temperature sensors based on non-thermally coupled levels NTCLS.pptx

non-thermally coupled levels

1. Coactivated cyan emitting phosphors in optical thermometry using thermally and non- thermally coupled levels Manisha Prasad , Vineet Kumar Rai Fig. 1. (a) XRD spectra of MgWO4 host, optimized Tm3 + /Yb3 + /Er3 + and Tm3 + /Yb3 + /Er3 + /Li + : MgWO4 phosphors; FESEM image of (b) Tm3 + /Yb3 + /Er3 + and (c) Tm3 + /Yb3 + /Er3 + /Li + : MgWO4 phosphors, inset showing the respective particle distribution (d) UV-vis spectra of MgWO4 host, Tm3 + /Yb3 + /Er3 + and Tm3 + /Yb3 + / Er3 + /Li + : MgWO4 phosphors.

2. Improving performance of luminescent nanothermometers based on non-thermally and thermally coupled levels of lanthanides by modulating laser power… Nanoscale, 2021, 13, 14139 Here we report the development of a ratiometric , optical nanothermometer, YVO4:Yb3+,Er3+ working in a broad spectral range (VIS-NIR) Synthesis Hydrothermal method The selected luminescence intensity ratios of the bands associated with TCLs and non-TCLs of Er3+ and Yb3+ are used as thermometric parameters the demonstration of a strong influence of the applied pump (laser) power on the values of the mentioned thermometric parameters, as well as on the thermometer performance

3. Thermally coupled levels (TCLs) and non-thermally coupled levels (NTCLs) Thermally coupled levels (TCLs) and non-thermally coupled levels (NTCLs) are two popular ways of applying the FIR technique for optical thermometry to the energy levels of lanthanides. In sensing using TCLs, the energy gap should lie within the 200-2000 cm-1 range. Thus, the sensitivity of material is very much dependent on the energy gap of TCLs. On the other hand, in NTCLs based thermometry, two transitions from the same activator or two different activators are considered. The concept of NTCLs has been developed to make the sensitivity independent of the energy gap and further improve the thermometric properties. In summary, TCLs rely on a specific energy gap range for sensitivity while NTCLs consider multiple transitions to improve thermometric properties and make sensitivity independent of energy gaps.

4. Fig. 2. (a) Frequency UC spectra of Tm3 + /Yb3 + , Tm3 + /Yb3 + /Er3 + and Tm3 + /Yb3 + / Er3 + /Li + : MgWO4 phosphors (b) Energy level diagram of Tm3 + /Yb3 + /Er3 + system (c) Decay curve and (d) CIE coordinates of Tm3 + /Yb3 + /Er3 + /Li + doped/ codoped MgWO4 phosphors (e) Optical bistability of Tm3 + /Yb3 + : MgWO4 phosphors.

5. Fig. 3. (a) ln FIR vs 1/T and (b) absolute & relative sensitivity using TCLs (c) FIR vs T and (d) absolute & relative sensitivity using NTCLs, FIR variation with temperature for two repeated observations of (e) TCLs and (f) NTCLs based optical thermometry of Tm3 + /Yb3 + / Er3 + /Li + : MgWO4 phosphors .

6. the thermometric potential of Tm3+/Er3+ co-activated MgWO4 phosphors by innovative ratiometric intensity read-out using both TCLs and NTCLs. the absolute and relative sensitivity in the non-thermally coupled levels is found to be maximum as compared to the system containing thermally coupled levels. NTCLs have shown better thermometric potential than TCLs the ratio of two emission intensities from different energy levels of the same activator or two different activators to calculate the temperature. Tm3+/Er3+ co-activated MgWO4 phosphors for temperature sensing applications and measured the emission intensities at 476 nm and 650 nm. calculated the ratio of these two intensities to obtain NTCLs the thermometric potential of NTCLs in Tm3+/Er3+ co-activated MgWO4 phosphors

7. Fig. 4. (a) Activation energy, temperature dependent UC spectra at 303K and 623 K (inset) (b) Boltzmann fitting to experimental data showing TQ1/2 of Tm3 + /Yb3 + / Er3 + /Li + : MgWO4 phosphors.

8. The major contributions of this paper are: 1. The researchers have achieved tunability in upconversion emission and observed optical bistability in Tm3+/Yb3+: MgWO4 phosphors. 2. They have developed coactivated cyan emitting display phosphors that can be used for temperature sensing applications. 3. They have investigated the thermometric potential of Tm3+/Er3+ co-activated MgWO4 phosphors by innovative ratiometric intensity using TCLs and NTCLs. 4. The effect of Li+ codoping on the optical properties has been realized and discussed. 5. The researchers have characterized the optimized phosphors by various techniques such as X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, X-ray photon spectroscopy, UV-vis-NIR spectroscopy, etc. Overall, this research provides valuable insights into the development of coactivated cyan emitting phosphors for optical thermometry applications.