Nanocarbon

NANO51Foothill College

Carbon Engineering

Current trends in fullerene chemistry and nanochemistry

Allotropy and Allotropes of Carbon (family)

http://chemistry.tutorvista.com/inorganic-chemistry/allotropes-of-carbon.html

Allotropes of CarbonThere are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon.[12] The physical properties of carbon vary widely with the allotropic form. For example, diamond is highly transparent, while graphite is opaque and black. Diamond is among the hardest materials known, while graphite is soft enough to form a streak on paper. Diamond has a very low electrical conductivity, while graphite is a very good conductor. Under normal conditions, diamond has the highest thermal conductivity of all known materials. More recent discoveries of carbon allotropes include fullerenes (buckyballs), carbon nanotubes (single and mutliwalled) and carbon nanospheres, also known as ‘nano-onion’ (graphitic) carbon.

http://en.wikipedia.org/wiki/Carbon

Nanocarbon Structures• Diamond• Fullerenes• Carbon nanotubes (CNT)

multiwalled (MWNT)• Diamond Like Carbon (DLC)• Amorphous carbon• Graphene • Nanospheres

Carbon Nanotubes

Note the twists in the sp2 C=C planar bond

http://education.mrsec.wisc.edu/nanoquest/carbon/

Nanotube GeometryThe (n,m) nanotube naming scheme can be thought of as a vector (Ch) in an infinite graphene sheet that describes how to "roll up" the graphene sheet to make the nanotube. T denotes the tube axis, and a1 and a2 are the unit vectors of graphene in real space

Armchair Nanocarbon

A SWNT can be rolled by a sheet of graphite, for example the armchair type SWNT

Graphene Nanostructure

Extended sp2 hybridized carbon and p-p* network

Graphene as a System

Graphene as a Network

Lattice constants m and n Delocalized pi e- bonding network

pi-stacking interactions from a ‘structure’ to a ‘system’

Networked Carbon Nanostructures

From the network architecture, add interactions, observe emergent properties

Buckyball (Fullerene)• 60 carbon atoms• 12 pentagons

surrounded by 20 hexagons (C60)

• All sp2 hybridized carbon double bonds

• All atoms identical• System is in full p-p*

bonding resonance

Phase Diagram of Deposited Carbon Material

http://drajput.com/notes/carbon_materials/images/carbon-ternary-phase-diagram.jpg

Properties => Uses

• Diamond => hard, thermal conductivity• Graphite => soft, clean industrial lubricant• Graphene => electrically conductive thin film• Fullerenes => conductive filler, biomedical,

ultrasensitive dispersed sensor, catalysts• Nanotubes => stiffness, strength / weight,

electrical conductivity, composite filler

Nanocarbon Applications• Nanolithography (decrease feature size; improve environmental impact)• High density data storage• In situ synthesis of electrical connects• Improve efficiency of internal combustion engines (laser spark plugs)• Ultra-high resolution displays (feature size)• Photo acoustic imaging• Cancer therapy (safe, biocompatible target for photo thermal ablation)• Explosion initiation (lower energy requirement and increase safety and

portability – extension of use as a catalyst in combustion efficiency)• Hydrogen storage and release at room temperature• Low-energy, catalyst-free carbon nanotube synthesis at room temperature• Ultra-high sensitivity oxygen sensors• Carbon overcoat on rigid magnetic disks (tribology)

Fabrication Techniques• Diamond

• Graphite

• Graphene

• Fullerenes

• Nanotubes

• Heat and pressure• CVD (with seed crystal)• High temperature

conversion of diamond• CVD / plasma deposition

(C2H2 plasma arc) • Gas phase reactions,

electrical arc carbon rods• Plasma / CVD (CH4/H2)

Partial list of fabrication techniques for various types of carbon nanostructures

Characterization ToolsCharacterization Tools• Raman Spectroscopy• XPS (X-ray Photoelectron

Spectroscopy)• FE-SEM (Field Emission

SEM)• FTIR (Fourier Transform

Infrared Spectroscopy• TEM (Transmission Electron

Spectroscopy)

Structure being analyzed• Carbon phase state

– Diamond– Graphite– Graphene– Fullerenes– Diamond Like Carbon (DLC)

• Carbon bonding– (C-C / C-H), C=C, branching

• Atomic / lattice imaging

Raman Spectroscopy

• Inelastic scattering• C-C/C=C bonds• Networked graphene• D peak (disordered)• G peak (graphene)• RBM – radial breathing

mode in carbon nanotubes• G’ peak => crystalline

Raman Spectroscopy Energy DiagramRaman spectroscopy utilizes the process of a coupled phonon electronic excitation giving rise to stokes and anti-stokes scattering, compare to Raleigh scattering.

Key Raman Peaks in Graphene

D Band (A1G selection) G Band (E2G selection) and G’ (overtone) for graphene, graphite, and carbon nanotubes.

D and G Bands on Graphite

A1G selection – D Band E2G selection – G Band

Forbidden in graphite Allowed in Graphite

Carbon Nanotube Raman

Graphite Flake Raman

System Name: XY ASCIIPass Energy: 100.00 eVShift (Bias): 0.0 (0.0) eVTue Oct 16 08:39:50 2012

Graphite Flake Raman

Counts

Kinetic Energy, eV1200 1800 2400 3000

1000

3000

5000

7000

9000

11000

13000

G b

andLabel KE (eV) FWHM Height Gauss Asymm

G band 1582.43 16.44 10532 25.0% 0.0%

Peak-Fit Baseline: 1454.10 to 1696.33 eVReduced Chi-Square: 2.024

A B

CD

E

Label KE (eV) FWHM Height Gauss AsymmA 2443.00 25.00 377.484 50.0% 0.0%B 2469.00 25.00 278.236 50.0% 0.0%C 2686.71 35.00 2461.64 50.0% 0.0%D 2730.13 35.00 6410 50.0% 0.0%E 3247.00 20.00 986.227 50.0% 0.0%

Peak-Fit Baseline: 2350.47 to 3286.52 eVReduced Chi-Square: 5.370

HOPG Raman

System Name: XY ASCIIPass Energy: 100.00 eVShift (Bias): 0.0 (0.0) eVTue Oct 16 08:39:18 2012

HOPG Disk Raman

Counts

Kinetic Energy, eV1200 1800 2400 3000

2000

6000

10000

14000

18000

22000

26000

30000

34000D ?

G?

Label KE (eV) FWHM Height Gauss AsymmD 1355.83 25.00 1022.2 50.0% 0.0%? 1476.75 25.00 395.9 50.0% 0.0%G 1583.04 24.13 29187.2 50.0% 0.0%? 1625.00 25.00 376.2 50.0% 0.0%

Peak-Fit Baseline: 1259.78 to 1744.22 eVReduced Chi-Square: 5.556

?

2D

? ?

Label KE (eV) FWHM Height Gauss Asymm? 2465.10 59.27 443.4 60.0% 0.0%2D 2711.86 56.56 11698.6 60.0% 0.0%? 3179.48 35.00 481.7 60.0% 0.0%? 3247.17 34.33 1030.1 60.0% 0.0%

Peak-Fit Baseline: 2372.36 to 3307.04 eVReduced Chi-Square: 7.614

Acetylene Black Raman

System Name: XY ASCIIPass Energy: 100.00 eVShift (Bias): 0.0 (0.0) eVFri Jan 04 21:22:55 2013

Acetylene Black

Counts

Kinetic Energy, eV1200 1800 2400 3000

1000

2000

3000

4000

5000

6000

7000

D p

eak

G P

eakLabel KE (eV) FWHM Height Gauss Asymm

D peak 1353.07 78.11 4402.2 70.0% 0.0%G Peak 1589.09 79.45 4966.52 70.0% 0.0%

Peak-Fit Baseline: 1129.77 to 1809.91 eVReduced Chi-Square: 6.636

A

B

C

D

Label KE (eV) FWHM Height Gauss AsymmA 2500.63 125.00 321.4 70.0% 0.0%B 2701.56 100.04 4587.69 70.0% 0.0%C 2929.44 150.00 1171.64 70.0% 0.0%D 3220.57 107.77 299.634 70.0% 0.0%

Peak-Fit Baseline: 2273.83 to 3343.99 eVReduced Chi-Square: 3.341

Carbon Nanospheres• Relatively newer form of carbon• Formed by CVD, thermal decomposition• Thought to have a fullerene core – then

wrapped with smaller sp2 graphene motifs• Motifs ‘converge’ upon heat treatment• Can grow from 100 to 1,000 Angstroms• Actually a ‘natural’ form of carbon (soot)

– But need heat treatment to become dense

TEM Image of Nanoonion

Researchers Apply Nanodiamond Nanoreinforced Polymer Composite Coatings by High-Velocity Oxy-Fuel Combustion Spraying

Onion-like carbon (OLC) was fabricated by annealing nanodiamond at 1000 °C for 2 hours in low vacuum (1 Pa). The OLC was characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). The experimental results show that the OLC exhibits similarity to the original nanodiamond particles in shape. The size of the OLC is found to be approximately 5 nm. The transformation mechanism of the OLC from nanodiamond was discussed also.

Carbon Nanosphere Characterization

• Nanocarbon (grey powder)• SEM – overall microstructure• TEM – detailed nanostructure• XPS – C/O ratio and degree of

graphitization (pi-pi* shake-up)• Raman spectroscopy – detailed

structural bonding (D/G ratio)

System Name: XY ASCIIPass Energy: 100.00 eVCharge Bias: 0.0 (0.0) eVTue Apr 12 10:18:00 2011

Nanocarbon grade 2

Counts

Binding Energy, (eV)02004006008001000

20000

60000

100000

140000

180000

220000

260000

300000

Peak Label/ID Atomic % BE (eV)O 1s 0.4% 532.48C 1s 99.3% 284.98Si 2p 0.2% 102.38

O K

LL-1

O 1

s

C 1

s

Si 2

s

Si 2

p

System Name: XY ASCIIPass Energy: 100.00 eVCharge Bias: 0.0 (0.0) eVTue Apr 12 10:18:00 2011

Nanocarbon grade 2

Counts

Binding Energy, (eV)296 292 288 284 2800

20000

40000

60000

80000

100000

120000

140000

160000

180000Peak Label/ID Atomic % BE (eV)O 1s 0.4% 532.48C 1s 99.3% 284.98Si 2p 0.2% 102.38

C-C

C-C

, C-O

C-C

, C=O

p-p*

Peak Label/ID BE (eV) FWHM (eV) Height Gauss %C-C 284.41 0.94 150941 75.0%C-C, C-O 285.82 1.50 13024.4 85.0%C-C, C=O 288.00 2.00 2745.88 85.0%p-p* 290.74 2.56 3693.68 85.0%

Reduced Chi-Square: 13.4131

System Name: XY ASCIIPass Energy: 100.00 eVCharge Bias: 0.0 (0.0) eVTue Apr 12 10:18:00 2011

nanocarbon grade 1

Counts

Binding Energy, (eV)02004006008001000

20000

60000

100000

140000

180000

220000

260000

300000

340000Peak Label/ID Atomic % BE (eV)F 1s 0.1% 687.58O 1s 5.6% 532.48C 1s 94.1% 283.88Si 2s 0.2% 152.98

O A

uger

O K

LL-1

F 1s

O 1

s

C 1

s

Si 2

s

Si 2

p

System Name: XY ASCIIPass Energy: 100.00 eVCharge Bias: 0.0 (0.0) eVTue Apr 12 10:18:00 2011

Nanocarbon grade 1

Counts

Binding Energy, (eV)296 292 288 284 2800

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

110000Peak Label/ID Atomic % BE (eV)F 1s 0.1% 687.58O 1s 5.6% 532.48C 1s 94.1% 283.88Si 2s 0.2% 152.98

C-C

C-C

, C-O

C-C

, C=O

p-p*

Peak Label/ID BE (eV) FWHM (eV) Height Gauss %C-C 284.31 1.27 92105.4 75.0%C-C, C-O 285.94 1.50 10568.7 85.0%C-C, C=O 287.69 2.05 4615.93 85.0%p-p* 290.11 2.51 2951.43 85.0%

Reduced Chi-Square: 4.67448

Raman Overlay Spectra

Carbon Nanotube Synthesis• Laser Ablation: Nanotubes produced by pulsed YAG

laser ablation of graphite target in a furnace at 1200 °C. (R. Smalley, 1996)

• Chemical Vapor Deposition (CVD): Nanotubes are grown from nucleation sites of a catalyst in carbon based gas environments (Ethylene, Methane, etc.) at elevated temperatures (600 - 1000 °C).

• Control Parameters for CVD nanotube synthesis: catalyst material, gas, temperature, flow-rate, synthesis time.

Electric Arc Discharge• Ebbesen and Ajayan 1992• Arc discharge involving various types of plasmas and electrodes are known to

produce a range of carbonaceous structures as the vaporized carbon is condensed. The condensed state can be described as a carbonaceous web, which generally radiates from the cathode, and a solid deposit on the cathode surface. Amorphous carbon, fullerenes, single- or multi-walled carbon nanotubes are among the structures present in these condensed areas.

Polymorphs of carbon contained in the web and cathode deposits are variable in terms of the arc discharge operating conditions which include pressure and composition of the gas, arc voltage, and catalyst particles. In this study, we explore the effects an accompanying magnetic and/or electrical bias has on the form of deposited carbon by analyzing the condensed states as a function of the operating characteristics. A primary goal is increasing the yield of single-walled carbon nanotubes formed.

Continuous carbon nanotube production in underwater AC electric arc

A simple, low cost and continuous growth method for the production of well graphitized multi-wall carbon nanotubes, combines the underwater growth with the use of an AC power supply and computer control. An AC electric arc is generated between two identical carbon rods of 6 mm in diameter, submerged in deionized water. Two computer controlled stepper motors are used to regulate the distance between the electrodes. At a voltage of 40 V the arc is stable in the range of 85–45 A. At lower current values a higher fraction of carbon nanotubes is obtained in the product. There is no product on the electrodes, the deposit peels off the actual cathode into the water in the next half cycle when the role of the electrodes is reversed. No vacuum is needed, a continuous flow of water makes easy the removal of the product from the system. This makes our method suitable for up-scaling. http://www.nanotechnology.hu/results/arc.html

Laser AblationLaser ablation of graphite doped with 1-2% metal ions such as nickel and cobalt produces loose nanotube material called single walled nanotubes (SWNTs) and single walled nanohorns (SWNHs). These short pulse duration lasers, however, produced only a few tens of watts and a rather low vaporization rate of about 0.2g/hour.

http://www.gsiglasers.com/MarketSectors.aspx?page=56

Early work in KrF excimer laser ablationThe plasma plume created above a graphite target irradiated by a KrF laser beam (248 nm) has been investigated using three experimental methods: ion detection, time and spatially resolved emission spectroscopy and double Langmuir probe. Measurements give information on the energetic distribution of ionic species, on the kinetic temperature of the gas and on the electronic density of the plasma plume. Carbon thin films have been deposited on silicon substrates: for high fluence values (above 1000 J cm−2) and low temperature (30°C), the films are harder than c-BN, their refractive index is 2.4, and XPS analysis gives spectra with a high sp3 configuration

http://www.sciencedirect.com/science/article/pii/0925963594902321

Chemical Vapor Deposition (CVD)

• Colomer et al 2000; Awasthi et al 2003• Thermal catalytic CVD• Acetylene, hydrogen, and argon mixtures• Methane, hydrogen, and argon mixtures• Hydrocarbon ~1%, hydrogen 10 to 30%• Temperature of 500 to 900 Celsius• Transition metal catalyst (lower temps)

Chemical vapor deposition of novel carbon materialsNanocrystalline diamond thin films have been prepared using hot filament CVD technique with a mixture of CH4/H2/Ar as the reactant gas. We demonstrated that the ratio of H2 to Ar in the reactant gas plays an important role in control of the grain size of diamonds and the growth of the nanocrystalline diamonds. In addition, we have investigated the growth of carbon nanotubes from catalytic CVD using a hydrocarbon as the reactant gas. Furthermore, focused ion beam technique has been developed to control the growth of carbon nanotubes individually. Fig. 1. Surface morphology of diamond thin films as a function of methane concentrations. (a) 3% of CH4, (b) 4% of CH4, and (c) 5% of CH4. The corresponding Raman spectra are shown on the right panel

L. Chow et al. / Thin Solid Films 368 (2000) 193-197

CVD DiamondChemical vapor deposition of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been considered too difficult to make economical. CVD diamond growth typically occurs under low pressure (1–27 kPa; 0.145–3.926 psi; 7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others.

http://en.wikipedia.org/wiki/Chemical_vapor_deposition_of_diamond

Nanocarbon Growth Mechanisms

• Hydrocarbons are first broken down into smaller carbon molecular/atomic fragments

• Hydrogen is lost in the process• PAH ‘motifs’ form from carbon fragments• PAH combines with other PAH ‘motifs’• Motifs assemble into graphene patterns

– Fullerenes, nanotubes, nanospheres, etc

Fullerene Synthesis

• Acetylene or methane• Mixed with argon and hydrogen• Plasma, arc discharge• Acetylene decomposes (transition metal)• Carbon fragments combine into PAH

– Corannulene is a common

Poly Aromatic Hydrocarbons (PAH)

• Polycyclic aromatic hydrocarbons (PAHs), also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents.[2] Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass).

http://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon

Polycyclic Aromatic Hydrocarbon (PAH)PAHs are one of the most widespread organic pollutants. In addition to their presence in fossil fuels they are also formed by incomplete combustion of carbon-containing fuels such as wood, coal, diesel, fat, tobacco, and incense.[8] Different types of combustion yield different distributions of PAHs in both relative amounts of individual PAHs and in which isomers are produced. Crystal structure of a hexa-tert-butyl derivatized hexa-peri-hexabenzo(bc,ef,hi,kl,no,qr)coronene, reported by Klaus Müllen and co-workers.[1] The tert-butyl groups make this compound soluble in common solvents such as hexane, in which the unsubstituted PAH is insoluble. Other PAH structures can include naphthalene, pyrene, and benzene additions to pyrene.

http://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon

Corannulene

http://en.wikipedia.org/wiki/Corannulene

Graphitization Process

Raman spectroscopy of amorphous, nanostructured, diamond-likecarbon, and nanodiamond By Andrea Carlo Ferrari and John Robertson

Carbon Soot Nanostructure – PAH motifsCarbon nanostructures including nanotubes, fullerenes, and nanospheres are comprised of ‘graphitic motifs’ which combine at varied geometries to produce extended networks of sp2 carbon. PAH motifs are thought to form in combustion flames, and also during annealing of amorphous carbon (soot etc.). During high temperature annealing, PAH motifs are hypothesized to ‘fuse’ and additionally drive off hydrogen along basal planes. Conversion of amorphous carbon to PAH can be both an external and internal process.

Nanocarbon forms in a series of steps with increasing time and temperature

NASA Analysis of Soot

HRTEM Fringe Analysis

Selected samples of heat-treated carbon black

TEM Analysis of Soot

Typical Soot Soot Annealed at 2000 Celsius

Summary• Carbon comprises a number of allotropes• Each has characteristic/novel properties• Fabricating nanocarbon uses a number of

approaches, each with special equipment• Applications of nanocarbon include

electronics, structural materials, and energy• We are still at the beginning of a relatively

long journey into nanocarbon engineering

References• Azonano.com• Journal Carbon• Raman spectroscopy of carbon nanotubes• Wikipedia – nanotechnology• CTIC Group• NASA Glenn• MIT Open Courseware http://ocw.mit.edu