Definitions and Size Effects Flashcards
How large or small is 1 nm and 1 Å relative to 1 m?
- 1 nm is 10^-9 of 1 m
- 1 Å is 10^-10
What is the size of an atom?
How many atoms do you need to line up a 10 nm long string of atoms?
- 0.1 nm to 5 nm
- 50 - 100
What is the required criterion to have a nanostructure?
What do we mean with the terms “0-dim”, “1-dim”, “2-dim” and “3-dim”?
- Nanostructure: One or more dimensions are in the range 1 - 100 nm
- 0-dim: Nanoparticle
- 1-dim: Rods, tubes
- 2-dim: Coatings, films, sheets
- 3-dim: Bulk material with nanostructure
What can be understood with the terms “cluster”, “nanoparticle”, and a “bulk material”?
How rigid are the different categories?
- Cluster: Assembly of small number of atoms or molecules
- Nanoparticle: Larger atomic aggregates with dimensions in the nanometer size regime
- Bulk material:
How do you estimate the number of atoms in a particle? Brief outline
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What do you understand with the term “size effect”? Which two factors are the key reason why we observe size effects in materials? Explain briefly
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What is a nanoparticle and what is a quantum dot?
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Explain why materials as Si, Ge, CdSe may give rise to color when the particle size goes down.
What is the root cause and how will the optic properties cange with size?
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Ferromagnetic and ferrimagnetic materials undergo a change in magnetic properties when size goes down. Explain in brief
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What does the Lindemann criterion state?
Melting initiates when the amplitude of vibration becomes large enough for adjacent atoms to partly occupy the same space
The Lindemann criterion states that melting is expected when the vibration root mean square amplitude exceeds a threshold value.
Au is considered as an inert metal, which hardly react with anything. What can be the reason why Au nanoparticles become reactive and are used in e.g. catalysis?
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Suggest and explanation to why certain crystallographic directions (facets) on a nanoparticle may become more/less reactive or favor formation of a specific product (product selectivity)?
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The interface or the dynamics between two or more different materials constituents may be critical to obtain a speceific feature. Explain some few examples we have discussed in this course or you have read/heard about.
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