Dear Abdellah, 

  To the best of my knowledge, you can talk about quantum confinement only when the particle size is of the order of atomic scales~few nm

Dear Tamás Haraszti Tank you for your  answer. in fact, I measured band gaps of my samples by UV-visible absorption (these materials are dielectric, 3.6

Dear abdou

The confinement effect is obtained when the size  is in order of the Broglie wave length Lb  ie few nm.

We can separate three types of conf

1 strong conf  if the size inf then Lb

2 low conf  if size sup then Lb

3 medium when the Lb# size

In all cases the band gap depends on the size

See kayanuma or brus 

Feddi

Dear Mustapha thank you so much for this very important clarification.