Introduction into the world of colloids. Joachim Koetz, Universität Potsdam

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1 Introduction into the world of colloids Joachim Koetz, Universität Potsdam

2 History of Colloid Chemistry Alchemy

3 Alchemist Elexier of life? drinking gold-solution (aurum potabile)

4 + reducing agent + 3 HAuCl 4

5 What you would expect is elementary gold What you find is an optically clear, red solution!!

6 + 3 HAuCl 4 Optically clear, red solution

7 History of Colloid Chemistry 1857 Faraday: Light scattering studies of colloidal gold sols

8 What is the reason for the red colour? If the particle dimensions are well defined a part of the visible light (blue light) will be absorbed (surface plasmon resonance) and the colour of the solution becomes red!

9 History of Colloid Chemistry 1871 Rayleigh: Theory of light scattering

10 History of Colloid Chemistry 1861 Graham: Diffusion behaviour

11 Definition (Graham) Colloids are glue-like substances, diffuse very slowly, and do not dialyse

12 What is a Colloid? DEFINITION: κολλα = glue Thomas Graham

13 History of Colloid Chemistry 1907 Wolfgang Ostwald: Different types of colloidal systems

14 DIE WELT DER VERNACHLÄSSIGTEN DIMENSIONEN (The world of neglected dimensions) EINE EINFÜHRUNG IN DIE KOLLOIDCHEMIE MIT BESONDERER BERÜCKSICHTIGUNG IHRER ANWENDUNGEN VON WOLFGANG OSTWALD PROF. DER KOLLOIDCHEMIE a. d. UNIVERSITÄT LEIPZIG 1927

15 Types of disperse systems (W. Ostwald) Disperse systems suspensions > 1000 nm colloidal dispersions 1 bis 1000 nm solutions < 1 nm

16 Definition Any particle that has some linear dimension between 1 nm and 1 µm is considered a colloid! However, the limits are rather arbitrary.

17 Definition: A state of subdivision in which the particles, droplets, or bubbles dispersed in another phase have at least one dimension between nm All combinations are possible between gas, liquid, and solid W. Ostwald

18 Colloidal Systems (according to Wolfgang Ostwald) Medium Gas Gas Liquid Liquid Liquid Solid Solid Solid Particle Liquid Solid Gas Liquid Solid Gas Liquid Solid Colloidal system Aerosol Aerosol Foam Emulsion Suspension Solid Foam Porous Material Solid Suspension

19 History of Colloid Chemistry 1927 Burry, Ekwall: Associating Colloids

20 Associating Colloids Amphiphilic self-organizing systems Colloids are associated physically, not chemically Size and shape of the associates can change

21 History of Colloid Chemistry 1929 Staudinger: Macromolecules

22 Macromolecules as colloidal systems Any macromolecule consisting of 10 3 up to 10 9 atoms Any dispersed macromolecular coil having colloidal dimensions

23 History of Colloid Chemistry 1923 Svedberg: Ultracentrifugation 1932 Ruska: First electron microscope

24 The Colloidal Domain One dimension between 1 and 1000 nm All combinations of dispersed matter Classification: - colloidal dispersions - associating colloids - macromolecules

25 Log (size in Meter) Macrocosmos Matterial Science Sun Earth Microcosmos TV tower House brick Hair Nanosized particles or macromolecules Molecule Atom Electron Life Science Whale Human Mouse Flea Bacterium Virus Colloidal region

26 Specifications: Ultra-high Resolution Scanning ElectronMicroscope S-4800 (Hitachi) REM deutsch Image resolution:1.0 nm / 15 kv 1.4 nm / 1 kv EDX-System: Thermo- NORAN system SIX Cryo preparation system: Gatan Alto 2500-S STEM Imaging

27 Colloidal systems in Nature

28 Biomineralization Inorganic component SiO 2 * Aragonite, CaCO 3 x H 2 O Hydroxylapatit, Ca 10 (PO 4 ) 6 (OH) 2 Organic component composite of hydrocarbon and protein composite of hydrocarbon and protein composite of collagenfilament and protein Organism Diatomeen Pearl Bone and teeth

29 Colloidal systems A state of subdivision in which the particles, droplets, or bubbles dispersed in another phase have at least one dimension between 1 and 1000 nm all combinations are possible between : gas, liquid, and solid W. Ostwald

30 Fields of Application for nanostructured systems

31 Disciplines and Topics for which Colloids and colloidal phenomena are important Analytical chemistry Physical chemistry Biochemistry Material Science Petroleum Science Household products Imaging technology Adsorption phenomena, chromatography Nucleation, supersaturation, liquid crystals Electrophoresis, osmosis, ultrafiltration Ceramics, fibres, powder metallurgy Oil recovery, Milk, beer, cosmetics Emulsions, printing inks, paper coating

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33 Colloids and Surfaces Special features of colloidal systems

34 Surface area of colloidal systems Cube (1cm; 1cm; 1cm) after size reduction to an edge length of 500 nm: surface area of 60 m 2 Spinning dope (1 cm 3 ) after spinning to a fibre with diameter of 1000 nm: fiber length of 1273 km 1 liter of a 0.1 M surfactant solution: interfacial area of m 2

35 Colloidal systems have very large surface areas

36 Surface atoms [in %] in dependence on the particle size [in nm] % nm part of surface atoms in %

37 Colloidal systems surface atoms become dominant

38 Surface tension Increase in Gibbs free energy per unit increment in area

39 Surface Tension Phenomena Droplet formation Coalescence Bubble formation Wetting

40 Marangoni-Effect Processes induced by a change of surface tension

41 Alcohol is evaporated from the liquid film at the glass wall Surface tension is increased Wine is absorbed at the glass wall Droplets are flowing back into the glas Wine Tears