Ultra-high response and low temperature NO2 sensor based on mesoporous SnO2 hierarchical microtubes synthesized by biotemplating process

The development of low temperature gas sensor with ultra-high response has important application value for actual monitoring of harmful gases. Herein, we utilized poplar branch (PB) as bio-template to synthesize SnO2 sensing material through immersing PB into SnCl4.6 H2O solution, followed by calcining the immersed precursor in air. The material calcined at 600 ℃ (named as SnO2-600) exhibits the hierarchical microtube structure inherited from PB, which is cross-linked by small-sized nanoparticles. Meanwhile, uniform mesoporous structure and abundant oxygen vacancies are also present on the inner and outer surface of SnO2-600 microtubes. The synergistic effect of these microstructure characteristics can not only greatly enhance surface chemical reaction of sensing materials, but also effectively improve surface diffusion, adsorption and desorption behavior of target gas. At 50 ℃, SnO2-600 sensor presents high response value (S = Rg/Ra) of 3411 and rapid recovery time of 17 s to 10 ppm NO2. In addition, the sensor also has low detection limit, good selectivity, satisfactory reproducibility, humidity resistance and long-term stability. Therefore, the present mesoporous SnO2-600 microtubes are available as candidate for detecting NO2 gas at low temperature.