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Home , Carbon nanotube, Fullerene

FROM TO PASSING THROUGH NANOTUBES : SYNTHESIS, PROPERTIES AND APPLICATIONS OF quasi-NEW .

Simone Musso spsp 22 and sp 33 hybridizations

Carbon, having an electron configuration 1s2 2s2 2p2, forms a great variety of crystalline and disordered structures because it can exist in three different hybridizations, sp 3, sp 2, sp 1.

sp 2 sp 3

Planar geometry Tetrahedral geometry Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite

Planar geometry Tetrahedral geometry Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite Diamond

Nanotube

Physical and chemical properties areFullerene a direct consequence of the carbon-carbon bonds and lattice configuration Nanotube/ sp 2 + sp 3 character Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite Graphene Diamond

Fullerene

Nanotube/Fullerene sp 2 + sp 3 character Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite Graphene Diamond

Fullerene Carbon Nanotube

Nanotube/Fullerene sp 2 + sp 3 character Discovery of fullerene or buckyball

H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl and R. E. Smalley, 318 (1985) 162–63. Discovery of fullerene

Before the C60 structure was considered beyond doubt, a sufficient amount of material had to be prepared for detailed spectroscopic analysis, but a lack of funds stopped the research.. Then, in 1990 Kratschmer and Huffman developed an arc discharge technique :

DC Arcdischarge

ddp ≈≈≈ 20 V I = 100200 A T° →→→ 40006000°C He or Ar (600mbar)

W. Krätschmer, L. D. Lamb, K. Fostiropoulos and D. R. Huffman, Nature 347 (1990) 354–58. Characterization of fullerene

XRD

MS

FTIR UVVis

W. Krätschmer, L. D. Lamb, K. Fostiropoulos and D. R. Huffman, Nature 347 (1990) 354–58. Fullerenes

8.34 Å ; 7.66 Å C240

C540

C960

C70 (rugby-ballDifferent shaped ) fullerenes can be separated by means of chromatographic column.

d= 7.1 Å

C60 (bucky ball) Fullerene properties

CHEMICAL REACTIVITY  Fullerenes are nontoxic and are soluble in several organic .

Fullerenes are quite stable. However the spherical curvature produces angle strain that allows fullerenes to undergo characteristic reactions of addition to double bonds (hybridization turns from sp 2 to sp 3).

C60 in organic solvents exhibits 5 stages of reversible oxidation/reduction, hence fullerene can work either as electrophiles or nucleophiles .

C60 F18 Image created by Chris Ewels, www.ewels.info Fullerene properties

DERIVATIVES: EXOHEDRAL , ENDOHEDRAL and ON-SITE

Fullerenes, packed in fcc structure, can be intercalated with alkali and alkalineearth atoms which provide electrons to the conduction band (from semiconducting to metallic behavior). In 1991 potassium doped fullerene (K 3C60 ) revealed superconducting behavior at 18K.

L. Forrò and L. Mihaly, Rep. Prog. Phys. 64 (2001) 649-699. Fullerene properties

DERIVATIVES: EXOHEDRAL , ENDOHEDRAL and ONSITE DOPING

 In the endohedral doping a foreign atom is inserted in the inner cavity (M @ C ). This doping can be performed either by implantation or 60 CNTs !!! coevaporation of C and metal in arc discharge system.

 The onsite doping is achieved by replacing one carbon atom with a atom ((C 59 N) 2 azafullerene).

Image created by Chris Ewels, www.ewels.info L. Forrò and L. Mihaly, Rep. Prog. Phys. 64 (2001) 649-699. Fullerenes applications

 Hydrogen or oxygen storage : of fullerene produces hydrides. The reaction is reversible and can be catalyzed with (low ).

 Catalyst : fullerene promotes the conversion of methane into higher hydrocarbons and inhibits coking reactions.

 Sensor : fullerene based capacitors can be used to detect ppm of H2S in N2, ppm of water in isopropanol.

 Diamond precursor : fullerene can be transformed to diamond at high pressure (RT) or can be used as a diamond nucleation center during CVD.

 Alloy strengthening/hardening (Ti), improvement of electrical conductivity of Cu alloys.

 Biomedical field : inhibition of human HIV replication and HIV-1 protease. Biological antioxidant (radical sponge). Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite Diamond

Fullerene Carbon Nanotube

Nanotube/Fullerene sp 2 + sp 3 character Discovery of CNTs

Arcdischarge: from to CNTs

Many scientific papers start citing ‘‘the discovery of carbon nanotubes by Iijima in 1991. . .’’

S. Iijima, Nature 354 , (1991) 56 Discovery of CNTs

First TEM evidences of nano sized carbon tubes

L.V. Radushkevich, V.M. Lukyanovich, Zurn. Fisic. Chim . 26 , (1952) 88 Discovery of CNTs What are CNTs?

Rolled graphene sheet Diameter: 0,7 100 nm Length: from few tens of nm up to several mm

Even ifif thethecurvature causes aahigherhigherstrain energy, aadefectdefect free CNT has anan overall lower energy state than graphite because dangling bonds areare removedremoved..ThisThisexplains high thermal stability and chemical inertnessinertness.. CNTs classification SWCNTs classification

A CNT is characterized by its Chiral Vector ((CChh))== n ââ11 + m ââ22 and by the Chrial Angle ( θθθ) with respect to the zig zag axis

Zig-zag n −−− m ≠≠≠ 3 ××× integer Semi-conductor behavior depending on the diameter. Chiral

Armchair n −−− m = 3 ××× integer Metallic conductor behavior SWCNTs classification

Armchair (5,5) θθθ = 30 °°°

Zig Zag (9,0) θθθ = 0 °°°

Chiral (10,5) 0°°°θθθ < 30° Characterization SEM HRTEM TGA Air 20°C/min

1.6 100 1.4

80 1.2

1.0 60 0.8

40 0.6 Weight[%] 0.4 20 0.2 Weightderivative [%/°C]

0.0 0

-0.2 200 400 600 800 [°C]

Raman spectroscopy XRD 1800 1591 cm 1 (100) 1600 G peak (002) 1400

1200 (*) 1 1344 cm 1000 D peak

(*) 800 Intensity (a.u.) 600 (004)

Intensity (arb.unit) 400 RBM 200

0 10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 2θ (°) Raman shift (cm -1 ) Properties of defect free CNTs

Young’s modulus Tensile Strength Density (GPa) (GPa) (g/cm 3) MWCNT 1200 ∼150 2.6 SWCNT 1054 75 1.3 SWCNT bundle 563 ∼150 1.3 Graphite (in-plane) 350 2.5 2.2-2.6 208 0.4 7.8

Thermal conductivity Electrical conductivity (W/mK) RT (A/cm 2)

MWCNT ∼3000 ≤10 9 SWCNT ∼6000 Depends on the

SWCNT bundle ∼3000 ≤10 9 Graphite (in-plane) ∼1700 ≤10 9

Diamond 2000 - 2500

Copper 401 10 6 Functionalization

Chemical functionalization can be used to tune CNTs properties.  Composite – improving compatibility matrix/filler  Biomedical – improving biocompatibility, drug delivery, diagnosis

Chemical (KMnO 4, HNO 3H2SO 4) or oxidation change surface properties while producing lattice defects (removable by annealing). Van der Waals interactions with porphyrin or pyrene derivatives are less effective. CNT properties/applications CNT synthesis

High temperature methods  Arc Discharge 

These techniques generate small amount of high quality CNTs by sublimation of graphite in presence of catalyst particles.

Gas (vapor phase) methods  Chemical Vapor Deposition (CVD) and plasma enhancedCVD (PECVD) During CVD a conventional heat source is used to form CNTs by thermal cracking of hydrocarbons. A plasma source is used in PECVD to create a glow discharge which provokes a low temperature precursor dissociation

Nanoparticles of Co, Ni or Fe are necessary to catalyze the growth CNT synthesis

CVD Gas or low bp liquids can be used. The CVD technique is simple, low-cost, easily scalable for commercial production and allows to produce large amounts of CNTs with high purity.

PECVD

Plasma discharge sources: - direct current (DC), - alternating current (AC), - radio frequency (RF), V= 600V T° →→→ 400800°C - hot-filament aided with DC, Ar or N 2 (0.130 Torr) - microwaves We do like gas phase techniques

CVD allows to produce cm long CNTs. With direct spinning is also possible the synthesis of very long CNT ropes in situ.

YaLi Li et al., Science 304 (2004) 276 S. Musso et al. Carbon 45 (2007) 11331136 CNT growth mechanism

Two theories for the carbonmetal interaction:  Dissolution and saturation of carbon atoms in metal and precipitation of carbon.  The catalyst provokes dehydroaromatization (DHA) of cyclic molecules of hydrocarbon.

Tip growth mechanism is due to a Base growth mechanism is due weak of the catalyst to to a strong adhesion of the the substrate. catalyst to the substrate. Tip growth mechanism

Stephan Hofmann et al., Nanoletters 7 (2007) 602 TOXICITY

Factors influencing the safety of CNTs in vivo .

Small CNT

Big CNT Allotropic forms of C

3.4 Å Planar, sp 2 Cubic, sp 3 hybridization hybridization

Graphite Graphene Diamond

Fullerene Carbon Nanotube

Nanotube/Fullerene sp 2 + sp 3 character Allotropic forms of C

Graphene Graphite

 Graphene was largely studied from a theoretical point of view.

 The unsuccessful attempts to synthesize it seemed to confirm the theory that truly two dimensional crystals (any kind of crystal) could not exist.

 InNanotube 2D the thermal vibration of the atoms should leadFullerene to a displacement comparable to interatomic distance (thermodynamically unstable).

 The very large perimetertosurface ratio of 2D crystals promotes a collapse. Discovery of Graphene?... Not yet

Epitaxial Growth by CVD

Graphene and few layers of graphene are grown on Ni

Graphene is not freestanding and its properties are strongly affected by substrate:  Significant charge transfer from the substrate to the epitaxial graphene

 Hybridization between the d orbitals of the substrate atoms and π orbitals of graphene, which significantly alters the electronic structure of the epitaxial graphene. Discovery of Graphene

Freestanding graphene films (10 m in size) were prepared by mechanical exfoliation (repeated peeling) of small mesas of highly oriented pyrolytic graphite (HOPG).

K.S. Novoselov et al., Science 306 (2004) 666-669 MultiMultilayerslayers graphene

 The electronic structure of graphene rapidly evolves with the number of layers, approaching the 3D limit of graphite at 10 layers.

 Only graphene and its bi-layer has simple electronic spectra: they are both zero-gap (or zero-overlap semimetals).

 For three or more layers, the spectra become more complicated, several charge carriers appear, and the conduction and valence bands start notably overlapping. This allows single-, double and few (3 to <10) layer graphene to be distinguished as three different types of 2D crystals (‘’).

 Thicker structures should be considered as thin films of graphite.

J.C. Meyer et al., Nature 446 (2007) 60-63 Characterization

HRTEM

500 nm

2 nm

1 nm J.C. Meyer et al., Nature 446 (2007) 60-63 Characterization

AFMSTM topography

STM

AFM

A. Charrier et al., J. Appl. Phys. 92 (2002) 2479-2484 M.I. Katsnelson, MaterialsToday 10 (2007) 20-27 Characterization

Nanobeam ediffraction

Since graphene is microscopically corrugated the e diffraction peaks of graphene become broader while increasing the tilt angle.

The elastic strain can intrinsically provide the thermodynamic stability of the film.

J.C. Meyer et al., Nature 446 (2007) 60-63 Characterization

Raman analysis

2D (G’)

Raman spectra of graphene flakes. 2D (G') Raman peak changes in shape width and position for an increasing number of layers reflecting a change in electron band structure and electron interactions.

A.C. Ferrari et al., Phys. Rev. Lett. 97 (2006) 187401 Characterization

Confocal Raman

Confocal Raman map (2D band center of mass position). 1, 2, 3 and 4- layered flakes can be easily distinguished when using a color palette scale. High yield graphene synthesis

Chemical Vapor Deposition CVD (or PECVE) of carbon precursor is used to deposit graphene on thin layer of (1 1 1) over substrate. The graphene can be transferred to various substrates, demonstrating viability for numerous electronic applications.

K.S. Kim et al., Nature 457 (2009) 706-710 Other graphene synthesis

Silicon carbide sublimation  Silicon carbide (6H-SiC) is heated between 1080 and 1320°C giving the growth of graphene. The face of the SiC used for graphene creation, Si- terminated or C-terminated, highly influences the thickness, mobility and carrier density of the graphene.

Hydrazine reduction  is reduced to single-layer graphene in a solution of pure hydrazine (NH 2-NH 2).

Sodium reduction of ethanol  Gram-quantities of graphene are produced by the reduction of ethanol by sodium metal, followed by of the ethoxide product, and washing with water to remove sodium salts.

Unfolding CNTs  Graphene ribbons are produced by cutting and unfolding CNTs via

chemical etching (KMnO 4-H2SO 4) o plasma etching. Graphene properties/applications

Electrical properties

Charge carriers (electrons and holes) have high density (1013 cm 2) and high mobility (15000 cm 2V1s1) at RT, and the mobility weakly depends on temperature (only impurity ):

 Ballistic field effect transistor (high speed electronic devices)

Rather modest on-off conductance ratio of ~30 at RT

K.S. Novoselov et al., Science 306 (2004) 666-669 Graphene properties/applications

Electrical properties

The transistor conductance can be significantly altered (10 6 onoff ratio at RT ) by a reversible chemical modification. In presence of humidity the electric field changes the graphene to graphane (hydrogenated derivative, 3.5 eV of ) and graphene oxide (OH, insulator).

 Non volatile memory application.

T.J. Echtermeyer et al., IEEE Electronic Device Letters 29 (2008) 952 Graphene properties/applications

Electrical properties

Graphene chip can double the frequency of an electromagnetic signal.  Graphene chips can transmit data faster than standard silicon chips, consuming less energy and having a higher S/N ratio.

Graphene has high electrical conductivity, high optical transparency, mechanical strength and flexibility.  Touchscreens, liquid crystal displays, organic photovoltaic cells, stretchable electrodes.

K.S. Kim et al., Nature 457 (2009) 706-710 Graphene properties/applications

Electrical properties

Graphene has an incredibly high surface area to mass ratio.  Ultracapacitors with great energy storage density.

Graphene has electrical conductivity can be tuned by gas molecule absorption.  High sensitive gas sensors.

Graphene stripes, called graphene nanoribbons (GNRs), have electrical properties that depends on the unbonded edges.  Armchair GNRs are semiconductors with a band gap that increases with the decreasing of the width.  Research is being done to create quantum dots by changing the width of GNRs at select points along the ribbon, creating quantum confinement. Graphene properties/applications

High (~ 5000 Wm 1K1)  Heat sinks.

Graphenen is very strong (Young’s modulus 0.5 TPa) and stiff (elastic constant 15N/m).  NEMS applications as pressure sensors or resonators . 

Small spinorbit interaction and near absence of nuclear magnetic moments in carbon. GNRs in the zigzag orientation, at low , show spin polarized edge currents.  Spintronics (magnetoelectronics) applications Graphene properties/applications

Graphene oxide is obtained by oxidizing (KMnO 4H2SO 4) and chemically processing graphite/graphene. The graphene oxide flakes dispersed in water can give wellordered structure with exceptional mechanical properties.  Nanocomposites

S. Stankovich et al., J. Mater. Chem . 16 (2006) 155

H. Chen et al., Adv. Mater. 20 (2008) 3557-3561 Thank you for your attention!