Emissão vermelha intensa do complexo β-dicetonato de Eu(III) em material híbrido sílica-orgânico: síntese e propriedades espectroscópicas

Abstract

The development of new red light-emitting phosphor materials has attracted considerable interest in various technological fields, including lighting devices and biosecurity systems. In this work, silica–organic hybrid xerogels based on 3- glycidyloxypropyltrimethoxysilane (GPTS) and tetraethyl orthosilicate (TEOS), doped with the europium complex Eu(bmdm)3(H2O)2, were synthesized via the sol–gel route and systematically characterized. X-ray diffraction and UV–Vis and infrared spectroscopy analyses confirmed the amorphous nature of the samples, as well as their high homogeneity and transparency, and the effective incorporation of the dopant without significant structural changes in the hybrid matrix. Photoluminescence spectra revealed an efficient ligand-to-metal energy transfer process (antenna effect), leading to intense red emission under UV excitation, dominated by the hypersensitive 5D0→7F2 transition of the Eu3+ ion, with no emission quenching observed within the investigated concentration range. Judd–Ofelt parameter analysis indicated a more symmetric coordination field around the Eu3+ ion in the hybrid matrix compared to the pure complex, a result corroborated by emission lifetime measurements, which showed higher values for the doped xerogels (up to 0.62 ms) than for the isolated complex (0.32 ms). This behavior is attributed to the less polar and more rigid microenvironment provided by the GPTS/TEOS matrix, which suppresses non-radiative processes. Photostability studies demonstrated a significant improvement upon incorporation of the complex into the hybrid matrix, with 66% of the initial emission intensity retained after 3 h of UV irradiation, compared to 34% for the pure complex. These results indicate that Eu(bmdm)3(H2O)2-doped GPTS/TEOS xerogels exhibit high potential for red light-emitting device applications, particularly as a complementary component for white light generation, considering their chromaticity coordinates (CIE ≈ 0.66, 0.34) and correlated color temperature values close to 1000 K, suitable for warm and visually comfortable lighting.