Shape Characterization Using Dynamic & Static Light Scattering
?
0 likes?147 views
Dynamic Light Scattering (DLS) and Static Light Scattering (SLS) are well-established ensemble techniques for characterizing colloids and macromolecules, providing insights into their size, molecular weight, and interactions. Beyond traditional applications, these methods also offer the potential to probe anisotropy which can be a critical parameter of today¡¯s increasingly complex functional materials. This presentation explores the principles and practical considerations of anisotropic particle characterization using modern goniometer-based DLS and SLS instrumentation. Several relevant applications to soft matter systems will be shared to highlight capabilities, advantages and limitations of the techniques.
Shape Characterization Using Dynamic & Static Light Scattering
- 1. Company presentation Shape Characterization Using Dynamic & Static Light Scattering Andrea Vaccaro PhD, CTO LS Instruments AG
- 2. In SLS/DLS, a laser beam is sent through a colloidal sample, the average scattered intensity and the auto/cross correlation of the resulting scattered light are computed. Why choose DLS as a characterization method? ? Fast ? Simple measurements with easy sample preparation ? In-situ, non-destructive approach Measuring particle size reliably 2 Static and Dynamic Light Scattering (SLS/DLS) ?
- 3. 3 SLS The measured intensity can be divided up into contributions from within particles (intraparticle) and between particles (interparticle): I(q) ¡Ö c ? Mw ? V? ? P(q) ? S(q) The Radius of Gyration can be determined from the so-called Guinier Plot: Slope = Ln (I) Guinier regime ??
- 4. DLS 4 Intensity fluctuation s I t <I > ? ? Diffusion Coefficient ?h= ?? ? 6 ?? ? Stokes- Einstein Relation Particle Size Intensity correlation function g 2 (t)-1 ¦Ó Correlato r
- 5. Structural Information from DLS/SLS: Coil to Globule Transition 5 Sun S. et al., J. Chem. Phys. 73, 5971 (1980) ?h ?? Temperature
- 6. Shape from DLS/SLS 6 Can we get detailed shape and size information from SLS/DLS?
- 7. 7 Depolarized Static and Dynamic Light Scattering (D-SLS/D-DLS) ? In D-SLS /D-DLS we add a polarizer at detection before the detector ? Depending on the orientation of the polarizer, vertical or horizontal we can measure in two different configurations, VV and VH ? In D-SLS /D-DLS gives access to advanced shape and size information
- 8. Decorrelation for Anisotropic Particles 8 Diffusion Translational Diffusion ?? Rotational Diffusion ?? For anisotropic particles, the diffusion mechanism is more complex as it involves translations and rotations
- 9. D-DLS in VV Configuration 9 Intensity fluctuation s ??? t <I > Intensity correlation function (t)-1 ¦Ó Correlato r ?? , ?? R. Nixon-Luke, G. Bryant, Part. Part. Syst. Charact. 2019, 36, 1800388.
- 10. D-DLS in VV Configuration: The Tobacco Mosaic Virus 10 For small scattering angles, : ?? ?? ?1? ??0 (? ) exp(? ?? ?2 ? ) log ?? ?? ?1 ? ? ?? ?? ? 2 ? log ? ? ?? ?1 ? ? For small scattering angles, the logarithmic plot of the correlation function is linear and yields the translational diffusion coefficient, ? ?? ?2 Wada A. et al., J. Chem. Phys. 55, 1798 (1971) Tobacco Virus
- 11. D-DLS in VV Configuration: The Tobacco Mosaic Virus 11 log ? ? ?? ?1 ? ? For large : ?? ?? ?1 ? ?2 exp (?( ?? ? 2 +6 ? ?)? ) log ?? ?? ?1 ? ? ? ?(?? ? 2 +6 ? ?)? ?(?? ? 2 +6 ??) For large the logarithmic plot of the correlation function is linear and yields the rotational diffusion coefficient, Wada A. et al., J. Chem. Phys. 55, 1798 (1971)
- 12. Shape and Size from Diffusion Coefficients For an axisymmetric particle of major size, , minor size, , and anisotropy factor ?? , ?? Microhydrodynami cs ?,?,? For rodlike particles, such as Tobacco Mosaic Virus: ? ?= 1 3 ?? (ln ? ? ?) ? ?0 ? 3 ?? = 1 3 ?? (ln ? ?? ) ? ?0 ? ?? =0.312+ 0.565 ? + 0.100 ? ? ??=?0.662+ 0.917 ? ? 0.050 ? ? Ortega A.; Garc a ?? de la Torre J., J. Chem. Phys. 119, 9914¨C9919 (2003) Shape and Size ? ?
- 13. Takeaways ? In VV Configuration at low angles DLS provides access to the translational diffusion of anisotropic particles ? At large angles and large lag times, knowing the translational diffusion coefficient, we can obtain the rotational diffusion coefficient ? From translational and rotational diffusion coefficients we can obtain size and shape parameters of anisotropic particles ? The procedure is complicated by the fact that in general correlation functions display an angle-dependent double decay
- 14. D-DLS in VH Configuration 14 Intensity fluctuation s ?? ? t <I > Intensity correlation function (t)-1 ¦Ó Correlato r ?? , ?? ?2 ? ? =1+ ? exp (?2 (?? ? 2 + 6 ?? )?) Simpler single exponential decay R. Nixon-Luke, G. Bryant, Part. Part. Syst. Charact. 2019, 36, 1800388. Decay Rate
- 15. D-DLS in VH Configuration 15 ? ¡Ô ?2 ?? +6 ? ? ? In VH configuration we obtain a simpler single exponential decay ? Plotting the decay rate vs we obtain the translational diffusion coefficient from the slope and the rotational diffusion coefficient from the intercept of the linear plot ? The procedure is simpler than in the VV configuration case Decay Rate: ? ?? ?? ?? ?
- 16. D-DLS in VH Configuration: Magnetic Nanoparticles with Tunable Shape Anisotropy 16 ? Anisotropic Magnetic NPs characterized by TEM and D- DLS ? The two techniques agree thus confirming the validity of D- DLS Martchenko I. et al., J. Chem. Phys. B 115(49), 14838-14845 (2011)
- 17. Contact us LS Instruments AG Passage du Cardinal 1 1700 Fribourg Switzerland www.lsinstruments.ch