Time-resolved luminescence study of CaF2:Eu2+ nanocrystals in glass-ceramics

Tuning into blue and red: europium single-doped nano-glass-ceramics for potential application in photosynthesis

“…A similar broadband emission has been reported in the Eu 2+ doped GCs containing CaF 2 NCs previously. 26,27 The characteristic excitation spectrum of Eu 2+ ions in the GC1 sample is also provided in Fig. 3a.…”

“…The lifetime in the nanosecond order is one of the characteristics of the Eu 2+ electric-dipole allowed 5d -4f transition. 28 Fu et al 26,27 found that the Eu 2+ emission in the glass ceramic containing CaF 2 NCs was much stronger than that in the precursor glass, due to the partition of Eu 2+ ions into the CaF 2 crystalline phase. However, for the presently investigated PG1 and GC1 samples, the emission intensity and lifetime of Eu 2+ (Fig.…”

“…As for europium, the occurrence of Eu 3+ -Eu 2+ conversion will be realized in any glass system synthesized under an air atmosphere only when its optical basicity is below a critical value of 0.585. Using Duffy's empirical formula, [20][21][22][23][24][25][26][27][28][29][30] the optical basicity of the present glass is calculated to be 0.511 based on the amount of oxygen or fluorine in each oxide or fluoride and their corresponding basicity values. [29][30][31] Thus, formation of Eu 2+ has been promoted in the present system as the optical basicity value is far lower than the reported critical optical basicity (0.585).…”

Eu3+ ion distribution in oxyfluoride glass nanocomposites

“…Europium ions can exist in two stable valence states -3+ and 2+each having its distinct luminescence properties. Preliminary room temperature optical spectroscopy measurements of our samples revealed Eu 3+ luminescence in the red spectral region (see inset of Figure 3), while the broad blue emission characteristic to Eu 2+ in oxyfluoride glasses [11,14,31,32] as well as in CaF 2 crystals [33,34] was not observed in the investigated glass ceramics. Literature is already abundant with room temperature Eu 3+ luminescence spectra in CaF 2 containing glass ceramics [12,13,[17][18][19][20][21][22], therefore only the novel aspects are emphasized here.…”

“…Eu 3+ and Eu 2+ ions are sensitive to crystallization induced local structure changes, which modify luminescence propertiesintegral intensity, spectral composition and decay timeof the material [10][11][12][13][14][15][16][17][18][19][20][21]. It has also been observed that crystallization of CaF 2 during the melt cooling process promotes reduction of Eu 3+ to Eu 2+ [22].…”