MXene/SnS₂ Heterojunction for Detecting Sub-ppm NH₃ at Room Temperature

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Detecting ultralow concentrations of ammonia (NH3) is crucial for environmental monitoring, agriculture, and healthcare.
• Chemiresistive gas sensors face challenges in detecting sub-parts-per-million (sub-ppm) ammonia levels.
• Two-dimensional (2D) materials offer promising properties for advanced gas detection.

Purpose of the Study:

• To develop a highly sensitive and stable chemiresistive sensor for detecting sub-ppm ammonia.
• To investigate the gas-sensing performance of a novel MXene/SnS2 heterojunction.
• To understand the sensing mechanisms at the material interface.

Main Methods:

• Fabrication of a MXene/SnS2 heterojunction-based chemiresistive sensor.
• Room-temperature gas sensing measurements for ammonia.
• Evaluation of sensor stability, selectivity, and sensitivity.
• In situ diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy.
• First-principles density functional theory (DFT) calculations.

Main Results:

• The MXene/SnS2 sensor achieved detection of ammonia down to 10 parts per billion (ppb) at room temperature.
• The sensor exhibited excellent long-term stability, with only a ~3.4% response decline over 20 days.
• High selectivity towards ammonia was demonstrated against common interferents like formaldehyde, ethanol, and nitrogen dioxide.
• DFT calculations and DRIFT spectra confirmed enhanced ammonia adsorption and charge transfer at the heterojunction interface.

Conclusions:

• The MXene/SnS2 heterojunction significantly enhances ammonia sensing performance at room temperature.
• The sensor's superior sensitivity, stability, and selectivity make it suitable for practical ultralow ammonia detection.
• The study highlights the potential of 2D material heterojunctions for next-generation gas sensors.