Pyranine doped hydrogel based pH-strips for low pH regions

A. Gelir*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The fluorescence spectra of the hydrophilic pyrene derivative 8-hydroxy-1,3,6-pyrenetri-sulfonate (pyranine) is firmly connected to the degree of ionization of the 8-hydroxyl group and hence to the pH of media, in the range of 0<pH<5. Once entrapped in a polyacrylamide (PAAm) hydrogel, pyranine does not readily leak out of the gel. The fluorescence properties of entrapped pyranine are similar to those of bulk pyranine solution from the point of pH sensitivity. Therefore, pyranine can be used as a reliable reporter of aqueous pH changes within hydrogels. In this study, pyranine in PAAm hydrogel was used to produce a sensitive pH sensor working for aqueous acidic media. The ratio of the maximum fluorescence emission intensities at 445 nm and 512 nm i.e., l445/l512, changes with the pH of the aqueous solutions. This ratio is unaffected by the choice of the excitation wavelength. l445/15122 versus pH curves were evaluated for different gel compositions and thicknesses. The response time of the sensor was found to be about 50 seconds for the gel of thickness around 1.5-2.5 mm. It turns out that this period may be shortened even further by changing the thickness of the slab gel. Also the pH-strips can be used reversibly for many times.

Original languageEnglish
Pages (from-to)293-303
Number of pages11
JournalJournal of Polymer Materials
Issue number2
Publication statusPublished - 1 Apr 2016

Bibliographical note

Publisher Copyright:
© Prints Publications Pvt. Ltd.


  • Fluorimetry
  • Hydrogel
  • PH


Dive into the research topics of 'Pyranine doped hydrogel based pH-strips for low pH regions'. Together they form a unique fingerprint.

Cite this