WALLIS Zeta Potential Analyzer Laser Doppler Electrophoresis LDE

WALLIS - Zeta Potential Analyzer Laser Doppler Electrophoresis (LDE) principle for Zeta potential measurements 2014/04/10

Why measuring Zeta potential? Charged particles repel each other Colloidal solution stability ? Stable systems Flocculations Uncharged particles are free to collide and aggregate Coagulation Sedimentation Ü Electrostatic or charge stabilization : This effect uses more natural interactions between particles through the distribution of charged species (ions) in the solution.

Zeta Potential: a phenomenological approach stable Positive Zeta + 30 m. V unstable 0 m. V IEP : Iso. Electric Point - 30 m. V stable Negative Zeta p. H § If surface has - charge, then Cations are attracted to the NP surface § Anions attracted to Cations, builds electric double layer § Slipping/shear plane: distance from particle surface where ions move with particle § Zeta Potential = potential (m. V) at slipping plane

Zeta Potential determination h z = µe f (k. a) e Calculated Measured z: Zeta Potential (m. V) µe: electrophoretic mobility e: medium permittivity h: medium viscosity a: particle radius k: invert of double layer thickness k-1 : Debye length f (k. a) : Henry’s function Zeta is dependent of the k. a factor value k is dependent of the solvent General cases 1≤ f (k. a) ≤ 1. 5 99% cases !!!

Electrophoresis & Electrophoretic mobility V µe: electrophoresis mobility E: electric field V : voltage applied q : electric charge Fe : electric force Ff : friction force elec • Applying an Electric field: the particles move with its surrounding layers. • Particle velocity directly related to its electrophoretic mobility and E

Laser Doppler Electrophoresis (LDE) Heterodyne optical Interferometer : retrieving doppler low frequency Splitter f laser + f doppler Laser d = 17° flaser + fmod er Combin fmod g Countin Photon Module f doppler tor Path Optical tion Modula Attenua f mod from pectrum S µe = l laser E sin d f. D FFT f mod ± f D µe: electrophoretic mobility (µmcm/Vs) E : applied electric field f. D : Doppler frequency

Wallis Measurement Sequence Heterodyning Signal Measured FFT Doppler shift Electrophoretic Mobility f. D µ Double Layer model Computed Zeta Potential Huckel ? Smoluchowski ? e By LDE (Laser Doppler Electrophoresis) f(k. a) Henry function z

What defines the measurement resolution? 1. 5 Detected signal fmod 1 0. 5 0 0 10 20 30 40 50 60 70 80 90 -0. 5 -1 -1. 5 ØSampling Freq ≥ 2 x fmod (Shannon criteria) ØNber of sampling points limited by : buffer size, acquisition duration, calculation time

WALLIS : High-Resolution Zeta Potential Analysis ØPurely designed and optimized for Charge/zeta potential measurement Ø Complementary tool to VASCO for colloid characterization Ø High resolution analysis down to 0. 5 m. V

Why WALLIS has higher resolution than others? Correlator High-speed digital acquisition: Wallis (2 in 1 concept Zeta+DLS other supplier) 256 to 1024 channels Fmod=256 Hz G 2(t) Intensité 8192 sampling points Fmod=8 k. Hz t t FFT Resolution 3 -5 m. V Resolution < 0. 5 m. V

Sample cell configuration : the dip cell approach Electro-osmosis effect Capillary 3 mm Connector Hellma Cell Quartz, Glass or polystyrene polished No need to focus at any ”stationary plane” Dip cell 10 x 10 mm (WALLIS) Vitreous Carbon Electrodes Laser beam • No electro-osmosis • Field proven concept • Custom made electrodes

Benefits of WALLIS sample cell configuration • • • Easy to handle Easy filling, no risk of bubbles ! (vs capillary cell/viscosity) Stand alone electrode holder-> easy to replace Vitreous carbon electrodes: extreme chemical resistance (No oxidation); low electrical resistance Easy cleaning of electrodes (rinsing and ultra sound bath tub)->No cross contamination Reusable quartz cell-> no consumable Easy to clean Excellent optical quality Compatible with organic solvent Compatible with standard cell (10 x 10 mm 2) … sample volume ≈750µL

Zeta. Q software : the brain of WALLIS § Unique and proprietary software § User friendly and intuitive GUI § SOP and programmable experiments (Time, T°, p. H) § Experiment storage in data base §Many other advanced functionalities

Performances example #1 with correlator (other suppliers) Résolution : 3. 7 m. V !!! with fast acquisition (WALLIS) Résolution < 0, 5 m. V !!!

Performances example #2 IEP characterization of an industrial surfactant WALLIS High resolution allows precise measurement of IEP even with sharp Zeta transition !

Further reading! [1] Hunter R, Zeta potential in colloidal science; Academic press, New York, 1981 [2] Reliang Xu; Particle Characterization: light scattering methods; Kluwer Academic Publishers [3] ISO 13099 B 1, Colloidal systems—Methods for zeta potential determination Part 1: Electroacoustic and electrokinetic phenomena [4] V. DELGADO et al. ; measurement and interpretation of electrokinetic phenomena; IUPAC Technical Report , Pure Appl. Chem. , Vol. 77, No. 10, pp. 1753– 1805, 2005

Thank you of your attention! Lab support: Customer support: Dr. Benoit MAXIT Eng. Boris PEDRONO Mail: benoit. maxit@cordouan-tech. com Mail: boris. pedrono@cordouan-tech. com CORDOUAN TECHNOLOGIES +33 556 157 545 +33 556 157 541 Cité de la photonique 11, Avenue Canteranne 33600 Pessac FRANCE www. cordouan-tech. com Follow Cordouan Technologies on Twitter!