Heterogeneous Porous WO3@SnO2 Nanofibers as Gas Sensing Layers for Chemiresistive Sensory Devices

Abstract

We employed an unprecedented technique to synthesize porous WO3@SnO2 nanofibers exhibiting core-shell and fiber-in-tube con- figurations. Firstly, 2-methylimidazole was uniformly incorporated in as-spun nanofibers containing ammonium metatungstate hydrateand the sacrificial polymer (polyacrylonitrile). Secondly, the 2-methylimidazole on the surfaces of nanofibers was complexed with tin(II)chloride (SnCl2) via simple impregnation of the as-spun nanofibers in ethanol containing tin(II) chloride dihydrate (SnCl2·2H2O). Thepresence of vacant p-orbitals in tin (Sn) and the nucleophilic nitrogen on the imidazole ring allowed for the reaction between SnCl2 and2-methylimidazole, forming adducts on the surfaces of the as-spun nanofibers. The calcination of these nanofibers resulted in porous WO3@SnO2 nanofibers with a higher surface area (55.3 m2·g 1) and a better response to 1-5 ppm of acetone than pristine SnO2 NFs synthesized using a similar method. An improved response to acetone was achieved upon functionalization of the WO3@SnO2 nano-fibers with catalytic palladium nanoparticles. This work demonstrates the potential application of WO3@SnO2 nanofibers as sensing lay- ers for chemiresistive sensory devices for the detection of acetone in exhaled breath.