Dispersion of single wall carbon nanotubes in aqueous solution using surfactant

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Dispersion of single wall carbon nanotubes in
aqueous solution using surfactant
Review Paper Presentation

• By Tri Phan

Fundamentals of Nanotechnology, Chem E 5480
December 13rd, 2006
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Background and Introduction

• In 1991, Iijima discovered carbon nanotubes with
  the exceptional properties such as excellent
  mechanical strength and optical properties, high
  electrical and thermal conductivities.
• SWNTs are in bundled tubes when synthesized ?
  lose outstanding properties of SWNTs ? need to
  debundle or disperse SWNTs before used in
  research or application.
• Chemical modification tube walls
  functionalization, strong acid attacks ? caused
  defects in the tube structures that lead to
  losses in mechanical and electronic properties
• dispersions of SWNTs in aqueous solutions
  special interests due to potential application in
  biochemistry and biomedical engineering.
• Surfactants can disperse SWNTs in aqueous
  slotution without forming chemical bonds with the
  tubes ? not affect the tube properties.

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Literature Review

• In 2002, OConnell et al ultrasonically
  agitating an aqueous solution of SWNTs in sodium
  dodecyl sulfate (SDS).
• In 2003, Islam et al evaluated a wide range of
  surfactants ? sodium dodecylbenzenesulfonate
  (NaDDBS) the most effective surfactant to
  disperse HIPCO SWNTs.
• In 2003, Matarredona et al NaDDBS to disperse
  CoMoCat SWNTs.
• Islam et al (2003) and Matarredona et al (2003)
  have contributed a great deal of understanding in
  this topic.
• In 2005, Tan and Resasco good or better
  performance compared to NaDDBS such as Na
  cholate, Surfynol CT324, Aerosol OS, and Dowfax
  2A1

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Theoretical Background

• Non-chemical interactions between the surfactants
  and the tubes ? the key to effectiveness of
  surfactant-based dispersions of SWNTs
• Surface charge of SWNTs ? point of zero charge
  (PZC-pH at the surface shows a net surface charge
  of zero)
• Structures of head group and tail of surfactant
  affects interractions among head/tail and the
  tube/solution.
• Surfactant concentration affect both
  interactions and economic aspect ? CMC When
  surfactant solution increases to a level called
  critical micelle concentration (CMC), surfactant
  micelles will be formed.

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Current Research and Application

• NaDDBS the most powerful surfactant to disperse
  SWNTs in aqueous solution so far
• enhance stability of SWNTs in water by 10-100
  times
• Highest concentration of 20 mg/mL of nanotubes
  (63 was dispersed individual nanotubes)
• Hydrophobic interaction between the surfactant
  tail and the tubes controls the adsorption of the
  surfactants
• Benzene ring structure in the hydrophobic tail
  plays an important role to enhance interraction
  between the surfactants and the tubes.
• Surfactant adsorption is based on monomer basis,
  the surfactant concentration used should be below
  CMC
• Sonication is needed to debundle the tubes into
  individual tubes so that the surfactants are able
  to adsorb on the tubes.

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Current Research and Application (cont)

• Hemimicelles adsorption model

Monolayer adsorption model
Random adsorption model
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Future Directions

• The successful dispersion of SWNTs in aqueous
  solution using surfactant has revealed the
  viability of this approach toward the goal of
  producing individual SWNTs in aqueous solutions.
• Great opportunities and challenges to explore
  many potential applications in biochemistry and
  biomedical engineering.
• This method needs to be further studied to meet
  various requirements of different applications
  and to understand more about mechanism that
  controls the process.