I initially interpreted "5D" in the title as five spatial dimensions, which would be incredible, but the reality is entirely credible:
> The information encoding is realised in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures.
I wonder how orientation is just a single degree of freedom though; somehow one of the polarization directions of the light must get lost along the way.
Perhaps it is because this is a crystal and there is a relationship or redundancy between the different axes of orientation.
EDIT: Actually, this [1] paper says in the abstract that they use wavelength, polarization and the three spatial dimensions. So it is wavelength and not direction!
It's just a conceptual link. Think about the higher dimensional symmetries in quasicrystals and how one might encode information using a mechanism that exploits that property.
> The information encoding is realised in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures.