Copper Nanoparticles Confined in a Silica Nanochannel Film for the Electrochemical Detection of Nitrate Ions in Water Samples

The nitrate ion (NO(3)(−)) is a typical pollutant in environmental samples, posing a threat to the aquatic ecosystem and human health. Therefore, rapid and accurate detection of NO(3)(−) is crucial for both the aquatic sciences and government regulations. Here we report the fabrication of an amino-functionalized, vertically ordered mesoporous silica film (NH(2)-VMSF) confining localized copper nanoparticles (CuNPs) for the electrochemical detection of NO(3)(−). NH(2)-VMSF-carrying amino groups possess an ordered perpendicular nanochannel structure and ultrasmall nanopores, enabling the confined growth of CuNPs through the electrodeposition method. The resulting CuNPs/NH(2)-VMSF-modified indium tin oxide (ITO) electrode (CuNPs/NH(2)-VMSF/ITO) combines the electrocatalytic reduction ability of CuNPs and the electrostatic attraction capacity of NH(2)-VMSF towards NO(3)(−). Thus, it is a rapid and sensitive electrochemical method for the determination of NO(3)(−) with a wide linear detection range of 5.0–1000 μM and a low detection limit of 2.3 μM. Direct electrochemical detection of NO(3)(−) in water samples (tap water, lake water, seawater, and rainwater) with acceptable recoveries ranging from 97.8% to 109% was performed, demonstrating that the proposed CuNPs/NH(2)-VMSF/ITO sensor has excellent reproducibility, regeneration, and anti-interference abilities.