Dynamics of Nanoparticles (borrowing, as Nano often does, from Macromolecular)

1. Dynamics of Nanoparticles (borrowing, as Nano often does, from Macromolecular) Yourcareer = 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.

2. 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 kT problem Internal viscosity inside devices: how fast can nanodevices work?

3. 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)

4. 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”

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

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

7. An exponential becomes a sigmoidal curve if you change the x-axis to logarithmic. g(t) Slow, big Fast, small Log( t ) G comes from inflection point.

8. Dynamic Light Scattering LASER LASER PMT PMT Uv Geometry (Polarized)  V Uv = q2Dtrans Hv Geometry (Depolarized)  V H Hv = q2Dtrans + 6Drot

9. 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.

10. Green Detected Light Blue input light Fluorescent Sample Fluorescence & Photobleaching

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

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

13. Cue The Movie

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

15. 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

16. r = a; meniscus r = b; bottom  Fb Fd Fc r Sedimentation: simple gravity + thermo Svedberg Nobel Prize Chemistry, 1926

17. OK, so let’s look at 5 applications 1. Can we measure the viscosity in a nanoreactor? (DLS) 2. Can we watch a bio/nano particle change? (DLS & LS) 3. Nanotech needs scaffolds: will they stand still? (FPR) 4. Controlling self assembly. (DLS) 5. 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

18. ZADS = special form of DLSPTFE latex microrheology of polyacrylamide gel PTFE Particles ~ 250 nm 1 Camins & Russo, Langmuir, 4053, 1994 See also: Piazza, Tong, Weitz

19. More ZADS 1

20. 1 Seedlings Sick Plants  And close-up of mosaic pattern. http://www.uct.ac.za/depts/mmi/stannard/linda.html

21. 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

22. Drotation ~ h-1 & Dtranslation ~ h-1Bottom line: TMV or nanoparticles can report the viscosity more or less accurately in a small system. 1

23. “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 2 “The Flu”

24. Guinier plots. ILS vs. q2 pH 7.4 900 Å pH 5 1330 Å pH 5 later 1710 Å 2

25. Dynamics of Flu “opening up”: Addition of citric acid for pH change is shown by the line at time 0. 2

26. Sproing!!! pH  2

27. PSLG: poly(stearyl-L-glutamate) Forms a reversible gel scaffold. 3

28. Temperature-ramped modulation FPR 3

29. 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! 3 This kind of molecular view of gelation is not available from mechanical methods, such as rheology.

30. Observe Control of Self-assembly 4 Bolaform amphiphiles have a dumb-bell shape hydrophilic hydrophilic hydrophobic

31. Arborol example: [9]-10-[9] 4 9 watery hydroxyl groups 10 oily methylene groups

32. Arborol properties 4 • Dissolve in warm water. • Gel on cooling—Why? How? • Apparently, they are “real gels” • Fibers inside the gels . • Self-assembly • Reversible

33. Why do we care? 4 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?

34. Terminator Dendrimer self-assembly challenges 4 • Can we control self-assembly? Synthesis! • How would we know? Analysis! • What if we did? New Physics & Materials!

35. Self-assembly of [9]-12-[9] by DLS 4 Self-assembly of Dilute Arborols—Rh Rh got from linear fit of gamma vs q2 of DLS data at five angles: 40, 50, 60, 70 and 90.

36. 2 is the key monomer for the supramolecule. 5 aids in Proof of structure. 5 New problem: Hexaruthenium terpyridyl supramolecular structures Newkome et al. Angew.Chem.Int.Ed. 1999, 38(24) 3717-21

37. Molecular snowflake by two methods 5

38. 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 + non-sedimenting stuff 0.006% (low!) M = 2600

39. Write the terpyridyl aggregate in shorthand form. 5 

40. 5 We see evidence of aggregation by SAXS, confirmed by DLS. Stacked disks? n ? Continue In this way to make aggregates of aggregates of aggregates etc. Note that this alphabet retains symmetry similar to the atomic alphabet

41. 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!