Synthesis of single crystalline In2O3 octahedra for the selective detection of NO2 and H2 at trace levelsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6tc03218d

• Main Authors: Roso, Sergio, Bittencourt, Carla, Umek, Polona, González, Oriol, Güell, Frank, Urakawa, Atsushi, Llobet, Eduard
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c6tc03218d

Single crystalline indium oxide (In 2 O 3 ) octahedra have been synthesized by means of a vapor phase transport method at high temperature. The resulting material has been characterized by FE-SEM, HR-TEM, XRD, XPS and PL. The gas sensing properties of this material against oxidizing and reducing gases have been examined and the conditions for selectively detecting such gases have been established. A high response towards NO 2 has been obtained at a relatively low optimal operating temperature ( i.e. , 130 °C) and even at room temperature. The fact that the response of the nanomaterial is more than two orders of magnitude higher for NO 2 than for H 2 , even in the presence of ambient moisture, makes it very promising for the selective detection of oxidizing species (at ppb levels) under real ambient conditions. The addition of noble metal nanoparticles (Pt and Pd) combined with an increase in the operating temperature ( i.e. , 250 °C) significantly increases H 2 sensitivity and dramatically decreases the response to NO 2 . However, in this case, the presence of humidity negatively affects the response to H 2 . The sensing mechanisms are introduced and discussed. Selective detection of oxidising or reducing species is achieved via selecting operating temperatures and metal loading of single crystalline In 2 O 3 octahedra.