Manufacturing lower dimensional structures Flashcards
Describe dynamic light scattering to measure the radius of nanoparticles.
laser through solution - light is scattered
1) the signal from scattering fitted using an exponential ( T~1/D)
2) theoretical calc. for Brownian motion diffusion - use Stoke-Einstein
What are two ways of stabilising nanoparticles against agglomeration?
- Electrostatic Double Layer
- Steric Repulsion
Describe Steric Repulsion.
polymer molecules are absorbed on the surface which cause repulsion against particle aggregation.
Describe the Electrostatic double layer.
absorption of surface ions screen interaction between charged particles in solution.
Describe a surfactant.
Surface Active Agent. molecules that reduce surface tension between liquid-gas, solid or other liquid. Amphiphilic molecules.
Describe a nonionic surfactant.
non-charged head group.
Describe a cationic surfactant.
negative head group.
Describe an anionic surfactant.
positive head group.
Describe a zwitterionic surfactant.
both positive and negative head groups.
At air-water interface, surfactant molecules absorb such that…
The hydrophobic part is in the air and the hydrophilic part is in water.
Describe a micelle.
self-assembled 3D structures made from surfactants.
Name three types of micelles.
micelle (water out), inverted micelle (water in), bilayer sheet.
Compare what happens in a polar and non-polar solvent.
polar: arrange around hydrophilic molecules -> inverse spherical micelles.
non-polar: hydrophilic out.
What is a use of micelles?
Drug delivery.
