Thermally stable, silica-doped ε-WO₃ for sensing of acetone in the human breath

Acetone in the human breath is a key marker for noninvasive diagnosis of diabetes. Here, sensing films of pure and SiO₂-doped WO₃ nanoparticles have been made, directly deposited and in situ annealed onto interdigitated electrodes by scalable flame aerosol technology. A unique innovation here is that these films consist of ε-WO₃, a metastable phase that has a high selectivity to acetone. The effect of nontoxic Si doping on the ε-phase content and crystal and grain sizes was investigated and correlated to the acetone sensing performance of these films. The thermal stability of these materials was characterized as well, revealing a unique opportunity for reliable sensing of acetone and noninvasive diagnostics of diabetes. An optimal doping level with 10 mol % SiO₂ resulted in highly sensitive and highly selective acetone sensors down to 20 ppb.