NO(2) sensing properties of WO(3)-decorated In(2)O(3) nanorods and In(2)O(3)-decorated WO(3) nanorods

In(2)O(3) nanoparticle (NP)-decorated WO(3) nanorods (NRs) were prepared using sol–gel and hydrothermal methods. The In(2)O(3) NRs and WO(3) NPs were crystalline. WO(3) NP-decorated In(2)O(3) NRs were also prepared using thermal evaporation and hydrothermal methods. The NO(2) sensing performance of the In(2)O(3) NP-decorated WO(3) NR sensor toward NO(2) was compared to that of the WO(3) NP-decorated In(2)O(3) NR sensor. The former showed a high response to NO(2) due to a significant reduction of the conduction channel width upon exposure to NO(2). In contrast, the latter showed a far less pronounced response due to limited reduction of the conduction channel width upon exposure to NO(2). When the sensors were exposed to a reducing gas instead of an oxidizing gas (NO(2)), the situation was reversed, i.e., the WO(3) NP-decorated In(2)O(3) NR exhibited a stronger response to the reducing gas than the In(2)O(3) NP-decorated WO(3) NR sensor. Thus, a semiconducting metal oxide (SMO) with a smaller work function must be used as the decorating material in decorated heterostructured SMO sensors for detection of oxidizing gases. The In(2)O(3) NP-decorated WO(3) NR sensor showed higher selectivity for NO(2) compared to other gases, including reducing gases and other oxidizing gases, as well as showed high sensitivity to NO(2).