Synthesis of water-soluble luminescent LaVO₄:Ln³⁺ porous nanoparticles

Abstract

Water-soluble luminescent Eu³⁺ and Tb³⁺-doped LaVO₄ porous nanoparticles were synthesized by co-precipitation method. X-ray diffraction (XRD), Field emission-transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis, Fourier transform infrared spectroscopy, UV/Vis absorption, and photoluminescence spectroscopic techniques were employed to characterize the structure and morphology of as-prepared products. The results of the XRD confirm the formation of well-crystallized LaVO₄ phase with a tetragonal zircon structure. The TEM images illustrate that the as-formed Eu³⁺ and Tb³⁺-doped LaVO₄ nanoparticles have irregular spherical shape, hairy nanoporous structures with an average particle size 50–130 nm. These nanoparticles were well-dispersed in polar and non-polar organic solvents to form clear colloidal solutions. The colloidal solutions of Eu³⁺ and Tb³⁺-doped zircon-type LaVO₄ nanoparticles show the most dominant characteristic emissions (hypersensitive transitions) of Eu³⁺ at 615 nm (⁵ D ₀ → ⁷ F ₂) and Tb³⁺ at 543 nm (⁵ D ₄ → ⁷ F ₅), respectively, as the result of an energy transfer from the VO₄ ³⁻ to luminescent metal ions activators. Compared with other-shape nanocrystals, the luminescence intensity of the irregular hairy spherical porous-like nanoparticles are obviously enhanced. It therefore, suggests that we could obtain function-improved materials by tailoring the size and shape of the LaVO₄:Ln³⁺ nanostructures that are very suitable for use in biological applications, such as protein-labeling, drug delivery, and fluorescent bioprobes.