Achieving One Part Per Billion Hydrogen Sulfide (H 2 S) Level Detection through Optimizing Composition and Crystallinity of Gold-Decorated Tungsten Trioxide (Au-WO 3 ) Nanofibers.

As a common environmental pollutant and an important breath biomarker for several diseases, it is essential to develop a hydrogen sulfide gas sensor with a low-ppb level detection limit to prevent harmful gas exposure and allow early diagnoses of diseases in low-resource settings. Gold doped/decorated tungsten trioxide (Au-WO 3 ) nanofibers with various compositions and crystallinities were synthesized to optimize H 2 S-sensing performance. Systematically experimental results demonstrated the ability to detect 1 ppb H 2 S with a response value ( R air / R gas ) of 2.01 using a 5 at % Au-WO 3 nanofibers with average grain sizes of around 15 nm. Additionally, energy barrier difference of sensing materials in air and nitrogen (Δ E b ) and power law exponent ( n ) were determined to be 0.36 eV and 0.7, respectively, at 450 °C indicating that O - is predominately ionic oxygen species and adsorption of O - significantly altered the Schottky barrier between the grain. Such quantitative analysis provides a comprehensive understanding of H 2 S detection mechanism.