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

The nitrate ion (NO) is a typical pollutant in environmental samples, posing a threat to the aquatic ecosystem and human health. Therefore, rapid and accurate detection of NO 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-VMSF) confining localized copper nanoparticles (CuNPs) for the electrochemical detection of NO. NH-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-VMSF-modified indium tin oxide (ITO) electrode (CuNPs/NH-VMSF/ITO) combines the electrocatalytic reduction ability of CuNPs and the electrostatic attraction capacity of NH-VMSF towards NO. Thus, it is a rapid and sensitive electrochemical method for the determination of NO 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 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-VMSF/ITO sensor has excellent reproducibility, regeneration, and anti-interference abilities.