Nanostructures and its Applications

1. Nanostructures and its Applications N. Ponpandian Department of Nanoscience and Technology Bharathiar University Coimbatore 641 046 Email: ponpandian@buc.edu.in Web: http://www.bunst.org

2. ELECTRON WAVES Separate NanoSCIENCE from MicroSCIENCE The discovery that electrons = waves led to QUANTUM MECHANICS A weird, new, counter intuitive, non-Newtonian way of looking at the nano world With a particular impact upon our understanding of electrons: Electrons => Waves How do you figure out an electron’s wavelength? electron = h / p “De Broglie’s Relationship” ( = electron wavelength, h = Planck’s Constant, p = electron’s momentum) This relationship was based on series of experiments late 1800’s / early 1900’s To put the size of an electron’s wavelength in perspective: 2

3. Quantum Mechanics • Planck’s Wavelength  = h/p (or) h/mv • When mv >> h – Quantum effects are not observables • mv ~ h - Quantum effects are observable 3

4. How to see the Nanoparticles?

5. Size of Things(red = man-made things) Millimeters Microns Nanometers Ball of a ball point pen 0.5 Thickness of paper 0.1 100 Human hair 0.02 - 0.2 20 – 200 Talcum Powder 40 Fiberglass fibers 10 Carbon fiber 5 Human red blood cell 4 – 6 E-coli bacterium 1 Size of a modern transistor 0.25 250 Size of Smallpox virus 0.2 – 0.3 200 – 300 ___________________________________________________________________________________________________ Electron wavelength: ~10 nm or less Diameter of Carbon Nanotube 3 Diameter of DNA spiral 2 Diameter of C60 Buckyball 0.7 Diameter of Benzene ring 0.28 Size of one Atom ~0.1

6. Surface Area in Nanomaterials 2a a a a • A = 4 x 2 a x a + 2 a2 = 8 a2 + 2 a2 = 10 a2 • A = 6 x a x a + 6 a x a = 12 a2

7. Surface Area in Nanomaterials

8. Surface Area in Nanomaterials

9. Surface Area in Nanomaterials

10. Surface Energy • Surface atoms posses more energy than bulk atoms • Consequently, surface atoms are more chemically reactive • Nanoparticles posses enhanced chemical reactivity • Example: NASA is exploring aluminum nanoparticles for rocket propulsion due to their explosiveness.

11. Nanoparticle Catalysis • Macroscopic Gold is chemically inert. • Gold nanoparticles are used to catalyze chemical reactions. • Example: Reduced pollution in oxidation reactions (i.e., environmentally friendly • Nanoparticle Catalysis Research Group, Tsukuba, Japan

12. Macroscopic melting temperature • At macroscopic length scales, the melting temperature of materials in size-independent. • For example, an ice cube and a glacier both melt at the same temperature (32˚ F)

13. Nanoscale melting temperature • Nanocrystal size decreases • Surface energy increases • Meling point decreases • Example: 3 nm CdSenanocrystal melts at 700 K compared to bulk CdSe at 1678 K

14. Optical absorption  = hc/Eg

15. What are Quantum dots? Types of materials • Metals – No band gap • Semiconductors – low band gap • Insulators – very high band gap

16. What are Quantum dots? • Quantum dots are nanocrystals of semiconductors that exhibit quantum confinement effects, once their dimensions get smaller than a characteristic length, called the Bohr’s radius. • ThisBohr’s radius is a specific property of an individual semiconductor • Bohr’s radius can be equated with the electron–hole distance in an exciton that might be formed in the bulk semiconductor.

17. What is special in QDs • Below this length scale (Bohr’s radius) the band gap (the gap between the electron occupied energy level, similar to HOMO, and the empty level, similar to LUMO), which are is size-dependent. • Band gap is Size Dependent Conduction band Valence band towards nm

18. Mechanical Properties - CNT Structural differences Nanoscale Carbon Bulk Carbon C60 (Buckeyball) Smalley, Curl, Kroto 1996 Nobel Prize Graphite Diamond Carbon Nanotubes Sumio Iijima - 1991

19. What makes CNTs different from one another?

20. Physics of carbon nanotube

21. CNT – Field emission displays

22. Fe filled MWCNT: Bio-compatible nanomagnets

23. Fe filled MWCNT: Bio-compatible nanomagnets

24. Magnetism

25. Automative Magnetics

26. A technology which impacts the environment !

27. Hysteresis Loop

28. Hysteresis Loop

29. Ferromagnetic Domains

30. Random Anisotropy Model Lex Grain size > exchange length soft magnetic properties as grain size  D Grain size < exchange length soft magnetic properties  as grain size  Effect of nanosize on magnetic property Why nanocrystalline materials t of have excellent soft magnetic properties ?

31. Magnetic properties of nanostructured materials

32. Superparamagnetism • Response of superparamagnets to applied field described by Langevin model • Qualitatively similar to paramagnets • At room temperature superparamagnetic materials have a much greater magnetic susceptibility per atom than paramagnetic materials

33. Biomedical Applications of Magnetic Nanoparticles

34. Magetism and medicine • Iron and living things • Many animals use magnetic fields to navigate • Synthesize hemoglobin • Role of iron in neurodegenerative disease • Medical applications • Removal of iron splinters, shrapnel, etc. • Holding prosthetics • Guiding instruments through the body • MRI

35. Biomedical applications of magnetic nanoparticles • Magnetic imaging • Magnetic heating (Hyperthermia) • Targeted drug delivery • Detection/purification/isolation • Manipulation

36. Goal: Separate/detect/isolate one type of cell from others, often when the target is present in very small quantities Magnetic Sorting

37. O R O Ligand - - O O Magnetic Sorting, Detection Functionalized nanoparticles

38. Magnetic Sorting Add to Samples Cells

39. Magnetic Sorting Magnetic nanoparticles bond with targeted cells

40. Magnetic Sorting Retain desired cells by applying a magnetic field

41. Hyperthermia • Cancer cell growth is slowed or stopped at 42 °C - 46 °C • Magnetic materials inside the body generate heat due to • Hysteresis • Brownian motion • Eddy currents • Nanoparticles provide • uniform heating • non-invasive delivery • multiple treatments • Human clinical trials in progress (Germany)

42. Magnetic Hyperthermia for Cancer Treatment

43. Magnetic resonance imaging Non-invasive method used to render images of the inside of an object Primarily used in medical imaging to demonstrate pathological or other physiological alterations of living tissues MRI is currently the most efficient imaging procedure used in medicine

44. Typical MRI device

45. Typical MRI images

46. Problems in MRI Low contrast between different tissues Low contrast between a healthy tissue and tumors

47. Contrast agents Different contrast agents are administered in 40–50% of all MR examinations in order to improve the efficiency of this procedure Contrast agents are diagnostic pharmaceutical compounds containing paramagnetic or superparamagnetic metal ions or nanoparticles that affect the MR-signal properties of surrounding tissues Gadolinium chelates are the most widely used extracellular, non-specific contrast agents Organ specific contrast agents include superparamagnetic iron oxides nanoparticles stabilized with appropriate biopolymers or biocompatible synthetic polymers

48. Clinically approved superparamagnetic contrast agents stabilized with biopolymers Ferumoxide (Endorem, Feridex)  dextran stabilized Ferumoxtran (Sinerem, Combidex)  dextran stabilized Ferucarbotranum (Resovist)  carboxydextran stabilized Used for intravenous applications

49. MRI of liver tumor Normal liver tissue contains phagocytic Kupffer cells  darkening after dextran-coated SPIO application Cancer cells do not contain Kupffer cells  after dextran-coated SPIO application tumor is brighter that surrounding tissue After SPIO application Before SPIO application

50. MRI of gastrointestinal tract Oral application of superparamagnetic nanoparticles Small bowel before (left) and after (right) application of the oral contrast agent