Laser-induced growth of YVO4:Eu3+ nanoparticles from sequential flowing aqueous suspension†
Ligand-free lanthanide ion-doped oxide nanoparticles have critical biological applications. An environmentally friendly and chemically green synthesis of YVO4:Eu3+ nanoparticles with high crystallinity is achieved using a physical method, laser irradiation from sequential flowing aqueous suspension in a free liquid reactor. The fabricated nanoparticles have an ovoid or spindle shape depending on the number of laser irradiation cycles. A transmission electron microscopy study showed that spindle-like particles are single-crystalline with high crystallinity, which is beneficial for high luminescence efficiency. Strong light emission even from a single particle was confirmed by cathodoluminescence mapping. A possible mechanism of nanoparticle formation was proposed as follows. Primary nanocrystals were produced from the plasma plume and self-assembled into ovoid-like nanoparticles via oriented attachment. After several cycles of laser irradiation, we observed spindle-like nanoparticles that were much longer than the ovoid-like particles. The spindle-like nanoparticles grew as a result of the diffusion and coalescence of the ovoid-like nanoparticles during repetitive laser irradiation. These findings provide useful information for the formation of ligand-free luminescent nanoparticles with different sizes based on YVO4.