Hello everyone!

I know it seems quite impossible to say that an object has no dimension. It's said that the QDs are zero-dimensional because they are basically a point.

Mathematically, the topological dimension is an entire number, which can be defined for any topological space. For a space formed by a point the topological dimension is 0, for a line it's 1, for the euclidean plane it's 2, etc.

An object has a dimension 'm' when any coating of that object has at least a dimension of 'm + 1'. So the point has a dimension m = 0

It seems very strange and difficult to understand, so I leave a photo.

[img] 0D.jpg [ /img]

In a one-dimensional material, electrons are confined in two directions (x, y / y, z / x, z). They can only be moved in one direction. A couple of examples of one-dimensional nanostructures are nanowires and nanotubes.

In contrast, in one of two dimensions the electrons are confined in only one direction (x / y / z). They can move in two directions. E.g. thin films.

In reference to the size dependency:When a QD is illuminated by UV light, the electrons inside receive enough energy to break free from the atoms. This ability allows them to move around, in this process they create a conduction band where electrons are free to move through the material and conduct electricity.

When these electrons drop into the outsider orbit around the atom (the valence band), they emit light. Its color depends on the difference of the energy between both bands, the conduction and the valence one.

The smaller the nanoparticle is, the higher the energy difference between the two bands, which results in a dark blue color.

For a larger nanoparticle, the energy difference between the bands is lower, which results in red.

Kind regards,

Laia