Tunable Thermofluorochromic Sensors Based on Conjugated Polymers

Abstract

Even though thermofluorochromic materials are eternal candidates for their use in multiple applications, they are still limited as they require complex synthetic strategies to accomplish tunable optical properties and/or provide optical changes only over a very wide temperature range. By taking advantage of the high sensitivity of the optical properties of conjugated polymers and oligomers to the external environment, herein phase change material (PCM)‐based thermofluorochromic mixtures are created, where the solid‐to‐liquid transition of the PCM host triggers a sharp fluorescence color change of the dispersed polymers/oligomers. Fluorophore conjugation length, concentration, and PCM nature can be used to vary the spectral properties of the resulting materials along the visible region, covering a large part of the CIE 1931 color space. For the preparation of functional devices, this behavior can be directly transferred to the solid state by soaking or printing cellulose papers with the obtained thermofluorochromic mixtures as well as by structuring them into solid lipid particles that can be dispersed within polymer matrices. The resulting materials show very promising features as thermal sensors and anticounterfeiting labels.

H-bond interaction traps vibrating fluorophore in polyurethane matrix for bifunctional environmental monitoring

“…Notably, the narrower half-peak width and a slight blue shift in solid DPAC-OH were mainly attributed to the higher rigidity of the solid-state environment and more obvious molecular p-p stacking effect. 11 PU DPAC exhibited pink fluorescence with typical dual emissions at 439 nm and 594 nm, in contrast to the single blue emission of DPAC in the solid state (Fig. 2d and e).…”

“…However, this process requires time-consuming and high-cost chemical modifications to the backbone and/or the functional side group. 11 Therefore, there is a need to develop new materials through more simple methods or to improve existing materials based on new concepts to drive innovation in environmental monitoring.…”

Solubilization and Photostabilization in a Sodium Deoxycholate Hydrogel of a Neutral Conjugated Thiophene Oligomer and Polymer

“…Conjugated oligomers and polymers are extensively used because of their optical and electronic properties. − These materials are suitable for optoelectronic devices, , based on their conductivity, and for sensors, , fluorescence imaging, , and dosimeters , based on changes in their emissive properties. Several of these applications are desired to be compatible with an aqueous environment, but most conjugated oligomers and polymers are sparingly soluble in water. ,,, This solubility can be enhanced by the synthesis of modified structures containing hydrophilic groups, such as charged functionalities, , and is essential for the development of these polymers for bioapplications .…”

The Rainbow Arching over the Fluorescent Thienoviologen Mesophases

“…These materials are known as fluorochromic, whose prefix depends on the external stimulus to which they are responsive, i.e., thermo-, electro-, vapo-, solvato-, and mechano- [ 4 , 5 , 6 ]. Thermofluorochromism (TFC) deals with the reversible modulation of the emission color by temperature [ 7 , 8 , 9 ]. These materials are gaining a lot of attention due to their potential applications in sensors, optoelectronic devices, and anticounterfeiting market, among others [ 10 , 11 , 12 , 13 , 14 ].…”

“…The main challenges in this field are the development of multithermofluorochromic materials by which a gradual color modulation could be achieved and of TFC materials capable of working in wide temperature ranges [ 17 ]. Moreover, TFC materials that respond to further stimuli other than the thermal one are highly desirable for multi-level anticounterfeiting technology [ 8 , 13 , 14 , 17 , 18 ]. Luminescent matrices based on liquid crystals (LCs) have received a great deal of attention because they can be developed either by incorporating a fluorophore in the LC mesophase [ 16 ] or by designing LCs with intrinsic photoluminescence [ 17 , 18 , 19 , 20 , 21 , 22 ].…”