Dynamics of Nanoparticles (borrowing, as Nano often does, from Macromolecular) Your career = Techniques X Problems Problems This talk concerns Techniques Tomas Hirschfeld: Most people work only on techniques, but not on finding problems. But remember, your career will be the vector cross product of techniques you learn and problems you choose.

Why do we need dynamics for nanoparticle characterization?

1. Dynamics give us size Microscopy does not always measure size well.

Microscopy cannot follow rapid size/shape changes well—e.g. self-assembly. Microscopy may alter the materials being studied. Small angle X-ray scattering and small angle neutron scattering are slow, expensive, can damage samples, and sometimes have contrast issues. 2. Dynamics tells us basic information Stability of structures: scaffolds to slow the work? kT problem Internal viscosity inside devices: how fast can nanodevices

Dynamics Techniques

 DLS = Dynamic light scattering  FPR = Fluorescence photobleaching recovery  AUC = Analytical ultracentrifugation  DOSY = Diffusion ordered NMR spectroscopy (not this trip—takes too long to explain)

DLS = Dynamic Light Scattering

• If you look closely at light scattered by a sample, it fluctuates.

• Some of that is just DUST, a nuisance, but some fluctuations are interesting.

• The fluctuations represent how quickly the molecules are moving. • This is tracked with a “correlation function”

Correlation Function

g

(

t

) 

E

( 0 )

E

(

t

)  lim

T

  1 2

T

 

T T E

(

t

' ) 

E

(

t

' 

t

)

dt

' Where E ( t ) is the instantaneous electric field of the scattered light t = 0 < E 2 > E ( t ) t’ t =  0 Thus, correlation Functions DECAY with time!

Quick decay = fast mover = small particle g ( t ) G = decay rate (Hz) Slow, big t Fast, small

An exponential becomes a sigmoidal curve if you change the x-axis to logarithmic.

g ( t ) Fast, small Slow, big Log( t ) G comes from inflection point.

LASER Dynamic Light Scattering  Uv Geometry (Polarized) G Uv =

q

2

D

trans

V

LASER

V

G Hv =

q

2

D

trans + 6

D

rot

q



H

4 

n

sin   

o

/ 2   Hv Geometry (Depolarized)

FPR = Fluorescence Photobleaching Recovery • First, measure fluorescence: step F • Then photobleach (“erase”) some with a bright flash of light: step P • Then observe recovery due to diffusion: step R The sample has to be fluorescently labeled. Destruction of the label must not damage the nanoparticle.

Blue input light Green Detected Light Fluorescent Sample Fluorescence & Photobleaching

Blue input light Green Detected Light Slowly Recovers Fluorescent Sample With Fluorescence Hole in Middle Recovery of Fluorescence

Modulation FPR Device Lanni & Ware, Rev. Sci. Instrum. 1982 SCOPE I F 5-10% bleach depth c PMT PA TA/PVD * D X  * DM S * OBJ RR * ARGON ION LASER AOM M M * = computer link

Cue The Movie

The FPR contrast decay resembles DLS. Contrast ( t ) G = decay rate (Hz) Slow, big t Fast, small

AUC = Analytical Ultracentrifugation—a Good Way to Characterize Self-assembled Species Sealed dual beam UV-Vis cell Rotor (side perspective) Spins at up to 60,000 rpm

Sedimentation: simple gravity + thermo

r

=

a

; meniscus

r

=

b

; bottom 

F b F d F c r

2

c

(

r

) 

c

(

a

) exp(  2

M

( 1  

v

2 2

RT

)(

r

2 

a

2 ) ) 1 Igor-Bricker sample T=20.0

o C 24,000 RPM v 2 =0.73 mL/g Svedberg Nobel Prize Chemistry, 1926 0 40 45 r 2 /cm 2 50

OK, so let’s look at 5 applications

1.

2.

3.

4.

5.

Can we measure the viscosity in a nanoreactor? (DLS) Can we watch a bio/nano particle change? (DLS & LS) Nanotech needs scaffolds: will they stand still? (FPR) Controlling self assembly. (DLS) Making a word using one of the most fascinating of the new nano alphabets. (AUC) Some of this is published: See http://macro.lsu.edu/russo  research articles link

ZADS = special form of DLS PTFE latex microrheology of polyacrylamide gel 2.0

PTFE Particles 470 s 1.8

~ 250 nm 1.6

1130 s 1 1.4

1340 s 1.2

1630 s 1.0

2470 s 1E-6 1E-5 1E-4 1E-3  /s 0.01

0.1

1 10 Camins & Russo, Langmuir, 4053, 1994 See also: Piazza, Tong, Weitz

More ZADS

1.0

0.8

0.6

0.4

0.2

0.0

0 1000

Time/s

2000 3000

1

Seedlings  Sick Plants  And close-up of mosaic pattern. http://www.uct.ac.za/depts/mmi/stannard/linda.html

1

What we have been trying to do: rotation and translation of a TMV through “random coil” solutions. Very hard to do right! 1. Cush et al.

Macromolecules

1997.

2. Cush & Russo

Macromolecules,

2004 (

in press, probably December)

1

D rotation ~ h -1 & D translation ~ h -1 Bottom line: TMV or nanoparticles can report the viscosity more or less accurately in a small system.

100 h  T h  R h 0.76 ± 0.01 1 10 (C) 1 100 1000 10000 100000 Dextran

M

W 1000000 1E7

“Virions are usually roughly spherical and about 200nm in diameter. The envelope contains rigid "spikes" of

haemagglutinin

and

neuraminidase

which form a characteristic halo of projections around negatively stained virus particles. “ Linda Stannard , of the Department of Medical Microbiology, University of Cape Town http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html

“The Flu”

2

5.4

5.2

5.0

4.8

4.6

4.4

4.2

4.0

3.8

3.6

3.4

3.2

3.0

2.8

2.6

Guinier plots.

I

LS vs.

q

2 From910921 ph 7.4 900 ± 30 Å From924935 ph 5 xxx min 1330 ± 30 Å From938949 ph 5 xxx min 1710 ± 50 Å  = 45 o  = 90 o 0 2 4 q 2 /10 10 cm 2 6 8 2

Dynamics of Flu “opening up”: Addition of citric acid for pH change is shown by the line at time 0. 1200 1000 800 600 400 200 0 -400 -200 0 200 400 t /s 600 800 80 60

R

h Intensity 40 20 1000 1200 0 1400 200 180 160 140 120 100 2

pH 

Sproing!!!

2

Forms a reversible gel scaffold.

PSLG: poly(stearyl-L-glutamate) O O 3

700 20 600 4 Temperature-ramped modulation FPR combinehigh 30 40 scan1062 50 2 DDSC 500 3 400 300 2 200 1 100 0 0 20 0 TRFPR: 30.7

o C 2040 s start ramp @ 0.3

o C/min DSC Melt at 30.9

o C 1000 2000 30 t (seconds) T/ o C 1 40 3000 50 Schmidtke

et al.

Figure 6 Schmidtke

et al.

Figure 7 3

Everything can move, yet the structure remains.

Means that even though you have built a scaffold (for example, to grow artificial skin or hold a sensor or drug delivery nanomachine in place) and even though it may seem to hold its shape, you must be careful! This kind of molecular view of gelation is not available from mechanical methods, such as rheology.

3

Observe Control of Self-assembly

4

Bolaform amphiphiles have a dumb-bell shape hydrophilic hydrophilic hydrophobic

Arborol example: [9]-10-[9]

9 watery hydroxyl groups

H O H O H O H O H N O

10 oily methylene groups

O H O H O H O H O H O N H N H O O O O H N H N N H OH OH OH OH OH OH OH OH OH

4

Arborol properties

• Dissolve in warm .

water.

• Gel on cooling— Why? How? • Apparently, they are “real gels” • Fibers inside the gels • Self-assembly • Reversible 4

Why do we care?

Self-assembling system Reversible Easy to vary headgroup and core size Possible applications in: • Porous media • Stationary phase for separations • Reversible, rigid rods  dynamic liquid crystals we can manipulate • Disease-inspired microfluidics—can we simulate sickle cell anemia? 4

Dendrimer self-assembly challenges • Can we control self-assembly? Synthesis!

Terminator 4 • How would we know? Analysis!

• What if we did? New Physics & Materials!

Self-assembly of [9]-12-[9] by DLS Self-assembly of Dilute Arborols— R h 4 1300 1200 1100 1000 900 800 700 600 500 400 0 [9]-10-[9]only [9]-10-[9] plus [9]-6 1 2 Number of Days 3 4

R h

got from linear fit of gamma vs q 2 of DLS data at five angles: 40, 50, 60, 70 and 90.

New problem: Hexaruthenium terpyridyl supramolecular structures

5 Newkome et al.

Angew.Chem.Int.Ed.

1999, 38(24) 3717-21

2

is the key monomer for the supramolecule.

5

aids in Proof of structure.

Molecular snowflake by two methods 5

Data on supposed snowflake supports several scenarios, but self assembly surely occurs 5 Same Data, Different Analysis 0.5% (NMR conc.) 80% @ M=1340 M=3250 20% @ M=5600 0.006% (low!) M = 2600 + non-sedimenting stuff

Write the terpyridyl aggregate in shorthand form.

5 

We see evidence of aggregation by SAXS, confirmed by DLS. 5 Stacked disks?

n ?

Note that this alphabet retains symmetry similar to the atomic alphabet Continue In this way to make aggregates of aggregates of aggregates etc.

Conclusions

The power of DLS, FPR and AUC has been demonstrated.

It was my purpose to familiarize you with these tools….but maybe I accidentally showed you some good problems to study as well. Maybe you can see a new vector cross product somewhere. The terpyridyl ruthenium business is an example of a supramolecule; however, the proponents of supramolecular thinking have less influence than the nano people. So…it must be nano!