Structural, morphological, and luminescent properties of tetragonal-phase YPO4:Eu3+

Eu-Doped YPO4 Luminescent Nanopowders for Anticounterfeiting Applications: Tuning Morphology and Optical Properties by a Rapid Microwave-Assisted Hydrothermal Method

“…4,11,31 Notably, the band around 1000 cm −1 is split into two bands (one above and one below 1000 cm −1 ) in the case of the classic hydrothermal synthesis (B), while in the case of MW-synthesized samples (C, D), only a shouldered main band below 1000 cm −1 is seen. The split band has been reported for highly hydrated Eu:YPO 4 nanopowders, while the main band below 1000 cm −1 has been reported for the materials with a low hydration degree, 11 and it is claimed diagnostic for tetragonal phase in these types of materials. 17 Therefore, the shape of this band in our samples is the first suggestion that the degree of hydration is lower in MWsynthesized samples than in the classic hydrothermal method, with both samples in a tetragonal phase.…”

“…As can be seen from the full spectra shown in Figures 2a and S5, the main characteristic bands of the YPO 4 or Eu 3+ :YPO 4 compounds are visible in the MW-synthesized samples with no additional peaks. 4,11,31 The two sharp bands at around 530 and 640 cm −1 can be ascribed to the symmetric and antisymmetric bending of the O−P−O group respectively, while the band around 1000 cm −1 is ascribed to the P−O antisymmetric stretching. 4,11,31 Notably, the band around 1000 cm −1 is split into two bands (one above and one below 1000 cm −1 ) in the case of the classic hydrothermal synthesis (B), while in the case of MW-synthesized samples (C, D), only a shouldered main band below 1000 cm −1 is seen.…”

“…4 Also, Garrido-Hernańdez et al reported a reduction in the particle size in Eu 3+ :YPO 4 samples with less H 2 O-coordinated molecules. 11 With increasing reaction time, the Ostwald dissolution and recrystallization process occurs, and the nanoparticles gradually grow, thus reducing the surface free energy. 32 This leads to particle shrinkage with consequent formation of mixed morphologies up to 20 min, whereas homogeneous elongated nanorods were obtained after 30 min of MW heating at 200 °C.…”

“…5 For these reasons, this material was investigated for applications in the fields of solid-state lighting, lasers, LED lighting, field emission displays, fluorescence lamps, cathode-ray tubes (CRTs), optoelectronic devices, solar cells, optical fibers, medical imaging, and bioimaging, particularly in time-resolved fluorescence imaging. 11 More recently, it was studied also as a thermometer in biological tissues, 10,12 environmental barrier coatings, 13 and labels for antifake 14,15 and biological applications. 16 In fact, the specific application may vary based on the concentration of europium, fabrication techniques, and the desired properties for the given application.…”

“…23,26−28 Conversely, the lack of coordinated water in the Xenotime-(Y) tetragonal phase improves its stability and reduces the quenching effect. 11 In order to obtain YPO 4 -based nanopowders with optimal luminescence properties, it is therefore essential to optimize a synthesis process that allows the formation of a suitable crystallographic phase and minimizes the concentration of water molecules on the surface of the nanoparticles. Up to now, several synthetic methods have been developed for the preparation of these types of luminescent materials in the nanometer size range.…”