Film bulk acoustic formaldehyde sensor with polyethyleneimine-modified single-wall carbon nanotubes as sensitive layer

Abstract Polyethyleneimine-modified single-wall carbon nanotubes were self-assembled as a sensitive coating for the micro-scale film bulk acoustic formaldehyde sensor. The film bulk acoustic resonator has a high working frequency (∼4.5 GHz) and can detect the ultra-small mass changes in the sensitive layer induced by the absorption of formaldehyde molecules. The proposed sensor demonstrated a reversible and linear response towards formaldehyde over the range of 50–400 ppb, with a limit of detection of 24 ppb. Both the response and recovery times were less than 1 min. The frequency response was improved with increasing coverage of carbon nanotubes on the resonator surface due to the larger surface area and adsorption space. The polyethyleneimine-modified single-wall carbon nanotubes provided an excellent selectivity towards formaldehyde over interfering organic vapors. The results show that the film bulk acoustic sensor is a promising candidate for the portable and convenient detection of indoor air pollution with high sensitivity.