Enhanced Formaldehyde-Sensing Performances of Mixed Polyethyleneimine-Multiwalled Carbon Nanotubes Composite Films on Quartz Crystal Microbalance

The development of a robust, reproducible, cheap, and low-power gas sensor for monitoring the low-level concentration of formaldehyde is in urgent demand. In this paper, mixed polyethyleneimine (PEI)-multiwalled carbon nanotubes (MWCNTs) nanocomposite thin film was coated on a quartz crystal microbalance (QCM) using a facile spraying process for formaldehyde detection at room temperature. The effects of spraying loads and ratios of PEI to MWCNTs on sensing properties were investigated. The hydrogen-bonding interaction between PEI and MWCNTs was proved by the X-ray photoelectron spectrometer (XPS) characterization, and the formaldehyde-sensing characteristics results revealed that the PEI-MWCNTs nanocomposite film sensor exhibited superior sensing properties than the pure PEI film sensor, with linear response characteristics, fast response, low detection limit (0.6ppm), good reproducibility and selectivity to formaldehyde within 6 ppm. A sensing mechanism model was introduced to understand the chemical reaction between formaldehyde gas molecules and amine functional groups of PEI along with the ultraviolet-visible absorption spectra analysis. This paper shows the great potential for developing sensitive and fast-response formaldehyde gas sensor with a simple spraying fabrication method.