Assembly of n-p In 2 O 3 -Co 3 O 4 heterostructures and their surface and structural analyses towards trace level detection of acetone

The accurate identification and quantification of volatile organic compounds is imperative in addressing environmental concerns, medical diagnostics, and industrial safety. Thus, the current study focuses on the fabrication of heterostructures based on In 2 O 3 –p-type metal oxides (i.e., In 2 O 3 -CuO, In 2 O 3 -Co 3 O 4, In 2 O 3 -Mn 3 O 4, and In 2 O 3 -NiO) utilizing a hydrothermal approach. Various techniques were utilized to characterize the heterostructures in detail. Among the tested sensors towards various analytes, the In 2 O 3 -Co 3 O 4 -based sensor disclosed a better response towards 2.3 ppm acetone (C 3 H 6 O) at 100 °C. The sensor also demonstrated outstanding sensitivity (2.38 ppm −1 ), an extremely low limit of detection (0.142 ppb), humidity resistance, and fast response-recovery time. The improved C 3 H 6 O gas sensing performance could be associated with the enhanced interfacial synergy in the In 2 O 3 -Co 3 O 4 heterostructure and the creation of oxygen vacancies, a reduced band gap, and a higher specific surface area revealing additional active sites to enable adequate gas molecules adsorption. The work further discusses the theoretical procedure that was evaluated using a crystal field theory to determine the strength of cobalt ions and to identify which electronic state is mostly exploited to form a possible In 2 O 3 -Co 3 O 4 heterostructure. These results provide a viable pathway to regulate the sensing characteristics of C 3 H 6 O at a low concentration for practical health assessment.