Core-shell Cu₂O@UiO-66 enabled pre-concentration electrochemical sensor for rapid, sensitive detection of ammonia...

Excess ammonia nitrogen in groundwater poses significant threats to human health and ecosystems. There is a growing demand for a simple, convenient, accurate, and highly sensitive in-situ sensing method for ammonia nitrogen quantification. In this study, conductive carbon cloth (CC) was employed for the in-situ growth of a core-shell Cu₂O@UiO-66 nanocomposite, resulting in the Cu₂O@UiO-66/CC electrochemical sensor. After optimizing the material ratio, synthesis time, electrolyte pH, and concentration, the Cu₂O@UiO-66/CC electrochemical sensor exhibited excellent sensing performance for ammonia nitrogen with a 285% increase in response peak current. This sensor detects ammonia nitrogen via cyclic voltammetry (CV), featuring a low detection limit of 0.231 μM, high sensitivity of 0.598 μA μM^-1 cm². It demonstrates excellent selectivity toward ammonia nitrogen and anti-interference ability from common groundwater anions, cations, and organic compounds. The enhanced electrocatalytic performance stems from the introduction of carboxyl groups, which generate oxygen vacancies (providing active sites), coupled with the nanoconfinement effect of the porous UiO-66 shell layer (pre-capturing ammonia nitrogen molecules to the Cu₂O core), thereby enabling highly efficient electrocatalytic oxidation. Spiked and recovery tests and real groundwater samples analysis demonstrated reliable recoveries (98.47% to 100.39%) and a satisfactory relative standard deviation (RSD) (<3%), confirming the accuracy and reliability of the sensor. This work offers a novel strategy for swift and accurate in-situ specific detection of ammonia nitrogen in groundwater, indicating a great potential for practical application.