The present disclosure relates to novel multifunctionalized silicon nanoparticles, to processes for their preparation and to compositions comprising the novel multifunctionalized silicon nanoparticles. The disclosure also relates to the use of the novel multifunctionalized silicon nanoparticles in electrochemiluminescence based detection methods and in the in vitro detection of an analyte. In particular, the disclosure relates to methods for measuring an analyte by in vitro methods employing the novel multifunctionalized silicon nanoparticles.