Carbon nanotubes (CNTs) are hexagonally arranged carbon atoms with exceptional mechanical, electrical, and thermal properties, making them promising for various applications including biotechnology. Their synthesis methods include arc discharge, chemical vapor deposition, and laser ablation, each with its advantages and challenges. Despite their potential, issues like high cost, toxicity concerns, and difficulties in large-scale production need to be addressed for broader use.

1. Carbon Nanotubes (CNTs)Carbon Nanotubes (CNTs)
By: Naghmeh Poorinmohammad

2. OUTLINE
• Introduction
• Properties
• Synthesis Methods
• Applications (general and biotechnology-related)
• Challenges
• Summary
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3. INTRODUCTION
• Carbon nanotubes (CNTs) are hexagonally shaped arrangements of
carbon atoms that have been rolled into tubes.
• Diameter: less than 1 nm.
• Length: from a few nanometers up to a millimeter.
• Rolling up a graphene sheet may lead to a CNT (For imagination only!).
Adopted from “http://www.physik.uni-regensburg.de”
what are they?
INTRODUCTION: HistoryINTRODUCTION
What are they?
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4. INTRODUCTION: History
• 1952:
Radushkevich and Lukyanovich showed hollow graphitic carbon fibers
with 50nm diameter.
• 1979
Abrahamson presented evidence of carbon nanotubes at the 14th Biennial
Conference of Carbon at Pennsylvania State University.
• 1981
A group of Soviet scientists published the results of chemical and structural
characterization of carbon nanoparticles produced by a thermocatalytical
disproportionation of carbon monoxide.
• 1991
Nanotubes discovered in the soot of arc discharge at NEC, by Japanese
researcher Sumio Iijima.
INTRODUCTION
History
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5. INTRODUCTION: CNT types
(n,m)
n= column
m= row
If:
n=m  Armchair
n≠m  Chiral
(n,0)  Zig-Zag
INTRODUCTION: HistoryCNT types
Based on symmetry
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6. INTRODUCTION: CNT types
Multiple Wall CNT
or
Single Wall CNT
or
Parchment model Russian doll model
INTRODUCTION: HistoryCNT types
Based on walls
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7. PROPERTIES: Mechanical
• Carbon nanotubes are the strongest, flexible and stiffest materials yet
discovered in terms of tensile strength and elastic modulus respectively.
• The hardness (152 Gpa) and bulk modulus (462–546 Gpa) of carbon
nanotubes are greater than diamond, which is considered the hardest material.
• The current Young’s modulus value of SWCNs is about 1 terapascal.
• The modulus of the multi walled carbon nanotubes correlates to the amount
of disorder in the carbon nanotube walls.
• when multi walled carbon nanotubes break, the outermost layers break first
Materials Young’modulus(Tpa) Tensile strength(Gpa) Elongation at
break(%)
SWNTE ~1 (from 1 to 5) 13-53 16
Armchair
SWNTT
0.94 126.2 23.1
Zigzag SWNTT 0.94 94.5 15.6-17.5
Chiral SWNT 0.92
MWNTE 0.2-0.8-0.95 11-63-150
Stainless steelE 0.186-0.214 0.38-1.55 15-50
KevlarE 0.06-0.18 3.6-3.8 ~2
EExperimental observation; TTheoretical prediction
INTRODUCTION: HistoryPROPERTIES
Mechanical
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8. PROPERTIES: Electrical conductivity
• CNTs can be metallic or semi-conductors due to their geometry.
• For a given (m,n) nanotube:
- If n=m (armchair)  the CNTS is metallic
- If n-m is multiple of 3  the CNTs is semiconducting with a
small band gap.
- Otherwise ,the CNTs is moderate semiconductor.
• In theory, metallic nanotubes can carry an electric current density of
4 × 109 A/cm2, which is more than 1,000 times greater than those of
metals such as copper.
• They are one dimensional conductors only along the axis
INTRODUCTION: HistoryPROPERTIES
Electrical conductivity
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9. PROPERTIES: Thermal conductivity
• SWNTs room-temperature thermal conductivity is about 3500 W/(m·K) and
over 3000 W/(m·K) for individual MWNT.
• Addition of nanotubes to epoxy resin can double the thermal conductivity for a
loading of only 1%, showing that nanotube composite materials may be useful
for thermal management applications.
• All nanotubes are expected to be very good thermal conductors along the tube,
but good insulators laterally to the tube axis.
INTRODUCTION: HistoryPROPERTIES
Thermal Conductivity
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10. PROPERTIES: Thermal conductivity
• Flourescence:
 Semiconducting SWCNTs emit and absorb NIR.
 No excitonic luminescence in metallic tubes.
 Photoluminescence is used for measuring the quantities of semiconducting
nanotube species in a sample.
 Also to identify the symmetry and (n,m) properties.
• Raman spectroscopy:
 Raman spectroscopy has provided an exceedingly powerful tool for
characterization of CNT’s with respect to their diameters, and quality of the
samples properties.
 SWCNT and MWCNT can be discriminated via this method.
INTRODUCTION: HistoryPROPERTIES
Optical
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11. SYNTHESIS
• The most common and perhaps easiest way to produce CNTs.
• Carbon contained in the negative electrode sublimates because of the
high-discharge temperatures.
• The yield for this method is up to 30% by weight and it produces both
single- and multi-walled nanotubes with lengths of up to 50 micrometers
with few structural defects.
• Produces a complex mixture of components, and requires further
purification - to separate the CNTs from the soot and the residual catalytic
metals present in the crude product.
INTRODUCTION: HistorySYNTHESIS
I. Arc discharge method
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12. SYNTHESIS
• A substrate is prepared with a layer of metal catalyst particles, most commonly
nickel, cobalt, iron , or a combination.
• The substrate is heated to approximately 700°C.
• two gases are bled into the reactor: a process gas (such as ammonia , nitrogen or
hydrogen ) and a carbon-containing gas (such as acetylene , ethylene , ethanol or
methane ).
• Nanotubes grow at the sites of the metal catalyst; the carbon-containing gas is broken
apart at the surface of the catalyst particle, and the carbon is transported to the edges
of the particle, where it forms the nanotubes.
• Attracted attentions for its feasibility and potential for large-area production with
reasonable growth rates at relatively low temperatures.
INTRODUCTION: HistorySYTHESIS
II. Chemical vapor deposition (CVD)
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13. SYNTHESIS
• A pulsed laser vaporizes a graphite target in a high-temperature reactor while an
inert gas is bled into the chamber.
• Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon
condenses.
• A water-cooled surface may be included in the system to collect the nanotubes.
• The laser ablation method yields around 70% and produces primarily single-
walled carbon nanotubes with a controllable diameter determined by the reaction
temperature .
• However, it is more expensive than either arc discharge or chemical vapor
deposition.
INTRODUCTION: HistorySYNTHESIS
III. Laser ablation
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14. APPLICATIONS
• More slender tips  higher resolution will gain in microcopy.
• In addition, due to the high elasticity of the nanotubes, the tips do not suffer from
crashes on contact with the substrates.
• Biological molecules, such as DNA can also be imaged with higher resolution using
nanotube tips, compared to conventional STM tips.
INTRODUCTION: HistoryAPPLICATION
I. AFM/STM Tips
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Tang et al., Nano Lett. 5(1), 11-14 (2005).
Si Tip
CNT Probe
Chang et al., Jpn. J. Appl. Sci. 43(7B), 4517-4520 (2004).
Chang et al., Jpn. J. Appl. Phys. 43(7B), 4517-4520 (2004).

15. APPLICATIONSINTRODUCTION: HistoryAPPLICATION
II. Filters/membranes
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16. APPLICATIONS
• An important issue in intracellular drug delivery is the poor permeability of
the plasma membrane to many drugs.
• Thus, various carriers, including polyethylene glycol, peptides and lipids,
have been developed to facilitate the cellular entry of drugs.
• Recently, the feasibility of using SWNTs for intracellular drug delivery has
been demonstrated.
• They have high drug loading capacities and good cell penetration
qualities.
• Problems: lack of solubility, clumping occurrences, and half-life
INTRODUCTION: HistoryAPPLICATION
III. Molecular carriers
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17. APPLICATIONS
• Semi-conductive SWNTs with appropriate chirality can generate a small
band gap fluorescence of 1 eV, which corresponds to NIR range (900-1600
nm).
• Biological tissues have very low absorption, scattering, and
autofluorescence in this range and therefore, are very useful for biological
imaging.
• CNTs show great promise in NIR photoluminescence imaging , Raman
imaging and optical absorption agent for photoacoustic imaging.
INTRODUCTION: HistoryAPPLICATION
IV. Biomedical imaging
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18. APPLICATIONS
• A biosensor is a bioanalytical
device consisting of 2
components:
a bioreceptor and a transducer.
• The bioreceptor is a
biomolecule that recognizes the
target analyte whereas the
transducer converts the
recognition event into a
measurable signal.
INTRODUCTION: HistoryAPPLICATION
V. Bio-sensing
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19. • SWNT biosensors can exhibit large changes in electrical impedance and
optical properties in response to the surrounding environment which is
typically modulated by adsorption of a target on the CNT surface.
• Low detection limits and high selectivity require engineering the CNT surface
(e.g., functional groups and coatings).
• CNT plays dual role in a biosensor both as immobilization matrices and as
electron mediator.
V. Bio-sensing
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20. CHALLENGES
• Cost: Too expensive (~ $ 200per gram)
• Toxicity: there are some reports showing CNTs can
damage DNA or causing pulmonery toxicity.
• Manipulation: hard to purify and the ability to
manipulate structures at the atomic scale.
• Large-scale production: Large quantity fabrication
process still missing.
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21. SUMMARY
• CNTs have special properties which makes them interesting
in many fields.
• There is still a great need of improving its production and
manipulation.
• In biotechnological applications, we must care especially
when studying them for biomedical applications.
• Using CNTs for us biotechnologists needs a team work
since a deep knowledge will be gained when working in
interdisciplinary discipline!
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22. • Shao, Wei, et al. "Carbon Nanotubes for Use in Medicine: Potentials and
Limitations." (2013).
• Ajayan, Pulickel M., and Otto Z. Zhou. "Applications of carbon
nanotubes."Carbon nanotubes. Springer Berlin Heidelberg, 2001. 391-425.
• Balasubramanian, Kannan, and Marko Burghard. "Biosensors based on
carbon nanotubes." Analytical and bioanalytical chemistry 385.3 (2006):
452-468.
• Popov, Valentin N. "Carbon nanotubes: properties and
application." Materials Science and Engineering: R: Reports 43.3 (2004):
61-102.
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KEY REFERENCES

23. Thank You
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