Quartz crystal microbalance-coated cellulose acetate nanofibers overlaid with chitosan for detection of acetic anhydride vapor

Acetic anhydride is one of the most often used reagents in the production of heroin, and the detection of this compound in the air is a methodological challenge. This work aims to devise cellulose acetate (CA) nanofibers overlaid with chitosan (Cs) on a quartz crystal microbalance (QCM) for the detection of acetic anhydride. A base layer of CA nanofibers was coated on QCM via electrospinning and then immersed in Cs solution to fabricate CA nanofibers overlaid with chitosan (CA/Cs nanofibers). On scanning electron microscopy (SEM) images, both CA and CA/Cs nanofibers appeared very smooth and homogenous. The increased nanofiber diameter following chitosan immersion indicated that the chitosan layer covered the CA nanofibers. In addition, coverage was verified by the existence of primary amine groups of Cs in CA/Cs nanofibers on the FTIR spectra. The addition of a chitosan layer on top of CA nanofibers clearly increased the sensory response. The sensitivity of the QCM CA/Cs nanofiber sensor exposed to 10–1000 ppm acetic anhydride vapor was up to 0.234 Hz/ppm, with a lower limit of detection (LOD) of 5 ppm. The sensor also showed a rapid response time (44 s), as well as repeatable and long-term stable behavior, during 5 months of measurements. The as-prepared sensor was also more sensitive to acetic anhydride vapor than to other vapors. A reversible nucleophilic addition interaction between acetic anhydride molecules and the primary amine groups in chitosan was believed to be responsible for the sensing mechanism. The high sensory ability implied that CA/Cs nanofiber coated QCM sensors will be highly suitable for use in the detection of acetic anhydride vapor.