Highly Sensitive Room‐Temperature Detection of Ammonia in the Breath of Kidney Disease Patients Using Fe2Mo3O8/MoO2@MoS2 Nanocomposite Gas Sensor

A novel Fe₂Mo₃O₈/MoO₂@MoS₂ nanocomposite is synthesized for extremely sensitive detection of NH₃ in the breath of kidney disease patients at room temperature. Compared to MoS₂, α-Fe₂O₃/MoS₂, and MoO₂@MoS₂, it shows the optimal gas-sensing performance by optimizing the formation of Fe₂Mo₃O₈ at 900 °C. The annealed Fe₂Mo₃O₈/MoO₂@MoS₂ nanocomposite (Fe₂Mo₃O₈/MoO₂@MoS₂-900 °C) sensor demonstrates a remarkably high selectivity of NH₃ with a response of 875% to 30 ppm NH₃ and an ultralow detection limit of 3.7 ppb. This sensor demonstrates excellent linearity, repeatability, and long-term stability. Furthermore, it effectively differentiates between patients at varying stages of kidney disease through quantitative NH₃ measurements. The sensing mechanism is elucidated through the analysis of alterations in X-ray photoelectron spectroscopy (XPS) signals, which is supported by density functional theory (DFT) calculations illustrating the NH₃ adsorption and oxidation pathways and their effects on charge transfer, resulting in the conductivity change as the sensing signal. The excellent performance is mainly attributed to the heterojunction among MoS₂, MoO₂, and Fe₂Mo₃O₈ and the exceptional adsorption and catalytic activity of Fe₂Mo₃O₈/MoO₂@MoS₂-900 °C for NH₃. This research presents a promising new material optimized for detecting NH₃ in exhaled breath and a new strategy for the early diagnosis and management of kidney disease.