Selective detection of multiple VOCs employing zinc oxide nanorods and principle component

Detection of toxic gases and volatile organic compounds (VOCs) selectively, in the atmosphere has become a major challenge. Two dimensional materials and metal oxide semiconductor-based gas sensors respond to different gases simultaneously, confirming poor selectivity. This paper represents an individual chemiresistive gas sensor for detecting multiple VOCs accurately, by employing extremely sensitive zinc oxide (ZnO) nanorods and principal component analysis on the extracted patterns. Different characterizations of ZnO nanorods were performed to ensure the formation of desired morphology and structural features. The sensor was fabricated by precise drop casting technique over interdigitated electrodes patterned with gold. The sensor displayed very high sensitivity towards acetone, along with appreciable cross sensitivity towards ammonia and ethanol among the seven VOCs. The sensor exhibited fast response and recovery time towards the three VOCs. The response of the sensor towards the VOCs was analyzed for 50 days, indicating stability of the sensor. The sensor revealed different dynamic characteristics (patterns) during detection of acetone, ammonia and ethanol. Various features were extracted from different patterns and principal component analysis (PCA) was performed to reduce the dimensionality of the feature vectors and achieve selectivity among VOCs. In comparison to e-noses (having array of sensors with various sensing material), an individual chemiresistive sensor with an effective pattern recognition technique is economic, simple, compact and easy to fabricate.