Design of a Janus-Type p-NiO/n-ZnO Heterostructure Enabling Enhanced Transducer Function for Highly Sensitive Acetone Detection.

The construction of a p-n semiconductor heterostructure has been recognized as an effective strategy to achieve high-performance gas sensing. However, the opposite resistance change (signal transducer function) behaviors of p-type and n-type sensing materials in response to the same target gas significantly limit the overall transducer function within the p-n heterostructure. In this study, we designed p-NiO/n-ZnO Janus hollow nanofibers that feature an ordered built-in electric field, enabling directed charge separation and confinement of the conduction path to the ZnO outer layer. The design of the Janus architecture effectively mitigates the conflicting electrical responses of p-NiO and n-ZnO to acetone gas. Therefore, the sensors exhibit a response that is threefold higher than mixed NiO/ZnO nanofibers and sevenfold higher than pristine ZnO nanofibers, illustrating the pronounced transducer enhancement enabled by the Janus configuration. Furthermore, by precisely controlling the ZnO shell thickness, we demonstrate a Debye-length-regulated gas-sensing amplification mechanism. This work establishes a general strategy for nanoscale heterostructure engineering, paving the way for the development of high-performance MOS gas sensors with superior signal transducer function.