Large-scale synthesis and luminescence of GdPO₄ hollow microspheres

GdPO₄ hollow microspheres were synthesized by using a novel multi-step transformation synthetic route for the first time with polystyrene (PS) spheres as the template, followed by the combination of a facile homogeneous precipitation method, an ion-exchange process, and a calcination process. The XRD results indicated that the GdPO₄ hollow microspheres have a pure hexagonal phase. The SEM and TEM images confirmed that the as-obtained GdPO₄ hollow spheres have a uniform morphology with an average diameter of 2.7 μm and shell thickness of about 150 nm. The up-conversion luminescence properties as well as the emission mechanisms of the GdPO₄:Yb³⁺, Ln³⁺ (Ln³⁺ = Tm³⁺, Er³⁺ and Ho³⁺) hollow microspheres were systematically investigated, which show blue (Tm³⁺, ¹G₄ → ³H₆), green (Er³⁺, ⁴S_3/2, ²H_11/2 → ⁴I_15/2), and red (Ho³⁺, ⁵F₅ → ⁵I₈) luminescence under 980 nm NIR excitation, providing potential applications in bioanalysis, optoelectronic and nanoscale devices, future color displays and light-emitting devices, and so on.