ABSTRACTThe presented work aims for the development of optically-traceable intracellular nanodiamond sensors, where photoluminescence can be changed by biomolecular attachment/delivery event. High biocompatibility, small size and stable luminescence from its color centers, makes nanodiamond (ND) particles an attractive alternative to molecular dyes for drug-delivery and cell-imaging applications. In our work we study how the surface modification of ND can change ND luminescence spectra. This method can be used as a novel detection tool for remote monitoring of chemical processes in biological systems. We discuss photoluminescence (PL) spectra of oxidized and hydrogenated ND and a single crystal diamond, containing engineered NV centers. The hydrogenation of ND leads to quenching of NV- related luminescence and a PL shift due to changing of occupation from NV- to NV0 states. We model this effect using electrical potential changes at the diamond surface.