Yttrium vanadate particles doped with europium are studied for their applications as biomolecule labels. Two parts of
our work will be presented. The first concerns the thermal treatment of particles incorporated in a silica matrix. After
annealing at 1000°C and redispersion in water by dissolution of the silica matrix, the structural and optical properties are
greatly improved: without any modification of size, the obtained nanoparticles appear as perfect single crystals of 33 nm
and have the same emission properties as the bulk material, with a quantum yield and emission lifetime increasing up to
40% and 0.8 ms. The second aspect concerns the detection of single nanoparticles and their emission properties as
compared to an ensemble of nanoparticles.