Use of Bipolar Electrochemistry to Control Nanofluidics Applications

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Use of Bipolar Electrochemistry to Control
Nanofluidics Applications
Bradley Group Sundar Babu (postdoc) Patrick
Ndungu (PhD, 2004) Guzeliya Korneva (graduate
student) Peter Hayes (undergraduate student)
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Outline

• Bipolar Electrochemistry Concepts
• Bipolar Electrodeposition onto nanofibers, MWNTs
• Nanofluidic device fabrication via bipolar
  electrodeposition proof of concept
• Proposed future work

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Polarization of A Metal Particle in an Electric
Field
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Advantages
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Exploitation of particle aspect ratio to carry
out bipolar electrochemistry at sub-micron scale
DV E 2r
DV E L
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Size and Site Selective Bipolar Electrodeposition
of Pd onto Carbon Nanofibers
Carbon nanofiber
Palladium
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Effect of Deposition Time
Nanocrystals of size between 5-10nm Ramified
deposits
Bradley et al. Fullerenes, Nanotubes and Carbon
Nanostructures, 2005, In Press.
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Bipolar Electrodeposition of Pd onto Carbon
Nanofibers
0 s
80 s
120 s
10 s
20 s
240 s
480 s
40 s
E 3000 V/cm
Bradley et al., Fullerenes, Nanotubes and Carbon
Nanostructures, 2005, In Press.
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Bipolar Electrodeposition of Co onto a MWNT
(Unipolar pulsing DC field)
Intensity 10 kV/cm, ton 1ms, toff 24 ms,
field time 25 min
Bradley et al, Mat. Res. Soc. Symp.Proc. 2004,
818 361-369
Bradley et al, Mat. Res. Soc. Symp.Proc. 2004,
818 361-369
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Effective and True Lengths of Carbon Nanofibers
and Nanotubes
Bradley et al, Mat. Res. Soc. Symp.Proc. 2004,
818 361-369
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Bipolar Electrodeposition of Sn onto CVD nanopipes
Intensity 10 kV/cm, ton 1ms, toff 24 ms,
field time 10sec
Bradley et al. ChemWeb Preprint Server,
CPSchemistry/0309001, 2003, http//preprint.chemw
eb.com/chemistry/0309001
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Bipolar Electrodeposition of Zn
Intensity 6 kV/cm, ton 1ms, toff 24 ms, field
time 40sec
Bradley et al. ChemWeb Preprint Server,
CPSchemistry/0312002, 2003, http//preprint.chemw
eb.com/chemistry/0312002
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Bipolar Electrodeposition of CdS
Intensity 9 kV/cm, ton 1ms, toff 24 ms, field
time 20 sec
(CdCl2 and sulfur were dissolved in DMSO)
Bradley et al, ChemWeb Preprint Server,
CPSchemistry/0312001, 2003, http//preprint.chemw
eb.com/chemistry/0312001
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Bipolar Electrodeposition of Polypyrrole
(anodic reactions)
Intensity 10 kV/cm, ton 1ms, toff 24 ms,
field time 10 sec
Sundar et al., Microfluidics and Nanofluidics, In
Press
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Double Deposition of Polypyrrole
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Guiding water into carbon nanopipes
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Step 2 Condensation of Water
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Polypyrrole Mediated Injection of Water into a
Nanopipe
4.9 Torr
5.2 Torr
5.2 Torr
5.7 Torr
5.8 Torr
5.9 Torr
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Blocking the tips
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Future Work

• Making tips hydrophobic to control condensation
  point of water vapor
• Surface modification of nanotubes for potential
  biological applications
• Fabrication of nanochannels with diameter gradient

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Nanopipes with hydrophobic tip

• Surfaces of gold or silver can be made super
  hydrophobic by self assembly of long chain alkane
  thiols.
• Bipolar deposition of gold or silver on carbon
  nanopipes followed by exposure to HDT should
  make the tip hydrophobic. Thus water condensation
  and subsequent entry of water into the nanopipe
  would occur only at the tip without the metal
  deposit.

Hexadecanethiol
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Surface modification of nanotubes
(Metal deposition by electroless plating method)
Gold will be deposited inside the nanopipe by
continuous flow of the plating solution through
the as synthesized membrane. Removal of the
alumina template would yield nanopipes coated
with a thin layer of gold deposit inside the
pipes. The affinity of metallic gold and silver
to biomolecules could be exploited to study
various reaction path ways.
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Fabrication of nanochannels with dimension
gradient
The pore diameter of the anodized alumina depends
on the applied potential, concentration of the
electrolyte and also the temperature. Therefore
it is possible to tune the current distribution
pathways and obtain a gradient in the pore
diameter by using various electrode geometries.
Since the process is highly diffusion limited,
it is also possible to obtain a gradient in the
thickness of the alumina layer.