Hierarchically interconnected porosity control of catalyst-loaded WO3 nanofiber scaffold: Superior acetone sensing layers for exhaled breath analysis

Electrospun WO3 nanofibers (NFs) with hierarchically interconnected porosity (HP_WO3 NFs) are designed by using dual sacrificial templates including zero-dimensional (OD) polystyrene (PS) colloids and one-dimensional (1D) multi-walled carbon nanotubes (MWCNTs). Multi-dimensionally interconnected pore-loaded structures offer much enhanced surface area and abundant gas penetration pathway into the inner sensing layers, which are essential requirements for effective gas adsorption-desorption reactions, fast gas diffusion, and high gas response. Moreover, such porous WO3 NFs are homogeneously decorated by Pt nanoparticles (Apo-Pt) encapsulated in a protein nanocage, i.e., apoferritin, which enables uniform catalyst sensitization in interior and exterior of highly gas accessible NFs. The HP_WO3 NFs sensitized by Apo-Pt (Apo-Pt@HP_WO3 NFs) exhibited highly selective and sensitive acetone response (R-air/R-gas = 10.80 +/- 0.06 @ 1 ppm) under high humidity atmosphere (90% RH). To investigate the potential suitability as exhaled breath analyzers, we tested three sensor arrays consisting of mesoporous WO3 NFs templated by MWCNTs (MP_WO3 NFs), HP_WO3 NFs, and Apo-Pt@HP_WO3 NFs. The result revealed that targeted acetone molecules were clearly classified against six different interfering molecules (H2S, C7H8, C2H5OH, CO, NH3 and CH4) through principle component analysis (PCA), confirming excellent acetone selectivity of the designed sensor arrays. (C) 2017 Elsevier B.V. All rights reserved.