Highly Sensitive Room-Temperature Detection of Ammonia in the Breath of Kidney Disease Patients Using Fe 2 Mo 3 O 8 /MoO 2 @MoS 2 Nanocomposite Gas Sensor.

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.