A Low-Cost Resilient Chalcogenide Ion-Sensitive Electrode for Copper Sensing With an LoD $< $20 ppb

A solid-state ion-sensitive electrode for the monitoring of copper metal ions in water based on a CdS chalcogenide thin film is fabricated using a low-temperature process. This sensor exhibits a limit of detection of 18.7 ppb. A sensing layer consisting of a chalcogenide material was deposited over a conducting substrate using a low-temperature chemical bath deposition process. Electrochemical impedance spectroscopy and potentiometric measurements were carried out to analyze the response of the sensing layer to the copper ions in water samples. The sensor yields a monotonic response in the concentration range of ${1\times 10^{-3}}$ to ${1\times 10^{-7}}\ \mathrm{M}$ with a response time of a few seconds. The resulting sensor is compatible with large-area fabrication techniques on flexible substrates.