Electrochemical piezoelectric sensors for trace ionic contaminants

摘要

Industrial processes, such as fossil fuel combustion and nuclearnmaterials processing, have resulted in heavy metal contamination ofnsoils and potentially of the surrounding groundwater. In particular,nmercury contamination of groundwater is a serious threat to thenecosystem, cumulating in serious health problems for humans as well asnwildlife. Monitoring of mercury contamination in groundwater requires anmethod of long-term verification. Sensors with lifetimes of months tonyears of operation without operator intervention are required. Onensensor geometry, which is capable of detecting relevant concentrationsnof aqueous ionic contaminants, such as mercury, while withstandingntypical environmental conditions, is the shear horizontal acoustic platenmode (SHAPM) sensor. This sensor protects the electronics from thenpotentially corrosive aqueous fluid environment while providing ansignificant interaction with the fluid. Gold films are employed tonaccumulate the mercury via surface amalgamation. The added mass isnmeasured as a change in the resonant frequency of the piezoelectricnsensing element. Electrochemical techniques are employed to impartnreversibility and to accelerate response kinetics. Results indicate ansensitivity of approximately 2.4 ng/mL, which approaches the 2.0 ng/mLnlimit imposed by the Safe Drinking Water Act (SDWA)