High-frequency spark discharges were applied to the following semiconducting and semi-metallic materials : Sb, Bi, Sn, As, Ge, GaAs, Si, Te and Se. The spark-processed (sp) samples were characterized by photoluminescence (PL) measurements using an excitation wavelength of 325 nm. With the exception of Se, PL signals in the visible region were obtained for all of the above-specified materials. The strongest and most stable PL was found in sp-Si and sp-Ge layers with peak wavelengths centred at 525 and 416 nm. respectively. The estimated increase of the bandgap energy due to the formation of nanocrystals was calculated using the effective mass approximation. The results are in accordance with the PL data. The particle sizes are expected to range from 3 to 8 nm. The findings support the quantum confinement model.