CuAg nanoparticles formed in situ on electrochemically pre-anodized screen-printed carbon electrodes for the detection of nitrate and nitrite anions

CuAg nanoparticles (CuAgNPs) were electrochemically formed in situ on pre-anodized, screen-printed carbon electrodes (SPCEs) that possessed many oxygen-containing functional groups capable of adsorbing metal ions, namely Cu2+ and Ag+. Pre-anodization was achieved using continuous cyclic voltammetry in the range of potential 0.3-2.0V under a scan rate of 50mV/s. Cu2+ and Ag+ ions were adsorbed on the pre-anodized SPCE by immersing the electrode in solutions containing both metal ions, and then CuAgNPs were formed in situ via electrochemical reduction in a deaerated, neat NaClO4 solution after the electrode was ultrasonicated to remove physically adsorbed metal ions. Although CuNPs showed higher activity than AgNPs toward both nitrate (NO3-) and nitrite (NO2-) ions, the instability of CuNPs hindered the application, so CuAgNPs were employed to achieve a compromise between sensitivity and stability. The SPCE/anodized/CuAgNP electrodes showed activity toward the electrochemical reduction of NO3- and NO2-, respectively, with the limit of detection (LOD) of 15.6M (0.97ppm) and 11.1M (0.51ppm), which is sufficient to fit the allowed values (50 and 3ppm, respectively) in drinking water as suggested by the World Health Organization (WHO).