Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe‐Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi‐Valent Catalysts

Abstract

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self‐assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe‐doped CuO hollow spheres as H2S gas‐sensing materials via spray pyrolysis. 4 at.% of Fe‐doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi‐valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti‐ or Nb ions into CuO sensors. Mechanistic details of these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe‐doped CuO sensing materials. The selective and reversible detection of H2S using the Fe‐doped CuO sensor suggested in this work opens a new possibility for halitosis self‐monitoring.

CuO nanostructure-decorated InGaN nanorods for selective H2S gas detection

“…13,14 Also, H 2 S is a useful analyte because of its connection with human health, and the exhaled H 2 S in human breath (<300 ppb) is a biomarker for lung cancer, diabetes, and microbial pathogenesis (150–300 ppb). 15,16 Moreover, accurate detection of H 2 S at the sub-ppm level has equal importance in the agricultural and food industries. 17 Copper oxide (CuO) is a well-documented material for H 2 S gas detection and its nanostructures, such as nanoflowers, nanowires, and nanorods have been widely investigated.…”

An electrochemical H2S sensor based on the screen printing Fe@Pt/C/PTFE sensing electrode

“…Gas sensors have played an important role in the detection of toxic gases in various fields such as security, environmental protection, industrial production, medical treatment, and automotive electronics. 1–3 Hydrogen sulfide is one of the most dangerous gases to human life and health in industrial production and daily life. H 2 S can cause “lightning death” at higher concentrations, and even at lower concentrations, it can damage the respiratory system.…”