Zeta potential : Definition
     ♦ Zeta potential : the potential at the shear plane
     ♦ Why Zeta potential for the sta...
Electrophoresis
     Electrophoresis : Moving of charged particle in a dispersion
                       under the electri...
Electrophoresis




Advanced Electronic Ceramics I (2004)




                                             Zeta Potential
...
Zeta Potential




                                                   Dark-field illumination




                        ...
Laser Doppler Velocimetry
     Laser Doppler Velocimetry (LDV).
     Moving particles in the measurement zone shift the fr...
Zeta-potential : application

        1. Sewage treatment
        2. Paints
        3. Printing Ink
        4. Monitor for...
E-paper & E-ink




      Micrograph of electronic ink, a bistable and
      printable microencaspulated electrophoretic
 ...
Extended View and Example




                        J.A.Rogers, MRS Bulletin, 26(7), 530 (2001)
Advanced Electronic Cera...
Very thin

                                                    E Ink Corporation of
                                      ...
TiO2 nanotube
                                                     Layer-by-layer-colloid-templating
                     ...
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Aem Lect11

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Aem Lect11

  1. 1. Zeta potential : Definition ♦ Zeta potential : the potential at the shear plane ♦ Why Zeta potential for the stable colloid? the interaction of the particles in polar liquids is not governed by the surface potential but by zeta potential Additional positive ions are still attracted by the negative colloid, but now they are repelled by the Stern layer as well as other positive ions that are trying to approach the colloid - dynamic equilibrium results in diffuse layer Strongly bounded layer Electric double layer = Stern layer + Diffuse Layer http://www.zeta-meter.com/ Advanced Electronic Ceramics I (2004) Zeta potential: ξ ♦ ξ : potential at the surface of shear ♦ the surface of shear : the boundary between the immobilized layer and the mobile fluid ♦ ξ is not always coincident to Stern potential (ψδ) - besides the specifically adsorbed layer(Stern layer), the more immobilized layer can be formed - however, usually ξ ≈ ψδ (it means the Stern surface is usually coincident to the surface of shear) ♦ why important? various motions such as Brownian motion and sedimentation which affect the stability of colloid are determined by this potential Advanced Electronic Ceramics I (2004)
  2. 2. Electrophoresis Electrophoresis : Moving of charged particle in a dispersion under the electric filed E : electric field (V/m) Fel = q E Fel : the force that an isolated ion experiences by E Fvis : opposing force due to the viscous medium Fvis = f v f : friction factor from the Stokes law f = 6πηR at stationary R : is the radius of the particle state v : velocity of the particle v=qE/f z : valence of the ion = q E /(6πηR) e : electron charge = zeE/(6πηR) u : electrophoretic mobility u=v/E Advanced Electronic Ceramics I (2004) Electrophoresis Hückel Helmholtz-Smoluchowski approximation approximation ξ = 3ηu/2ε ξ = ηu/ε = q / (6πεR) =q / (4πεR) κR < 0.1 κR > 100 R is small compared to κ-1 R is large compared to κ-1 κ-1 is large κ-1 is small ionic strength(I) small high concentration of electrolyte non-aqueous media polar aqueous solution Advanced Electronic Ceramics I (2004)
  3. 3. Electrophoresis Advanced Electronic Ceramics I (2004) Zeta Potential - The effective particle surface charge in a liquid-solid sample is measured by the application of a preset constant electric current applied across the suspension. By determining the rate at which particles migrate into or out of a sample cell (electrophoretic mobility), zeta potential measurement is obtained. This measurement is typically performed over a range of different conditions to optimize the influence of one or more variables. - A rotating chamber eliminates the settling of coarse particles and minimizes thermal current effects. http://www.micromeritics.com/ Advanced Electronic Ceramics I (2004)
  4. 4. Zeta Potential Dark-field illumination Www.zeta-meter.com Advanced Electronic Ceramics I (2004) Experimental aspect of electrophoresis Stationary layer (no Electro-osmotic effect) 1. Error coming from sedimentation can be corrected by comparing the result with that under no electric field 2. Convection - working at low current, effective thermostating 3. Electro-osmotic effect - moving liquid relative to the stationary chamber Advanced Electronic Ceramics I (2004)
  5. 5. Laser Doppler Velocimetry Laser Doppler Velocimetry (LDV). Moving particles in the measurement zone shift the frequency of scattered light proportional to their velocity. the particle image ⇒ the illumination of particles by intersecting laser beams the observer’s eye ⇒ the photomultiplier the stopwatch ⇒ the correlator. Advantage for LDV - Statistically better measurements - Seconds measurement time rather than 10-30 minutes - Measurement of smaller particles, 5-10nm rather than a minimum of 200nm - Measurement of zeta potential distributions - Improvement in measurement repeatability due to a reduction in the Joule heating effect http://www.silver-colloids.com/Tutorials/Intro/zetaintro.html Advanced Electronic Ceramics I (2004) Microelectrophoresis Laser illumination and video interface allows submicronic particle measurement. 1. The cell consists of two pairs of palladium electrodes fitted into perfectly symmetrical, high quality Suprasil Quartz chambers 2. Easy to clean: a kinematics mounting gives easy access to the measuring chamber 3. The mounting allows rapid and precise positioning of the cell after cleaning 4. Replaceable main electrodes 5. Sample temperature is permanently measured in-situ by fast response micro-probe http://www.lavallab.com/eng/zeta-eng/zeta-meter.htm Advanced Electronic Ceramics I (2004)
  6. 6. Zeta-potential : application 1. Sewage treatment 2. Paints 3. Printing Ink 4. Monitor for flocculation 5. Slip casting Www.zeta-meter.com Advanced Electronic Ceramics I (2004) Display Advanced Electronic Ceramics I (2004)
  7. 7. E-paper & E-ink Micrograph of electronic ink, a bistable and printable microencaspulated electrophoretic display material created in MIT media lab and currently being developed at E Ink Corp. http://www.media.mit.edu/nanomedia/index.html http://www.eink.com/pdf/key_benefits.pdf B Comiskey, JD Albert, H Yoshizawa, J Jacobson, Nature 394 (6690) 253-255 1998 Advanced Electronic Ceramics I (2004) Principle & Fabrication Figure Step for fabricating organic transistors and circuits. Microcontact printing (µCP) with a cylinderical stamp provides a fast, low-cost method to produce high-resolution source/drain electrodes and interconnects. SAM stands for self-assembled monolayer. J.A.Rogers, MRS Bulletin, 26(7), 530 (2001) Advanced Electronic Ceramics I (2004)
  8. 8. Extended View and Example J.A.Rogers, MRS Bulletin, 26(7), 530 (2001) Advanced Electronic Ceramics I (2004) Principle The balls(called as ‘gyricon’) are about the size of a dot made with a very fine pen. Inside each one is another, smaller sphere, half white and half black, suspended in oily silicon so that it can rotate freely. The black half of the inner sphere is positively charged, while the white half is negatively charged. When an electronic charge is applied to the sheet of e-paper (using a special printer attached to a computer, or a hand-held scanning device), the inner sphere rotates to show either its white half or black half, according to the print instruction. The result is a black-and-white image. http://www.eink.com/technology/index.htm Advanced Electronic Ceramics I (2004)
  9. 9. Very thin E Ink Corporation of Cambridge, Mass. has introduced the world's thinnest active matrix display that is just 0.3 mm thick, or half the thickness of a credit card. The company is working with leading device makers to integrate these ultra-thin electronic ink displays into next generation portable devices by 2004-2005. http://www.eink.com/news/releases/pr60.html Advanced Electronic Ceramics I (2004) Benefits 1. Paper-like readability 2. Write using electronic stylus(can be stored and sent via email) 3. Cheaper and more flexible than LCDs 4. Low power http://www.eink.com/solutions/appliances.htm Advanced Electronic Ceramics I (2004)
  10. 10. TiO2 nanotube Layer-by-layer-colloid-templating (LbL-CT approach) The surface charge reversal at the end of each deposition cycles ξ bare Ni rods: -48 mV ξ after PDADMAC: +40mV ξ After PSS: -30mV ξ After PDADMAC: +30mV ξ After TALH: -25 mV TALH: Titanium bis ammonium lactato dihydroxide PDADMAC: poly diallyldimethylammonium chloride K.Subramanya et al., Nano Letters, 1, 727 (2001) Advanced Electronic Ceramics I (2004) TiO2 nanotube K.Subramanya et al., Nano Letters, 1, 727 (2001) Advanced Electronic Ceramics I (2004)

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