A Broad-Range Fluorescence Lifetime pH Sensing Material Based on a Single Organic Fluorophore

  • Christian TotlandEmail author
  • Peter J. Thomas
  • Bodil Holst
  • Naureen Akhtar
  • Jostein Hovdenes
  • Tore Skodvin


A general drawback for optical based pH sensors is that their response is typically limited to within 2–3 pH units centered around the pKa of the indicator. Fluorescence lifetime (FL) is a particularly compelling basis for highly stable pH sensors since this is an intrinsic property of the indicator molecule. Here we demonstrate that it is possible to broaden the sensing range of FL based sensors significantly by placing the indicator in a support material where the indicator’s chemical environment itself changes with pH. For acridine immobilized in amine-modified porous silica, a total FL change of 20 ns in the pH range 2–12 is achieved. A linear pH vs FL relationship is observed with three break points occurring at pH 4, 6 and 9 that are related to the pKa values of the indicator and the silica material. This proves the concept that tuning the fluorophore’s chemical environment can broaden the FL pH sensing range, where currently available fluorophores do not cover the full pH range.

Graphical Abstract


Acridine Fluorescence lifetime Amine-modified silica pH sensor Solid-state NMR 



The present study was supported by the Research Council of Norway (grant number 269090), and by Aanderaa – a Xylem brand.

Supplementary material

10895_2019_2426_MOESM1_ESM.docx (113 kb)
ESM 1 (DOCX 113 kb)


  1. 1.
    Wencel D, Abel T, McDonagh C (2014) Optical chemical pH sensors. Anal Chem 86:15–29CrossRefGoogle Scholar
  2. 2.
    Lin J, Liu D (2000) An optical pH sensor with a linear response over a broad range. Anal Chim Acta 408:49–55CrossRefGoogle Scholar
  3. 3.
    Strobl M, Rappitsch T, Borisov SM, Mayr T, Klimant I (2015) NIR-emitting aza-BODIPY dyes - new building blocks for broad-range optical pH sensors. Analyst 240:7150–7153CrossRefGoogle Scholar
  4. 4.
    Qi J, Liu D, Liu X, Guan S, Shi F, Chang H, He H, Yang G (2015) Fluorescent pH sensors for broad-range pH measurement based on a single fluorophore. Anal Chem 87:5897–5904CrossRefGoogle Scholar
  5. 5.
    Berezin MY, Achilefu S (2010) Fluorescence lifetime measurements and biological imaging. Chem Rev 110:2641–2684CrossRefGoogle Scholar
  6. 6.
    Ryder AG, Power S, Glynn TJ, Morrison JJ (2001) Time-domain measurement of fluorescence lifetime variation with pH. Proc SPIE 4259Google Scholar
  7. 7.
    Draxler S, Lippitsch ME (1996) Lifetime-based sensing: influence of the microenvironment. Anal Chem 68:753–757CrossRefGoogle Scholar
  8. 8.
    Malins C, Glever HG, Keyes TE, Vos JG, Dressick WJ, MacCraith BD (2000) Sol-gel immobilized ruthenium(II) polypyridyl complexes as chemical transducers for optical pH sensing. Sensors Actuators B Chem 67:89–95CrossRefGoogle Scholar
  9. 9.
    Price JM, Xu W, Demas JN, Degraff BA (1998) Polymer-supported pH sensor based on Hydrophobically bound Luminecent ruthenium(II) complexes. Anal Chem 70:265–270CrossRefGoogle Scholar
  10. 10.
    Carmody WR (1961) Easily prepared wide range buffer series. J Chem Educ 38:559CrossRefGoogle Scholar
  11. 11.
    Ryder AG, Power S, Glynn TJ (2003) Evaluation of Acridine in Nafion as a fluorescence-lifetime-based pH sensor. Appl Spectrosc 57:73–79CrossRefGoogle Scholar
  12. 12.
    Ryder AG, Power S, Glynn TJ (2003) Fluorescence-lifetime-based pH sensing using Resorufin. SPIE, OPTO IrelandCrossRefGoogle Scholar
  13. 13.
    van der Maaden K, Sliedregt K, Kros A, Jiskoot W, Bouwstra J (2012) Fluorescent nanoparticle adhesion assay: a novel method for surface pKa determination of self-assembled monolayers on silicon surfaces. Langmuir 28:3403–3411CrossRefGoogle Scholar
  14. 14.
    Vezenov DV, Noy A, Rozsnyai LF, Lieber CM (1997) Force titrations and ionization state sensitive imaging of functional groups in aqueous solutions by chemical force microscopy. J Am Chem Soc 119:2006–2015CrossRefGoogle Scholar
  15. 15.
    Mengistu TZ, Goel V, Horton JH, Morin S (2006) Chemical force titrations of functionalized Si(111) surfaces. Langmuir 22:5301–5307CrossRefGoogle Scholar
  16. 16.
    Diverdi LA, Topp MR (1984) Subnanosecond time-resolved fluorescence of Acridine in solution. J Phys Chem 88:3447–3451CrossRefGoogle Scholar
  17. 17.
    Dong Y, Pappu SV, Xu Z (1998) Detection of local density distribution of isolated Silanol groups on planar silica surfaces using nonlinear optical molecular probes. Anal Chem 70:4730–4735CrossRefGoogle Scholar
  18. 18.
    Ong S, Zhao X, Eisenthal KB (1992) Polarization of water molecules at a charged Interface: second harmonic studies of the silica/water Interface. Chem Phys Lett 191:327–335CrossRefGoogle Scholar
  19. 19.
    Bakker HJ, Physical Chemistry (2012) Water's response to the fear of water. Nature 491:533–535CrossRefGoogle Scholar
  20. 20.
    Nilsson A, Pettersson LGM (2015) The structural origin of anomalous properties of liquid water. Nature Comm 6:8998CrossRefGoogle Scholar
  21. 21.
    Lowe BM, Skylaris C-K, Green NG (2015) Acid-Base dissociation mechanisms and energetics at the silica–water Interface: an Activationless process. J Colloid Interface Sci 451:231–244CrossRefGoogle Scholar
  22. 22.
    Wolfbeis OS, Urbano E (1983) Fluorescence quenching method for determination of two or three components in solution. Anal Chem 55:1904–1906CrossRefGoogle Scholar
  23. 23.
    Draxler S, Lippitsch ME (1995) pH sensors using fluorescence decay time. Sensors Actuators B Chem 29:199–203CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of ChemistryUniversity of BergenBergenNorway
  2. 2.NGI – Norwegian Geotechnical InstituteOsloNorway
  3. 3.NORCE Norwegian Research Center ASBergenNorway
  4. 4.Department of Physics and TechnologyUniversity of BergenBergenNorway
  5. 5.Aanderaa – a Xylem brandNesttunNorway

Personalised recommendations