2D/0D S-WSe2@Fe3O4 Heterostructure: Synergistic Enhancement of Room-Temperature Ammonia Sensing Performance through Lattice Doping and Interfacial Charge

Room-temperature NH3 detection is critical for environmental monitoring, industrial safety, and medical diagnostics; however, achieving sensors that simultaneously deliver high sensitivity, fast response, and good selectivity remains a significant challenge. In this work, we synthesize a series of 2D/0D heterostructures composed of S-doped WSe2 decorated with Fe3O4 nanoparticles via a facile annealing and self-assembly process. Sulfur doping introduces abundant active sites into the WSe2 lattice, while the incorporation of Fe3O4 nanoparticles forms numerous p−n heterojunctions at the interfaces, synergistically enhancing the NH3 sensing performance. The composite with 10 wt % Fe3O4 achieves a response of 154.34% toward 100 ppm NH3 at 25 °C and 45% relative humidity6.32 times higher than that of pristine WSe2. The sensor exhibits response and recovery times of 20.6 s and 113.5 s, respectively, with a detection limit as low as 459.41 ppb. It also demonstrates excellent selectivity against various interfering gases and retains 88.9% of its initial response after 40 days. Density functional theory calculations reveal that S doping reduces the work function of WSe2 from 4.696 to 4.518 eV, facilitating charge transfer, while the p−n heterojunctions promote spatial charge separation and effective carrier modulation. Collectively, these findings demonstrate that combining lattice doping with heterojunction engineering offers a promising strategy for developing high-performance, room-temperature NH3 sensors suitable for applications in breath analysis, environmental monitoring, and industrial safety.