Titanium Nitride Thin Film Based Low-Redox-Interference Potentiometric pH Sensing Electrodes

In this work, a solid-state potentiometric pH sensor is designed by incorporating a thin film of Radio Frequency Magnetron Sputtered (RFMS) Titanium Nitride (TiN) working electrode and a commercial Ag|AgCl|KCl double junction reference electrode. The sensor shows a linear pH slope of -59.1 mV/pH, R-2 = 0.9997, a hysteresis as low as 1.2 mV, and drift below 3.9 mV/h. In addition, the redox interference performance of TiN electrodes is compared with that of Iridium Oxide (IrO2) counterparts. Experimental results show -32 mV potential shift (E-0 value) in 1 mM ascorbic acid (reducing agent) for TiN electrodes, and this is significantly lower than the -114 mV potential shift of IrO2 electrodes with sub-Nernstian sensitivity. These results are most encouraging and pave the way towards the development of miniaturized, cost-effective, and robust pH sensors for difficult matrices, such as wine and fresh orange juice.

Automated summary

A solid-state potentiometric pH sensor was designed with high linearity, low hysteresis, and drift values. Results showed better redox interference performance for TiN electrodes compared to IrO2 electrodes, paving the way for the development of pH sensors for difficult matrices.