Detection of PPB-Level H₂S Concentrations in Exhaled Breath Using Au Nanosheet Sensors with Small Variability, High Selectivity, and Long-Term Stability

Abstract

The continuous monitoring of hydrogen sulfide (H 2 S) in exhaled breath enables the detection of health issues such as halitosis and gastrointestinal problems. However, H 2 S sensors with high selectivity and parts per billion-level detection capability, which are essential for breath analysis, and facile fabrication processes for their integration with other devices are lacking. In this study, we demonstrated Au nanosheet H 2 S sensors with high selectivity, ppblevel detection capability, and high uniformity by optimizing their fabrication processes: (1) insertion of titanium nitride (TiN) as an adhesion layer to prevent Au agglomeration on the oxide substrate and (2) N 2 annealing to improve nanosheet crystallinity. The fabricated Au nanosheets successfully detected H 2 S at concentrations as low as 5.6 ppb, and the estimated limit of detection was 0.5 ppb, which is superior to that of the human nose (8−13 ppb). In addition, the sensors detected H 2 S in the exhaled breath of simulated patients at concentrations as low as 175 ppb while showing high selectivity against interfering molecules, such as H 2 , alcohols, and humidity. Since Au nanosheets with uniform sensor characteristics enable easy device integration, the proposed sensor will be useful for facile health checkups based on breath analysis upon its integration into mobile devices.

Cobalt–Nitrogen Bonding for Triggering the Low-Power Dual Detection of NO2 and NH3 by Mixed-Valence Co2+ and Co3+

“…Most often, the sensitivity of gas sensors is determined by surface interactions between gas and sensing materials . These sensing materials include metals, metal oxides, metal chalcogenides, graphene derivatives, carbon nanotubes, black phosphorus (BP), perovskites, polymers, and composites . Among them, metal oxides, such as Co 3 O 4 , can sense gases with high performance due to the miniaturized dimensions, tailored morphology, and long operation time.…”

Ppb-Level Ammonia Sensor for Exhaled Breath Diagnosis Based on UV-DOAS Combined with Spectral Reconstruction Fitting Neural Network

“…Levels of such substances always correlate with the severity of specific diseases and are biomarkers for health disorders. Measuring these substances makes it possible to early identify and treat various diseases in the medical field. − In particular, ammonia (NH 3 ) in EB is used as a biomarker for screening and diagnosis of liver and kidney impairment. − Since kidney injury can indirectly affect liver function, leading to changes in NH 3 concentration in exhaled breath, the development of ultrasensitive online NH 3 sensor at parts per billion (ppb) level for detecting breath NH 3 is a matter of urgency.…”