Computer Simulations of Colloidal and Nanoparticle Assembly

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Computer Simulations of Colloidal and
Nanoparticle Assembly 

• Amit Chakrabarti
• Kansas State University

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Transition from Dispersed Phase to Clusters

• Grand Problem of small particles in a dispersed
  phase coming together to form clusters
• Parts of this grand problem
• limiting nonequilibrium models of aggregation
  and gelation (such as DLCA and RLCA Models)
  ---- formation of fractal aggregates in
  colloids and aerosols
• models of nucleation and spinodal decomposition
• early studies of growth during precipitation ---
  formation of precipitated crystalline solids
  from solutions
• Gelation in Colloidal and Protein Solutions

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Snapshots from Simulations
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Klabunde Sorensen Nanoparticles

• Metal particles with alkane chains
• Typically in Toluene
• van der Waals Steric Repulsion possible
  ligand-ligand interactions

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van der Waals for 5nm Au
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Polymer ligand model

• Interaction potential
• Core/Core Vdw (depends on H for material)
• Ligand mixing
• Entropy loss
• Solvent effects
• Ligand compression

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No ligand contact (ligDodecanethiol soltoluene)
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Interparticle Potential Ligand overlap region
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Interparticle Potential Ligand overlap with
compression
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Potential Minimum
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5nm Au NP/dodecanethiol lig. in toluene fv 0.02
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5nm Au NP/dodecanethiol lig. in toluene fv 0.001
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5nm Au NP dodecanethiol lig. in dodecane fv 0.02
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Atomistic Model

• Atomistic Model
• Ligand bond lengths and angles conserved
• Dihedral angle Interaction between groups
  separated by 3 bonds
• LJ interactions between groups on same ligand
  separated by 4 or more bonds
• LJ interactions between all groups on different
  ligands
• Integrated van der Waals interaction between Au
  core and groups on ligand
• Au-S interactions not included due to lack of
  surface diffusion of S groups once placed
• S groups are placed randomly on surface of Au
  core with a minimum separation 0.8rideal where
  rideal gives required surface packing fraction of
  SH groups

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Hydrogen Bonding
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DNA-induced Specific Interactions
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Other Research Interests

• Wetting and Spreading of Polymers and
  Nanodroplets at Surfaces