Trace Detection of Nitrogen Dioxide via Porous Tin Dioxide Nanopods with High Specific Surface Area and Enhanced Charge Transfer

Nitrogen oxides, particularly nitrogen dioxide (NO₂), contribute significantly to environmental pollution and pose serious risks to public health. Therefore, detecting even low concentrations of NO₂ is significant for effective environmental monitoring and public health protection. Existing NO₂ gas sensors, however, have limitations such as low sensitivity, insufficient selectivity, and slow response and recovery times. In this work, we synthesized tin-based metal-organic framework nanorods using phthalic acid as the ligand and subsequently fabricated porous tin dioxide (SnO₂) nanopods through high-temperature calcination. The resulting SnO₂ nanopods feature one-dimensional rod-like SnO₂ frameworks filled with plenty of SnO₂ nanoparticles. This micronanostructure exhibits a large specific surface area (299.8 m²/g) and a large pore size (30.8 nm), which facilitates the adsorption, diffusion, and surface reactions of NO₂. The sensors demonstrate excellent performance in detecting NO₂, with a response value of 64 to 1 part per million (ppm) NO₂ at a working temperature of 250 °C, a response time of 15 s, and a recovery time of 20 s. Moreover, the SnO₂ nanopod sensors show a wide detection range from 10 parts per billion to 100 ppm, good repeatability, long-term stability, and reliable NO₂ detection at low concentrations even under high humidity conditions (90% relative humidity).