Uhlíkové nanotrubice

Rozdělení, struktura

Eva Košťáková

KNT, FT, TUL

UHLÍK

Uhlík je chemický prvek, tvořící základní kámen všech

organických sloučenin a tím i všech živých organizmů.

Charakteristickou vlastností atomů uhlíku je schopnost

vytvářet řetězce, což je dáno mimořádnou pevností

jednoduché a dvojné vazby C-C.

Diamant Grafit

Fuleren C60 Fuleren C250

Amorfní uhlíkNanotrubice

Formy uhlíkových materiálů

Diamant Grafit

Formy uhlíkových materiálů

Čistý uhlík je obecně znám ve dvou molekulárních formách: diamant, grafit.

Krystalizace v kubické struktuře

nejčastěji v osmistěnech. Ve formě grafitu uhlík krystalizuje ve vrstvách.

Grafit

Struktura grafitu je vysoce anizotropní.

Je tvořen grafenovými vrstvami.

V jejich rovině jsou atomy pojeny pevnými

kovalentními vazbami

Ve směru kolmém na tyto vrstvy jsou

slabé vazby – Van der Waalsovy.

Fullereny

Představují třetí známou formu uhlíku!

Od C20 dále (mimo C22)

C20 C60

Uhlíkové nanomateriál - Fullereny

Nejméně stabilní C20 – pravidelný dvanáctistěn jehož stěny jsou

pětiúhelníky.

Fulereny jsou „kulovité“ (často mnohostěnné)

obří molekuly tvořené dvaceti a více atomy uhlíku.

Pak téměř pro každý sudý

počet atomů uhlíku (vyjma 22)

existuje další fulleren.

C540

Uhlíkové nanomateriály – kulovité fullereny

Fuleren C60

Uhlík je čtyřmocný!

Výjimečné postavení má C60 – nejkulatější, nejsymetričtější.

Nejobvyklejší fuleren C60 (povrchové napětí)

Mezi šestiúhelníky musí být pětiúhelníkové poruchy –

vytvoření uzavřeného prostorového útvaru.

CENA: Sigmaaldrich.com C60 25mg = 1300Kč (97% čistota), 1kg = 21000Kč

Jméno fulleren – dle podoby ke kopulím geodetických budov architekta

Richard Buckminster Fullera == Buckminsterfullerene C60

Nobelova cena za chemii - 1996

The first fullerene to be discovered, and the family's

namesake, was buckminsterfullerene C60, made in 1985 by

Robert Curl, Harold Kroto and Richard Smalley.

By 1991, it was relatively easy to produce gram-sized samples

of fullerene powder

Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize

in Chemistry for their roles in the discovery of this class of

compounds.

Fullerene (Buckyball) colloids, 1,000,000X.

http://www.nature.com/nnano/journal/v1/n2/full/nnano.2006.62.html

The nucleus to nucleus diameter of a

C60 molecule is about 0.71 nm

nano-onions

Fulereny jsou „kulovité“ (často mnohostěnné)

obří molekuly tvořené dvaceti a více atomy

uhlíku.

Uhlíkové nanomateriál – válcovité

fullereny - Nanotrubice

A large percentage of academic and popular

literature attributes the discovery of hollow,

nanometer-size tubes composed of graphitic carbon

to Sumio Iijima in 1991.

Sumio Iijima (born 1939) is a Japanese physicist,

often cited as the discoverer of carbon nanotubes.

SWNTs (single wall nanotubes) –

jednostěnné uhlíkové nanotrubice

Diameter of SWNTs

Optimal 1,4nm

Possible 0,4 – 2,5 nm

TEM microstructure of SWNT-rope

3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 1

Carbon nanotubes - struktura

a) Zigzag structure

b) Armchair structure

c) Chiral structure

Most single-walled nanotubes (SWNT)

have a diameter of close to 1 nanometer,

with a tube length that can be many

millions of times longer. The structure of a

SWNT can be conceptualized by wrapping

a one-atom-thick layer of graphite called

graphene into a seamless cylinder. The

way the graphene sheet is wrapped is

represented by a pair of indices (n,m)

called the chiral vector. The integers n and

m denote the number of unit vectors along

two directions in the honeycomb crystal

lattice of graphene. If m = 0, the nanotubes

are called "zigzag". If n = m, the nanotubes

are called "armchair". Otherwise, they are

called "chiral".

Multi-walled nanotubes (MWNT) consist of multiple rolled layers

(concentric tubes) of graphite. There are two models which can be used

to describe the structures of multi-walled nanotubes. In the Russian Doll

model, sheets of graphite are arranged in concentric cylinders, e.g. a

(0,8) single-walled nanotube (SWNT) within a larger (0,10) single-walled

nanotube

A "zig-zag" carbon nanotube.

A „arm-chair" carbon nanotube.

A „chiral" carbon nanotube.

"zig-zag"

„chiral"

The end caps of a nanotube are

one of a half bucky ball and the

repeating axial hexagonal

patterns are graphite structures;

however, the electrical

properties of nanotubes are

dependent on the precise

orientation[5] of the repeating

hexagons. The nanotubes can

be semiconductors (similar to

“doped silicon” used in

integrated circuits) or metal-like

conductors (such as copper

used as electric wiring). The

inset micrographs show the

orientation axes that distinguish

between these electronic

behaviors. These micrographs

also show another important

development – that of single-

walled nanotubes or SWNT.

Using optimum synthesis

conditions one can make SWNT

tubes with diameters of 1.38 ±

0.02 nm, very close to the

diameter of geometrically ideal

nanotubes.

Optimální průměr SWNT = 1,4nm

Kolik šestiúhelníků je v obvodu takové

trubice, např. při uspořádání zig-zag?

Vzdálenost atomů uhlíku v

šesterečné struktuře je 1,44 Å

CH3

CH3

1

2

34

5

Postup při kreslení nanotrubic

MWNTs (multi wall nanotubes)

TEM microstructure of MWNTs and nanoparticle

the multi-walled nanotubes

are concentric (a good

analogy is a Russian

babushka doll). The inset

diagram shows micrographs

for 5, 2 and 7 MWNT

respectively from left to right

c-MWNTs (multi wall nanotubes)

cb-MWNTs (bamboo multi wall nanotubes)

Vícestěnná uhlíková trubice typu „bambus“

Typical TEM images of BCNTs grown at 850 ºC using a 10 wt.% Cu/Mo/MgO catalyst: (a) low magnification TEM image of BCNTs, (b) TEM image of catalyst particles located inside and at the tips of

the nanotubes, (c) TEM image of carbon nanotubes filled with a catalyst nanoparticle which is responsible for the formation of BCNTs with an outer diameter of 20 nm, (d) a high-resolution TEM

image of a BCNT with the curved graphite sheets.

www.azonano.com/Details.asp?ArticleID=2037

www.materials.ox.ac.uk/peoplepages/grobert.html

h-MWNTs ( herringboneMWNTs – rybí kost)

hb-MWNTs (bamboo herringbone multi wall nanotubes)

Hetero-nanotubes

X@SWNT or X@MWNT - Hybrid carbon nanotubes

An uncapped single-wall carbon nanotube with

encapsulated buckyballs. This type of tube is

sometimes referred to as a ‘peapod’ carbon nanotube.

Nanotube peapod – hrachový lusk

If the nanotube is big enough, there

is room for metal atoms, molecules,

and even fullerenes to fit inside.

A nanotube filled with fullerenes is

known as a "peapod". A model of a

peapod is shown below.

Under electron irradiation in TEM mesurements, the fullerenes

become mobile and merge to a second tube inside the tube

http://iffwww.iff.kfa-juelich.de/~cmeyer/filling/fillCNTs.html

Nanotrubice se dají „plnit“ oxidy kovů Ni, Co,

Fe, Zr, Cd, Sn atd. a čistými kovy Ag, Au, Pd,

Rh atd a fulereny.

http://gtresearchnews.gatech.edu/newsrelease/NANOTUBE.html

MWNT

Ag

Snaha o výrobu extrémně jemných kovových drátků – významné zlepšení elektrických vlastností.

SWNTs – 70%purity 1g = 300Euro

MWNTs – 90%purity 1kg = 1000Euro

MWNTs – 95%purity 1g = 40 Euro

MWNTs – 95%purity surface modified 1g = 50-65Euro

Cena uhlíkových nanotub

Orientace MWNTs

ZÁKLADNÍ VLASTNOSTI CNTs

Comparison of mechanical properties[

Material Young's Modulus

(TPa)

Tensile strength

(GPa)

Elongation at break (%)

SWNT ~1 (from 1 to 5) 13–53E

16

Armchair SWNT 0.94T

126.2T

23.1

Zigzag SWNT 0.94T

94.5T

15.6–17.5

Chiral SWNT 0.92

MWNT 0.8–0.9E

11–150E

Stainless Steel ~0.2 ~0.65–3 15–50

Kevlar ~0.15 ~3.5 ~2

KevlarT

0.25 29.6

EExperimental observation; TTheoretical prediction

ZÁKLADNÍ VLASTNOSTI CNTs

Because of the symmetry and unique electronic structure of

graphene, the structure of a nanotube strongly affects its electrical

properties. For a given (n,m) nanotube, if n = m, the nanotube is

metallic; if n − m is a multiple of 3, then the nanotube is

semiconducting with a very small band gap, otherwise the nanotube

is a moderate semiconductor. Thus all armchair (n = m) nanotubes

are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are

semiconducting. In theory, metallic nanotubes can carry an

electrical current density of 4 × 109 A/cm2 which is more than 1,000

times greater than metals such as copper[25].

3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 32

Carbon nanofibers: no hollow, diameter -

between 50-200nm, length – several

micrometers.

Carbon nanotubes: presence of hollow, -

from 1nm to several tens of micrometers (It

depends on number of walls), length – several

micrometers.

Nanowires: presence of hollow, - Not from

CARBON, from 1nm to several tens of

micrometers (It depends on number of walls),

length – several micrometers.