A trimeric tri-Tb3+ including antimonotungstate and its Eu3+/Tb3+/Dy3+/Gd3+-codoped species with luminescence properties

Abstract

A trimeric tri-Tb³⁺-including antimonotungstate (AMT) hybrid Na₁₇{(WO₄)[Tb(H₂O)(Ac)(B-α-SbW₉O₃₁(OH)₂)]₃}·50H₂O (Tb₃W₂₈) was successfully synthesized, in which the capped tetrahedral {WO₄} group plays a significant template role in directing the aggregation of three [B-α-SbW₉O₃₃]⁹⁻ fragments and three Tb³⁺ ions. Eu³⁺/Tb³⁺/Dy³⁺/Gd³⁺-codoped AMT materials based on Tb₃W₂₈ were firstly prepared and their luminescence properties were investigated. The red emitter Eu³⁺, yellow emitter Dy³⁺, and nonluminous Gd³⁺ ions were codoped into Tb₃W₂₈ to substitute Tb³⁺ ions for investigating the energy transfer (ET) mechanism among Eu³⁺, Tb³⁺, and Dy³⁺ ions. Upon the ⁶H_15/2 → ⁴I_13/2 excitation at 389 nm of the Dy³⁺ ion, the ET₁ mechanism (Dy³⁺ → Tb³⁺) was confirmed as a non-radiative dipole–dipole interaction. Under the ⁷F₆ → ⁵L₁₀ excitation at 370 nm of the Tb³⁺ ion, the ET₂ mechanism (Tb³⁺ → Eu³⁺) was identified as a non-radiative quadrupole–quadrupole interaction. Under excitation at 389 nm, the two-step successive Dy³⁺ → Tb³⁺ → Eu³⁺ ET₃ process was proved in Dy_1.2Tb_3zEu_0.03Gd_1.77−3zW₂₈. Through changing the excitation wavelengths, the emission color of Dy_1.2Tb_1.2Eu_0.03Gd_0.57W₂₈ can vary from blue to yellow, in which a near-white-light emission case was observed upon excitation at 378 nm. This work not only provides a systematic ET mechanism study of hetero-Ln-codoped AMTs, but also offers some useful guidance for designing novel performance-oriented Ln-codoped polyoxometalate-based materials.