Facile engineering of n-p-n In2O3-Co3O4-ZnO ternary: Influence of structure and optical band gap toward acetone detection
Katlego L. Morulane, Zamaswazi P. Tshabalala, H.C. Swart, David E. Motaung
Abstract
Acetone gas monitoring and detection must be done fast and precisely to preserve air quality and detect diabetes non-invasively. Thus, herein, we report on the fabrication of various n-p-n ternary structures of In 2 O 3 -Co 3 O 4 -CeO 2 (In-Co-Ce), In 2 O 3 -Co 3 O 4 -SnO 2 (In-Co-Sn), In 2 O 3 -Co 3 O 4 -ZnO (In-Co-Zn), and In 2 O 3 -Co 3 O 4 -ZrO 2 (In-Co-Zr) using a hydrothermal approach. Structural disclosed the formation of ternary structures. Comparing the performance of the tested In-Co-Ce, In-Co-Sn, In-Co-Zn, and In-Co-Zr sensors, the In-Co-Zn sensor displayed n-type characteristics with excellent sensitivity, selectivity, and reliable stability to acetone (C 3 H 6 O) at 150 °C. These exceptional gas sensing characteristics are recognized by the improved interfacial synergy between the In 2 O 3 , Co 3 O 4 , and ZnO, which enhanced the electrical conductivity and resulted in better sensing performance. Furthermore, the improved oxygen vacancies and establishment of the n-p-n heterojunction modulated the heterojunction barrier. The higher BET surface area of In-Co-Zn, consisting of a large pore diameter, enabled the gas molecules to penetrate and interact with the sensing surface, leading to improved sensing. The fabricated In-Co-Zn ternary structure exhibited a reduced band gap compared to other ternary nanostructures, making it minimal for capturing electrons by C 3 H 6 O in the conduction band. The molecular orbital diagram of ZnO was used to justify the improved sensing performance of In-Co-Zn ternary structures toward C 3 H 6 O. Therefore, the engineering of n-p-n In-Co-Zn ternary structures provided a facile approach for the detection of acetone at low ppm levels. • n-p In 2 O 3 -Co 3 O 4 incorporated with n-type SMOs was synthesized using a hydrothermal approach. • The integrated n-p-n In-Co-Zn-based sensor responded more to 2.3 ppm acetone at 150 °C. • In-Co-Zn sensor showed limit detection of 100 ppb and sensitivity of 0.14 ppm −1 to acetone. • The sensor demonstrated enhanced response towards acetone in relative humidity at 150°C.