Ag-Ag2O decorated multi-walled carbon nanotubes/NiCoAl hydrotalcite sensor for trace nitrite quantification.

Ag-Ag2O-decorated multiwall carbon nanotube/NiCoAl-hydrotalcite (CNT/LDH-Ag) composites were designed and synthesized for nitrite quantification. The materials were characterized by various techniques, and their electrochemical NO2- detection performances investigated using amperometric and differential pulse voltammetry (DPV) techniques. The Ag-Ag2O nanoparticles (NPs) were anchored on the surface of the CNT/LDH-Ag composites. At a suitable amount of the Ag-Ag2O loading, the Ag-Ag2O NPs with small particle size were distributed evenly on the CNT/LDH surface, increasing the surface area of the composites. The optimal CNT/LDH-Ag3 composite exhibited a high electrochemical activity for NO2- oxidation in pH 7.0. Furthermore, the optimal CNT/LDH-Ag3 composite was fabricated for trace NO2- quantification. The proposed sensor displayed a high sensitivity (0.0960 μA·μM-1·cm-2) and fast response (< 3 s) toward NO2- in a wide linear range from 0.250 μmol·L-1 to 4.00 mmol·L-1 with a low detection limit of 0.0590 μmol·L-1(S/N = 3). The sensor provided an outstanding analytical performance with a desirable recovery (95.3 ~ 107%, RSD < 1.05%) in real sample. As a result, the proposed sensor can be used for the real-time quantification of trace NO2- in the biological, food, and environmental fields.