An ultramicro interdigital array electrode modified by palladium-gold was developed for nitrate detection in neutral water. The ultramicro interdigital array electrode was fabricated based on silicon substrate by Micro Electro-Mechanical System (MEMS) technique. The nanostructured palladium-gold (Pd-AuNPs) composite sensing film was electrodeposited on the surface of a working electrode by electrochemical method. The synergistic effect of Pd-AuNPs composite was investigated and its enhancement of the catalytic activity and stability was revealed. The Pd-AuNPs modified electrode showed good linearity (R² = 0.99) from 1 mg/L to 15 mg/L (as N) for nitrate determination in a neutral water environment (pH = 7.2), with a sensitivity of 4.7 μA·mg⁻¹·L. The results showed that the developed Pd-AuNPs-modified ultramicro interdigital array electrode chip can achieve sensitive and environmentally-friendly detection for nitrate in neutral water.

This work describes the fabrication, characterization, and application of a gold microband array electrode (MAE) for the determination of phosphate in fresh water samples. The working principle of this MAE is based on the reduction of a molybdophosphate complex using the linear sweep voltammetric (LSV) method. The calibration of this microsensor was performed with standard phosphate solutions prepared with KH₂PO₄ and pH adjusted to 1.0. The microsensor consists of a platinum counter electrode, a gold MAE as working electrode, and an Ag/AgCl electrode as reference electrode. The microelectrode chips were fabricated by the Micro Electro-Mechanical System (MEMS) technique. To improve the sensitivity, gold nanoparticles (AuNPs) were electrodeposited on the working electrode. With a linear range from 0.02 to 0.50 mg P/L, the sensitivity of the unmodified microsensor is 2.40 µA per (mg P/L) (R² = 0.99) and that of the AuNPs-modified microsensor is 7.66 µA per (mg P/L) (R² = 0.99). The experimental results showed that AuNPs-modified microelectrode had better sensitivity and a larger current response than the unmodified microelectrode.

This paper investigated two different modification methods of graphene (GN) on ultramicroelectrode array (UMEA) and applied the GN modified UMEA for the determination of dissolved oxygen (DO). The UMEAs were fabricated by Micro Electro-Mechanical System (MEMS) technique and the radius of each ultramicroelectrode is 10 μm. GN-NH₂ and GN-COOH were modified on UMEA by using self-assembling method. Compared with GN-NH₂ modified UMEA, the GN-COOH modified UMEA showed better electrochemical reduction to DO, owing to better dispersing and more active sites. The GN-COOH on UMEA was electroreduced to reduced GN-COOH (rGN-COOH) to increase the conductivity and the catalysis performance. Finally, the palladium nanoparticles/rGN-COOH composite was incorporated into DO microsensor for the detection of DO.