Facile engineering of n-p-n In2O3-Co3O4-ZnO ternary: Influence of structure and optical band gap toward acetone detection

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 In₂O₃-Co₃O₄-CeO₂ (In-Co-Ce), In₂O₃-Co₃O₄-SnO₂ (In-Co-Sn), In₂O₃-Co₃O₄-ZnO (In-Co-Zn), and In₂O₃-Co₃O₄-ZrO₂ (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 (C₃H₆O) at 150 °C. These exceptional gas sensing characteristics are recognized by the improved interfacial synergy between the In₂O₃, Co₃O₄, 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 C₃H₆O 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 C₃H₆O. 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.