Morphology-controllable synthesis and photoluminescence properties of t-LaVO₄:Ln³⁺ nanostructures on glass substrates

Tetragonal t-LaVO₄:Ln³⁺ (Ln³⁺ = Eu³⁺, Dy³⁺, Sm³⁺) microrod array and 3D hierarchical nanostructures with sheaf-like, flower-like, cauliflower-like, and spherical morphologies have been successfully synthesized on glass substrate through a simple hydrothermal process assisted by ethylenediaminetetraacetic acid disodium salt (Na₂H₂L). The morphologies of the products varied dramatically when Na₂H₂L/La³⁺ molar ratio and reaction time were changed in system. A possible crystal growth mechanism is proposed for the self-assembly of nanorods into the observed microstructures based on detailed experiments. Due to an efficient energy transfer from VO₄ ³⁻ to the Ln³⁺ dopants, the self-assembled t-LaVO₄:Ln³⁺ (Ln³⁺ = Eu³⁺, Dy³⁺, Sm³⁺) superstructures showed strong characteristic dominant emissions of the Eu³⁺, Dy³⁺, Sm³⁺ ions at 616 nm (⁵D₀ → ⁷F₂, strong red), 573 nm (⁴F_9/2 → ⁶H_13/2, yellow), 603 nm (⁴G_5/2 → ⁶H_7/2, orange-red) under ultraviolet excitation, respectively. This work not only gives insight into understanding the hierarchical growth behaviour of t-LaVO₄:Ln³⁺ nanoarchitectures in a solution-phase system, but also provides a potential route to building other superstructures assembled from one-dimensional nanoparticles.