A review and outlook of ratiometric optical thermometer based on thermally coupled levels and non-thermally coupled levels

Cr3+-Doped InTaO4 phosphor for multi-mode temperature sensing with high sensitivity in a physiological temperature range

“…Fast and accurate temperature monitoring is essential for many fields in scientific research, industrial production, biomedicine, and even daily life. [1][2][3][4] However, the traditional contact thermometers (e.g., thermocouples and thermistors) are barely effective under corrosive conditions, in an intracellular environment, or for temperature detection of fast-moving objects, and other complex situations. 1 Recently, optical thermometers have been widely explored due to their advan-tages of non-contact and non-invasive operating modes.…”

“…20 Among the optical thermometers based on the single emission center, the temperature sensing method based on the thermally coupled energy levels of trivalent rareearth (Re 3+ ) ions is the most studied and applied. 2,12,13,[21][22][23][24] For example, Zhu et al realized real-time monitoring of microscopic temperature in photothermal therapy with an Er 3+doped nanophosphor by utilizing the thermally coupled energy levels of 2 H 11/2 and 4 S 3/2 of Er 3+ . 25 Balabhadra et al reported a novel Nd 3+ -doped Gd 2 O 3 phosphor that exhibited high-performance thermometry with an optimal relative sensitivity of 1.75% K −1 at 288 K. 13 In principle, the relative sensitivity (S r ) value obtained from such optical thermometry involving thermally coupled energy levels (TCELs) of Re 3+ is proportional to the energy difference ΔE between the two coupled levels.…”

Frequency upconversion based thermally stable molybdate phosphors in a temperature sensing probe

“…18 Although the temperature sensing ability based on the FIR technique has been witnessed in Er 3+ , Ho 3+ , Tm 3+ , Nd 3+ , and Eu 3+ based phosphors, Er 3+ -Yb 3+ based upconverting materials have been widely studied in most of the work on temperature sensing. 12,[18][19][20][21] Still, researchers are working on temperature sensing to improve phosphors' temperature range and thermal sensitivity using different techniques to build reliable temperature probes. Due to the lower absorption cross-section at the 4 I 15/2 -4 I 11/2 transition, Er 3+ ions possess low UC efficiency.…”

“…22 This technique encountered some limitations and, in this regard, temperature sensing based on Stark sublevels has emerged as a successful tool in the FIR technique. 21,23 While monitoring the thermal behavior of Er 3+ –Yb 3+ :MgMoO 4 phosphors, Mondal and Rai found that the Stark sublevels can deliberately enhance the sensitivity and temperature uncertainty of the phosphors. 3 In another report, Liu et al proposed the ratiometric thermometry of the Er 3+ –Yb 3+ -codoped NaGd(WO 4 ) 2 phosphors using Stark sublevels of the green emission under 980 nm excitation.…”

Boltzmann- and non-Boltzmann-based thermometers in the first, second and third biological windows for the SrF2:Yb3+,Ho3+ nanocrystals under 980, 940 and 915 nm excitations

“…Nevertheless, this additional requirement greatly restrains the utility of numerous NTCLs in lanthanide ions. Thus, the thermometers based on the NTCLs, which are no longer restricted to limitation of ΔE and can expand the detection wavelengths in a relatively wide range, can achieve relatively high S r and low δT and further expand their applications [13][14][15]. Generally, the quantitative NTCLs model is established by using the Arrhenius equation which can break the restriction of the ΔE between the NTCLs and well predict the FIR and the accuracy of temperature measurement.…”