Owing to their ability to monitor pH in a precise and rapid manner, optical probes have widely been developed for biological and nonbiological applications. The strategies thus far employed to determine pH rely on two types of processes including reversible protonation of amine nitrogen atoms and deprotonation of phenols. We have developed a novel dual, colorimetric/fluorescence system for determining the pH of a solution. This system utilizes an o-hydroxymerocyanine dye that undergoes a nucleophilic addition reaction that subsequently causes reversible structural changes interconverting a merocyanine to a spirocyanine and a spirocyanine to a spiropyran. It was demonstrated that the dye can be employed to measure the pH of solutions in the 2.5-5.75 and 9.6-11.8 ranges with color changes from yellow to dark blue and then to lavender. Moreover, the fluorescence response associated with the spirocyanine-spiropyran transformation of the dye occurring in alkaline solutions provides a precise method. Strike that, reverse it! A novel dual, colorimetric/fluorescence system for determining the pH of a solution has been developed. This system utilizes an o-hydroxymerocyanine dye, which undergoes a nucleophilic addition reaction that subsequently causes reversible structural changes interconverting a merocyanine to a spirocyanine and a spirocyanine to a spiropyran (see scheme).
Bibliographical noteFunding Information:
Y.Y. and F.H. were supported by the National Natural Science Foundation of China (No. 21472118), the Taiyuan Technology star special (No. 12024703), the Program for the Top Young and Middle-aged Innovative Talents of Higher Learning Institutions of Shanxi (2013802), Talents Support Program of Shanxi Province (2014401), and the Shanxi Province Outstanding Youth Fund (No. 2014021002). F.H. and C.Y. received the Shanxi University fund for study aboard 2014. J.Y. was supported by the grant from the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP) (No. 2012R1A3A2048814).
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- colorimetric probe
- fluorescent probe
- nucleophilic addition
- pH sensors