lecture nano 13

7/30/2019 Lecture Nano 13

1/33

1

Carbon:

(fullerenes, nanotubes, diamond UNCD)

StructureSynthesis

Properties

Graphene fabrication & structure

electronic properties

potential for applications

http://www.pa.msu.edu/cmp/csc/nanotube.html


2/33

2

Allotropes of Carbon


3/33

3

Fullerenes Nobel Prize 1996

http://nobelprize.org/nobel_prizes/chemistry/laureates/1996/index.html


4/33

4

Discovery of Fullerenes


5/33

5

Allotropes of Carbon

"Environmental Applications of Carbon-Based Nanomaterials", Environmental Science & Technology, 42, 5843 (2008)


6/33

6

Carbon: Electronic structure

C*: 1s2, 2s1, 2px1, 2py

1, 2pz1

C*: 1s2, 2s2, 2p2

sp2sp3

C: 1s2, 2s2, 2px1, 2py

1, 2pz0


7/33

7

Carbon orbitals

sp2 (graphene)

sp3 (diamond)


8/33

8

Fullerenes C60

f - facese -edgesv - vertices

2+=+ evf

Diameter of C60 is 0.71 nm

Functionalization of C60:


9/33

9

Superconductivity in M3

C60

K3C60 superconducting at 18K (discovered in 1991)Cs3R60 superconducting at 33K (discovered in 2008) Ganin et al. Nature Materials 7 (2008) 367


10/33

10

Nanotube Classification


11/33

11

Carbon Nanotube Chirality & Diameter


12/33

12

CNT Chirality vs Physical Properties

Chirality (n,m)

If n-m=0,3,6,9 metallic

S-M junction


13/33

13

Structure verification by STM and Raman


14/33

14

Carbon Nanotube Properties

Raman spectroscopy of SWNT


15/33

15

CNT Growth: Arc Discharge

Fullerenes deposited as sootSWNT in soot if anode contains metal catalyst (Fe, Co, Ni-Co, etc.)

MWNT deposited on cathode under hydrogen gas (0.34 nm layer spacing)

L. C. Qin, Nature (2000) 408, 50

Yoshinori Ando, Xinluo Zhao, Toshiki Sugai, and Mukul Kumar, Materials Today, 2004, p. 22-49.


16/33

16

CNT Growth: Laser Ablation

YAG or CO2 laser aimed at carbon target containing catalytic metals

SWNT diameter depends on furnace temperature and catalyst


17/33

17

CNT Growth: Chemical Vapor Deposition

Hydrocarbon vapor passed through a tube furnace.SWNTs or MWNTs depends on size and temperature of catalyst (Fe, Ni with NH3).Low-temperature (600-900C) yields MWNTs, higher temperature (900-1200C) favors SWNTs.

A nickel cap is on the tip of each nanotube(except arrow)


18/33

18

CNT Growth: Chemical Vapor Deposition

Ni-catalyzed CNT root growth recorded in 810-3 mbar C2H2 at 615 C,Hofmann, et al., Nano Lett., 7 (3), 602 -608, 2007


19/33

19

CNT Growth: SWNT vs MWNT


20/33

20

CNT Growth Problems

Problems with CNT production

Mixture of metallic and semiconductingAlignment and positioning

A breakthrough?

ST-cut single crystal quartz substratesethanol/methanol as carbon sourceCu nanoparticles as catalysts

Results

1.55 to 1.78 nm diameter SWNT95% semiconductingCNT aligned


21/33

21

CNT: State of the Art Aligned SWNT


22/33

22

CNT in Scanning Probe Microscopy600 nm deep trenches;

250 nm wide

conventional AFM tip

CNT AFM tip


23/33

23

CNT Electronic Properties


24/33

24

CNT Functionalization

"Superhydrophobic Carbon Nanotube Forests,"Nano Letters, 3, 1701-1705 (2003)

Teflon-coated CNT

a) Plasma discharge chemical vapor deposition ofacetylene and ammonia on nickel catalyst islandsgives 50 nm diameter carbon nanotubes with a heightof 2 m.

(b) Hexafluoropropylene oxide gas thermallydecomposes to form CF2 radicals which polymerize

into PTFE on the nanotube forest substrate.

(c) The surface roughness templated by the nanotubeforest and the low surface energy imparted by thePTFE coating produce a superhydrophobic surface.


25/33

25

Functionalized CNTs in Medical Applications

Functionalized carbon nanotubes (green) taken up by cancer cellswith folate receptors (top) and normal cells (bottom). Magnification 20x.

Biological systems are highly transparent to 700-1100 nmnear-infrared (NIR) light

Single-walled carbon nanotubes (SWNTs) strongly absorb NIR light

Folate (vitamin B9) phospholipid functionalized SWNTs taken upby tumors with folate receptors

Selective cancer cell destruction can occur by NIR local heating,without harming receptor-free normal cells


26/33

26

Functionalized CNTs

Immobilization of Rh nanocatalyst on CNT


27/33

27

CNT Applications

CNT as Field Emitters in DisplaysSamsung Field Emission Display


28/33

28

CNT-Based Radio

still

vibrating

Radio transmissions tuned to the nanotube's resonance frequency force thecharged nanotube to vibrate.

Field emission of electrons from the tip of thenanotube is used to detect thevibrations and also amplify and demodulate the signal.

A current measuring device, such as a sensitive speaker, monitors the output ofthe radio.

K. J ensen, J . Weldon, H. Garcia, and A. Zettl, Nano Letters 7 (11), 3508-3511 (2007)

NEMS Mechanical Resonant Frequency ~ 300 MHz


29/33

29

CNTs in Composites

SEM image of fractured polycarbonate composite loaded at1 wt% with Zyvex processed SWNTs. The nanotubes remainembedded in the matrix even after fracture.

With a tensile strength eight times that of stainless steel and with a thermal conductivity five timesthat of copper, CNTs are obvious choices for creating a new class of composite materials.


30/33

30

CNT Ropes

M. Zhang, K.R. Atkinson, and R. H. Baughman, Science, 19 November 2004, 1358-1361.


31/33

31

Application of CNTs


32/33

32

Nanocrystalline Diamond

Ultra Nanocrystalline Diamond (UNCD)

Good conductor

Hard material

Resistant to wear

Low thermal expansion

Field emitter tips coated by UNCD

UNCD Growth by PECVD


33/33

33

Nanocrystalline Diamond

UNCD coated AFM tips (commercially available)

http://www.thindiamond.com

lecture nano 13

Documents