Solid Tunable Ratiometric Fluorescence Thermometers Based on Triarylboron-Phase Change Materials
Microregion viscosity and free volume of phase change materials(PCMs)undergo reversible and rapid changes near the melting point,which can amplify the responses of fluorescent probes.In this study,two novel triarylborons,4-(1-{4-[bis(4-bromo-2,3,5,6-tetramethylphenyl)boraneyl]-2,3,5,6-tetramethylphenyl}piperidin-4-yl)morpholine(MPDB1)and 4,4'-({[(4-bromo-2,3,5,6-tetramethylphenyl)boranediyl]bis(2,3,5,6-tetramethyl-4,1-phenylene)}bis(piperidine-1,4-diyl))dimorpholine(MPDB2),with ratiometric-responsive fluorescence to high viscosity were synthesized and then combined with PCMs,thus high-sensitivity ratiometric fluorescence thermome-ters were prepared.Due to the compounds'rare high viscosity responsiveness,the temperature fluorescence response ranges in the PCMs are lower than their melting point,thus producing pure solid-state PCMs fluorescent thermome-ters with better processability.As viscosity probes,the fluorescence of the mono-substituted compound MPDB1 shows a ratiometric response range of 100-3000 mPa·s with high sensitivity,while the fluorescence of the compound MPDB2 responds from 100 to 46000 mPa·s,covering a wider range.As temperature probes,the fluores-cence temperature response range of the MPDB1-polyethylene glycol 20000(PEG20000)system is ‒10-50℃,with a high maximum relative sensitivity of 3.5%(Sr,10℃)and absolute sensitivity of 4.6%(Sa,30℃).Also,the temperature measurement range of these thermometers can be adjusted by changing the number of substituents and selecting PEG substrates with different melting points,rendering better applicability.
Intramolecular charge-transferRatiometric fluorescence thermometerPhase change materialTriaryl-boronTunable temperature measurement range
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