Natalia Pawlik

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

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 → 7FJ (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+ (λexc = 273 nm) in comparison to direct excitation of Eu3+ ions (λexc = 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.

Optical properties of silica sol-gel materials singly- and doubly-doped with Eu3+and Gd3+ ions

Abstract In present work, the optical and structural properties of silica sol-gel glasses and glass-ceramic materials singly- and doubly-doped with Eu 3+ and Gd 3+ ions were investigated. The optical properties of studied systems were determined based on absorption, excitation and emission spectra as well as luminescence decay analysis. Conducted studies clearly indicated a significant enhancement of visible emission originated from Eu 3+ ions as a result of changing the excitation mechanism, via Gd 3+ →Eu 3+ energy transfer. The luminescence intensity R-ratio was analyzed before and after heat-treatment process upon excitation at γ ex =393 nm and γ ex =273 nm. Moreover, the influence of excitation wavelength on luminescence decay time of the 5 D 0 excited state was also analyzed. The Gd 3+ →Eu 3+ energy transfer efficiencies for precursor and annealed samples were calculated based on luminescence lifetime of the 6 P 7/2 level of Gd 3+ ions. The X-ray diffraction measurements were conducted to verify the nature of obtained sol-gel materials. In result, the formation of orthorhombic GdF 3 nanocrystal phase dispersed in amorphous silica glass host was identified after annealing. Obtained results clearly indicated an incorporation of Eu 3+ activators into formed GdF 3 nanocrystals. Thus, conducted heat-treatment process led to considerable changes in surrounding environment around Eu 3+ ions. Actually, it was found that energy transfer phenomenon and heat-treatment process were responsible for significant improvement of Eu 3+ luminescence in studied sol-gel samples.

Multicolor emission in silica sol-gel materials co-doped with Tb3+ and Eu3+ for near-UV photonic devices

In this work, the luminescence properties of silica materials singly- and doubly-doped with Tb3+ and Eu3+ ions derived by low-temperature sol-gel technique were investigated. The optical properties of prepared samples were evaluated based on photoluminescence excitation (PLE) and emission spectra (PL) as well as luminescence decay analysis. The PL measurements of investigated Tb3+/Eu3+ co-doped systems were conducted using different excitation wavelengths. Prepared sol-gel materials exhibit bright multicolor, wavelength-tunable luminescence under near-UV illumination. Indicated emission is originated from electronic transitions within 4f6 and 4f8 manifolds of Eu3+ and Tb3+, respectively. Additionally, based on recorded decay curves, the luminescence lifetimes (τm) for the 5 D0 state of Eu3+ and the 5D4 level of Tb3+ were also evaluated. Obtained results indicated that co-doping with Tb3+ ions led to prolongation of luminescence lifetime of the 5D0 state of Eu3+ up to ~24% due to Tb3+ → Eu3+ energy transfer process. The interpretation of obtained results may suggests the potential usage of fabricated Tb3+/Eu3+ co-doped sol-gel materials in optical devices operating under near-UV excitation.