GaN-based anion selective sensor: Probing the origin of the induced electrochemical potential

Abstract

The gallium nitride (GaN) semiconductor has been used as the sensing element in a chemical sensor for the measurement of charged species in solution. The sensor shows remarkable selectivity for anions, such as sulphate (SO42−) and hydroxide (OH−). It is shown that the GaN surface interacts selectively with Lewis bases as shown by impedance spectra. In addition, both the impedance spectra and the surface induced potential of the sensor element correlate very well with the activity of both the negatively charged hydroxide and the sulphate anions used. These results indicate that there is a direct interaction of the electron deficient gallium in the GaN surface with the Lewis base anionic ligands. A band model for the investigated GaN∕KOH-solution system has been deduced.

Evaluation of GaN and In0.2Ga0.8N Semiconductors as Potentiometric Anion Selective Electrodes

“…51.9 AE 3.7 mV/decade and are generally consistent with those reported by Chaniotakis [13,14]. The largest difference occurs for KSCN (À 51.9 AE 3.7 mV/decade in our study versus À 69.5 mV/decade in Chaniotakis [13,14] ).…”

“…The linear regions of the GaN electrode in this research are generally of similar magnitude or wider than those reported by Chaniotakis [13,14] with the same electrolyte solutions.…”

“…The largest difference occurs for KSCN (À 51.9 AE 3.7 mV/decade in our study versus À 69.5 mV/decade in Chaniotakis [13,14] ). This suggests that the response mechanisms of both electrodes are similar.…”

“…The parameters of the calibration plots obtained with the GaN and In 0.2 Ga 0.8 N semiconductor electrodes are summarized in Table 2. For comparison, the table also contains the parameters of the calibration plots presented by Chaniotakis [13,14], which were extracted from their published experimental data.…”

Impedance Study of GaN and InGaN Semiconductor Anion Selective Electrodes

“…Chaniotakis [11] used EIS experiments to show that the potentiometric sensitivity of GaN electrodes is controlled by the Helmholtz and Gouy layers formed at the GaN/ electrolyte interface. To our knowledge, the origin of the interfacial potential observed at In 0.2 Ga 0.8 N electrodes/ solution phase boundary has not yet been investigated.…”