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DYNAMIC LIGHT SCATTERING Particle Size Analysis Group 2 KIM DONGMIN CHAE JONGMIN SONG SI NAE IM SUNHA YOON JIHWAN THEORY Theory Brownian Motion Hydrodynamic Diameter Rayleigh Scattering Mie Theory Doppler Effect Theory Brownian Motion Brownian motion is the random movement of particles due to the DLS is concerned with measurement of particles suspended within a liquid. The larger the particle, the slower the Brownian motion will be… Theory Brownian Motion Theory Hydrodynamic Diameter The diameter that is measured in Dynamic Light Scattering is called the hydrodynamic diameter and refers to how a particles diffuses within a fluid. Factors that affect the diffusion speed of particles 1. Ionic Strength of Medium 2. Surface Structure 3. Non-Spherical Particles Theory Hydrodynamic Diameter Ionic Strength Of Medium kT d(H) = 3πηD d(H) = hydrodynamic diameter D = translational diffusion coefficient k = Boltzmann’s constant T = absolute temperature η = viscosity Theory Hydrodynamic Diameter Surface Structure : Any change to the surface of a particle that affects the diffusion speed will correspondingly change the apparent size of the particle Non-Spherical Particle : Diameter of a sphere that has the same transational diffusion speed as the particle Theory Rayleigh Scattering Rayleigh scattering (named after Lord Rayleigh) is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. Main reason why the sky is blue. Theory Mie Theory When the size of the particles becomes roughly equivalent to the wavelength of the illuminating light, then a complex function of maxima and minima with respect to angle is observed. Theory Doppler Effect Theory Doppler Effect The change in frequency and wavelength of a wave for an observer moving relative to the source of the waves. It is commonly heard when a vehicle sounding a siren approaches, passes and recedes from an observer. DYNAMIC LIGHT SCATTERING Dynamic Light Scattering 1. The speed at which the particles are diffusing due to Brownian motion is measured. 2. This is done by measuring the rate at which the intensity of the scattered light fluctuates when detected using a suitable optical arrangement. Dynamic Light Scattering Sample Cell Incident Beam LASER Screen Speckle Pattern Dynamic Light Scattering Dynamic Light Scattering Large Particle Intensity Intensity Small Particle Time Time Dynamic Light Scattering L A S E R Attenuator Nano S Nano ZS Nano S90 Nano ZS90 173º 173º 90º 90º Detector Cell 90º Digital Signal Processor LET’S DO IT Particle Size Measurement Particle Size Measurement Particle Size Measurement 1. Go to the system menu of apparatus and click on “Size Measurement” 2. Change the angle on the apparatus to 60º by turning the knob. Particle Size Measurement 3. Now enter the value of angle 90º in the system menu. Particle Size Measurement 4. Select the appropriate solvent from the solvent list in system menu. If the sample contains water as solvent, then check the water in solvent category. Particle Size Measurement 5. Now fill the sample in the DLS cell, for inorganic solvents use plastic cell and dispose it after use. For organic solvents use Quartz glass cell. Particle Size Measurement 6. Check the intensity on the intensity monitor, it should be between 8000~14000 and its color should be blue. Particle Size Measurement 7. Now press the “GO” button on the toolbar. Particle Size Measurement 8. A small window will appear on the monitor, enter the filename, grouping, and comments. 9. Then press the “Save Auto” button, the equipment will start analyzing the sample. Particle Size Analysis 1. Go to the system menu and select “Size Analysis”. 2. Click on the DLS button in the toolbar. 3. Select the grouping where the size measurement file was saved and open the required file. 4. Then click on the “Re-Analysis” button. Particle Size Analysis 5. It will show the analysis of the selected file, now if you want to edit more options, click on the preview button in toolbar. Then you can add more options to the analysis ANY QUESTIONS?