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Title
Japanese: 
English:D–π–A Fluorophores with Strong Solvatochromism for Single-molecule Ratiometric Thermometers 
Author
Japanese: 堀有琉斗, 松本惇志, 池ノ内順一, 小西玄一.  
English: Alto Hori, Atsushi Matsumoto, Junichi Ikenouchi, Gen-ichi Konishi.  
Language English 
Journal/Book name
Japanese: 
English:Journal of the American Chemical Society 
Volume, Number, Page Vol. 147    No. 11    pp. 9953–9961
Published date Mar. 5, 2025 
Publisher
Japanese: 
English:American Chemical Soceity 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL https://pubs.acs.org/doi/10.1021/jacs.5c01173
 
DOI https://doi.org/10.1021/jacs.5c01173
Abstract Fluorescence thermometry has emerged as a significant area of research in the field of remote temperature sensing with high accuracy. However, the development of noninvasive and reliable small organic fluorescence thermometers (FTs) remains challenging. In this study, we developed a high-sensitivity, high-resolution small organic ratiometric FT with a solvatochromic dye and analyzed its temperature response mechanism. π-Extended fluorene-based D−π–A-type small solvatochromic dyes (FπAc, FπF, and FπVC) were synthesized and characterized. A significant solvatochromic shift of >200 nm was observed between n-hexane and tetrahydrofuran (THF) for both FπF and FπVC, with emission in THF reaching the red region (701 nm, 828 nm). This substantial solvatochromic shift was accompanied by a concurrent decrease in the fluorescence quantum yield and is attributable to accelerated internal conversion. The fluorescence spectra of FπF in THF and FπVC in diethyl ether exhibited blue shifts and increased fluorescence intensities with a decrease in polarity at increased temperatures. Our observations revealed an absolute sensitivity of 21%/°C and a relative sensitivity of 3.0%/°C at the maximum. These results represent the highest sensitivity and resolution reported for single fluorophore small organic ratiometric FTs dispersed in solution. The positive temperature coefficient of the fluorescence intensity was attributed to control of the nonradiative decay pathway by solvatochromism. The temperature responsiveness of FπF could be detected in living HeLa cells by ratiometric confocal microscopy. Using the proposed strategy to develop FTs, we plan to build a library of FTs that will cover various environments of interest in both simple and complex systems.

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