YVO₄:Eu fluorescent nanoparticles were synthesized by hydrothermal method using poly acrylic acid (PAA) as modified reagent. The luminescence properties of the samples synthesized at different expe- rimental conditions including the PAA amount, the pH value of reacting solutions, the reacting temperature and reaction time were investigated. Under the optimal conditions the as-prepared particles showed quite good water solubility meanwhile their solutions emitted strong and stable fluorescence under 263 nm excitation. The products were characterized by IR, XRD and TEM. The IR spectrum indicates that YVO₄:Eu nanoparticles are coated by PAA. XRD pattern shows that the particles are single-phase YVO₄ crystals in tetragonal system and the solid solution is formed via the doped Eu^3＋ entering into the YVO₄ crystal lattice instead of Y^3＋. The TEM image shows a good dispersion of YVO₄:Eu nanoparticles in water with nearly uniform size which is about 25 nm. Moreover, the system of fluorescence resonant energy transfer (FRET), where YVO₄:Eu nanoparticles and Malachite Green (MG) served as energy donors and energy acceptors respectively, was constructed. Based on the FRET system, a new method for the determination of MG was established with the detection limit of 2.0×10^－5 g•L^－1 and the linear response range of 5.00×10^－5～5.00×10^－3 g•L^－1.

Key words: fluorescence, nanoparticle, lanthanide, fluorescence resonant energy transfer, malachite green