Single‐Sample Ratiometric Organic Films for Naked‐Eye High‐Temperature Multi‐Threshold Indication

Abstract

Threshold temperature sensors are crucial for recording the thermal histories of environments under different scenarios. However, most organic threshold thermometers are not suitable for high‐temperature indication due to significant thermo‐facilitated emission quenching. Here, a series of ratiometric luminescent high‐temperature threshold organic film indicators have been realized by synergetic effects of intramolecular local excited to charge transfer states and disaggregation from excimer to monomer. Varying the polymer matrixes with different glass transition temperatures effectively tunes the threshold sensing temperatures. More importantly, the wide sensing span of the high‐temperature region enables the single‐sample films (in one kind of polymer matrix) to achieve multiple temperature threshold indications, directed only by multiple naked‐eye emission color changes. These drop‐casting organic film thermometers indicate great potential in robust and low‐cost outdoor applications, as well as large‐area and flexible threshold temperature sensing.

Three‐Output Naked‐Eye High Temperature Organic Film Threshold Thermometers Based on Non‐Invasive Chemical Reaction

“…[ 13,21 ] Nevertheless, the reports on high‐temperature threshold sensing above 100 °C are rather scarce. [ 14,19,22–24 ] This is because organic chromophores generally encounter significant emission quenching at heating due to thermally induced nonradiative deactivation. [ 25 ] Therefore, development of organic film threshold thermometers for large area and flexible high‐temperature indication is still highly demanded.…”

“…To realize fast and convenient high temperature threshold readout, a robust and highly‐visible temperature indication is usually required. This is generally dependent on high‐contrast luminescence ON/OFF switching, [ 14,26 ] ambient thermochromism, [ 27,28 ] or luminescent thermochromism [ 11,22,29 ] for naked‐eye detection in an ambient atmosphere. Thermochromic chromophores have aroused enormous attentions to fabricate functional temperature threshold sensors because they provide fast and convenient naked‐eye detection, especially those which allow two or more outputs of those mentioned naked‐eye signals.…”

“…[ 50–52 ] By further molecular modification, multi‐threshold ratiometric high‐temperature indication in single film samples has been demonstrated, based on synergetic intramolecular and intermolecular thermally induced photophysical mechanism. [ 22 ] The present work demonstrates a series of high‐performance and highly stable ratiometric high‐temperature (120–180 °C) film threshold thermometers based on non‐invasive intramolecular chemical reactions, with three naked‐eye high‐contrast output signals (ambient thermochromism, fluorescent thermochromism, and fluorescence intensity). Moreover, these threshold thermosensors do not require extra additives or operational treatments, which much simplifies the process and are highly promising for low‐cost robust outdoor thermal threshold indication.…”

Fabrication of Flexible High‐Temperature Film Thermometers and Heat‐Resistant OLEDs Using Novel Hot Exciton Organic Fluorophores

“…Previously, we have developed a series of high-temperature ratiometric thermosensors and threshold thermometers in both solution and solid films based on triarylphosphine oxides by employing thermally controlled competition between different emissive behaviors. [33,[46][47][48][49] In this work, we have developed a series of novel heat-resistant organic fluorophores based on pyrrole-substituted triarylphosphine oxides and demonstrated that these materials show prominent hot exciton characteristics for high-temperature sensing and heat-tolerant OLEDs. This work demonstrates that such materials show great promise for use in high-temperature flexible thermomapping and information display.…”

Molecular Conformation Engineering To Achieve Longer and Brighter Deep Red/Near-Infrared Emission in Crystalline State

“…Although there are many fluorescent molecules have been developed for sensing temperature in recent years, these molecules are commonly used in the dispersed state (e.g., solutions or polymers) to facilitate the change of molecular conformation or aggregation responding to different temperatures. − Thus, the sensing temperatures of these reports are relatively high, at least above the melting point of solutions or above the glass transition point of polymers (commonly higher than 200 K). In this point of view, it is an exceptional advantage that crystal 4 is capable of sensing very low temperature (77–155 K).…”