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With the recent advancement in artificial intelligence and machine learning (AI/ML), the electronic nose (e-Nose) technology has improved significantly in the last decade. However, relying on the signals produced by an array of gas and volatile organic compound (VOC) sensors used as the hardware of an e-Nose, the overall performance of the system is limited by the sensor types and sensing mechanisms. The majority of the commercially available gas/VOC sensors are using metal-oxide (MOX) thin films. Although MOX sensors are relatively stable, they are extremely power-hungry. Therefore, other materials have been investigated for gas and VOC sensing. In this work, we have focused on the application of organometallic compounds as a low-cost and low-power alternative to the MOX sensors. Copper Phthalocyanine (CuPc) has been tested in both forms of a chemiresistor and an electrochemical cell. In the electrochemical design, the material presented a unique selectivity to formic acid due to a protonation reaction. However, removing contaminants from the electrolyte of an electrochemical cell is challenging and limits the repeatability of the sensor response. In contrast, in a thin-film design (chemiresistor), CuPc responds to various VOCs including ethanol, isoproapanol, and acetone, but due to the lack of the protonation mechanism, the selectivity response was not observed. Our studies on ZnPc and CoPc, also, are promising for designing an array of metal phthalocyanines (MPcs) as the hardware of an e-Nose to address the shortcomings in the MOX technology.
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