Fouling Mechanisms in Y-shaped Carbon Nanotubes. Jason Myers, SeongJun Heo, and Susan B. Sinnott Department of Materials Science and Engineering University of Florida. Funded by the Network for Computational Nanotechnology at Purdue University, NSF Grant No. EEC -02288390. Outline.
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Jason Myers, SeongJun Heo, and Susan B. Sinnott
Department of Materials Science and Engineering
University of Florida
Funded by the Network for Computational Nanotechnology at Purdue University, NSF Grant No. EEC-02288390
The chemical and biomedical fields have a constant demand for solutions of greater purity.
Current filtration methods (zeolites) do not offer uniform pore size, and are susceptible to fouling.
Carbon nanotubes (CNTs) have the potential to be custom designed for optimal molecular filtration.
Nanofluidics: Confinementof fluids to nanopores
Carbon nanotubes (CNTs):
Honeycomb graphene lattice rolled
into a cylinder
Sinnott et al. (2002)Carbon Nanotubes
Analagous to a rolled graphene sheet.
- One-dimensional axial symmetry.
- Spiral conformation: ChiralityCarbon Nanotubes, cont.
Chiral vector Ch = (n,m) = na1 + ma2
Small arm – large molecule is energetically discouraged from enteringY-shaped CNTs
Large arm – no similar barrier for large molecules
Result? Only the small molecule will pass through the small arm.
Classical molecular dynamics (MD) simulations (numerically integrating F = ma)
Reactive Empirical Bond Order (REBO) Potential
Lennard-Jones (LJ) Potential
van der Waals Interaction
Covalent InteractionMolecular Dynamics
Three different molecules:
Rigid Argon Box
10, 5, 3, and 0 m/s
Rigid integrating F = ma)
Direction of Flow
Each system consists of a Y-shaped CNT and reservoir.System Design
Ytube2, 10 m/s at… integrating F = ma)N-butane + Methane
Ytube1 shows no tendency for filtration. There is evidence of size-based diffusion in the methane systems. Ytube2 shows no similar behavior.
The isobutane + methane systems exhibit fouling. This is attributed to the steric interactions of the isobutane molecule with the junction area, and is not due to a potential energy well. Prior to the formation of the block, filtration occurred in ytube2.
There is neither fouling nor filtration in the n-butane + methane systems. Once the driving force is sufficient, the n-butane aligns itself to pass easily down both arms.