Pico-molar level detection of copper ion with extraordinarily high response by Ti-doped copper nitride fabricated via high power impulse magnetron sputtering

Various specific methods have been exercised in recent years to detect heavy metal ions in drinking water or body fluids for environmental as well as health safety. Likewise, development of a simple, fast, and robust method for copper ion (Cu2+) sensing is of paramount importance. Here, we demonstrate an effective Cu2+ sensor by exploiting the change in electrical conductivity of Ti-doped copper nitride (Cu3N) in presence of Cu2+ in solution. The Cu2+ sensor was fabricated with a Ti-doped Cu3N film deposited on indium-tin-oxide (ITO) coated quartz glass substrate by co-deposition method using high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering system simultaneously. DC sputtering power of Ti source was tuned from 0 W to 200 W with 50 W steps to achieve the Cu3N film with doping concentrations of 0, 0.19, 0.33, 0.87, and 1.6 at% respectively. Application of a diluted Cu2+ solution on the Ti-doped Cu3N film increases its electrical conductivity dramatically as manifested in the increase in current measured between two consecutive ITO electrodes beneath the thin film. The extraordinarily high copper sensitivity of the Ti-doped Cu3N film (1.6 at%) originated from the nitrogen-rich surfaces leads to detection of Cu2+ in water at as low as 8 pM concentration. The sensor exhibits not only high response but also a large linear dynamic range of 8 pM to 80 nM well below the maximum contaminant level goal for copper ion in drinking water. The high selectivity and reasonable cross-sensitivity of the sensor show potential commercialization in near future.

Automated summary

In recent years, various methods have been used to detect heavy metal ions in drinking water or body fluids for environmental and health safety. The development of a simple and fast copper ion (Cu2+) sensor is of great importance. In this study, researchers have demonstrated an effective Cu2+ sensor by utilizing the change in electrical conductivity of Ti-doped copper nitride (Cu3N) in the presence of Cu2+ in solution. The sensor exhibits high response and a large linear dynamic range, making it a potential candidate for commercialization in the near future.