1. Liquid crystals
Conducting polymers
Molecular conductors, superconductors
Molecular electronics
Nanomaterials
More detailed presentations on Conducting Polymers and Nanomaterials are also available on the website

2. Liquid crystals

3. (Institute of Plant physiology, University of Prague)
Discovery:
1888 – Friedrich Reinitzer
(Institute of Plant physiology, University of Prague)
working on cholesteryl benzoate
solid  cloudy liquid  clear liquid
contacted Otto Lehmann (a German physicist)
recognized the ‘cloudy liquid’ as a new state
called it ‘liquid crystal’ (1904)
145.5oC
178.5oC

4. Types of liquid crystals
Director, n
Nematic n
Smectic A n
Smectic C n
Chiral nematic

5. Hexagonal columnar discotic
Nematic discotic
Hexagonal columnar discotic
S. Chandrasekhar & coworkers
Bangalore

6. Anisotropic properties
Dielectric anisoptropy,
  dielectric permittivity
Birefringence,
n  refractive index
e  extraordinary [electric vector parallel to optic axis]
o  ordinary [electric vector normal to optic axis]
Polarizability anisoptropy,
  polarizability

7. Twisted nematic effect: Displays

8. Courtsey: http://en.wikipedia.org/wiki/File:LCD_layers.svgP1 P2 E2 E1 LC
Reflector

9. Evolution of molecular design for LC Strong colour, Negative 
Chemical instability
Strong colour, Negative 
Colour

10. Conducting polymers

11. Natural polymers

12. Synthetic polymers Polytetrafluoroethylene Polyethylene (Teflon)
Phenol-formaldehyde
(Bakelite)
Polyethylene
Polytetrafluoroethylene
(Teflon)
Polyhexamethylene adipamide
(Nylon 6,6)
Polyethyleneterephthalate
(PET)
Polycarbonate

13. Discovery of conducting polymers
Lethby (College of London Hospital)
Oxidation of aniline in sulfuric acid
1970’s Shirakawa (Japan)
Acetylene gas
Ti(OBu)4 & Et3Al
Toluene
–78oC
Ti(OBu)4 & Et3Al
Hexadecane
150oC
silvery film
trans-polyacetylene
copper-coloured film
cis-polyacetylene

14. Polyacetylene (PA) Electrical conductivity ()
cis PA – 10-9 S cm-1
trans PA 10-5 – 10-4 S cm-1
For comparison :  (copper) ~ 106 S cm-1
:  (teflon) ~ S cm-1

15. Doping leads to enhanced conductivity
s ~ 10-5 S cm-1
Semiconductor
+ e-
- e-
s ~ 104 S cm-1
Metal

16. Discoverers - Nobel Prize 2000
A. Heeger, A. McDiarmid, H. Shirakawa
(this photograph taken at the International Conference on Synthetic Metals, 2000, was kindly provided by Prof. Heeger)

17. Polyacetylene - electronic structure
-electronic energy levels and electron occupation
(a) ethylene
(b) allyl radical
(c) butadiene
(d) regular trans-PA
(e) dimerised trans-PA

18. Examples of conducting polymers

19. Electrical conductivities
Copper
Platinum
Bismuth
Graphite
10+6
10+4
10+2
100
10-2
10-4
10-6
10-8
10-10
10-12
10-14
10-16
10-18
S cm-1
Conducting
Polymers
Germanium
Silicon
Polyethylene
Diamond
Quartz

20. Applications of conducting polymers
Polyaniline (PANI) Transparent conducting electrodes
Electromagnetic shield
Corrosion inhibitor
‘Smart windows’ (electrochromism)
Polypyrrole (Ppy) Radar-invisible screen coating
(microwave absorption)
Sensor (active layer)
Polythiophene (PT) Field-effect transistor
Anti-static coating
Hole injecting electrode in OLED
Polyphenylenevinylene (PPV)
Active layer in OLED

21. Molecular conductors, superconductors

22. TTF-TCNQ
 = 105 S cm (58 K)

23. Organic superconductors
(TMTSF)2X
X = ClO4- TC = 1.2 K (6.5 kbar)
= PF6- TC = 1.4 K
(ET)2X
X = Cu(NCS)2- TC = 11.4 K

24. Oxidation of donor / Reduction of acceptor

25. Partial ionicity

26. Peierl’s instability

27. Organic donor molecules

28. Organic acceptor molecules

29. Molecular electronics

30. Molecular Rectifier

31. Molecular Amplifier
100 mV
20 mV
Vin, Vout : input and output voltage, VP : bias voltage
RP : polarisation resistance, RL : load resistance
X : capacitor to isolate external circuit from bias voltage

32. Nanomaterials

33. Nanomaterials Nanoscale Concept of Molecules Size matters !
Unique effects
Concept of Molecules
Metal nanoparticles
Parallels with molecules

34. Chemical Composition
CuSO4.5H2O
K2Cr2O7
NiCl2.6H2O

35. Structure
Carbon
Graphite
Diamond
Fullerene (C60)

36. Properties of materials depend upon :
Chemical composition
Structure

37. Size Chemical composition Structure Identical millimeter micrometer
Silicon
Size
Chemical composition
Structure
Identical
millimeter
Silicon
micrometer
nanometer

38. 8 1021 1 cm 2 cm 1 nm Surface area of 1 cube = 6 cm2
Surface area of 8 cubes = 48 cm2
2 cm
Surface area = 6 x 22 = 24 cm2
1021
Total surface area = 6 x 1021 nm2
= 6 x 107 cm2
= 6000 m2 = 1.5 acre
1 nm

39. layer of graphite - graphene
DNA
2.5 nm
STEM image of a single
layer of graphite - graphene
Scale bar = 2 nm

40. Atomic Force Microscope
Thickness = 2.5 nm
AFM image of a
monolayer of surfactants

41. Top-down
Bottom-up

42. Sequential extraction of adsorbed atoms -
one by one - from Germanium surface
Dujardin, G., Mayne, A., Robert, O., Rose, F., Joachim, C., and Tang, H. Science 1998, 251, 1206.

43. AuCl3 Au Michael Faraday 1791 - 1867 P CS2
‘finely divided metallic state’ of gold
(M. Faraday, Philos. Trans. R. Soc.London, 1857, 147, 145)

44. Dramatic change in Colour

45. Plasmon Resonance Absorption

46. Same chemical composition but colour changes with size !
Increasing particle size
Quantum dots, nanoparticles of semiconductors, of different sizes, illuminated by a single light source, emit intense fluorescence of different colours
(Felice Frankel, MIT)

47. Fluorescence imaging in medical diagnostics
Rat vasculature injected
with water solution of
Quantum Dots (CdSe-ZnS)
Excitation at 780 nm
2-photon fluorescence at 550 nm
Larson et al, Science 2003,
300, 1434
Using conventional
fluorescent dyes

48. Carbon nanotubes - highly versatile nanomaterials
The strongest and most flexible molecular material
High thermal conductivity
Very good electrical conductivity
Can be metallic or semiconducting depending on structure
Can be chemically modified

49. Carbon nanotube based DNA sensor
CNT
Carbon nanotube (CNT) array with attached DNA probe acts as
an ultrasensitive sensor for detecting the hybridisation of target
DNA from the sample using signals from the redox bases in the
excess DNA single strands. The signal is amplified using metal
ion mediators– oxidation of [Ru(bpy)3]2+ by guanine.

50. Nanotechnology and Industry
Computing, data storage and communication
Materials
Manufacturing industry
Health & medicine
Energy & environment
Transportation & space exploration