It is a question of scale and approximation. Nanofibers and nanorods are said to be 1D materials, films 2D materials, and nanoparticles sometimes 0D materials (a dot).

However, it is clear that there are all 3D materials.

Hello,

in some fields, like semiconductors physics, it also can be acknowledged that the number of degrees of freedom  is defining dimension of a material (e.g. 2D electron gas). On the other hand, clearly mechanically, nano wire which has 10 nm of diameter and 20 um of length can be approximated as a 1D material, because of the r/L relation.