A Simple Absorbent Cotton Biotemplate to Fabricate SnO₂ Porous Microtubules and Their Gas-Sensing Properties for Chlorine

SnO₂ porous microtubules (PMs) were synthesized by a two-step immersion-calcination method, and absorbent cotton is used as the biotemplate. This method is simple, eco-friendly, and cost-efficient. The absorbent cotton as a biotemplate not only supported the formation of microtubule-like structures but also provided a hypoxia atmosphere to introduce oxygen vacancies in the calcination process. The as-synthesized SnO₂ PMs maintain the morphology of absorbent cotton - long, curly, and twisted. The gas-sensing property of the SnO₂ PMs sensor was systematically investigated for detection of chlorine (Cl₂). On the basis of such porous microtubules, the sensor exhibited excellent sensitivity and selectivity to Cl₂ at 200 °C. Compared with SnO₂ particles, the gas response (R_gas/R_air) of the SnO₂ PMs sensor to 10 ppm of Cl₂ at 200 °C was increased about 100 times. Finally, the enhanced gas-sensing performance was associated with the hollow morphology of SnO₂ PMs and the formation of abundant oxygen vacancies because of the decomposition of absorbent cotton.