The NH4+ Electrochemical Sensor with the 3D–2D Electron Transfer Channel Based on ZIF-8/rGO Composite Frameworks

A highly sensitive electrochemical sensor based on a composite of two-dimensional (2D) reduced graphene oxide (rGO) and three-dimensional (3D) zeolitic imidazolate framework-8 (ZIF-8) for detecting the NH4+ ion is reported. The ZIF-8/rGO composite electrode is in situ grown to be anchored on the Si/Ag substrate. Here, the rGO layer has high conductivity, while ZIF-8 has a large specific surface area, which provides a large number of active sites. This structure significantly increases the electrical conductivity and enhances the electrochemical performance. With a differential pulse voltammetry measurement at the pH value of 7.00, the multidimensional composite electrode with the optimal ZIF-8 structure exhibits a sensitivity of 9.30 μA μM–1, and a detection range of 5–50 μM with a low detection limit of 3.00 × 10–9 M, as well as high repeatability, stability, and selectivity. These results might be due to the oxidation reaction of NH4+ with the ZIF-8 framework and the special 2D–3D electron transfer channel formed by the composite.