Preparation of miniaturized pH sensors based on metal oxide modified pencil lead electrode

In this study, sensitive potentiometric solid state pH sensors based on metal oxide nanoparticles electrodeposited on pencil lead electrode were reported [1-4]. The prepared electrodes were carefully characterized by SEM, XRD and electrochemical techniques. To miniaturize the prepared pH sensors, a stainless steel 304 needle was used as a reference electrode. Selectivity, response time, stability and reproducibility of the miniaturized pH sensor were studied and compared with conventional glassy pH electrode. According to experimental results, near-Nernstian slope and linearity over the pH range of 1.5˗12.5 were obtained for the developed sensors. The prepared electrodes represented high ion selectivity to mono-valence and multi-valence ions with Pot log KA,B values around 6.49. Fast response time of about 20 s in acidic medium and 50 s in alkaline medium, long-term stability and reproducibility in two months, simplicity of fabrication, low cost and accuracy makes these sensors a suitable choice for rapid pH recording in micro volume samples.