400 nm0.2 mg/ml

B

0.8 mg/ml

B

0.8 mg/ml

5 µm

400 nm

B

0.8 mg/ml

B

0.8 mg/ml

5 µm

400 nm

B

0.8 mg/ml

B

0.8 mg/ml

5 µm

400 nm

Low concentration High concentration

/ / / / /2 sin 2 ( )o w p w p oE RL RL

Where / /

/

cos p w p o

o w

L>>R

2/ / / / /( ) ( )2p w o w p o p w p oE R Rh

Oil

Oil

Oil

Oil

Oil

Oil

1. Concentration2. pH value3. Ionic strength4. In-plane compression

Conditions

Au nanoparticles: EG4-058ACitrate-stabilized gold nanoparticles in water

~20 nm in diameter~1 mg/ml in water

Di-sulfonated poly(arylene ether sulfone) (BPS):BPS-XY series, X = mol% of disulfonated monomer (0<X<100), Y = “H” (free acid form) , “N” (sodium salt form), or “K” (potassium salt form).

Acid/base tolerance: steady water permeability and salt rejection over a wide range of pH

1. Measured in cross-flow cells. Feed solution: 2000 ppm NaCl, pressure = 27.2 atm (400 psig), flow rate = 1 gpm, temperature = 25oC.

2. BPS-32K/0.5%Au: BPS-32K with 0.5 wt% of Au nanoparticles (EG4-058A)

Binding energy of nanoparticles at oil-water interface

0 25 50 75 1000

20

40

60

80

salt conc. (M)

R=2.5 nmR=5 nm

0.8

1.2

1.6

0.00 0.01 0.02 0.03

R=10 nm

R2 (nm2)

E(k

BT

)

Salt concentration 0.007 mol/L0.017 mol/L0.027 mol/Llinear fit

E/R

2(k

BT

/nm

2 )

0 25 50 75 1000

20

40

60

80

salt conc. (M)

R=2.5 nmR=5 nm

0.8

1.2

1.6

0.00 0.01 0.02 0.03

0.8

1.2

1.6

0.8

1.2

1.6

0.00 0.01 0.02 0.030.00 0.01 0.02 0.03

R=10 nm

R2 (nm2)

E(k

BT

)

Salt concentration 0.007 mol/L0.017 mol/L0.027 mol/Llinear fit

E/R

2(k

BT

/nm

2 )

Nanoparticle binding energy (E) is measured from the change of interfacial tension as particles adsorb on a droplet. This data is for citrate-stabilized gold nanoparticles assembling on a droplet of octafluoropentylacrylate. We find E ~ R2 (R is the nanoparticle radius), as predicted from a continuum-scale model [Pieranski, PRL 45, 569 (1980)]. We also find that E can be increased by adding salt or by using ethylene glycol polymer ligands. These data provide the first measurements of E for nanoparticles at oil-water interfaces, and guide the design and fabrication of new materials via interfacial assembly.