City Research Online

Abstract

A set of optical fibre sensors (OFSs) for pH detection have been prepared by doping hybrid xerogel (XG) matrices with pH indicators for environmental monitoring. The hydrophobic sol-gel siliceous materials were synthesised from propyltriethoxysilane (pTEOS) and tetraethoxysilane (TEOS), and subsequently doped with phenolphthalein, bromophenol blue and cyanidin chloride, resulting in three photonic pH devices (OFS5pTEOSPH, OFS5pTEOSBP and OFS5pTEOSCY). Among them, OFS5pTEOSBP exhibited the best sensing performance, showing a reversible optical response in the pH range from 2 to 6 with an intensity ratio variation from 0.92 to 0.52. The developed sensors exhibit negligible dye leaching, good stability, reproducibility, reversible response, and low hysteresis, with response time from 5 to 190 s depending on the pH. Moreover, their applicability was validated through pH measurements in real soil samples.

Publication Type:	Article
Additional Information:	© 2026 IEEE. This accepted manuscript is made available under the terms of the Creative Commons Attribution License (CC-BY), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.
Publisher Keywords:	Sensors, Sensor phenomena and characterization, Optical fiber sensors, Optical fibers, Soil, Silicon dioxide, Leaching , Chemical sensors , Surface treatment, Optical films
Subjects:	Q Science > QC Physics
Departments:	School of Science & Technology School of Science & Technology > Department of Engineering
SWORD Depositor:	Symplectic Administrator

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