of luminescence signal in comparison to other methods, relatively fast response, and a good spatial resolution. Temperature can be determined from different features of luminescence, such as excitation and emission band positions and bandwidths, emission band intensities, luminescence intensity ratio (LIR; the ratio of intensities of two emission bands), anisotropy, emission decay-or rise-times, etc. [2] Temperature readouts from LIR and emission lifetime are by far the most exploited luminescence thermometry methods. Both readouts are self-referencing and are not affected by fluctuations in the excitation and signal detection. Luminescence of any substance is strongly affected by temperature, and, thus, variety of materials may be utilized as a luminescence thermometry probe. The choice is commonly made on quantum dots, organic dyes, metal-organic complexes and frameworks, and lanthanide or transition metal ion based phosphors, the last of which are the most exploited ones. When screening materials for the suitable luminescence thermometry probe for the specific application, attention is given to material's structural, chemical, luminescent, and thermographic properties. Most of all, luminescence of material should notably change with temperature to provide sensitive measurement with adequate temperature resolution. Also, a probe should provide repeatable and reproducible temperature determination. Furthermore, for the practical realization of thermometer, some other materials properties are of interest, such as excitation and emission wavelengths and bandwidths, which should facilitate production of cost-effective and simple measurement devices.Regarding structural and chemical properties, lanthanide and transition metal ion based materials and material's systems meet most of above mentioned conditions. They are thermally and chemically stable, provide sufficient brightness, and exceptional photostability. They also facilitate thermometry with excellent repeatability and reproducibility. However, they generally lack sensitivity and, consequently, temperature resolution. LIR readout scheme with trivalent lanthanide ion activated phosphors exploits emissions from two closely separated and thermally coupled excited states (either in the upconversion or downshifting processes). [3] In such case, the relative sensitivity is limited by the energy difference between these excitedThe binary luminescence thermometry probe is prepared from Y 2 O 3 :Ho 3+ and Mg 2 TiO 4 :Mn 4+ powders. This probe facilitates self-referencing temperature readouts with excellent repeatability from both emission intensity ratio and excited state lifetimes. The ratio of intensities of Mn 4+ deep red emission from 2 E, 4 T 2 → 4 A 2 electronic transitions, and Ho 3+ green emission from 5 F 4 , 5 S 2 → 5 I 8 electronic transitions provides temperature measurements over the room temperature to 100 °C temperature range with a superior relative sensitivity of 4.6% °C −1 and temperature resolution of 0.1 °C. Over the same temperature range, the tem...

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Cr3+-doped Mg2SiO4 orthorhombic nanoparticles are synthesized by a combustion method. The 3d3 electron configuration of the Cr3+ ion results in the deep-red emission from optical transitions between d–d orbitals. Two overlapping emissions from the Cr3+ spin-forbidden 2Eg→ 4A2g and the spin-allowed 4T2g→ 4A2g electronic transitions are influenced by the strong crystal field in Mg2SiO4 and, thus, are suitable for ratiometric luminescence thermometry. The temperature-induced changes in Cr3+-doped Mg2SiO4 emission are tested for use in luminescence thermometry from cryogenic to physiologically relevant temperatures (10–350 K) by three approaches: (a) temperature-induced changes of emission intensity; (b) temperature-dependent luminescence lifetime; and (c) temperature-induced changes of emission band position. The second approach offers applicable thermometry at cryogenic temperatures, starting from temperatures as low as 50 K, while all three approaches offer applicable thermometry at physiologically relevant temperatures with relative sensitivities of 0.7% K−1 for emission intensity, 0.8% K−1 for lifetime and 0.85% K−1 for band position at 310 K.

In this study, halloysite nanotubes (HNT) were modified by: 3-glycidyloxypropy ltrimethoxysilane (GLYMO), 3-aminopropyltrimethoxysilane (APTES), and 2,2-Bis[4-(glycidyloxy) phenyl] propane (DGEBA), and incorporated in the epoxy resin matrix to enhance its mechanical properties. The HNT/epoxy nanocomposite materials were prepared by mixing different ratios of untreated/ treated HNT with neat epoxy resin. Characterization of untreated/treated HNT was performed by Fourier-transformation infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). The quantity of grafted molecules and thermal stability of newly synthesized materials were determined by thermogravimetric (TG) and derivative thermogravimetric (DTG) analysis. Tensile properties of newly synthesized materials were compared, and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis of the fracture surfaces were performed. Incorporation of APTES modified HNT (HNTAPT) and twostep modification APTES followed by DGEBA (HNTAPTDG) has increased the tensile strength of the nanocomposite materials up to 72% and 61%, and strain at break up to 1082% and 1216%, respectively, compared to neat epoxy. It was concluded that the modification of HNT contributed to the enhancement of the dispersion and the cross-linking in the epoxy resin matrix.

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