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Light Scattering Techniques

Discover the potential of light scattering techniques, including Dynamic Light Scattering (DLS) and Static Light Scattering (SLS), in analyzing materials. This comprehensive overview covers key concepts such as intensity, diffusion coefficients, and relaxation times, while highlighting important formulas like I~m² and I~D6. Learn about the nuances of DLS data, including the occurrence of slow phases in different samples and conditions, whether in situ or ex situ. Enhance your understanding of zeolite formation and system behavior under varying temperatures.

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Light Scattering Techniques

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  1. Light Scattering Techniques …and what they can do for You! Tom Caremans 24/10/2005

  2. Equipment Laser Detector Sample

  3. Qué? Scattering Dynamic Light Scattering Static Light Scattering INTENSITY (and don’t you forget that!) Rh RG Mol Weight (Mw) Relaxation time of the different modes DIFFUSION COEFFICIENT of different modes You measure a collective!!

  4. DLS: basic formula’s Remember! : I~m² so: I~D6

  5. What can DLS tell you?

  6. Be careful with DLS data!

  7. DLS and silicalite formation Occurrence of slow phases?? • Twomey, Thompson, Zeolites 14, 1994 • Schoeman, Zeolites 18, 1997 In-situ at 105° (full ns, 125°C) Slow phases were systematically cut out!!!

  8. However… Diluted CS shows a different story when measured in-situ CS: H2O 1:9

  9. Ex-situ vs In-situ; concentrated vs diluted Undiluted CS In-situ: regular case No slow modes visible Ex-situ: slow modes visible That disappear after a certain moment Slow modes appear upon cooling?? Diluted CS Upon heating at 55-60°C slow modes appear Reversibly disappear when cooling Is this the same process happening? More analysis/measurements needed

  10. Books & Texts • No “DLS for dummies” available • The DLS Bible: Robert Pecora, Bruce Berne, Dynamic Light Scattering • SLS: Charles Johnson, Laser Light Scattering, easy to read

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