Photoluminescence tuning and energy transfer process from Tb³⁺ to Eu³⁺ in GPTMS/TEOS–derived organic/silica hybrid films

Highlights: • Tb³⁺:Eu³⁺–doped GPTMS/TEOS–derived films. • Highly homogeneous and transparent doped films obtained by sol-gel process. • Photoluminescence tuning and energy transfer evaluation. - Abstract: In this work the photoluminescence study and energy transfer from Tb³⁺ to Eu³⁺–β–diketonate complexes incorporated into organic/Silica hybrid films derived from 3–glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) alkoxysilanes were investigated. Highly homogeneous and transparent films of Ln³⁺–doped GPTMS/TEOS–derived organic/silica hybrids were obtained from the organic/silica sols prepared by sol–gel. Tb³⁺:Eu³⁺–doped GPTMS/TEOS–derived films showed very intense luminescence when excited with UV light. Films co–doped with Tb³⁺ concentration fixed at 40.0×10¹⁸ ions/cm³ and Eu³⁺ concentrations of 0, 0.03, 0.05, 0.1, 0.3, 0.5, 1.0, 1.5, and 2.0×10¹⁸ ions/cm³ were studied. The films presented characteristic transitions ⁵D₄–⁷F_6-3 of Tb³⁺ ions and ⁵D₀–⁷F_0-4 of Eu³⁺ ions measured on the visible spectrum region. Energy transfer from Terbium to Europium was studied through emission decay time measurements of ⁵D₄–⁷F₅ transition of Tb³⁺ (547 nm) which showed an accentuated decrease (from 1329 to 55 µs) due to the co–doping with Eu³⁺ ions concentrations varied from 0.03 to 1.5×10¹⁸ ions/cm³. Energy transfer rate ($W_{\mathrm{ET}}$) of 17.4×10³ s⁻¹ and relative energy transfer efficiency (${\eta }_T$) of 96% were observed for films samples co–doped with 40×10¹⁸ ions/cm³ of Tb³⁺ and 1.5×10¹⁸ ions/cm³ of Eu³⁺. Due to the variation in $W_{\mathrm{ET}}$ and ${\eta }_T$ from Tb³⁺ to Eu³⁺, the intensity ratios of Tb³⁺ band at 547 nm (⁵D₄–⁷F₅) and Eu³⁺ band at 617 nm (⁵D₀–⁷F₂) vary remarkably making the co–doped film samples exhibit different luminescence colors varying from green to orange and red which can be tuned by the Tb³⁺/Eu³⁺ ratio incorporated into the samples.