Waveguide microwave gas sensor based on monolithic In₂O₃ for enhanced ammonia detection.

Area of Science:

• Materials Science
• Chemical Sensing
• Microwave Engineering

Background:

• Room-temperature chemical resistance sensors often suffer from reduced performance.
• Microwave gas sensors offer room-temperature operation and low power consumption.
• Waveguides enhance microwave sensor sensitivity due to their high quality factor.

Purpose of the Study:

• To develop a highly sensitive room-temperature ammonia gas sensor.
• To investigate the effect of porous monolithic indium oxide (In2O3) and waveguide resonators on sensing performance.
• To explore the influence of pore size on gas sensing capabilities.

Main Methods:

• Fabrication of a microwave gas sensor utilizing a waveguide resonator.
• Synthesis of monolithic In2O3 with hierarchical porous structures by adjusting polyvinylpyrrolidone (PVP) content.
• Characterization of In2O3 samples and evaluation of ammonia (NH3) sensing properties.

Main Results:

• The hierarchical porous In2O3 synthesized with 3.0 g PVP (3.0-HPS In2O3) showed optimal NH3 sensing.
• The sensor achieved a wide detection range (0.01-2000 ppm) and a low limit of detection (7 ppb).
• Excellent selectivity, moisture resistance, and long-term stability were observed.

Conclusions:

• Porous monolithic In2O3 integrated with a waveguide resonator is a promising approach for room-temperature ammonia gas sensing.
• Optimized pore structure significantly enhances gas diffusion and sensing performance.
• The study provides insights into tailoring pore size for improved gas sensor applications.