Selective, Stable and Humidity-Robust NO₂ Sensing at Room Temperature with Porous WS₂ Films

Area of Science:

• Materials Science
• Environmental Science
• Sensor Technology

Background:

• Nitrogen dioxide (NO₂) is a hazardous air pollutant with significantly lowered exposure limits set by the WHO.
• Existing sensors often lack the sensitivity, selectivity, or stability required for detecting these low concentrations, especially under varying humidity.

Purpose of the Study:

• To develop a low-power, cost-efficient sensor for detecting low concentrations of NO₂ at room temperature.
• To achieve high selectivity against common interferents and robustness against humidity fluctuations.

Main Methods:

• Fabrication of highly porous (98%) nanostructured tungsten disulfide (WS₂) films using flame-aerosol deposition and dry sulfidation.
• Characterization of the sensor's performance for NO₂ detection, including response, response time, selectivity, humidity robustness, and long-term stability.

Main Results:

• The WS₂ films demonstrated a 5-fold increase in response and an order-of-magnitude faster response time compared to conventional films.
• Achieved remarkable NO₂ detection down to 1 ppb with high selectivity (>164) against various interferents.
• Exhibited high robustness against humidity (0-90% RH) and stability over 6 months.

Conclusions:

• The developed WS₂ sensor offers superior performance for NO₂ detection at room temperature compared to existing technologies.
• Its characteristics make it highly suitable for integration into environmental monitoring devices and wearable personal exposure sensors.