Polyamide 6 composite nano-fiber/net functionalized by polyethyleneimine on quartz crystal microbalance for highly sensitive formaldehyde sensors

A nanostructured complex, polyethyleneimine (PEI) functionalized polyamide 6 (PA 6) (PEI-PA 6) nano-fiber/net (NFN), is developed as a novel sensing coating on quartz crystal microbalance (QCM) for highly sensitive formaldehyde detection. The NFN structured substrate comprising common electrospun nanofibers and two-dimensional (2D) spider-web-like nano-nets fabricated by a facile electro-spinning/netting (ESN) process, exhibit large specific surface area, high porosity and large stacking density, which make them optimal candidates for sensing applications. The responses of the sensors in response to formaldehyde were analyzed in terms of PA 6 NFN membranes morphologies, PA 6 substrate and sensing PEI coating loads, and the comparison with nanoporous fibers. Experimental results show that this new PEI-PA 6 NFN nanostructure based QCM sensor exhibits excellent formaldehyde sensing performances in terms of remarkably low detection limit (50 ppb), rapid response, superior selectivity and good reproducibility. We expect the highly sensitive and robust NFN-based QCM sensor may serve as a practical and powerful tool for gas sensing and chemical analysis.