Influence of silicate sol–gel host matrices and catalyst agents on the luminescent properties of Eu3+/Gd3+ under different excitation wavelengths

Abstract

Sol–gel silicate glasses co-doped with Gd³⁺ and Eu³⁺ ions were successfully obtained and the pronounced effect of the matrix composition on the energy transfer process from Gd³⁺ to Eu³⁺ was confirmed. Qualitative compositions of the examined matrices were varied while the europium and gadolinium ion concentrations were kept constant. Different chemical compositions of the sol–gel matrices were clearly marked by changes in the photoluminescent properties. The effect of gadolinium ions on the visible emission of europium ions has been studied. The characteristic emission bands corresponding to the ⁵D₀ → ⁷F_J (J = 0–4) transitions of Eu³⁺ were registered. The emission of Eu³⁺ ions significantly increased during indirect excitation via the energy transfer process Gd³⁺ → Eu³⁺ (λ_exc = 273 nm) in comparison to direct excitation of Eu³⁺ ions (λ_exc = 393 nm). The beneficial influence of the energy transfer process on the ⁵D₀ luminescence lifetimes of Eu³⁺ ions was definitely stated. The structure of the prepared silica sol–gel materials was examined using X-ray diffraction measurements (XRD) and FT-IR spectroscopic techniques. The formation of GdF₃ and Gd₂O₃ nanocrystalline phases was confirmed.