A Novel 3D Architecture of GdPO₄ Nanophosphors: Multicolored and White Light Emission

Homogeneous monoclinic GdPO₄ particles composed of three intersecting lance-shaped crystals forming a penetration twin have been synthesized following a very restrictive, simple, and fast (10 min) method consisting of the hydrothermal reaction of gadolinium acetylacetonate with H₃PO₄ in a mixture of ethylene glycol and water at 180 °C. Slightly increasing the amount of water in the solvent mixture leads to hexagonal rodlike GdPO₄·0.5H₂O nanoparticles, whereas the variation of the Gd source, PO₄ source, aging temperature, and polyol type gave rise to heterogeneous particles. The synthesis procedure is also suitable for the preparation of Eu³⁺-, Tb³⁺-, and Dy³⁺-doped GdPO₄ particles with the same morphology and crystalline structure as the undoped materials. The effect of the doping level on the luminescent properties of the twinlike nanophosphors was evaluated, finding optimum doping levels of 5, 5, and 1% for the Eu³⁺-, Tb³⁺-, and Dy³⁺-doped materials, respectively. The twinlike GdPO₄ nanophosphors were found to be more efficient than the rodlike GdPO₄ ones in terms of emission intensity. Finally, a solid-state single-phase white-light-emitting nanophosphor has been fabricated for the first time in this system by triply doping the GdPO₄ twined particles with appropriate concentrations of Eu³⁺, Tb³⁺, and Dy³⁺ and exciting through the Gd–Ln energy-transfer band at 273 nm. In addition to this energy transfer band, other energy charge transfer processes among the three dopants (Eu³⁺, Tb³⁺, and Dy³⁺) have been observed in the triply doped material.