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).