Polyetherimide/carbon black composite sensors demonstrate selective detection of medium-chain aldehydes including nonanal

This study presents the synthesis, fabrication, and development of a selective polyetherimide (PEI)/carbon black (CB) sensor, engineered to detect aldehydes such as nonanal. Using a novel approach, spin coating of the PEI/CB in 1-methyl-2-pyrrolidone (NMP) was followed by a reduction of the composite through heat treating at 200 degrees C resulting in a highly sensitive and selective film (with low hydrophilicity) for detection of nonanal. This represents a key step, as it decreased surface oxygen and increased surface amine/imine sites. XPS analysis demonstrated the engineered surface was comprised of > 3.5% nitrogen (including 1.2% amines/imines) and displayed a contact angle of 80 degrees. The sensor response to nonanal (1 ppm to 80 ppm) ranged from 0.02% to 1.9%. Fabricated sensors showed over 14 times more sensitivity to nonanal than volatiles with similar molecular weights but different functional groups such as 2-nonanone, dodecane, and 1-octanol. This confirms the sensing film has high selectivity to aldehydes over ketones, hydrocarbons, and alcohols. Importantly, the proposed sensor maintained its response to nonanal over a period of 36 days. In addition, a multifactor machine learning algorithm was developed based on principal component analysis (PCA) to detect the type and concentration of a VOC using the temporal response of the sensor. Fabrication, characterization, testing methods, and results are presented and discussed.