Reason for high quality from nano-tech

Quantum confinement

Quantum confinement is responsible for the increase of energy difference between energy states and band gap. A phenomenon tightly related with the optical and electronic properties of the materials. Quantum confinement effect can be observed once the diameter of the particle is of the same magnitude as the wavelength of the electron wave function. When materials are this small, their electronic and optical properties deviate substantially from those of bulk materials.

A particle behaves as if it were free when the confining dimension is large compared to the wavelength of the particle. During this state, the bandgap remains at its original energy due to a continuous energy state. However, as the confining dimension decreases and reaches a certain limit, typically in nanoscale, the energy spectrum turns to discrete. As a result, thebandgap becomes size dependent. This ultimately results in a blue shift in optical illumination as the size of the particles decreases.

Specifically, the effect describes the phenomenon  results from electrons and electron holes being squeezed into a dimension that approaches a critical quantum measurement, called the exciton Bohr radius. In current application, a quantum dot such as a small sphere confines in all three dimensions, a quantum wire confines in one dimension, and a quantum well confines in two dimensions.

For more see the wikipedia.org...