Application of Carbon

Nanotubes in chromatography

ByAbdollah karim

golanInstructor:

Dr.yadollah yamini

What are Carbon Nanotubes ?• Carbon Nanotubes (CNTs) are allotropes of

carbon. These cylindrical carbon molecules have interesting properties that make them

potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science, as well as potential

uses in architectural fields. They exhibit extraordinary strength and unique electrical

properties, and are efficient conductors of heat. Their final usage, however, may be limited by

their potential toxicity.

Discovery

They were discovered in 1991 by the Japanese electron microscopist Sumio Iijima who was studying the material deposited on the cathode during the arc-evaporation synthesis of fullerenes. He found that the central core of the cathodic deposit contained a variety of closed graphitic structures including nanoparticles and nanotubes, of a type which had never

previously been observed

The way to find out how the carbon atoms are arranged in a molecule can be done by joining the vector coordinates of the atoms. By this way it can be identified whether if the carbon atoms are arranged in a zig-zag, armchair or in a helical shape.

armchair

1

Zig zag

chiral

Nanotubes are formed by rolling up a graphene sheet into a cylinder and capping each end with half of a fullerene molecule. Shown here is a (5, 5) armchair nanotube (top), a (9, 0) zigzag nanotube (middle) and a (10, 5) chiral nanotube. The diameter of the nanotubes depends on the values of n and m.

armchair

zigzagchiral

•

Arc discharge methodConnect two graphite rods to a power supply, place them millimeters apart,

and throw switch. At 100 amps, carbon vaporizes in a hot plasma.

Can produce SWNT and MWNTs with few structural defects

Tubes tend to be short with random sizes and directions

Chemical vapor deposition

Place substrate in oven, heat to 600 C, and slowly add a carbon-bearing gas

such as methane. As gas decomposes it frees up carbon atoms, which recombine in the form of NTs

Easiest to scale to industrial production; long length

NTs are usually MWNTs and often riddled with defects

Laser ablation (vaporization)

Blast graphite with intense laser pulses; use the laser pulses rather than electricity to

generate carbon gas from which the NTs form; try various conditions until hit on one that produces prodigious amounts of SWNTs

Primarily SWNTs, with a large diameter range that can be controlled by varying the reaction

temperature By far the most costly, because requires

expensive lasers

Properties

Electrical

Thermal

Strength Properties

• carbon nanotubes have the strongest tensile strength of any material known.

• it also has the highest modulus of elasticity.

MaterialYoung'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 150

Stainless Steel ~0.2 ~0.65-1 15-50

Kevlar ~0.15 ~3.5 ~2

KevlarT 0.25 29.6

Electrical Properties• If the nanotube structure is armchair then the

electrical properties are metallic

• If the nanotube structure is chiral then the electrical properties can be either semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor

• 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

Thermal Properties• All nanotubes are expected to be very good thermal

conductors along the tube, but good insulators laterally to the tube axis.

• It is predicted that carbon nanotubes will be able to transmit up to 6000 watts per meter per Kelvin at room temperature; compare this to copper, a metal well-known for its good thermal conductivity, which transmits 385 watts per meter per K.

• The temperature stability of carbon nanotubes is estimated to be up to 2800oC in vacuum and about 750oC in air.

Some applications of Carbon Nanotubes include the following

• Micro-electronics / semiconductorsConducting CompositesControlled Drug Delivery/releaseArtificial musclesSupercapacitorsBatteriesField emission flat panel displaysField Effect transistors and Single electron transistorsNano lithographyNano electronicsDopingNano balanceNano tweezersData storageMagnetic nanotubeNanogear

• Nanotube actuatorMolecular Quantum wiresHydrogen StorageNoble radioactive gas storageSolar storageWaste recyclingElectromagnetic shieldingDialysis FiltersThermal protectionNanotube reinforced compositesReinforcement of armour and other materialsReinforcement of polymerAvionicsCollision-protection materialsFly wheels"

applicationapplication

In gas chromatographyIn gas chromatography

In HPLC In HPLC

Gas-Liquid ChromatographyGas-Liquid Chromatography

Oven

Detector

Injection port

Nitrogen cylinder

Column

Recorder

•SWCNTswith a diluted solution of IL under controlled temperature. In thisway, when IL is immobilized on the inner wall of the SWCNTcapillary column, the nanotubes assist IL forming a network-likestructure. This improves the column chromatographic propertiesdue to the higher surface area available to analytes

application

• Seprate alkyl benzenes from alkane

• analysis of esters and C1–C4 alcoholic

Compounds

• allowing separation of primary and secondary alcohol isomers

MWCNTs-R-NH2 proved to be better performing than nonderivatizedones also for separation of a number of alcoholsand esters [29], with good reproducibility in retention time (RSDs < 1.5%)

SEM images of (a) original steel tubing surface, (b) surface after air oxidation at 550 ◦C, (c) CNT-coating after ethanol CVD, and (d) CNT-coating after functionalization.

GC chromatograms obtained on a SWCNT-bonded capillary column (A), column temperature 30 ◦C, linear velocity 15.5 cm s−1; IL capillary column (B), columntemperature 90 ◦C, linear velocity 13.8 cm s−1; IL + SWCNT capillary column (C), column temperature 110 ◦C, linear velocity 19.2 cm s−1.

Separation of test mixtures: naphthalene (1), fluorene(2), phenanthrene (3), and fluoranthene (4). Mobile phase:acetonitrile/water535:65 v/v. Conditions:; flow-rate, 1.0 mL/min; temperature,201C; injection volume, 20 mL, detection, UV at 254 nm.

MWCNTs/SiO2-1 column

Separation of test mixtures: naphthalene (1), fluorene(2), phenanthrene (3), and fluoranthene (4). Mobile phase:acetonitrile/water535:65 v/vflow-rate, 1.0 mL/min; temperature,201C; injection volume, 20 mL, detection, UV at 254 nm.

MWCNTs/SiO2-3 column

Separation of test mixtures: naphthalene (1), fluorene(2), phenanthrene (3), and fluoranthene (4). Mobile phase:acetonitrile/water535:65 v/v. flow-rate, 1.0 mL/min; temperature,201C; injection volume, 20 mL, detection, UV at 254 nm.

MWCNTs/SiO2-5 column

Separation of test mixture of sulfanilic acid (1),p-amino benzoic acid (2), phenol (3), benzene (4), benzaldehyde(5), acetophenone (6), and ethyl benzenecarboxylate (7). Mobilephase: water (A); methanol/water560:40 v/v (B). Conditions:MWCNTs/SiO2-5 (A), commercial HPLC column (B); other

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