Measure and Modify Colloidal Stability - Horiba

1 2012 Horiba , Ltd. All rights and Modify Colloidal StabilityFeaturing the SZ-100 Nanoparticle Analyzer 2012 Horiba , Ltd. All rights DefinitionTwo phases: Dispersed phase(particles) Continuous phase(dispersion medium, solvent) May be solid, liquid, or gaseous Size range 1 nm 1 micronHigh surface area creates unique properties(suspension) 2012 Horiba , Ltd. All rights or Nanoparticle? Colloid: 1 nm 1 m Nanoparticle: 1 100 nm So a suspension of 50 nm gold particles in water: colloid or nanoparticle? Both, mostly terminology Also hear nanocolloid, nanoparticle (<100 nm) 2012 Horiba , Ltd.

2 All rights or Not?SSA = 6/ D50 nmD from SEM ~50 nmD from SSA ~60-70 nmD from DLS ~250 nmSo: is this a nanoparticle?ultrasoundUsed ultrasound to disperseto primary particles or useweak acid to break bondsD from DLS ~50 nm 2012 Horiba , Ltd. All rights Want stable dispersion Either suspensions or emulsions Suspensions sediment & flocculate Emulsions phase separate, creaming or coalescencegoodbadgoodbad 2012 Horiba , Ltd. All rights Stability 2012 Horiba , Ltd. All rights Steric stabilization: coat surface with polymers Particles can t touch so they don t interact Electrostatic stabilization: alter surface chemistry to put charge on particle surface Repel like magnets 2012 Horiba , Ltd.

3 All rights Potential If surface has + charge, then - ions attracted to surface + ions attracted to ions, builds electric double layer Slipping plane: distance from particle surface where ions move with particle ZP = potential (mV) at slipping plane 2012 Horiba , Ltd. All rights Potential 2012 Horiba , Ltd. All rights TheoryElectrostatic Stability (DVLO) Approaching particles undergo two forces Van der Waals attraction (Vvdw) Electrostatic repulsion(Ver) Total energy = balance of two Vtotal= Vvdw+ VerSteric Stability Approaching particles undergo two forces Van der Waals attraction (Vvdw) Forces from adsorbed polymers (Vster) Total energy = balance of two Vtotal= Vvdw+ Vster 2012 Horiba , Ltd.

4 All rights Interaction Energy Curve: DVLOI mportant parameters:Secondary minimum Flocculation ReversiblePrimary minimum Coagulation PermanentVvdwVerVtotDistance between particlesTotal energy 1/K Debye Length, double layer thickness: depends on concentration a particle size surface charge A Hamaker constant, nature of particle 2012 Horiba , Ltd. All rights Potential: Measurement Apply electric field Measure particle motion Direction tells + or + particles move to - particles move to + Speed tells amplitude Get speed from frequency shift from motion of particlesdistance-measurement zone 2012 Horiba , Ltd.

5 All rights Potential Measurement 2sin2 EnUd Mobility)( 2 3 .kafU 0 0+ dUZeta potentialParticle motion causes Doppler shiftFrequency mobilityMobility zeta potential 2012 Horiba , Ltd. All rights Results HzIntensity mV Polystyrene Polymer Micro spheres: 500nm (100ppm) Average value of zeta potential from three times measurementsfd123 2012 Horiba , Ltd. All rights Details First Measure conductivity Then decide applied electric field Auto or manually Reverse electric field to avoid polarization & electroosmosis To avoid electroosmotic effect near cell walls Uzgiris type cells avoid this problem 2012 Horiba , Ltd.

6 All rights Potential Cells-10-50510152002468101214pHzeta potentialGold coated electrodes (ruined) Carbon coated electrodesIEP nm protein 800 measurements with one cell 2012 Horiba , Ltd. All rights reserved. Thin vs. Thick Double LayerTHICK DOUBLE LAYERTHIN DOUBLE LAYERD ebye lengthparticle diameterSmoluchowski a >> 1 Huckel a = 1 Debye length = -1 EDL thickness a << 1a a)( 2 3 'kafU 2012 Horiba , Ltd. All rights Software Default is Smoluchowski Selection for Huckel Or enter manually for other model 2012 Horiba , Ltd. All rights Potential Predicts StabilityDifferent guidelines+30 mV0 mV-30 mVstablestablenot stablepositive zpnegative zpSample Dependency Oil/water emulsions > 10 mV Polymer latices > 15 mV Oxides > 30 mV Metal sols > 40 mV 2012 Horiba , Ltd.

7 All rights Potential: Emulsion Isoelectric Point (IEP)Isoelectric point:pH where zetapotential = 0 Automate IEPstudies withauto titrator 2012 Horiba , Ltd. All rights IEP Study: Stability 2012 Horiba , Ltd. All rights of Some Materials Another use of IEP is to characterize the surface of complex particles TiO2 coated with alumina will have the IEP of aluminaalpha aluminium oxide Al2O3 8-9alpha iron (III) oxide (hematite) (V) oxide Sb2O5< to (IV) oxide (ceria) (III) oxide (chromia) (II) oxide , beta-MnO2 [5]gamma aluminium oxide Al2O37-8gamma iron (III) oxide (maghemite) (II, III) oxide (magnetite) (III) oxide La2O310lead(II) oxide oxide (magnesia) (IV) oxide MnO24-5nickel(II) oxide ilicon carbide (alpha) dioxide (silica)

8 Nitride Si3N46-7silicon nitride Si3N49tantalum(V) oxide, Ta2O5 (I) oxide Tl2O:8tin(IV) oxide (IV) oxide (rutile or anatase) (VI) oxide (V) oxide (vanadia) V2O51 to 2yttrium (III) oxide (yttria) oxide (IV) oxide (zirconia) ZrO24-11 2012 Horiba , Ltd. All rights Concentration Effect 2012 Horiba , Ltd. All rights Concentration EffectsSurfactant concentration vs. pH, surfactant concentration vAlter the surface chemistry alter the zeta potential 2012 Horiba , Ltd. All rights Can also use zeta potential to study how to cause instability Example: water treatment Add chemicals to IEP Particles flocculate Easier to filter 2012 Horiba , Ltd.

9 All rights : Colloidal Gold Stable base particle Used in drug delivery Attach proteins, DNA, etc. to surface 2012 Horiba , Ltd. All rights Gold: Drug DeliveryColloidal Gold Modified with a Genetically Engineered Nitroreductase: Toward a Novel Enzyme Delivery System forCancer Prodrug TherapyVanessa V. Gwenin, Chris D. Gwenin, and Maher Kalaji Langmuir, 2011, 27(23), pp 14300 14307 Particle size and zeta potential for Colloidal gold base particles (average size 51 nm prior to modification) after immobilizing a prodrug activating enzyme onto the surface at different concentrations.

10 Data generated on SZ-100 2012 Horiba , Ltd. All rights Colloidal GoldTechniqueSize nmAtomic Force Microscopy Electron Microscopy Electron Microscopy Mobility Analysis Light X-ray nmAtomic Force Electron Electron Mobility Analysis Light Scattering173 scattering 90 scattering X-ray Scattering nmAtomic Force Microscopy Electron Microscopy Electron Microscopy Mobility Analysis Light Scattering173 scattering scattering X-ray Scattering St devSample nm1,8 Sample.