DEVELOPMENT OF A POLYANILINE BORONIC ACID (PABA) CARBON DIOXIDE (CO2) SENSOR FOR USE IN THE AGRI-FOOD INDUSTRY
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In the agri-food industry, carbon dioxide sensors can be used for process control, monitoring quality, and assessing safety. A carbon dioxide sensor was developed using poly aniline boronic acid (PABA) conducting polymer as the electrically conductive region of the sensor for use in the agri-food industry and was demonstrated for use in detecting incipient or ongoing spoilage in stored grain. The developed sensor dynamically detected up to 2455 ppm CO2 concentration levels. The performance of the sensor in measurements of low concentrations of dissolved CO2 was characterized using standard solutions of NAHCO3. The dynamic range for the detection of H2CO3 was 4.91X10-4 to 9.81X10-3 mol L-1. The dc resistance values decreased with increasing CO2 concentration indicating an increase of conductivity due to increase in the amount of protonation. The developed CO2 sensor was evaluated for the influence of temperature (by storing it at – 20°C and 0°C as well as at operating temperatures of +10°C to 55°C) and relative humidity (from 20 to 70%). Temperature dependence of sensor's resistance values were observed possibly due to the change in conduction mechanism at different temperatures. The variation in the resistance with humidity was curvi-linear and repeatable, indicating that humidity has a less pronounced effect on the sensor’s performance. The sensor’s response to changes in CO2 concentrations at various humidity and temperature levels was stable indicating that the sensor can detect CO2 levels under fluctuating environmental conditions. The response of the PABA film to CO2 concentration was not affected by the presence of alcohols and ketones, proving that the developed CO2 sensor is not cross-sensitive to these compounds which may be present in spoiling grain. The sensor packaging components were selected and built in such a way to avoid contamination of the sensing material and the substrate by undesirable components including grain dust and chaff. The developed conducting polymer CO2 sensor exhibited dynamic performance in its response, recovery times, sensitivity, selectivity, stability and response slope when exposed to various CO2 levels inside simulated grain bulk conditions.