Influence of the Synthesis Conditions on the Morphology and Thermometric Properties of the Lifetime-Based Luminescent Thermometers in YPO₄:Yb³⁺,Nd³⁺ Nanocrystals

Abstract

An increase in the accuracy of remote temperature readout using luminescent thermometry is determined, among other things, by the relative sensitivity of the thermometer. Therefore, to increase the sensitivity, intensive work is carried out to optimize the host material composition and select the luminescent ions accordingly. However, the role of nanocrystal morphology in thermometric performance is often neglected. This paper presents a systematic study determining the role of synthesis parameters of the solvothermal method on the morphology of YPO 4 :Yb 3+ ,Nd 3+ nanocrystals and their effect on the lifetime of Yb 3+ ion-based luminescent thermometer performance. It was shown that by changing the RE 3+ :(PO 4 ) 3– ratio and the concentration of Nd 3+ ions, the size, shape, and aggregation level of the nanocrystals can be modified changing the thermometric parameters of the luminescent thermometer. The highest relative sensitivity was obtained for the low RE 3+ :(PO 4 ) 3– ratio and 1% Nd 3+ ion concentration.

The role of Nd3+ concentration in the modulation of the thermometric performance of Stokes/anti-Stokes luminescence thermometer in NaYF4:Nd3+

“…It should be also mentioned that the particle size may affect the thermometric properties of luminescence thermometers. However, as shown in the previously published studies 38 , the dopant concentration plays a far more important role than particle size. The clear correlation between the dopant concentration and the thermometric parameters of NaYF 4 :Nd 3+ is a clear confirmation of this hypothesis.…”

“…Powder diffraction data were obtained using a PANalytical X'Pert Pro diffractometer equipped with an Anton Paar TCU 1000 N Temperature Control Unit using Ni-filtered Cu Kα radiation ( V = 40 kV and I = 30 mA) 38 , 39 . Transmission electron microscope (TEM) images were recorded with a Philips CM-20 SuperTwin transmission electron microscope, operating at 160 kV.…”

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

“…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 . More recently, it was studied also as a thermometer in biological tissues, , environmental barrier coatings, and labels for antifake , and biological applications . In fact, the specific application may vary based on the concentration of europium, fabrication techniques, and the desired properties for the given application.…”

“…Eu 3+ :YPO 4 can be organized in four different crystalline forms: Xenotime-(Y) with a tetragonal structure, Monazite and Churchite with a monoclinic structure, and Rhabdophane with a hexagonal structure. , The hexagonal and monoclinic phases contain coordinated water molecules in their crystalline structures, while the tetragonal structure is formally anhydrous. It is well-known that the luminescence properties of nanomaterials are influenced by various factors such as the crystal phase, degree of crystallinity, lattice defects, particle size, and morphology. ,, Indeed, the shape of particles can influence the distance between Eu 3+ ions in the phosphor, which can affect the fluorescence lifetime or the energy transfer. − In addition, for some specific applications, such as anticounterfeiting inks, the use of nanopowders with a uniform, well-defined morphology and a narrow particle size distribution could be crucial for the preparation of stable dispersions in aqueous or organic media, which would allow printing motifs with higher resolution . To this end, the high surface-to-volume ratio inherent in the rod-like morphology was shown to have the advantage of increasing the dispersibility of the phosphors. , Lastly, the luminescence properties of nanomaterials depend also on the presence of functional groups on the surface end/or in the volume .…”

“…It is well-known that the luminescence properties of nanomaterials are influenced by various factors such as the crystal phase, degree of crystallinity, lattice defects, particle size, and morphology. ,, Indeed, the shape of particles can influence the distance between Eu 3+ ions in the phosphor, which can affect the fluorescence lifetime or the energy transfer. − In addition, for some specific applications, such as anticounterfeiting inks, the use of nanopowders with a uniform, well-defined morphology and a narrow particle size distribution could be crucial for the preparation of stable dispersions in aqueous or organic media, which would allow printing motifs with higher resolution . To this end, the high surface-to-volume ratio inherent in the rod-like morphology was shown to have the advantage of increasing the dispersibility of the phosphors. , Lastly, the luminescence properties of nanomaterials depend also on the presence of functional groups on the surface end/or in the volume . For example, it was demonstrated that the −OH groups of coordinated water molecules in hexagonal and monoclinic hydrated RE-doped YPO 4 structures promote luminescence quenching, which decreases the fluorescence quantum yield and is therefore detrimental to the optical properties. ,− Conversely, the lack of coordinated water in the Xenotime-(Y) tetragonal phase improves its stability and reduces the quenching effect .…”