Development of Novel pH Sensor Based on Nanoparticle Modified Electrochemical Sensing Platform

Abstract

In biological and environmental applications, pH is an important parameter that needs to monitor in regular basis. Conventionally, the measurement processes take a considerable amount of time involving several calibration steps and handling of fragile electrodes. In this work, we propose a new, robust and reliable way of sensing pH. The sensor has been fabricated based on tungsten oxide nanoparticle modified glassy carbon electrode (WO3/GCE). WO3 is a promising material for pH sensor because of its availability, stability, good morphological and structural control of the synthesized nanostructures. In this work, hydrothermal synthesis method was used for the fabrication of WO3 nanoparticles. For the fabrication of the pH sensor, the nanoparticles were mixed with Nafion and chitosan before drop coating onto the GCE surface. Scanning electron microscopy (SEM), x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX) and Raman spectroscopy were used to characterize the nanoparticle. Cyclic voltammetry (CV), zero current potentiommetry (OCP) and square wave voltammetry (SWV) were used to monitor the potential shift based on different pH in the buffer solutions. This electrochemical pH sensor showed a sensitivity of 60 mVpH-1 and a potential drift of 2.4 – 5.0 % after three hours of continuous use. The sensor showed linearity range of pH 3 -11 and could retain 95% of its initial activity after 1 week of use. The electrode was found to respond both in the presence and absence of oxygen, further expanding the potential applications to include de-oxygenated environments. The WO3 based sensor showed good sensitivity and long term stability, which would be a potential platform to develop a low cost pH sensor for a wider range of applications.