Sensitive pH Monitoring Using a Polyaniline-Functionalized Fiber Optic-Surface Plasmon Resonance Detector.

Iulia Antohe,Luiza-Izabela Jinga,Gabriel Socol,Vlad-Andrei Antohe

doi:10.3390/s21124218

Abstract

In this work, we report results on the fabrication and characterization of a surface plasmon resonance (SPR) pH sensor using platinum (Pt) and polyaniline (PANI) layers successively coated over an unclad core of an optical fiber (FO). The plasmonic thin Pt layer was deposited using a magnetron sputtering technique, while the pH-sensitive PANI layer was synthesized using an electroless polymerization method. Moreover, the formation of PANI film was confirmed by X-ray photoelectron spectroscopy (XPS) technique and its surface morphology was investigated using scanning electron microscopy (SEM). It was found that the PANI/Pt-coated FO-SPR pH sensor exhibits a fast and linear response in either acid or alkali solutions (pH operational range: 1 to 14). The proposed FO-SPR sensor could be used for biomedical applications, environmental monitoring or any remote, real-time on-site measurements.

Highlights

IntroductionVarious pH sensing techniques based on optical, electrochemical, or physicochemical methods have been developed
We report results on the fabrication and characterization of a reflectiontype FO-surface plasmon resonance (SPR) pH sensor built by coating platinum (Pt) and electro-conductive PANI layers over the unclad core of an optical fiber tip
Fiber Optic - Surface Plasmon Resonance (FO-SPR) sensors was evaluated by performing refractive index (RI) measurements in sucrose dilutions (0, 2, 4, 8, 12% w/w)

Summary

Introduction

Various pH sensing techniques based on optical, electrochemical, or physicochemical methods have been developed. In the last decade, advanced sensing materials including metal, metal oxides, polymers, semiconductors, as well as nanoparticles and nanotubes, were used to build cost-effective and user-friendly integrated pH monitoring systems [3]. The conventional and widely employed method for pH measurement uses a pH glass electrode and potentiometric technique. These sensors are bulky in size, they often exhibit a rather poor performance in both extremes of the pH scale and they have to be re-calibrated in a discontinuous way [4]. Substantial efforts were invested towards the development of optical fiber-based pH sensors [4,5,6]

Methods

Results

Conclusion