Synthesis and functionalization of nanoparticles of yttrium vanadate doped with europium is described. Synthesis of yttrium vanadate leads to ovoid nanoparticles, with an average size of 24 nm. These nanoparticles are unstable in water, and surface charge can be brought by silicate, as proven by PCS, Zetametry and IR analyses. The nanoparticle surface is then functionalized with glycidoxypropyltrimethoxysilane. The rafting is characterized by 29Si MAS NMR, and ThermoGravimetric Analyses. This alkoxysilane presents an epoxy function which can then react with a nucleophilic molecule. The functionalization is studied by 29Si MAS NMR and TGA, whereas opening of the epoxy ring is studied by 13C MAS NMR. As an example of further reactivity, we chose to graft on the nanoparticles the active part of saxitoxin, a guanidinium group. This last functionalization is proven by optical experiments performed on a cell in biological conditions.