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A Broad-Range Fluorescence Lifetime pH Sensing Material Based on a Single Organic Fluorophore
Christian Totland1,2, Peter J Thomas3, Bodil Holst4
1Department of Chemistry, University of Bergen, Allégaten 41, 5007, Bergen, Norway. christian.totland@ngi.no.
Journal of Fluorescence
|August 11, 2019
Summary
This study broadens the sensing range of fluorescence lifetime (FL) pH sensors. By altering the indicator
Area of Science:
- Analytical Chemistry
- Materials Science
- Spectroscopy
Background:
- Optical pH sensors typically have a limited response range (2-3 pH units) around the indicator's pKa.
- Fluorescence lifetime (FL) offers a stable, intrinsic property for pH sensing.
- Expanding the pH sensing range of FL-based sensors is crucial for broader applications.
Purpose of the Study:
- To significantly broaden the pH sensing range of fluorescence lifetime (FL) based sensors.
- To demonstrate that modifying the indicator's chemical environment can enhance pH sensing capabilities.
- To achieve a wider, linear pH vs. FL relationship for improved sensor performance.
Main Methods:
- Immobilizing an indicator (acridine) within a pH-responsive support material (amine-modified porous silica).
- Measuring fluorescence lifetime changes across a wide pH range (2-12).
- Analyzing the relationship between pH and FL, identifying key inflection points related to pKa values.
Main Results:
- Achieved a total FL change of 20 ns over the pH range of 2-12.
- Observed a linear pH vs. FL relationship with distinct break points at pH 4, 6, and 9.
- Demonstrated that the indicator's chemical environment modification effectively broadens the FL pH sensing range.
Conclusions:
- Tuning the fluorophore's chemical environment is a viable strategy to expand FL pH sensing range beyond the limitations of individual indicators.
- The developed method overcomes the narrow sensing range of conventional FL pH sensors.
- This approach enables the development of robust sensors capable of covering the full pH spectrum.
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