Hierarchical UiO-66-NH₂/GO composite enables enhanced sensitivity for electrochemical nitrite detection in environmental waters

Developing electrochemical sensors for nitrite (NO2-) detection is very important due to its high toxicity and widespread occurrence in aquatic environments. In this project, the integration of metal–organic frameworks (MOFs) with graphene oxide (GO) has emerged as an effective strategy to enhance the electrocatalytic performance of sensing materials. Herein, a UiO-66-NH₂.GO composite was successfully synthesized via a one-pot hydrothermal method and employed as an advanced sensing material for electrochemical NO2- detection. To the best of our knowledge, this is among the first to utilize UiO-66-NH₂.GO composites for electrochemical NO2- detection in environmental waters. The synthesized composite was characterized using different physical techniques, which confirmed the formation of a hierarchical structure and successful integration of UiO-66-NH2 on GO. Square-wave voltammetry showed that the proposed sensor exhibited a wide linear detection range (0–7.36 ppm) along with a low limit of detection (LOD) of 0.057 ppm for NO2-. Cyclic voltammetry (CV) demonstrated significantly enhanced oxidation current at UiO-66-NH2.GO/GCE electrode compared with the individual electrode components. The sensor was applied to environmental water samples, where NO2- was below the detection limit in most river and stormwater samples, whereas measurable concentrations were detected in wastewater. Standard addition experiments in wastewater yielded satisfactory recovery values (95.5-102.25 %), demonstrating reliable quantitative performance in complex environmental matrices. The developed sensor also showed excellent selectivity and reproducibility.