Self-powered RT dual-gas sensing of NH3 and C7H8 using a ZnO nanorods/carbon dots/PEDOT:PSS heterojunction

A zero-bias ZnO NRs/NPCDs/PEDOT:PSS sensor detects NH 3 and C 7 H 8 at room temperature. • N/P co-doped carbon dot-sensitized ZnO NRs exhibit superior dual-gas sensing performance. • Wireless signal transmission enables real-time monitoring on mobile and computer terminals. Conventional gas sensors often rely on external heating sources or high operating voltages, whereas many self-powered alternatives still suffer from complex materials and fabrication processes. Herein, we demonstrate a structurally simplified, low-cost, self-powered heterojunction device capable of detecting ammonia (NH 3 ) and toluene (C 7 H 8 ) at room temperature (RT) and under zero-bias operation. The device is constructed by integrating carbon-dot (CD)-sensitized, vertically aligned ZnO nanorod arrays with a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) hole-transport layer, thereby forming an organic–inorganic p-n heterojunction. XRD, SEM, TEM, XPS, FTIR, PL, UV–vis and BET analyses confirm the formation of the CD-sensitized ZnO nanorod arrays and clarify the roles of the microstructure, surface states, and interfacial charge transfer in gas sensing. The built-in electric field promotes carrier separation, enabling zero-bias gas sensing. Elemental doping of the CDs shows that nitrogen/phosphorus co-doped CD (NPCD) modification leads to a superior dual-gas response, with the ZnO NRs/NPCDs200/PEDOT:PSS device exhibiting responses of 489% and 454% toward 100 ppm NH 3 and C 7 H 8 , respectively, outperforming the P-doped and N-doped CD-modified counterparts. Repeated cycling tests further demonstrate stable response-recovery behavior, with corresponding responses of approximately 418% and 339% toward 10 ppm NH 3 and C 7 H 8 , respectively, confirming good repeatability and cycling stability for dual-gas detection. Wireless signal transmission to mobile and computer terminals via self-developed software further highlights its potential for IoT-based remote monitoring. These results establish a practical material-and-device strategy for developing low-power, dual-gas sensors operable under ambient conditions. Download: Download high-res image (155KB) Download: Download full-size image