Preparation and Selectivity of Resistive Acetone Gas Sensors Based on Polyaniline/Au Interdigitated Electrode

The acetone gas sensor can be applied in the fields of the occupational safety, the prevention of fire accident and explosion in plants and the diabetic patients breathe analysis. The properties of the sensing materials and the sensing characteristics of the acetone gas sensors based on polyaniline (PANI)/Au/porous ceramic plate prepared by the microfabrication technologies and the electrochemical methods are studied in this work. PANI with stable sensing performance is prepared by a three-stage chronopotentiometric method onto Au/porous ceramic plate. The PANI nanowires are uniformly distributed on Au interdigitated electrode surface characterized by field emission scanning electron microscopy (FESEM).The sensitivity and the response time of the resistive acetone gas sensor are obtained to be 4.0×10-3% ppm-1and 3 min when using N2as carrier gas. Based on the same sensing electrode, the sensitivities of the gas sensor to mixed gas containing acetone are measured.Key words: gas sensor; acetone; polyaniline; sensitivity; selectivity

CONVERSION OF LATENT EVAPORATION TO POTENTIAL EVAPOTRANSPIRATION

Potential evapotranspirometers and various evaporation pans are commonly used to estimate potential evapotranspiration. These instruments are expensive, large, difficult to install and use. A black Bellani plate atmometer is suggested as a simple instrument to replace these large tanks. It consists of a black, porous, ceramic plate, mounted on a glazed ceramic cup. The plate surface is kept moist by the water held in the cup. Evaporation from this surface is a measure of the drying ability of the air and is called "latent evaporation". Comparisons of various evaporimeters have shown the Bellani atmometer to be accurate and responsive to meteorological variables.Latent evaporation was compared with open-pan evaporation (from a 4-foot diameter buried tank) at several sites across Canada. Latent evaporation was also compared with evapotranspiration from irrigated field plots and evapotranspirometer tanks. The conversion factor of 0.0034 inches of evapotranspiration from irrigated fields, and 0.0032 inches of open-pan evaporation for each cubic centimetre of latent evaporation has been tentatively established. Latent evaporation and moisture block methods have shown excellent agreement in scheduling irrigation.