Detection and response mechanism of CN− using Ag2S coated piezoelectric crystal sensor

A new method of determination of trace CN− in water was proposed. A thin film of Ag2S was electrochemically deposited on both sides of a silver coated piezoelectric crystal. The Ag2S−Ag films can react with CN− selectively, which causes the frequency shifts of the plezoelectric crystal. The frequency shifts are proportional to the concentration of CN− in the range of 10−6≈10−3 g/L. XPS experiments indicated the sensing film was Ag2S−Ag. A coordination complex Ag−CN− was formed when Ag2S−Ag film contacted with solution containing CN− ion. A response mechanism was proposed based on the XPS data.