Carbon Nano Tubes (CNTs)
Carbon Nanotubes (CNTs) are nanostructures derived from rolled graphene
planes and posess various interesting chemical and physical properties.
Figure Graphene is a honeycomb lattice
of carbon atoms.Also has sp2
hybridization
Figure left ones SWNTs and right ones MWNTs
CNTs
CNTs exist as single (SWNTs),and multi-walled (MWNTs) structures.
The discovery of carbon nanotubes by Iijima
in 1991 using High Resolution Electron Microscopy
(HREM)
Figure3
Properties of CNTs
They present several interesting properties,such as;
▪ High aspect ratio(higher than 1000)
▪ Ultra-light weight
▪ Tremendous strength(10-100 times stronger than steel)
▪ High thermal conductivity
▪ Remarkable electronic properties from metallic to semiconducting
An Example of SWCNT from Market
Outer Diameter: 1-4nm
Inner Diameter: 0.8-1.6nm
Length: 5-30um
Ash: <1.5 wt%
Purity: >90 wt%
Additional MWNT content: >5wt%
Amorphous Carbon Content: <3wt%
Specific Surface Area: 407 m2/g
Electrical Conductivity: >100 S/cm
Bulk density: 0.14 g/cm3
True density: ~2.1 g/cm3
Methods of Carbon Nanotube Synthesis
▪Plasma based synthesis method or Arc discharge evaporation method
▪Laser Ablation Method
▪Thermal Synthesis Process
▪Chemical vapor deposition (CVD)
▪Plasma Enhanced CVD (PECVD)
Synthesis of CNTs by CVD
Critical Parameters for CVD
▪Carbon source
▪ Catalyst
▪ Growth temperature
CNT synthesis with CVD animation
Electronic Sturucture of CNTs
The general condition for a CNT to be metallic ;
In-mI=3q where q=0,1,2,3,…
We have three type of CNTs structure according to chiral vector
which showed below;
• Illustration of Chiral vector C and
unit vectors a1 and a2, A and B the
two lattice sites of the graphene
lattice.
• The graphene sheet when rolled
over Chiral vector C.
𝐶ℎ = 𝑛𝑎1 + 𝑛𝑎2
▪ Armchair (n=m)
▪ Zig-zag (n or m=0,always metallic)
▪ Chiral
Figure a)0 Band gab for
Semiconductor
b)Band gab for metallic
Advantages of CNTs
▪Biocompatible
▪Highly elastic nature and have the possibility of intracellular delivery.
▪May exhibit minimum cytotoxicity.
▪Ultra-light weight and do not break down during processing.
▪ It has an open end on both sides, which makes the inner surface accessible and subsequent
incorporation of species within nanotubes is particularly easy.
▪Nanotubes have longer inner volume relative to the diameter of nanotubes for entrapment.
▪ CNTs are able to enter cells by spontaneous mechanism due to its tubular and nano needle shape.
▪ It has distinct inner and outer surface, which can he differentially modified for chemical biochemical
functionalization.
CNTs in Biomedicine
The functionalization of CNTs makes them useful in a range of different applications.
CNTs can be conjugated with various biological molecules including drugs, proteins and nucleic
acid to afford bio-functionalities.
Their structure means that the tubes have an inner and an outer core which can both be modified
by different functional groups. Thus the CNTs can be designed for very specific purposes.
In the area of biomedicine, the applications of CNTs are investigated in especially four main
fields: drug delivery, biomedical imaging, biosensors and scaffolds in tissue engineering
Some Examples where CNTs Used in Medicine
Cancer Treatments
Figure Shows delivery system of SWNT-PTX is more effective
for reducing tumor size even more medicine itself.
Drug Delivery
Figure Schematic representation of drug delivery
Blood Cancer Treatment
Leukemia is a cancer that begins in the bone marrow (the soft inner part of some bones), but in
most cases, moves into the blood. It can then spread to other parts of the body, such as organs and
tissues.
An intensified targeted delivery of daunorubicin (Dau) to acute lymphoblastic leukemia was
achieved by Taghdisi et al., they developed a tertiary complex of Sgc8c aptamer
International Journal of Pharmaceutical Science and Research 18 daunorubicin, and SWCNT
named as Dau-aptamer SWCNTs.
References
https://www.indiamart.com/proddetail/multi-walled-carbon-nanotubes-11744308148.html
https://www.laboratory-journal.com/science/material-science/wonder-material-graphene
https://www.nanoshel.com/single-walled-carbon-nanotubes-swnts
https://www.intechopen.com/books/electronic-properties-of-carbon-nanotubes/electronic-bandstructure-of-carbon-nanotubes-in-equilibrium-and-none-equilibrium-regimes
https://www.researchgate.net/publication/303994564_Carbon_nanotubes_Types_methods_of_pre
paration_and_applications
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2562710/figure/F1/
https://www.cheaptubes.com/product/single-walled-double-walled-carbon-nanotubes-90/