Upconversion nanoparticles are appealing to various applications due to their energy conversion capabilities. However, their potential is limited by low efficiency, reproducibility, and poor morphology control. In this work, the synthesis of NaYF4 co-doped with Yb3+ and Tm3+ ions using both thermal decomposition (TD) and microwave irradiation heating (MW) using non-polar solvent were explored. Finding that the samples obtained by MW irradiation not only reduced reaction time but also decreased particle size from micrometers to nanometers. Also, their particle size distribution and shape control improved. The upconverted emission obtained in both cases is in consistency with the characteristic emission band of thulium located at 360, 451, 476, 645, and 802 nm corresponding with 1D2→3H6, 1D2→3F4, 1G4→3H6, 1G4→3F4, and 3H4→3H6 transitions, respectively.
This study investigates the feasibility of inducing crystallization in tellurite-phosphate glass within the TeO2-P2O5-BaF2- ZnF2-Na2O-Er2O3 system by direct laser writing (DLW) technique using a femtosecond laser beam operating at 1030 nm with a pulse duration of 230 fs. Two irradiation modes were examined: stationary-mode (1 MHz repetition rate, 160 nJ pulse energy, 120 s exposure time, for dot patterning) and translational-mode (200 kHz repetition rate, 10 μm/s translation speed, 470 nJ pulse energy, for line patterning) of laser irradiation. Our results, validated by Raman spectroscopy and scanning electron microscopy, revealed the formation of barium fluoride and zinc barium phosphate crystals in the areas irradiated employing stationary-mode. However, only barium fluoride nanocrystals were detected in the lines induced by the fs-laser employing the translational-mode. SEM analysis of the morphology and size of the laser-induced crystals showcased intriguing findings. In stationary-mode, barium fluoride crystals were distributed across the entire dot pattern area (30 μm), while zinc barium phosphate crystals were predominantly located at the edges of the dot spheres (with a size of 10 μm). Interestingly, barium fluoride nanocrystals with a size below 100 nm were detected in the area of laser irradiation in translational mode. Further structural analysis revealed alterations in the tellurite (TeO4) and phosphate (Q0) structural units within the glass matrix of the fs-laser crystallized tellurite-phosphate system. Moreover, we discussed the changes in erbium emission across the UV-NIR region in both laser-induced crystals and the parent glass. Notably, a stronger emission of erbium ions was observed in the glass compared to the crystalline phases, which needs further investigations. These preliminary findings underscore the potential of fs-laser writing for the development of telluritephosphate glass-ceramics.
Fluoroindate glasses co-dopped with Er3+ at different concentrations were synthesized using the melting quenching technique, where it was observed that the emission peak located at 1.53 μm associated with 4I13/2→4I15/2 transition of Er3+ increases up to 11.5 times with increasing ErF3 content up to 1.4 mol. %. Such increase is significant due to their proximity with one of the most important telecommunication windows (1.55 μm) which the spite of all the studies around it, some challenges like its efficiency need to be optimized. The effect of sensitization of the Er3+ by Yb3+ ions was also evaluated. The increase in luminescence intensity (~19%) was obtained by co-doping of 1.4ErF3 glass by 0.8YbF3. This effect is related to the efficient Yb3+→ Er3+ energy transfer.
Fluoroindate glass is characterized by low phonon energy (500 cm-1 ), which enables most of the radiative transitions in the lanthanides to occur in the range VIS-NIR. It allows considering this matrix as a potential host glass for NIR emission and light sources. This work reports the fabrication and analysis of luminescence properties, and structure of the fluoroindate glasses and glass-ceramics (GC) co-doped with Eu3+ ions. The materials' microstructure and structure were analysed using X-ray diffraction (XRD) and Raman measurement techniques, respectively. It has been shown that the basic structural units in the glass network are [InF6] octahedrons tetrahedrons. The luminescence analysis was performed in the glass and glass-ceramics samples doped with EuF3 showing the excitation and emission properties and changes in the lifetimes. The excitation at 395 nm resulted in different emissions in blue, green, and red which correspond to the transitions from 5DJ (J=0 to 3) multiples to the 7FJ (J= 0 to 6), which is the effect of the low phonon energy of the matrix and is comparable with other low phonon materials. In the glass-ceramics, the effect of network ordering around the Eu3+ ions was noticed. The fluorescence intensity ratio R/O related to 5D0→7F2 and 5D0→7F1 transitions in Eu3+ decreased from 0.74 to 0.56 value. Obtained results allowed to consider this GC material as a potential host for luminescent material and possibly glass fiber sources.
Eu3+ - doped oxyfluoride tellurite-germanate glass-ceramics were fabricated by the controlled crystallization method. The microstructure and structure of samples were analysed using x-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared spectroscopy (IR). The EuF3 introduction caused the rise of the non-bridging oxygens/fluorides in glass network in a consequence of the [TeO,F4] and [GeO,F4] structural units transformation into the [TeO,F3]/[TeO,F3+1], and [GeO,F6], respectively. These changes were caused by Eu3+ ions, which played the role as a network modifier and led to the new non-bridging oxygens/fluorides Te–O,F− Eu3+O,F−–Te, and Ge– O,F−Eu3+O,F−–Ge, linkages formation and the ZnTe crystalline phase. The structure changes caused by the Eu3 + ions incorporation in the crystalline phase have been discussed in accordance to analysed the photoluminescence (PL) spectra and decay curves. It was showed a significant increase of the 5D0 → 7F1 magnetic-dipole transition intensity and decay times for transparent glass-ceramics sample. It confirmed the migration of Eu3+ ions from the amorphous network into ZnTe nanocrystals.
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