Modification of surface of solid state materials allow to control on the one hand interface interactions and on the other hand physical properties of modified semiconductor or dielectric. Especially this is true in case of carbon nanoparticles due to their electron acceptor properties. In this paper modification of a ZnS:Cu electroluminescent phosphor by the deposition of shungite carbon nanoclusters is described. Modification resulted in increased intensity of "blue" band in its luminescence spectra and oscillating change of EL brightness. Effect is discussed in terms of possible mechanisms relating to electric field concentration at the areas of nanocarbon adsorption on specific surface sites connected with "blue" luminescent centers. This effect is promising for an adjustable control over electrolu-minescence spectra and brightness as well as control of interface interactions.