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Mass transport through vertically aligned large diameter MWCNTs embedded in parylene.
P Krishnakumar1, P B Tiwari, S Staples
1Department of Physics, Arizona State University, Tempe, AZ 85287, USA.
Nanotechnology
|October 16, 2012
Summary
Porous membranes from carbon nanotubes enable selective transport of small molecules and nanoparticles using electric fields. Chemical modifications enhance control over particle movement through these advanced nanomaterials.
Area of Science:
- Nanotechnology
- Materials Science
- Physical Chemistry
Background:
- Vertically aligned forests of multi-walled carbon nanotubes (MWCNTs) offer unique nanoscale channels for transport studies.
- Parylene encapsulation provides structural integrity for fabricating robust nanotube-based membranes.
- Understanding charged particle transport through nanoscale pores is crucial for filtration and separation technologies.
Purpose of the Study:
- To investigate the transport mechanisms of charged particles through MWCNT membranes under electric fields and pressure.
- To evaluate the selectivity of MWCNT membranes for small molecules, nanoparticles, and biomolecules.
- To explore the impact of surface modification on particle translocation through these membranes.
Main Methods:
- Fabrication of porous membranes using parylene-encapsulated, vertically aligned MWCNTs.
- Application of electric fields and pressure gradients across the membranes to study particle transport.
- Characterization of transport phenomena, including electrophoresis and electroosmosis.
- Assessment of particle interactions with the hydrophobic inner surface of MWCNTs.
Main Results:
- Electrophoresis, not electroosmosis, dominates ion transport under applied electric fields.
- Small molecules and 5 nm gold nanoparticles can be transported, but DNA oligomers cannot.
- Hydrophobic interactions between charged particles and CNT surfaces significantly influence selectivity.
- Chemical modification of CNT ends alters the translocation of DNA oligomers and gold nanoparticles under pressure.
Conclusions:
- MWCNT membranes exhibit selective transport properties driven by electrophoresis and particle-surface interactions.
- These membranes show potential for size- and charge-based separations.
- Surface functionalization offers a pathway to tune the transport characteristics for specific applications.
