Self-assembly and Molecular Self-assembly Flashcards
What do you put into the term “self-assembly”? Give some examples connected to the curriculum of this course.
- Emulsions, homogeneous nucleation NP synthesis, packing of NPs, etc
Suggest why we observe Au clusters with the magic numbers, Au_13, Au_55, Au_147 whereas Na form stable clusters as Na_2, Na_8, Na_18, Na_20, Na_3+, Na_9+, Na_19+, Na_7- and Na_17-.
- Au: Surface minimization
- Na: Electron configuration (full shell)
What is the Hume-Rothery substitution rules saying? Based on this, would you expect the two metals Au and Ag to form a solid solution?
- H-R: Same crystal structure (similar coord. polyhedra for atoms), equal atomic size (within 15%), similar electronegativity, same oxidation state (cat/ani).
Au and Ag should be expected to form a solid solution
Suggest why the various Au nanoparticle distributions pack in different configurations. What may be the driving force?
Depletion attraction and weak vdW forces between particles
Whitesides et al talk about organic synthesis at four different levels. Describe each of them briefly.
1) Sequential covalent synthesis: Generate arrays of covalently linked atoms with well-defined properties.
2) Covalent polymerization: Most important for preparing molecules with high molecular weights. Monomer caused to react with itself –> molecule (polymer) comprising many covalently connected monomers.
3) Relies on weaker/less directional bonds (ionic, H-bonds, vdW). “Self-organizing synthesis”. Want to reach a thermodynamic minimum.
4) Molecular self-assembly (most relevant to nanostructures). Spontaneous assembly of molecules into structured, stable, noncovalently joined aggregates.
Explain in short, how Mother Nature produce DNA utilizing the fourth-level strategy as outlined by Whitesides et al.
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Discuss thermodynamic constraints in the formation of self-assembled molecules similar to DNA. How well do the chemist do this type of synthesis in the laboratory?
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With basis in the lecture notes “Molecular self-assemblyat”, explain in short why localized surface Plasmon’s on certain metals give rise to strong colors and why pH tuning (in the Au example) induce a switch in color.
Localized surface plasmons (LSPs)