Week 1 Flashcards
what are nanomaterials?
nano comes from greek, it means tiny. When we say nanomaterials we generally refer to particles with a size of approximately 1 to 100 nm. At least one of the 3 dimensions of the object needs to be in the nanoscale (up to 100 nm). If this confinement happens in all three axes we have a 0D nanomaterial (e.g., quantum dots, spherical nanoparticles), if the confinement is in one direction we have a 2D material (layers or sheets such as graphene), if the confinement is in 2 directions we have a 1D material (nanorods such as GaAs nanorod capped with Au)
numerical values range for the visible portion of the electromagnetic spectrum?
It goes from 380 nm to 700 nm.
The VIS portion is tiny compared to the whole electromagnetic spectrum.
The order of colors is: purple, ble, ligth blue, green, yellow and red.
For smaller wavelength we have the UV region, for longer wavelength we have the NIR and IR region.
you see a black background with floating brigth colorful nanoparticles. What is this? Why different colors? Microscopy tecnique used to take this video?
These are metallic NPs. We’re looking at plasmonic resonances. The different colors refer to different sizes of the particles.
The background is dark because the only ligth that is collected is the scattered ligth, while the incendent ligth (illumination ligth) is not collected because of the geometry of the microscope: illumination comes from the side.
They used optical microscope. The resolution of the optical microscope is lambda/2 * NA so it cannot, in principle, resolve a size that is smaller than 200 nm.
However these particles have a size of 20-60 nm and you can resolve them individually.
The trick that makes this possible is using a very diluted dispersion of NPs. So that you just have a few particles moving around. You can measure the size of the particle by looking at the color (see Rayleigh scattering: sigma=lambda ^(-4))
What are the relevant physical and chemical parameters?
size, shape
composition
solubility
crystallinity
surface chemistry, surface modification
