Carbon nanomaterials. Gavin Lawes Wayne State University.

Transcription

1 Carbon nanomaterials Gavin Lawes Wayne State University

2 Outline 1. Carbon structures 2. Carbon nanostructures 3. Potential applications for Carbon nanostructures

3 Periodic table from bpc.edu

4 Carbon atom Electron (-) Proton (+) Neutron

5 Carbon-based molecules are somewhat important for life on Earth amino group Amino acids from msu.edu/gallego carboxylic acid group

6 Lecithin from indiana.edu/oso Phospholipids

7 and are also important for all industrial activity Pentane from wikimedia.org

8 Electron orbitals s orbital p orbital from britannica.com

9 Hybridization from ASDN.net

10 sp 3 hybridized C crystals from diamonds.net from cnx.org

11 sp 2 hybridized C crystals from cochise.edu/wellerr

12 Graphite consists of layers of hexagonal Carbon sheets. from chem.wisc.edu

13 Diamond Graphite Electrical insulator Electrical conductor* Very hard Very soft* Transparent Opaque Expensive Cheap

14 Nanoscale carbon structures

15 Buckminsterfullerene Molecule consisting of 60 C atoms sp 2 hybridized bonds Has 20 hexagons, 12 pentagons Other related structures have 70 or 84 C atoms from sciencedaily.com

16 C 60 is named for Buckminster Fuller who designed geodesic domes. from unusualife.com

17 Original report of C 60

18 1996 Nobel Prize in Chemistry Robert Curl, Sir Harold Kroto, Richard Smalley for their discovery of fullerenes. from Nobelprize.org

19 Carbon nanotubes Rolled up sheet of sp 2 bonded carbon atoms from informaworld.com

20 Carbon nanotubes can be formed from a single sheet of C atoms or several sheets Single walled carbon nanotube (single sheet of carbon atoms) Multiwalled carbon nanotube (several sheets of carbon atoms) from rice.edu

21 Carbon sheets can also be rolled up in different directions to give different types of nanotubes.

22 The properties of nanotubes depend on how they are rolled up Electrical conductor Electrical insulator from phycomp.technion.ac.il

23 Nanotube sizes also depend on how they are rolled up

24 Graphene (single sp 2 bonded carbon sheet)

25 C atoms in hexagonal array from cnx.org

26 From ncem.lbl.gov Scale bar 0.2 nm

27 Nobel Prize in Physics 2010 Andre Geim and Konstantin Novoselov for groundbreaking experiments regarding the two-dimensional material graphene. from Nobelprize.org

28 Carbon nanostructures

29 Why are carbon nanostructures interesting?

30 They are strong Multiwall carbon nanotube breaking

31 Multiwall carbon nanotube composite Silica fibres +MWCNT Mechanical properties can improve by 50% or more by adding carbon nanotubes.

32 Damascus sabre steel contains nanotubes Multiwalled carbon nanotubes found in 17 th century sword. 10 nm These are formed during the synthesis and may have produced the very good mechanical properties.

33 They have good electrical properties from bpc.edu

34 Carbon nanostructures may be used in new electronic devices from nanotechweb.org

35 Devices made with carbon nanotubes

36 Carbon nanotubes can be used for making electronic devices Carbon Nanotubes. Advanced Topics in the Synthesis, Structure, Properties and Applications, , 2008

37 Properties of graphene depend on the subtrate from als.lbl.gov

38 Geometry of graphene may also affect the properties From nanotechweb.org

39 Graphene may be used as a transparent electrode

40 Carbon nanotube mechanical oscillator Force sensitivity of 1 fn Hz -1/2

41 Graphene mechanical oscillator

42 Carbon nanotubes may have biomedical applications Carbon nanotubes can be functionalized with different biologically relevant molecules.

43 Cells incubated with functionalized carbon nanotubes

44 Electronic bandgap Energy Momentum Metal Semiconductor

45 The electronic bandgap for graphene looks like a pair of cones touching at their tips for certain positions (in momentum space). This leads to interesting electronic properties. from wikipedia.com

46 Schrodinger Equation i t ψ = 2 2m 2 ψ + Vψ (for massive particles) E~p 2 Dirac Equation i t Ψ = ( iσ a e µ ( a µ ia ) µ + βm)ψ E~p (for relativistic particles) Appropriate for electrons in graphene

47 How do you make carbon nanotubes? 1. Carbon arc discharge. Hold two carbon (graphite) electrodes at some potential difference in a Helium atmosphere and bring the electrodes together. At some separation and arc will be produced, and carbon nanotubes will grow on the cathode. These will normally be multiwalled nanotubes, but single walled nanotubes can be grown by adding Ni, Fe, or Co to the cathode.

48 2. Laser ablation. Heat up a lump of graphite to ~1200 C in an Ar atmosphere, and then blast it with a laser. This can make single walled nanotubes if the graphite has a catalyst like Co or Ni included. 3. Catalytic growth. Heat up hydrocarbons (e.g. acetylene) to high temperatures and then let them settle on a substrate coated with a catalyst (Fe, Co, Ni). This will form either multiwalled nanotubes or single walled nanotubes depending on the growth conditions. How do you make graphene? Graphite and scotch tape.

49 Open problems 1. To be useful for devices, these carbon nanomaterials need to be prepared on and/or connected reliably to electrodes. 2. Since the properties of these nanomaterials depend strongly on structure (e.g. armchair vs zig-zag nanotubes), we need to have good control over these structural details. 3. Many unanswered physics questions remain, including the magnetism, superconductivity, and optical properties of these materials.

50 Summary 1. A number of carbon allotropes naturally form interesting nanostructures 2. These nanostructures have enormous potential in developing new electronic, optical, and nano-mechanical devices.

51 End