Microsensor integrated with ultramicroelectrode array for trace nitrate detection in potable water

Abstract

This paper presents an electrochemical microsensor based on ultramicroelectrode array modified with copper nanoparticles to perform trace nitrate detection in potable water. The microsensor is fabricated with standard micromachining technology. As the working-electrode, an ultramicroelectrode array constructed of 421 disk-shaped ultramicroelectrodes provides enhanced electrochemical performance for the microsensor, with faster response time and higher current density than conventional plate electrodes with the same area. Copper nanoparticles with an average diameter of 20 nm are electrodeposited onto the surface of disk-shaped ultramicroelectrodes as the sensing material for nitrate ions. The copper nanoparticles increase the sensitive surface area of the ultramicroelectrode array and further improve the current response. The developed microsensor is examined with the method of linear sweep voltammetry, and displays a linear range from 12.5 µmol/L to 200 µmol/L of nitrate concentrations in the acidic sodium sulfate buffer solutions. Compared with the conventional copper modified disk electrode, our proposed ultramicroelectrode array shows a higher sensitivity of 0.0892 µA/µmolL−1 for nitrate ions. The microsensor is also used to detect nitrate in running water samples. The results are consistent with the data obtained by the standard ultraviolet spectrophotometric method, and the maximal difference is 13.1%.