AN ACOUSTIC PLATE MODE AQUEOUS MERCURY SENSOR

THERE IS A CRITICAL NEED FOR A FAST, SIMPLE SENSOR FOR AQUEOUS MERCURY IN WASTE, SURFACE, AND GROUND WATER. THIS SENSOR IS REQUIRED FOR THE DOE REMEDIATION EFFORTS AS WELL AS THE MORE WIDESPREAD EFFORTS IN ENVIRONMENTAL PROTECTION. SUCH A SENSOR SHOULD BE ABLE TO REACT TO NANOGRAM PER MILLILITER LEVELS OF MERCURY. THE SENSOR IS CAPABLE OF DIRECT IMMERSION IN SOLUTION AND SHOULD PROVIDE CONTINOUS DATA ON EITHER CUMULATIVE MERCURY EXPOSURE OR INSTANTANEOUS CONCENTRATION. SPECTROSCOPIC METHODS, SUCH AS ATOMIC ABSORPTION, ATOMIC EMISSION, AND ATOMIC FLUORESCENCE PROVIDE ADEQUATE SENSITIVITY; HOWEVER, THESE ARE DISCRETE LABORATORY TECHNIQUES AND CANNOT BE EMPLOYED FOR CONTINUOUS MONITORS OR IN THE FIELD. ONE METHOD OF DETECTING PPB TO PPM LEVELS OF MERCURY IN SOLUTION INVOLVES THE USE OF NOVEL CLASS OF PIEZOELECTRIC SENSORS, KNOWN AS THE SHEAR HORIZONTAL ACOUSTIC PLATE MODE (SHAPM) SENSOR. THESE SENSORS MEASURE THE PERTURBATION OF ACOUSTIC WAVE, IN SITU, TO CHANGES IN ELECTRICAL AND MECHANICAL PROPERTIES. THEY ARE READILY OPERATED IN CONTACT WITH A FLUID MEDIUM AND ARE SENSITIVE TO SUBNANOGRAM QUANTITIES OF MASS ADSORBED ONTO THEIR SURFACE. THE SHAPM HAS THE POTENTIAL TO RIVAL COLD VAPOR ATOMIC ABSORPTION AND ATOMIC FLUORESCENCE SPECTROSCOPY TECHNIQUES, WHILE SIMULTANEOUSLY OFFERING IN-SITU, CONTINUOUS MONITORING. THE MONITOR IS EXPECTED TO PROVIDE A MEASURE OF THE MERCURY CONCENTRATION IN MINUTES AND TO BE REUSABLE MANY TIMES. PHASE I WILL DEMONSTRATE THE PRINCIPAL OF OPERATION OF THE NEW SENSOR TO DETECT NANOGRAM PER MILLILITER LEVELS OF MERCURY IN SOLUTION. THIS EFFORT WILL INCLUDE THE FABRICATION OF SEVERAL DEVICES WITH DIFFERENT FILMS WHICH ARE EXPECTED TO CONFER SPECIFICITY FOR MERCURY. RESPONSES OF THE SENSORS WILL THEN BE MEASURED OVER VARIOUS MERCURY CONCENTRATIONS. EFFECTS OF POSSIBLE INTERFERENTS WILL ALSO BE EXAMINED. PHASE II WILL CONCENTRATE ON OPTIMIZATION OF THE MOST PROMISING DEVICE WHICH WILL INCLUDE ASPECTS SUCH AS DURABILITY, REUSABILITY, SIGNAL PROCESSING, AND PACKAGING.