Silicon nanocrystals embedded in silicon nitride films were irradiated with Si-ions at 8 MeV in order to modify their optical response. The samples were characterized by means of Rutherford Backscattering Spectrometry, Elastic Recoil Detection Analysis, High-Resolution Transmission Electronic Microscopy and Photoluminescence analysis. It was found a blue-shift in the photoluminescence emission from the as-grown films after they were irradiated with high energetic silicon ions. According to the quantum confinement theory, this fact is related to a decrease in size of the silicon nanocrystals, which means that a higher silicon fluence irradiation is related with a diminishing in silicon nanocrystal size.