Abstracts

Concerning photophysical properties, trivalent lanthanide ions (Ln³⁺) are unique among the periodic table elements due to their intrinsic electronic configuration. Features such line-like absorption and emission bands, large Stoke shifts and long-lived emission decay times, besides monochromatic emissions from visible to NIR spectral range also make these ions a current alternative to organic dyes, avoiding practical disadvantages like photobleaching and re-absorption process. In fact, Eu³⁺ and Tb³⁺ are by far, the most common Ln³⁺ ions in terms of visible light, with red and green monochromatic emissions, respectively. Such applications include photonics, biomarkers, temperature sensors, hybrid materials, luminescent solar concentrators (LSCs) and downshifting layers (DSLs) to name a few. Another feature in which the Ln³⁺ ions can be significantly helpful is the search for micro and nano scale thermometers that have been significantly growing in the last decades. Such approach allows overcome limitations of more traditional temperature measurements e.g. liquid-filled bulbs or stems and thermocouples and allows even cellular level monitoring. The measurements are focused mainly on three methodologies i.e. i) the spectral shift of a given transition, ii) the integrated intensity of one or two transitions (in case of doped systems) and iii) lifetime measurements. It is noteworthy that the measurement based on integrated intensity ratio has been one of the most promising ones due to the short response time, self-calibration, high precision, and reliability. It is noteworthy, however, that Ln³⁺- complexes can show features such as low photo and thermal stability besides poor mechanical and conductive properties, that poses practical limitations for some of their direct applications. Thus, the engineering of hybrid materials containing Ln³⁺- complexes have been arising in the past twodecades as an alternative to such drawbacks and are generally denoted as lanthanide-based luminescent hybrid materials. Such materials usually present synergistic effects associating features such as flexibility, transparency and relatively ease of production of the polymer with the remarkable photonic properties of the Ln³⁺-complexes. In this way, this work reports the synthesis, characterization, and optical-thermal study of a tetrakis Tb³⁺/Eu³⁺- complex with thenoyltrifluoroacetone (tta) containing tetraethylammonium (Et₄N) as counterion. In addition, the complex was doped at 1% in weight in PMMA and PVA polymeric matrices. The complex present general formula Et₄N[Tb_0,999Eu_0,001(tta)₄] and was fully characterized via elemental and thermal analysis, mass spectrometry, infrared absorption spectroscopy, X-ray diffraction analysis. The complex and the doped polymeric materials, showed a remarkable excitability either in the NUV-Vis range (even far beyond 400 nm) and under sunlight exposure (mainly for the PMMA film). The thermometric parameters of the Et₄N[Tb_0,999Eu_0,001(tta)₄] complex determining the ratio between the integrated intensities of the ⁵D₄ → ⁷F₅ (Tb³⁺) and ⁵D₀ → ⁷F₂ (Eu³⁺) transitions and the relative thermal sensitivity (S_r) and the temperature uncertainty (δT), were discussed.