Development of highly-sensitive chemi-resistive gas sensor for detection of nitrogen dioxide using hydrothermal carbonaceous nanospheres

다국어 초록 (Multilingual Abstract)

The chemi-resistive detection of nitrogen dioxide (NO2) has attracted significant interest due to its sensitive gas detection performance in environmental assessment and healthcare applications. Recently, the metal-free carbon-based polymeric semiconducting materials have exhibited potential as promising candidates for chemi-resistive gas sensing with processing flexibility and tunable characteristics. In this study, hydrothermal carbonaceous nanospheres (HC-NSs) constitute a new category of high-performance gas sensing materials for NO2 detection. Synthesized via an eco-friendly and simple hydrothermal process, HC- NSs comprise a conjugated sp2-hybridized carbon structure with oxygenated functional groups on the surface and display a large specific surface area with mesoporous architecture, leading to abundant active sites and efficient gas diffusion pathways. In addition, these characteristics impart p-type semiconducting behavior and increased surface reactivity, yielding an impressive −74.4% gas response to 50 ppm NO2 exposure and a detection limit of 80.6 ppb. The superior sensitivity, selectivity, and environmental robustness of HC-NSs were confirmed via comparative evaluation against benchmark Tellurium nanowires (TeNWs)-based gas sensor. The HC-NSs retained consistent gas sensing performance under diverse relative humidity conditions ranging from 20–80% and high temperature conditions up to 200℃, demonstrating their reliability in diverse operating conditions. The improved gas sensing performance arises from synergistic interactions between oxygenated functional groups and the sp2 carbon networks, which facilitate efficient NO2 capturing and charge carrier transport.

목차 (Table of Contents)

• I. Introduction 1
• 1. Harmful Effects of Nitrogen Dioxide (NO2) 1
• 2. Overview of Chemi-Resistive Gas Sensing 3
• 3. Carbon-based Nanomaterials for Gas Sensing 6
• 4. Hydrothermal Carbonaceous Nanospheres (HC-NSs) for Gas Sensing 8
• II. Experimental Methodologies 11
• 1. Synthesis of HC-NSs and Tellurium Nanowires (TeNWs) 11
• 2. Instruments and Methodologies for Characterization of HC-NSs and TeNWs 13
• 3. Gas Sensing Experiments 14
• 4. Limit of Detection (LOD) Calculation 16
• III. Results and Discussions 18
• 1. Structural Characteristics 18
• 2. Electronic Properties of HC-NSs 23
• 3. NO2 Gas Sensing Performance 26
• 4. Humidity Effects on Gas Sensing Properties 32
• 5. Temperature Effects on Gas Sensing Properties 38
• 6. Gas Sensing Properties Toward Low NO2 Concentration for Determination of LOD 43
• 7. Selectivity Test 45
• 8. Long-Term Stability Test 47
• IV. Conclusion 49