Thermochromic Narrow Band Gap Phosphors for Multimodal Optical Thermometry: The Case of Y³⁺-Stabilized β-Bi₂O₃:Nd³⁺

Abstract

The design and development of effective luminescent thermal sensors have been driving technological progress in many different fields ranging from catalysis to biology and microelectronics, to name a few. The ratiometric concept of using the ratio between two luminescent emissions of lanthanide-doped phosphors allows overcoming some limitations resulting from the single emission-based thermometers. A fundamental requirement for the development of effective luminescent thermometers relies on efficient luminescence output, which is not always accessible. Therefore, alternative methods to probe the temperature in a reliable and simple way are still a challenge. Despite the conventional limits of using narrow band gap materials as hosts for lanthanoid ions, a smart design allows for the development of unusual phosphors with appealing properties. By taking advantage of the narrow band gap of Bi 2 O 3 polymorphs, here we demonstrate the potential of the tetragonal Y-stabilized β-Bi 2 O 3 :Y 3+ ,Nd 3+ system as a multimodal thermometer combining the conventional Boltzmann thermometry based on Nd 3+ together with the thermochromism of the host. With the aim of testing this new concept, the temperature dependence of the reflectance spectra was investigated. Moreover, from the application point of view, the chromaticity variations of the material described by means of simple thermometric parameters such as the ratio a*/b* and the hue angle h ab are demonstrated to be particularly promising and already implemented in software commonly used worldwide. The results suggest the potential of the strategy of combining narrow band gap semiconductors with lanthanoid ions to design reliable and multimodal thermal sensors, paving the way to a new family of thermochromic and luminescent thermal sensors.

Ultrahigh sensitivity upconversion low temperature sensorsviamanipulating the non-thermally coupled levels of Er3+ions

“…Traditional Boltzmann thermometers based on Nd 3+ and Cr 3+ also exhibit excellent optical temperature measurement performance in terms of relative and absolute sensitivity, as well as thermal resolution. [17][18][19][20][21][63][64][65][66] Compared with these excellent Boltzmann thermometers, the performance of the Er,Yb:-NaYF 4 GC sensor based on 2 H 11/2 -2 H 9/2 NTCL has higher relative sensitivity and slightly poorer thermal resolution. At low temperature (90 K), the GC sensor has thermal resolution comparable to Nd 3+ and Cr 3+ based thermometers, indicating that it possesses certain advantages in low temperature measurement.…”

Effect of Sr2+ ions on the structure, up-conversion emission and thermal sensing of Er3+, Yb3+ co-doped double perovskite Ba(2−x)SrxMgWO6 phosphors

“…15 Other rare-earth ions, such as Nd 3+ , Tm 3+ , and Cr + , also follow Boltzmann distributions and have been used in temperature sensing for ratiometric measurements. 16,17,18,19,20,21 In some systems, Tm 3+ ions embody superior NIR thermometer performance over Nd 3+ ions, 22 while Nd-based thermometers also have the potential to be used for NIR optical imaging. 23,24 Owing to the special crystal field environment of Cr + , it exhibits 2/3 orders of magnitude superior performance to that of Er 3+ in the NIR thermometric range.…”

Strategy to probe multimodal light emissions from Eu3+/Yb3+activated garnet nanophosphors for LED devices and solar cell applications

“…1,2 All of the previously mentioned characteristics of Ln 3+ ions fascinate researchers, who use them to design new luminescent materials containing Ln 3+ ions for potential applications in the fields of lighting, displays, solar cells, optical thermometry, bio-imaging, and so on. [3][4][5][6] Such luminescent materials have capabilities of spectral conversion by one or more than one process such as down shifting (DS), quantum cutting (QC), and upconversion (UC). 7,8 Many attempts have been made to develop Ln 3+ doped phosphors for use in phosphor-coated white light emitting diode (pc-WLED) applications.…”