A titanium nitride nanotube array for potentiometric sensing of pH

An electrochemically cleanable pH electrode based on an electrodeposited iridium oxide-ruthenium oxide-titanium composite

Biological contamination is an important issue in environmental pH detection, and our prepared electrochemically cleanable electrode may be an effective solution. By electrodepositing an iridium oxide-ruthenium oxide composite on a titanium sheet substrate, the electrode shows a sensitivity of 59.4 mV per pH in the pH range of 2-12 with high reproducibility, low hysteresis, high selectivity and high stability. It is worth mentioning that the electrode was proved to be electrochemically cleanable from biological contamination. When the cleaning time was 30 minutes, the electrode sensitivity rose from 50 to 58 mV per pH. Furthermore, the pH sensor, assembled from the prepared iridium-ruthenium oxide electrode and a home-made Ag/AgCl electrode, has similar electrode properties to those of commercial glass electrodes, but is also mechanically strong and electrochemically cleanable, which is promising for long-term deployment in natural environments.

Electromagnetic Field Enhancement of Nanostructured TiN Electrodes Probed with Surface-Enhanced Raman Spectroscopy

We present a facile approach for the determination of the electromagnetic field enhancement of nanostructured TiN electrodes. As model system, TiN with partially collapsed nanotube structure obtained from nitridation of TiO₂ nanotube arrays was used. Using surface-enhanced Raman scattering (SERS) spectroscopy, the electromagnetic field enhancement factors (EFs) of the substrate across the optical region were determined. The non-surface binding SERS reporter group azidobenzene was chosen, for which contributions from the chemical enhancement effect can be minimized. Derived EFs correlated with the electronic absorption profile and reached 3.9 at 786 nm excitation. Near-field enhancement and far-field absorption simulated with rigorous coupled wave analysis showed good agreement with the experimental observations. The major optical activity of TiN was concluded to originate from collective localized plasmonic modes at ca. 700 nm arising from the specific nanostructure.

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, R² = 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 (E⁰ 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.