Time-Resolved Spectroscopy of Fluorescence Quenching in Optical Fibre-Based pH Sensors

Katjana Ehrlich, Tushar R. Choudhary, Muhammed Ucuncu, Alicia Megia-Fernandez, Kerrianne Harrington, Harry A. C. Wood, Fei Yu, Debaditya Choudhury, Kev Dhaliwal, Mark Bradley, Michael G. Tanner

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)
40 Downloads (Pure)


Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes. We demonstrate that the change in fluorescence intensity of carboxyfluorescein with pH in this "high-density" regime is opposite to that normally observed, with complex variations in fluorescent lifetime across the emission spectra of coupled fluorophores. Improved understanding of such highly loaded sensor beads is important because it leads to large increases in photostability and will aid the development of compact fibre probes, suitable for clinical applications. The time-resolved spectral measurement techniques presented here can be further applied to similar studies of other optodes.

Original languageEnglish
Article number6115
Issue number21
Early online date27 Oct 2020
Publication statusPublished - 1 Nov 2020


  • Biological sensor
  • Fluorescence spectroscopy
  • Optical fibre sensing
  • Time-resolved spectroscopy

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electrical and Electronic Engineering


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