Microstructure and luminescence properties of Eu³⁺ doped tungsten trioxide nanoparticles prepared by hydrothermal method 

Abstract

Tungsten oxide is widely used in the photolysis of water for hydrogen production, photocatalysis, photoelectric conversion, and electrochromism. Eu³⁺ doped tungsten trioxide nanoparticles were prepared by hydrothermal method with the addition of sodium tungstate (NaWO₄ · 2H₂O). Two different samples were obtained at the temperature set at 160 and 180 °C. The third sample obtained from ammonium paratungstate ((NH₄)₁₀H₂(W₂O₇)₆) was used at the temperature of 160 °C. The samples’ morphology, structure, and optical performance were then observed and analyzed. The results show that a rod-like structure of WO₃ : Eu³⁺ nanoparticle with a monoclinic crystal system can be successfully generated using sodium tungstate. A spherical structure of WO₃ : Eu³⁺ nanoparticle with a triclinic crystal system was prepared using ammonium paratungstate. The finished sample with ammonium paratungstate at a reaction temperature of 160 °C has the smallest grain average size of 45.98 nm and Eu³⁺ ions successfully doped. Under the excitation of different wavelengths, the three samples demonstrate pronounced emission peaks at around 615 nm, corresponding to the 5D₀ → 7F₂ electronic transition of Eu³⁺. Using ammonium paratungstate as the tungsten source, the prepared WO₃ : Eu³⁺ nanoparticle at 160 °C has the highest luminous intensity. The luminescence intensity of the prepared WO₃ : Eu³⁺ nanoparticle from ammonium paratungstate as a tungsten source is higher than the other two samples obtained from sodium tungstate as a tungsten source at two temperatures. However, the three samples with excitation wavelength λ = 254 nm were monitored at the wavelength of 615 nm. All three samples samples exhibited the most substantial excitation peaks at about 508 nm, which belonged to the electron transition in 4f of Eu³⁺.