1. www.panstanford.com Chapters 5-8 Presentation Slides for Science at the Nanoscale: An Introductory Textbook by Chin Wee Shong, Sow Chorng Haur & Andrew T. S. Wee National University of Singapore ISBN: 9789814241038 Hardcover August 2009 228 pages More information at www.panstanford.com/nanotextbook

2. www.panstanford.com Chapter 5

3. www.panstanford.com Name Abbrev. Sci. Unit Representative objects with this size scale metre m 100 Height of a 7-year-old child. deci- dm 10 −1 Size of our palm. centi- cm 10 −2 Length of a bee. milli- mm 10 −3 Thickness of ordinary paperclip. micro- μm 10 −6 Size of typical dust particles. nano- nm 10 −9 The diametre of a C60 molecule is about 1 nm. pico- pm 10 −12 Radius of a Hydrogen Atom is about 23 pm. femto- fm 10 −15 Size of a typical nucleus of an atom is 10 fm. atto- am 10 −18 Estimated size of an electron. Just how small is nano?

4. Percentage of surface atoms 1 cm 3 gold cube 1 cm Total number of atoms ~ 5.9  10 22 Number of surface atoms ~ 1.2  10 15 % of surface atoms to total atoms ~ 2  10 -6 1 nm 3 gold cube Unit cell length of gold ~ 0.4 nm Approximately 2.5 fcc units Total number of atoms ~ 108 Number of surface atoms ~ 84 % of surface atoms to total atoms ~ 78 www.panstanford.com Percentage of Surface Atoms

5. Surface Relaxation and Restructuring In surface relaxation, atoms in the surface layer may shift inwardly or laterally (c) (a) d 12 = d bulk d bulk (b) d 12 < d bulk d bulk dangling bonds Dangling bonds may combine to form strained bonds between themselves, the surface layer is restructured with different bond lengths and/or angles. www.panstanford.com Surface Relaxation and Restructuring

6. Sintering and Ostwald ripening Sintering : the individual nanostructures change their shapes when they combine with each other, and this often results in a polycrystalline material Ostwald ripening produces a single uniform structure with the larger nanostructures growing at the expense of the smaller ones www.panstanford.com Sintering and Oswald ripening

7. Catalysis at the Nanoscale With kind permission from Springer Science Business Media: J.Phys. D, Atomic Resolution electron microscopy of small metal clustes, 19, 293 (1991), J.-O. Boyin and J.- O. Malm. Copyright © 1991, Springer Berlin/Heldelberg. www.panstanford.com Catalysis at the Nanoscale

8. The electrical double layer Stern layer : the fairly immobile layer of ions that adhere strongly to the particle surface Guoy layer : a diffuse layer of oppositely charged mobile ions that are attracted to the first layer www.panstanford.com The electrical double layer

9. The theory is developed by B. Derjaguin and L. Landau, and independently E. Verwey and J.T.G. Overbeek. DLVO potential www.panstanford.com DLVO Potential

10. Surfactants www.panstanford.com Surfactants

11. AOT-water-isooctane system www.panstanford.com AOT-water-isooctane system

12. www.panstanford.com Chapter 6

13. www.panstanford.com Schematic of the energy bands

14. www.panstanford.com Energy distribution functions

15. Band structure of a semiconductor at different temperatures www.panstanford.com Band structure of a semiconductor at different temperatures

16. Spherical volume of radius R encompassing a number of possible states www.panstanford.com

17. The functions f(E) and g c (E) www.panstanford.com The functions of f(E) and g c (E)

18. Density of states for 3D, 2D, 1D, and 0D structures www.panstanford.com Density of States

19. www.panstanford.com One-dimensional density of states

20. www.panstanford.com GaAs/AlGaAs/GaAs heterostructure Band diagram, i.e. the energy of the conduction band. The dashed line is the Fermi energy Cross-section through the heterostructure grown by MBE with nearly atomically sharp interfaces

21. www.panstanford.com Ballistic conductance

22. www.panstanford.com Electronic properties of a quantum dot

23. www.panstanford.com Energy level diagram Energy level diagram of the single electron transistor

24. www.panstanford.com Chapter 7

25. www.panstanford.com Variation of Gibbs energy during the nucleation process

26. www.panstanford.com The nucleation and growth processes

27. www.panstanford.com Effect of capping molecule CdS nanocrystals produced with (a) higher and (b) lower amounts of the capping molecule hexadecylamine

28. www.panstanford.com STM images of α-sexithiophene (6T) molecules adsorb on Ag(111) surface Self-assembly of mono- and bi-layer of 6T to form nanostripes Self-assembly of C 60 onto the 6T bilayer patterns

29. www.panstanford.com Self-assembled monolayers (SAMs)

30. www.panstanford.com Close-packed Assembly SEM images showing close-packed assembly of micron-sized nanoparticles

31. www.panstanford.com Capillary actions between particles

32. www.panstanford.com Chapter 8

33. www.panstanford.com Optical microscope

34. www.panstanford.com The Rayleigh criterion

35. www.panstanford.com Scanning Electron Microscope

36. www.panstanford.com Light beam profile vs electron beam profile

37. www.panstanford.com Main components of a SEM

38. www.panstanford.com Electron gun (a) a thermionic electron gun (b) a field emission electron gun

39. www.panstanford.com Electron trajectory Spiral trajectory of an electron passing through the electromagnetic lens in a SEM Magnetic field profile generated by a typical electromagnet used in SEM and the focusing effect of the magnetic field on the electron beam

40. www.panstanford.com Detectable signals generated when an energetic electron beam is incident on a thick sample

41. www.panstanford.com Transmission Electron Microscope (TEM)

42. www.panstanford.com Detectable signals generated when an energetic electron beam is incident on a thin sample

43. www.panstanford.com Scanning Tunneling Microscope

44. www.panstanford.com A UHV STM System Close-up of STM sample stage and tip

45. www.panstanford.com STM image of Si(111)-(7 × 7)

46. www.panstanford.com

47. STM operation (b) Constant current (a) Constant-height

48. www.panstanford.com Energy band diagrams of the STM tip (a) (a) without any voltage bias

49. www.panstanford.com Energy band diagrams of the STM tip (b) (b) when the tip is negatively biased with respect to the sample

50. www.panstanford.com Energy band diagrams of the STM tip (c) (c) when the tip is positively biased with respect to the sample

51. www.panstanford.com Atomic Force Microscope Image of the cantilever and probe tip

52. www.panstanford.com Various detection modes of AFM

53. www.panstanford.com Optical Tweezer

54. www.panstanford.com Laser beam profile passing through the microsphere

55. www.panstanford.com Optical trapping of an array of microspheres

56. www.panstanford.com