Introduction to Chemistry – Background for Nanoscience and Nanotechnology UEET 101 Part II

1. Introduction to Chemistry – Background for Nanoscience and NanotechnologyUEET 101Part II Prof. Petr Vanýsek NIU – Chemistry and Biochemistry

2. Wide dynamic range of dimensions Electromagnetic spectrum

3. Why dimensions matter? Nanomaterials – particles of nanometer size Nano-scale materials often have very different properties from bulk materials e.g. color and reactivity • 3nm iron particle has 50% of atoms on the surface • 10nm particle has 20% of atoms on the surface • 30nm particle has 5% of atoms on the surface

4. Forms of materialCARBON - GRAPHITE

5. Forms of materialDIAMOND - GRAPHITE

6. Form of materialCARBON - FULLERENE

7. How to go about making materials?Through chemistryand of course, the same is about NANOMATERIALS

9. Top-down and bottom-up approachChemistry is good in the bottom-up

10. The ‘bottom-up’ approach Small molecules or particles pre-designed to self assemble into larger, organised structures e.g. surfactants Hydrophilic head group “Water loving” oil oil oil water oil Hydrophobic tail “Water hating” oil Spherical micelle

11. Flocullation of water by iron oxide

14. Chemical Bonding • Covalent bonds • Ionic bonds • Metal bonding

15. Covalent bonds • Covalent bonding is when electrons are shared between to atoms or more. • The number of covalent bonds an atom is likely to form is determined by its place in the periodic table and the number of valence electrons it has. • An atom will share electrons with another atom so that it results in them both having a full valence shell. Usually this will be 8 electrons.

16. Ionic bonds • When a metal and a non-metal form bonds they are typically ionic bonds where electrons are transferred from the metal to the non-metal. • Some metals will lose enough electrons to achieve a complete valence shell. • Non-metals will usually gain enough electrons to achieve a complete valence shell. • Many metals are able to form ions with more than one charge.

17. Metal bonding • In metals the atoms are held together by metal bonding. Electrons can easily transfer from one atom to the next. This suggests a model of positive ions in a sea of electrons. Metals can conduct electricity because electrons flow easily in any direction.

18. Polar Molecules • Polar Molecules • If the electron density is not distributed evenly around a molecule then they are polar.

19. H H O O H H Hydrogen Bonding

20. Dipole Interaction • http://www.chemguide.co.uk/atoms/bonding/vdw.html • The partial positive and negative ends of the molecules hold the molecules together.

21. London Forces London forces are induced dipoles caused by temporary rearrangement of the electron cloud. Two hexane molecules approach. The hexane molecules bump into each other. The electron clouds rearrange to form a temporary dipole. - - - + + + - - - + + +

22. H H ( ) nCH2=CH2 C C n H H Polymers • Polymers are large chainlike molecules that are built from smaller molecules called monomers. • For example polyethylene is formed from ethylene: • Proteins are natural polymers. • http://www.pslc.ws/macrog.htm

23. Grains Crystal Crystals Electron orbitals Atom Unit Cell Structure of Materials

26. Encapsulation of a drug (cis-platin) into a nanotube Hilder and Hill, conference paper

27. www.ewels.info/img/science/nano.html Carbon nanotubes • Allotrope of carbon • Graphite sheet rolled into a tube • 50,000x smaller than human hair • Members of fullerene family • (including buckyballs)

28. Carbon nanotubes http://www.seas.upenn.edu/mse/images/nanotube1.jpg

29. Single-walled nanotubes • Capped or uncapped • All covalent sp2 bonding • Metallic conductors or semiconductors • Bundles • Defects – points for reaction

30. Multi-walled nanotubes • 63GPa tensile strength • (steel 1.2GPa) • Inner tubes slide without friction http://www.msm.cam.ac.uk/polymer/research/nanointroCNT.html

31. Ancient nanotubes? Nature, 16th November 2006 • Damascus steel swords extremely strong • Middle Eastern origin 1100-1700AD • Manufacturing secret lost • Thought to be pattern welded • Recent study showed nanowires • and carbon nanotubes

32. Nanotubes today Carbon nanotubes incorporated in bike frame

33. Class activity Estimate the inside dimension – diameter and volume of the C-60 fullerene.

34. Top-down and bottom-up approach

36. “bumps on bumps” Superhydrophobic effect based on nanostructure of the leaf surface

38. “SMALL”

43. Gold nanoparticles • Element 79 • Inert • Need extreme conditions to react (chlorine, fluorine, cyanide, aqua regia 1:3 nitric acid:HCl)

44. Not so inert • Masatake Haruka (Japan) • Gold nanoparticles catalyse carbon monoxide oxidation • Highly active even BELOW ROOM TEMPERATURE

45. Catalysis – the golden age • Most car pollution in first 5 minutes • Cold Engine • Pt/Pd catalysts good >200C • Gold nanoparticles (8nm) • Active below room temperature (Science, October 2004, Volume 306, pp. 234-235)

46. Emulsions Add surfactant and mix OIL WATER EMULSION (water in oil)

47. The ‘bottom-up’ approach Use emulsion to make nanoparticles Precipitation inside micelles

48. Gold nanoparticles Reducing agent KBH4 (potassium borohydride) Au3+ ions (potassium tetrachloroaurate KAuCl4)

49. Gold nanoparticles oil oil oil oil oil oil oil oil oil oil • Micelles collide • Reagents mix inside micelles • Gold ions reduced to gold metal • Gold trapped in micelle – forms sphere

50. Changing faces Calcium carbonate (CaCO3) Image courtesy of Dr Alex Kulak