Carbon quantum dots/polypyrrole nanocomposite film as a quartz-crystal microbalance-based formaldehyde sensor

Abstract

Formaldehyde is a hazardous indoor air pollutant due to its adverse effects on human health, highlighting the importance of precise monitoring and detection. Carbon quantum dots (CQDs)/polypyrrole (PPy) nanocomposites are attractive due to the synergistic behavior of constituents, and hence their films were selected to form a quartz-crystal microbalance (QCM) sensor for formaldehyde vapor. The CQDs/PPy nanocomposite film coated on the QCM electrode was fabricated by embedding CQDs into the PPy film through their adsorption from an aqueous medium onto the PPy film. The frequency change was linearly correlated with the formaldehyde concentration. The CQDs/PPy composite film detected a low concentration range of 0.58–5.82 mg L−1, which supports the high sensitivity of the composite film-based QCM sensor. The sensor exhibited good selectivity, reproducibility, stability, and repeatability for formaldehyde detection. The adsorption mechanism was explored. The diffusion of formaldehyde into the PPy and the CQDs/PPy nanocomposite films was studied.