Absolute Temperature Sensitivity Research Articles

Upconversion and luminescence temperature sensitivity of Er3+ ions in yttrium oxysulfate nanophosphor

Near infrared-to-green upconverted emissions of Er3+-doped Y2O2SO4 yttrium oxysulfate nanophosphor have been studied exciting the sample with a 975 nm laser radiation. Temporal dynamics of the green emission indicates that the main mechanism responsible for the upconversion processes is energy transfer between Er3+ ions. The relative intensities of the near infrared-to-green upconverted emissions from the 2H11/2 and 4S3/2 thermalized levels to the 4I15/2 ground state have been calibrated as a function of temperature in order to develop an optical temperature sensor both in the biological range, from 295 up to 330 K, and in the industrial application range up to 475 K. The temperature scale obtained shows a relative sensitivity with temperature of 1.1 %K−1 at 300 K, and an absolute temperature sensitivity of 73 × 10−4 K−1 at 467 K. These results suggest that the Er3+-doped yttrium oxysulfate can be used as an optical temperature sensor by exciting in the infrared range for biomedicine and industrial applications.

The Enhancement of Upconversion Luminescence of Gd2O3:Yb,Er Nanoparticles by Ca2+ Codoping for Temperature Sensing at Room and High Temperatures

We prepared a series of Gd2O3:Yb,Er,Ca (3/1/[Formula: see text][Formula: see text]mol.%, [Formula: see text] represents the nominal concentration of Ca element including 0, 2, 3, 4, 5, 7, 10) upconversion nanoparticles (UCNPs) with regular morphology via a wet-chemical route. We observed a simultaneous enhancement of upconversion luminescence (UCL) emission of Gd2O3:Yb,Er after Ca[Formula: see text] ions were doped. When the doping level of Ca[Formula: see text] reaches its optimal concentrate at 5[Formula: see text]mol.%, the red and green emissions increased by 6.3 and 11 times, respectively. The potential application of Gd2O3:Yb,Er,Ca material as a noninvasion optical thermometry based on FIR technique was investigated. The sensing of temperature at both high and room temperatures was realized by choosing different parameters. The absolute temperature sensitivity ([Formula: see text]) of Gd2O3:Yb,Er nanoparticles at 293[Formula: see text]K reached 0.0875[Formula: see text]K[Formula: see text], whereas Gd2O3:Yb,Er, 5[Formula: see text]mol.%Ca was chosen as sensor of high temperature due to its considerable Sa of 0.0060[Formula: see text]K[Formula: see text] at 573[Formula: see text]K. The resultant UCNPs provided a new way for sensitive thermal detection at various target temperatures.

Novel ratiometric optical thermometry based on dual luminescent centers from europium doped LiCa3MgV3O12 phosphor

Abstract In this paper, an optical thermometry strategy based on dual emission centers involving rare earth ions and self-activated host luminescence has been proposed, which can be used to design self-referencing optical thermometer with high temperature sensitivity and signal discriminability. Herein, we prepared non-rare-earth self-activated and rare-earth activated LiCa3MgV3O12 (LCMV) phosphors by a conventional high-temperature solid-state reaction method. Their structure, luminescence as well as temperature sensing property have been systematically investigated. In this sample, the emissions of Eu3+ ions and [VO4]3− group have been simultaneously monitored under 335 nm UV light excitation. The FIR of Eu3+ to [VO4]3- shows great temperature sensing property in temperature range from 303 K–523 K,owing to the energy transfer and thermal quenching behavior. The measured maximum absolute and relative temperature sensitivity of this phosphor are 0.011 K−1 and 1.689%K−1, which is remarkably higher than most of luminescent materials reported previously. Meanwhile, the emission peaks of [VO4]3- (475 nm) and Eu3+ (610 nm) provide a good signal discriminability for temperature detection. What's more, the emitting color in the temperature-dependent CIE diagram can highly be influenced by the external temperature and the color coordinate is verified from (0.257, 0.332) to (0.503, 0.342), which can be fitted well with the linear equation. All results indicate that the obtained phosphors not only can be promising materials for optical temperature sensors, but can be used as a color-temperature indicator.

Temperature sensitive properties of Eu2+/Eu3+ dual-emitting LaAlO3 phosphors

In this study, Eu2+/Eu3+ coexisting perovskite LaAlO3 phosphors were synthesized by a traditional high-temperature solid-phase reaction method and investigated via X-ray diffraction data, X-ray photoelectron spectroscopy and temperature-dependent photoluminescence spectra. The Eu2+/Eu3+ coexisting LaAlO3 phosphors exhibit excellent optical temperature sensing characteristics and are potential inorganic materials for temperature detection. The measured maximal absolute temperature sensitivity reaches 0.014 K-1, and the corresponding largest relative temperature sensitivity is 1.193% K−1, which are superior to most of previous reports of that. Meanwhile, the monitored signal peaks are well separated, providing a good signal discriminability. The energy level crossover relaxation of Eu2+ and Struck-Fonger crossover process involving O2–-Eu3+ charge transfer band were used to explain the different temperature-dependent responses of Eu2+ and Eu3+. This work may give new ideas for the future research of optical thermometric materials with high sensitivity and high discriminability.

Yb/Er/Tm tri-doped Na3ZrF7 upconversion nanocrystals for high performance temperature sensing

Abstract Non-contact optical thermometry based on fluorescence intensity ratio (FIR) technique has been widely researched over the past few decades. However, the reported systems exhibit two important shortcomings including the existence of a few interferential signals in addition to the required spectral bands for FIR and the absence of internal standard for reference signal. Herein, only two emission bands of Er3+:4F9/2→4I15/2 (~673 nm) and Tm3+:3H4 → 3H6 (~800 nm) are achieved in Yb/Er/Tm tri-doped Na3ZrF7 nano-system. Moreover, the upconversion (UC) emission intensity of Er3+ keeps unchanged with the rising of temperature, which is applied as reference signal; while that of Tm3+ enhances evidently, which is applied as temperature signal. The calculated maximum absolute temperature sensitivity (Sa) and relative temperature sensitivity (Sr) are 0.17 K−1 at 393 K and 1.76% K−1 at 313 K, respectively.

The luminescence thermometry based on analysing of 3P0-3H5 emission band of Pr3+ ions in Pr3+:LiYF4 nanoparticles and microparticles

The study is devoted to the possibility of using and Pr3+:LiYF4 microparticles and nanoparticles as luminescent thermometers in the temperature range of 80-320 K. The ratio of luminescence peaks corresponding to the transitions from the 3P0 state to two Stark sublevels of the 3H5 state of Pr3+ ions is considered as a temperature-dependent parameter. This system demonstrates an absolute temperature sensitivity of 0.0009 K-1 at a temperature of 185 K.

Controlling optical temperature detection of Ca3Al2O6: Yb3+,Er3+ phosphors through doping

This work introduces a method to effectively improve optical temperature detection of novel Ca3Al2O6:Yb3+,Er3+ through co-doping with Ba2+, Mg2+, Y3+, La3+ and Lu3+ as well as the control of excitation power. The fluorescence intensity ratio of the green emissions at 526 nm and 551 nm in Ca3Al2O6:Yb3+-Er3+ was studied as a function of temperature in the temperature range from 298 K to 573 K. By analyzing the temperature dependent upconversion spectra, total emission intensity, ratios of fluorescence intensity, and sensitivity, the effect of doping ions on the optical temperature detection of Ca3Al2O6:Yb3+, Er3+ is studied. The relative and absolute temperature sensitivity of Ca3Al2O6:Yb3+,Er3+ can be effectively enhanced by co-doping with Ba2+, Mg2+, Y3+, La3+, and Lu3+ ions and controlling excitation powers. The temperature sensitivity of Ca3Al2O6:6%Yb3+, 0.6%Er3+, 1.2%Mg2+ can reach a maximum relative sensitivity of 0.0078 K−1 at 145 K, which is higher than the values in some reported works.

Controlling optical temperature behaviors of Er3+ doped Sr2CaWO6 through doping and changing excitation powers

A method to modify the spectra and optical temperature behaviors of Er3+ doped Sr2CaWO6 phosphors through doping La3+, Y3+, and Al3+ ions is reported. The thermometric parameters such as fluorescence emission intensity, fluorescence intensity ratio of red to green emissions, emission intensity ratios of thermally coupled levels (2H11/2/4S3/2), and temperature sensitivity can be effectively controlled by doping with La3+, Y3+, and Al3+ ions into Er3+ doped Sr2CaWO6. Moreover, the relative temperature sensitivity SR and the absolute temperature sensitivity SA are proved to be dependent on the pump power of 980 nm laser. The sensitivity values of SR in Er3+ doped Sr2CaWO6 increase about 85.2% by doping with 0.15 mol% La3+, when the excitation power is 526 mW/mm2.

Exploring the 4I13/2 → 4I15/2 radiative transition from Er3+ in Y2O3 for temperature sensing

The influence of temperature on the near-infrared emission band corresponding to the radiative relaxation from 4I13/2 to 4I15/2 electronic states of Er3+ was investigated in Y2O3 powder prepared by combustion synthesis. We observed that the electronic population distribution among various Stark levels of 4I13/2 and 4I15/2 changes with temperature in a way that is favorable for temperature sensing based on the luminescence intensity ratio technique. We also observed that the absolute temperature sensitivity varies by around 300% depending on the Stark transitions of choice with the highest relative temperature sensitivity value being around 2 × 10−3 K−1 at room temperature. Optically induced heat was found to be negligible under our experimental conditions.

Investigation on Two Forms of Temperature-Sensing Parameters for Fluorescence Intensity Ratio Thermometry Based on Thermal Coupled Theory.

Absolute temperature sensitivity (Sa) reflects the precision of sensors that belong to the same mechanism, whereas relative temperature sensitivity (Sr) is used to compare sensors from different mechanisms. For the fluorescence intensity ratio (FIR) thermometry based on two thermally coupled energy levels of one rare earth (RE) ion, we define a new ratio as the temperature-sensing parameter that can vary greatly with temperature in some circumstances, which can obtain higher Sa without changing Sr. Further discussion is made on the conditions under which these two forms of temperature-sensing parameters can be used to achieve higher Sa for biomedical temperature sensing. Based on the new ratio as the temperature-sensing parameter, the Sa and Sr of the BaTiO3: 0.01%Pr3+, 8%Yb3+ nanoparticles at 313 K reach as high as 0.1380 K-1 and 1.23% K-1, respectively. Similarly, the Sa and Sr of the BaTiO3: 1%Er3+, 3%Yb3+ nanoparticles at 313 K are as high as 0.0413 K-1 and 1.05% K-1, respectively. By flexibly choosing the two ratios as the temperature-sensing parameter, higher Sa can be obtained at the target temperature, which means higher precision for the FIR thermometers.

Effect of doping Ge into Y2O3:Ho,Yb on the green-to-red emission ratio and temperature sensing.

A series of Ge-doped monophase Y2O3:Ho,Yb phosphor materials has been synthesized using solid state reactions. The addition of Ge to the Y2O3 host decreases the Ho green emission (5F4/5S2 → 5I8) and increases the red emission (5F5 → 5I8), providing a new means to tune the green-to-red emission intensity ratio. It is proposed that the Ge-induced multiphonon relaxation process enhances the transition from the intermediate state 5I6 to 5I7, which tunes the green and red emission intensities. Most importantly, with the addition of Ge, the non-thermally coupled Ho green and red emitting levels are associated together, and the red-to-green emission intensity ratio becomes sensitive to environmental temperature change. The absolute thermal sensitivity is enhanced by a factor of >5 times that in the absence of Ge. The matched green and red emission intensities, as well as the high thermal sensitivity, make Y2O3:Ho,Yb,Ge an ideal probe for optical temperature sensing at the single particle level in live biological samples. This study demonstrates a new mechanism to channel non-thermally coupled energy levels to achieve high temperature sensitivity.

Enhanced up-conversion luminescence and optical thermometry characteristics of Er3+/Yb3+ co-doped transparent phosphate glass-ceramics

Novel Er3+/Yb3+ co-doped transparent glass-ceramics (GCs) containing orthorhombic NaZnPO4 nanocrystals (NCs) were successfully prepared for the first time by a conventional melt-quenching and subsequent heating. Under 980nm laser prompting, the GC samples produced intense red and green up-conversion emissions. The emission intensities varied with Yb3+ concentration and heat treatment conditions. Optimum emission intensities were obtained for the sample with 2mol% of Yb3+ heat treated at 580°C for 4h. Furthermore, the temperature dependent fluorescence intensity ratio (FIR) of thermally coupled emitting states (4S3/2, 2H11/2) in Er3+/Yb3+ co-doped GCs was evaluated under 980nm. A high relative temperature sensitivity of 1.329% K−1 was obtained at 303K and the maximal absolute temperature sensitivity at 612K was evaluated to be 5.732 × 10−3K−1. It is expected that the as-fabricated GCs containing NaZnPO4 NCs are an efficient up-conversion material with potential application in optical temperature sensor.

Self-calibrating optic thermometer based on dual-emission nanocomposite

A new approach to optical thermometers with high sensitivity was developed herein by using In2O3 quantum dots (QDs) emission as temperature detecting signal and Eu3+ ions emission as reference one. Originated from the diverse thermal quenching behavior between the defect-related emission of In2O3 QDs and 4f-4f transitions of Eu3+ ions, fluorescence intensity ratio of In2O3 to Eu3+ in nanocomposite exhibited excellent temperature sensing property in the range from 303 K to 543 K. The maximum absolute and relative temperature sensitivity can reach as high as 4.43 × 10−2 K−1 and 0.89% K−1, respectively. We believe that this work exploits an effective pathway for developing other innovative optical thermometers.

Rapid laboratory measurement of the temperature dependence of soil respiration and application to changes in three diverse soils through the year

Determining the temperature dependence of soil respiration is needed to test predictive models such as Arrhenius-like functions and macro-molecular rate theory (MMRT). We tested a method for rapid measurement of respiration using a temperature gradient block, cooled at one end (~2 °C) and heated at the other (~50 °C) that accommodated 44 tubes containing soil incubated at roughly 1 °C increments. Gas samples were taken after 5 h incubation and analysed for CO2. The temperature gradient block allowed rapid assessment of temperature dependence of soil respiration with the precision needed to test models and explore existing theories of how temperature and moisture interact to control biochemical processes. Temperature response curves were well fitted by MMRT and allowed calculation of the temperature at which absolute temperature sensitivity was maximal (Tinf). We measured temperature response of three soils at seven moisture contents and showed that the absolute rate and sensitivity of respiration was partly dependent on adjusted moisture content. This result implied that comparisons between soils need to be made at a common moisture content. We also measured potential changes in the temperature dependence (and sensitivity) of respiration for three different soils collected at one site throughout a year. Tinf ranged from 43 to 51 °C for the three soils. Tinf and temperature sensitivity were not dependent on soil type collected but was partly dependent on time of year of collection. Temporal changes in temperature response suggested that the microbial communities may tune their metabolisms in response to changes in soil temperatures.

Influence of Doping and Excitation Powers on Optical Thermometry in Yb3+-Er3+ doped CaWO4

Optical thermometry has been widely studied to achieve an inaccessible temperature measurement in submicron scale and it has been reported that the temperature sensitivity depends mainly on host types. In this work, we propose a new method to improve the optical temperature sensitivity of Yb3+-Er3+ co-doped CaWO4 phosphors by doping with Li+, Sr2+, and Mg2+ ions and by controlling excitation powers of 980 nm laser. It is found that the thermometric parameters such as upconversion emission intensity, intensity ratio of green-to-red emission, fluorescence color, emission intensity ratios of thermally coupled levels (2H11/2/4S3/2), and relative and absolute temperature sensitivity can be effectively controlled by doping with Li+, Sr2+, and Mg2+ ions in the Yb3+-Er3+ co-doped CaWO4 system. Moreover, the relative sensitivity SR and the absolute sensitivity SA are proved to be dependent on the pump power of 980 nm laser. The sensitivities of SR and SA in Yb3+-Er3+ co-doped CaWO4 increase about 31.5% and 12%, respectively, by doping with 1 mol% Sr2+.

Intervalence charge transfer state interfered Pr3+ luminescence: A novel strategy for high sensitive optical thermometry

In this study, the Ruddlesden-Popper type perovskite Na2La1.96Pr0.04Ti3O10 micro-crystals are synthesized and demonstrated to be one of the most promising optical temperature sensing materials. The measured maximal absolute temperature sensitivity of this phosphor reaches as high as 0.40K−1, remarkably superior to those of the inorganic optical thermometric materials reported previously; while the relative sensitivity is 1.96%K−1, ranking among the highest ones for the inorganic optical thermometric materials. Analysis of the configurational coordinate diagram indicates that thermo-induced relaxation between the Pr3+ 3Px and 1D2 levels through Pr3+-Ti4+ intervalence charge transfer state is the primary cause for the temperature sensing characteristics. Based on these results, a novel temperature sensing strategy utilizing the intervalence charge transfer state interfered Pr3+ luminescence to perform optical thermometry is proposed, which is further demonstrated to be universally valid for the Pr3+ doped oxides containing d0 configured transition metal ions, as long as energy of the intervalence charge transfer state is moderate. This work may provide useful inspiration for developing high sensitive optical thermometric materials.

Precipitation Mediates the Response of Carbon Cycle to Rising Temperature in the Mid-to-High Latitudes of the Northern Hemisphere.

Over the past decades, rising air temperature has been accompanied by changes in precipitation. Despite relatively robust literature on the temperature sensitivity of carbon cycle at continental to global scales, less is known about the way this sensitivity is affected by precipitation. In this study we investigate how precipitation mediates the response of the carbon cycle to warming over the mid-to-high latitudes in the Northern Hemisphere (north of 30°N). Based on atmospheric CO2 observations at Point Barrow (BRW) in Alaska, satellite-derived NDVI (a proxy of vegetation productivity), and temperature and precipitation data, we analyzed the responses of carbon cycle to temperature change in wet and dry years (with precipitation above or below the multiyear average). The results suggest that, over the past three decades, the net seasonal atmospheric CO2 changes at BRW were significantly correlated with temperature in spring and autumn, yet only weakly correlated with temperature and precipitation during the growing season. We further found that responses of the net CO2 changes to warming in spring and autumn vary with precipitation levels, with the absolute temperature sensitivity in wet years roughly twice that in dry years. The analyses of NDVI and climate data also identify higher sensitivity of vegetation growth to warming in wet years for the growing season, spring and summer. The different temperature sensitivities in wet versus dry years probably result from differences in soil moisture and/or nutrient availability, which may enhance (inhibit) the responsiveness of carbon assimilation and/or decomposition to warming under high (low) precipitation levels. The precipitation-mediated response of the terrestrial carbon cycle to warming reported here emphasizes the important role of precipitation in assessing the temporal variations of carbon budgets in the past as well as in the future. More efforts are required to reduce uncertainty in future precipitation projections, and to better represent the nonlinearity of carbon cycle responses to climate in current state-of-the-art land surface models.

Thermodynamic theory explains the temperature optima of soil microbial processes and high Q10 values at low temperatures

Our current understanding of the temperature response of biological processes in soil is based on the Arrhenius equation. This predicts an exponential increase in rate as temperature rises, whereas in the laboratory and in the field, there is always a clearly identifiable temperature optimum for all microbial processes. In the laboratory, this has been explained by denaturation of enzymes at higher temperatures, and in the field, the availability of substrates and water is often cited as critical factors. Recently, we have shown that temperature optima for enzymes and microbial growth occur in the absence of denaturation and that this is a consequence of the unusual heat capacity changes associated with enzymes. We have called this macromolecular rate theory - MMRT (Hobbs etal., , ACS Chem. Biol. 8:2388). Here, we apply MMRT to a wide range of literature data on the response of soil microbial processes to temperature with a focus on respiration but also including different soil enzyme activities, nitrogen and methane cycling. Our theory agrees closely with a wide range of experimental data and predicts temperature optima for these microbial processes. MMRT also predicted high relative temperature sensitivity (as assessed by Q10 calculations) at low temperatures and that Q10 declined as temperature increases in agreement with data synthesis from the literature. Declining Q10 and temperature optima in soils are coherently explained by MMRT which is based on thermodynamics and heat capacity changes for enzyme-catalysed rates. MMRT also provides a new perspective, and makes new predictions, regarding the absolute temperature sensitivity of ecosystems - a fundamental component of models for climate change.

Pr(3+)-doped beta-NaYF4 for temperature sensing with fluorescence intensity ratio technique.

Pure beta-NaYF4:0.8%Pr3+ powder sample was synthesized by the hydrothermal method. The temperature dependence of the fluorescence intensity ratio (FIR) of emission bands corresponding to the 3P1 --> 3H5 and 3P0 --> 3H5 transitions was measured in the temperature range of 120 K to 300 K excited by a 473 nm continuous wave (CW) laser. The dependence of the FIR on temperature is well fitted with an exponential function and the effective energy difference obtained is 457 cm(-1), which gives further an absolute temperature sensitivity of 0.01352 K(-1) at 300 K. The monotonous increase of FIR with temperature and high absolute temperature sensitivity demonstrate that this material can be used as temperature sensor. In addition, mono-dispersed NaYF4:1%Pr3+ nanoparticles were also synthesized.

Effect of soil water stress on soil respiration and its temperature sensitivity in an 18‐year‐old temperate Douglas‐fir stand

AbstractWe analyzed 17 months (August 2005 to December 2006) of continuous measurements of soil CO2 efflux or soil respiration (RS) in an 18‐year‐old west‐coast temperate Douglas‐fir stand that experienced somewhat greater than normal summertime water deficit. For soil water content at the 4 cm depth (θ) > 0.11 m3 m−3 (corresponding to a soil water matric potential of −2 MPa), RS was positively correlated to soil temperature at the 2 cm depth (TS). Below this value of θ, however, RS was largely decoupled from TS, and evapotranspiration, ecosystem respiration and gross primary productivity (GPP) began to decrease, dropping to about half of their maximum values when θ reached 0.07 m3 m−3. Soil water deficit substantially reduced RS sensitivity to temperature resulting in a Q10 significantly < 2. The absolute temperature sensitivity of RS (i.e. dRS/dTS) increased with θ up to 0.15 m3 m−3, above which it slowly declined. The value of dRS/dTS was nearly 0 for θ < 0.08 m3 m−3, thereby confirming that RS was largely unaffected by temperature under soil water stress conditions. Despite the possible effects of seasonality of photosynthesis, root activity and litterfall on RS, the observed decrease in its temperature sensitivity at low θ was consistent with the reduction in substrate availability due to a decrease in (a) microbial mobility, and diffusion of substrates and extracellular enzymes, and (b) the fraction of substrate that can react at high TS, which is associated with low θ. We found that an exponential (van't Hoff type) model with Q10 and R10 dependent on only θ explained 92% of the variance in half‐hourly values of RS, including the period with soil water stress conditions. We hypothesize that relating Q10 and R10 to θ not only accounted for the effects of TS on RS and its temperature sensitivity but also accounted for the seasonality of biotic (photosynthesis, root activity, and litterfall) and abiotic (soil moisture and temperature) controls and their interactions.