Primary amine-functionalized polyaniline nanothin film sensor for detecting formaldehyde

Formaldehyde is a suspect carcinogen, an allergen, and a contributor to the sick-building syndrome (SBS) and the Occupational Health and Safety Administration (OSHA) has set a permissible exposure limit (PEL) of 750 ppb. Thus, there is a need to sensitively and selectively monitor formaldehyde in real-time. Herein, we report a primary amine-functionalized polyaniline (PANI) nanothin film chemiresistor sensor utilizing nucleophilic addition of amines of the sensor to the carbonyl group of formaldehyde. The reaction between the amines and formaldehyde produced water and Schiff base that changed the resistance of the PANI film as a function of formaldehyde concentration. The sensor response was investigated as a function of the functionalizing primary amine nucleophilicity and humidity/temperature of the background medium. The lysine-functionalized polyaniline nanothin film sensor exhibited the best sensor performance with a lower limit of detection of 400 ppb, which is nearly half of the PEL, and very good selectivity against acetaldehyde, acetone and formic acid.