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.