Surface Activity-Tuned Metal Oxide Chemiresistor: Toward Direct and Quantitative Halitosis Diagnosis

Abstract

Continuous monitoring of hydrogen sulfide (H2S) in human breath for early stage diagnosis of halitosis is of great significance for prevention of dental diseases. However, fabrication of a highly selective and sensitive H2S gas sensor material still remains a challenge, and direct analysis of real breath samples has not been properly attempted, to the best of our knowledge. To address the issue, herein, we introduce facile cofunctionalization of WO3 nanofibers with alkaline metal (Na) and noble metal (Pt) catalysts via the simple addition of sodium chloride (NaCl) and Pt nanoparticles (NPs), followed by electrospinning process. The Na-doping and Pt NPs decoration in WO3 grains induces the partial evolution of the Na2W4O13 phase, causing the buildup of Pt/Na2W4O13/WO3 multi-interface heterojunctions that selectively interacts with sulfur-containing species. As a result, we achieved the highest-ranked sensing performances, that is, response (R air/R gas) = 780 @ 1 ppm and selectivity (R H2S/R EtOH) = 277 against 1 ppm ethanol, among the chemiresistor-based H2S sensors, owing to the synergistic chemical and electronic sensitization effects of the Pt NP/Na compound cocatalysts. The as-prepared sensing layer was proven to be practically effective for direct, and quantitative halitosis analysis based on the correlation (accuracy = 86.3%) between the H2S concentration measured using the direct breath signals obtained by our test device (80 cases) and gas chromatography. This study offers possibilities for direct, highly reliable and rapid detection of H2S in real human breath without the need of any collection or filtering equipment.

Co,N-doped GQDs/SnO2 mesoporous microspheres exhibit synergistically enhanced gas sensing properties for H2S gas detection

“…Sensitive real-time monitoring of trace H 2 S (100-500 ppb) in exhaled breath can help provide useful information for clinical disease diagnosis. [6][7][8] Therefore, it is imperative to develop a high-efficiency H 2 S gas sensor with excellent sensitivity, high selection, and fast response.…”

The Progress of Research into Flexible Sensors in the Field of Smart Wearables

“…Additionally, the sensor exhibited reliability and reproducibility, ensuring its long-term use in practical situations. Meanwhile, Bezdek et al [ 104 ] based SWCNTs on non-covalently functionalized P4VP, a carbon nanotube that doped (Pt-POM) CH4 oxidation catalyst onto the sensor through P4VP coordination, resulting in a significant improvement in all sensor properties. Additionally, Shin et al [ 105 ] performed a simple co-functionalization of WO3 nanofibers with alkali metal (Na) and noble metal (Pt) catalysts by the simple addition of NaCl and Pt nanoparticles followed by electrostatic spinning, which produced a highly sensitive and flexible H 2 S gas sensor.…”

“… Application of a flexible sensor based on a chemical formula: ( a ) schematic diagram of a self-powered H 2 gas sensor [ 103 ]; ( b ) surface-active tuned metal oxide chemical resistor for direct analysis of human mouth odor [ 104 ]. …”

Recent advances in noble metal MXene-based catalysts for electrocatalysis

“…Noble metals have broad application prospects in catalysis, [1][2][3][4] sensing, [5][6][7] optics, 8,9 and diagnosis. [10][11][12] Especially in the eld of catalysis, they have high-efficiency catalytic activity and stability, owing to their suitable d-band center position, which can effectively adsorb and activate reactants and desorb the reaction products efficiently. 13,14 However, the high cost and low reserves of noble metals hinder their wide application in the eld of electrocatalysis.…”