Ultrahigh sensitivity and selectivity chlorine gas sensing of In₂O₃ hollow microtubules by bio-template method with degreasing cotton

A simple two-stage procedure of immersion-calcination method has been developed for preparing In₂O₃ hollow microtubules by using degreasing cotton as soft bio-templates. The morphological feature was characterized as hollow microtubules with the range of 50–70 μm in length, 5–6 μm in width, and about 1 μm in thickness. The Cl₂ sensing properties were remarkably enhanced in sensitivity and selectivity for In₂O₃ hollow microtubules. The gas response (R_gas/R_air) of the In₂O₃ hollow microtubules sensor was 1051 to 10 ppm Cl₂ at 200 °C, which was 25 times higher than In₂O₃ particles. Such outstanding gas sensing performance was ascribed to the hollow morphology, which revealed high specific surface area, abundant oxygen vacancies and low band gap. The gas sensing mechanism was deduced that Cl₂ molecules are directly adsorbed on the metal oxide surface and oxygen vacancies.