80 th ACS Colloid & Surface Science Symposium Boulder, Colorado June 19, 2006 Grigor B. Bantchev , Robin L. McCarley, Robert P. Hammer & Paul S. Russo

80th ACS Colloid & Surface Science Symposium

Boulder, Colorado June 19, 2006

Grigor B. Bantchev, Robin L. McCarley, Robert P. Hammer & Paul S. Russo

Louisiana State University

National Science Foundation-Division of Materials ResearchNational Science Foundation-Chemistry

National Institutes of Health-Aging

Bootstrap Dynamic Light Scattering Approach to Size and Viscosity in Complex Fluids

2

Can we start with nothing and get something? How does DLS work again?

Depolarized DLS—often overlooked tool.

Lifting ourselves up by our DLS bootstraps.

DLS can be dangerously wrong.

Making regular DLS faster and safer.

http://www.mouthmag.com/issues/58/graphics/bootstraps.gif

Normal DLS Depolarized DLS Bootstrapping Applications Fringe Benefits

3

Normal DLS works by interference among multiple scatterers,

detected coherently.


10 coh f

q set by scattering angle, refractive index,

wavelength

trans2Dq

T

T

tT

efdtttItIIT

tg 2coh2

)2( 1')'()(lim2

1)(

Intensity

4

In normal DLS, you sometimes can get by with one angle (q value)—i.e., Dtrans=/q 2.

Uh-oh!

0 1 2 3 4 5 60

2

4

6

silica-homopolypeptide composite particles

Dap

pare

nt /

10-7cm

2 s-1

q2/1010cm-2

human influenza virus

Very good.

Size essentially comes from inverting D . Size would seem to depend on q for influenza virus: not good.

Fong and Russo, Langmuir 1999, 15(13); 4421-4426

Campbell, Epand, and RussoBiomacromolecules 2004, 5, 1728-1735


5

Depolarized DLS senses rotational motion, in addition to translational motion.

θ

V

H

Now we can measureg (2)

Vv(t ) or g (2)Hv(t)

• This only happens if the object is optically anisotropic.

• Many but not all rods qualify.

• Some spheres qualify. • This rotational motion

contributes fluctuations even when q = 0.

Incident polarizerAlways vertical (v)

Detection analyzerVertical (V) orHorizonal (H)


v

H

6

Which has stronger depolarized signal, and why?


PTFE LatexTMV: Tobacco Mosaic Virus

Shape highly anisotropicBarely depolarizes at all

Shape barely anisotropicDepolarizes like crazy!

Depolarized signal strength arises from optical anisotropy, not anisotropy of

shape.

7

Dynamic Light Scattering: Summary

Hv = q 2Dtrans + 6Drot

LASER

vv HH

PMTHv Hv

Geometry Geometry (Depolarized(Depolarized

))

Vv Geometry Vv Geometry (Polarized)(Polarized)vv

Vv = q 2Dtrans

o

nq

2/sin4

PMT

LASER


VV

Requires optical anisotropy

8

Let’s look at those equations graphically.

Vv

q 2

6Drot

Hv

Dtrans

Dtrans

q 2


We’ll see real data later.

9

Probe diffusion, a form of microrheology: invert the Stokes-Einstein relations. Rather than get a size, know the size and solve for

the (micro)viscosity.

Originators: Turner & Hallett, Phillies & coworkers. Many others since the 1980’s. Other ways: fluorescence or phosphorescence depolarization.Mixed opinions about equality of and .

transtrans 66 RD

kTR

kTD

rot33rot 88 DR

kTR

kTD


10

Bootstrapping: using two transport measurements eliminates viscosity. We get size without knowing viscosity, then we get viscosity anyway.

rottrans2

3rot

trans43

34

8

6D

DRR

RkT

RkT

DD

Look, ma!

No viscosity!

Then: transrot

3 68 RDkT

DRkT


http://admin.urel.washington.edu/uweek/archives/issue/images/22_22/large_bike0594.jpg

Review of Scientific Instruments (2006), 77(4), 043902/1-043902/6

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MADLS=MultiAngle DLSHow fast? How much?

x2π/q

Laser

MultipleCorrelator

4-8 angles at once.Depends on Typically 1 minute

$20,000


12

We built MADLS because we need it.

Other LSU DLS equipmentConventional LSU-constructed DLS/SLS system #1Conventional LSU-constructed DLS/SLS system #2

Union Carbide-Dow Prodigal DLS/SLS SystemWyatt Dawn-AqueousWyatt Dawn-Organic

2 ALV50001 BI9000

LSU’s Malvern zetasizer LSU’s Wyatt Rex/Heleos-QELS/Viscostar/E

clipse-AF4/GPC

13

Low-resolution Movie of MADLS instrument in action.


14

Glycerin-water depolarized (Hv) MADLS results

0 1 2 3 4 5 6

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

/ s

-1

q 2 / 1010 cm-2

0.92 cp 1.8 cp 2.2 cp 2.9 cp 85 cp


15

MADLS compares well to a conventional instrument.

0 500 1000 15000

500

1000

1500

0 5 10 15 20 250

5

10

15

20

25

4 points

MA

/ s-1

Conv

/ s-1


Only 6 Hz

16

Bootstrapping the size and viscosity for PTFE latex in various glycerin-water mixtures, with comparison

to conventional instrument, looks promising. / cP 0.92 1.8 2.2 2.9 83 MADLS RI / nm

121 ± 6 143 ± 8 146 ± 5 137 ± 2 149 ± 3

Conventional Instrument. RI / nm

114 ± 5 121 ± 3 n/a n/a 128 ± 9

The viscosities were within 25% of cone-and-plate values in the range 1.8 to 83 cP.

OK, but there is room for improvement:• better polarizers (coming soon).• better probes (smaller, more monodisperse, more

spherical and also rodlike)• simultaneous monitoring of SLS as probe

aggregation checkNormal DLS Depolarized DLS Bootstrapping Applications Fringe Benefits

17

So far, it may seem we have only made the rheology of simple fluids more complex. Depolarized DLS can do rheology of complex fluids, though.

100 1000 10000 100000 1000000 1E71

10

100

T

R

/cP

Dextran MW

0.76 ± 0.01

(C)

Microviscosities from TMV translation and rotation through 15% dextran solution follow the same trend as conventional rheology.

Cush, Dorman & Russo Macromolecules 2004, 37(25); 9577-9584

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The Main Bootstrap Applications include:

Particle size in a fluid of unknown viscosity.

Particle size in a fluid of changing viscosity.

Viscosities that are difficult to measure, where precision may be more important than accuracy:

• Supercritical fluids• Confined fluids• Zero gravity

Probe diffusion when the probe may aggregate—this will have a minor effect if the aggregation is moderate.

Only in transparent fluids!You still need to know the refractive index.


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Fringe benefits of multiple-angle, multiple-correlator techniques for normal, polarized DLS.

Find out quickly if you can get away with a simple, commercially available

instrument operating at just one angle.


Aggregating or responsive systems, such as amyloid fibrils. You can follow in real-time in a meaningful way. Combine with

multi-angle SLS: get Rh/Rg ratios in real time shape.

Very torpid systems: measure the lowest angle right and the others are done already and waiting for you.

0 10000 20000 30000 40000 50000 60000 700000

10000

20000

30000

40000

50000

-Amyloid1-40 incubated in 100% DMSO followed by dilution in PBS pH 7.4

Addition of 5L of 500M Murphy Peptide dissolved in water

Sonicate in water bath for 10 mins with probe sonicator

R h

,app

/ Å

Time/s

20Boulder Canyon

A new wrinkle in the fabric of DLS.Something new from the Stokes-Einstein relations (!) If the particle depolarizes, you can get size without viscosity.Then you can go back and get the (micro) viscosity.We find that microviscosity is generally pretty close to viscosity for probes

of reasonable size.Accuracy/precision are already respectable for log-log work, but…Much development work remains:

Better probes, better polarizers, better alignment.A multiple-angle, multiple-correlator is a helpful appliance for normal DLS, too.

I welcome your questions, but address the deep technical ones to Dr. Grigor Bantchev, who is at this meeting. If you need a talented designer…

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• Monday, 19 June 2006 - 10:10 AMEng Ctr 105 (University of Colorado at Boulder)92

• Bootstrap Dynamic Light Scattering Approach to Size and Viscosity in Complex Fluids

• Grigor B. Bantchev, Paul S. Russo, Pavan Bellamkonda, Robin L. McCarley, and Robert P. Hammer. Louisiana State University, Baton Rouge, LA

• Commercial dynamic light scattering instruments are widely available, but at any one time most of them can only measure the signal from a single detector positioned at a particular angle. A real-time, multiple-angle, multiple-correlator system will be described. It is equipped for the measurement of the depolarized signal. Such a system can rapidly measure the size of optically anisotropic particles without knowledge of the fluid viscosity. Once the size is known, the viscosity can be obtained in the continuum limit. This capability may be useful in regular or complex fluids that can be probed by visible light, including systems that pose difficulty to conventional mechanical rheometers. Another potential application is to particle growth in complex media. Supported by NSF and NIH.

•Back to Rheology and Dynamics of Complex Fluids I: New ProbesBack to The 80th ACS Colloid and Surface Science Symposium (June 18-21, 2006)

http://acs.confex.com/acs/csss06/techprogram/S2075.HTM

http://acs.confex.com/acs/csss06/techprogram/MEETING.HTM

Documents

80 th ACS Colloid & Surface Science Symposium Boulder, Colorado June 19, 2006 Grigor B. Bantchev , Robin L. McCarley, Robert P. Hammer & Paul S. Russo