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

Abstract A novel Fe 2 Mo 3 O 8 /MoO 2 @MoS 2 nanocomposite is synthesized for extremely sensitive detection of NH 3 in the breath of kidney disease patients at room temperature. Compared to MoS 2 , α‐Fe 2 O 3 /MoS 2 , and MoO 2 @MoS 2 , it shows the optimal gas‐sensing performance by optimizing the formation of Fe 2 Mo 3 O 8 at 900 °C. The annealed Fe 2 Mo 3 O 8 /MoO 2 @MoS 2 nanocomposite (Fe 2 Mo 3 O 8 /MoO 2 @MoS 2 ‐900 °C) sensor demonstrates a remarkably high selectivity of NH 3 with a response of 875% to 30 ppm NH 3 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 NH 3 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 NH 3 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 MoS 2 , MoO 2 , and Fe 2 Mo 3 O 8 and the exceptional adsorption and catalytic activity of Fe 2 Mo 3 O 8 /MoO 2 @MoS 2 ‐900 °C for NH 3 . This research presents a promising new material optimized for detecting NH 3 in exhaled breath and a new strategy for the early diagnosis and management of kidney disease.