High-Quantum-Yield Upconverting Er³⁺/Yb³⁺-Organic–Inorganic Hybrid Dual Coatings for Real-Time Temperature Sensing and Photothermal Conversion

Abstract

Flexible coatings with dual capabilities for remote real-time temperature sensing and photothermal conversion have a huge potential in the field of advanced thermal actuated optoelectronic applications. In this work, we demonstrated that plastic free-standing films of Er 3+ /Yb 3+ -codoped GeO 2 −Ta 2 O 5 particles dispersed in poly(methyl methacrylate) (PMMA) having intriguing upconversion high absolute emission quantum yield (∼0.1452, excited at 980 nm, 760 W•cm −2 ) can simultaneously operate as photothermal converters and real-time primary thermometers. The emission of the films was studied at the microscale, revealing emission homogeneity detected through surface hyperspectral microscopy. One factor that contributes to the unusually high absolute emission quantum yield, when compared with other oxides-based materials, is the high occurrence (probability) of the shortest Yb−Er distances obtained when the YbTaO 4 phase is formed. This, as demonstrated by computational simulations of doping processes, favors the Yb-to-Er energy transfer rates, enhancing the population of the Er 3+ emitting levels. Besides, the films combined a relative thermal sensitivity of ∼1.1% K −1 (at 300 K) with a temperature uncertainty of ∼0.7 K and a maximum photothermal efficiency of ∼44%, which permits the prospect of using this material as a coating with photothermal and thermometer functions. Moreover, as an added benefit, the thermal resistance of the composite in PMMA was estimated, yielding a maximum value of 760 ± 8 K•W −1 . This is the first example of an active coating for photothermal conversion with the simultaneous ability to remotely sense temperature that can be explored in NIR-pumped free-space telecommunications without the need of additional optoelectronics devices.

One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3+

“…Recently, there has also been progress in reverting this scheme and performing thermometry by detecting a reference emission from the same excited level upon dual excitation from two thermally coupled ground levels 24 – 26 . Luminescence (nano)thermometry has been demonstrated to be both a precise and accurate technique for probing fundamental thermodynamic phenomena at the micro- and nanoscale 27 – 29 and helps to assess the local temperature fluctuations in tissue 30 – 35 or in chemical reactors 36 – 40 . Currently, there has been observable progress on how to implement and standardize this technique for applications 41 – 45 , the connected limitations 46 , 47 , or how to couple temperature sensing with other functionalities such as single-molecule magnetism 48 , 49 and (meso-)porous materials 50 , 51 , e.g., theranostics 52 .…”

Customized Luminescent Multiplexed Quick‐Response Codes as Reliable Temperature Mobile Optical Sensors for eHealth and Internet of Things

“…[ 17–20 ] However, some recent works raise concerns on the reliability of the technique caused by experimental artifices. [ 21–28 ] One solution to overcome these limitations is the use of primary thermometers characterized by a well‐established equation (e.g., Varshni's law for semiconductor nanoparticles [ 21,29 ] or Boltzmann distribution when using intensity ratio between two thermally coupled levels [ 13,30–35 ] ), where all parameters are known without the need of a prior calibration. Nonetheless, the theoretical knowledge of the mechanism behind the emission dependence on the temperature is unattainable in most cases, disabling the a priori building of a primary thermometer.…”

mOptical Sensing for the Internet of Things: A Smartphone‐Controlled Platform for Temperature Monitoring

“…[ 47,53–58 ] The solution lies in primary thermometers, characterized by a well‐established state‐equation that directly relates a particular measured value to the absolute temperature without the need for calibration. So far, only a few primary luminescent thermometers have been reported, [ 43,53,58–65 ] most of which based on the intensity ratio between two thermally coupled electronic levels, for instance, the Er 3+ 2 H 11/2 and 4 S 3/2 levels. In this case, the thermometric parameter is based exclusively upon the validity of the Boltzmann distribution.…”

“…[ 46,55,59,66–89 ] The S r values for primary luminescent thermometers are shown in Figure 3b. [ 43,53,58–64 ] Noticeable, only one example refers to smartphone‐based luminescence thermometry, and presents the largest S r value. [ 59 ]…”