This study reports the synthesis of CdS/WS2 composites via a green and ultra-low-cost hydrothermal method. By controlling the relative mass ratio between WS2 and CdS, an n–n type CdS/WS2 heterostructure, with excellent NH3 gas-sensitive properties, was developed and investigated at room temperature. Compared with pristine WS2 and CdS, the CdS/WS2-40%wt composite exhibited excellent selectivity of more than 4 orders of magnitude for sensing NH3, a very short recovery time of 3 s, and ultrahigh selectivity at room temperature. The large specific surface area of the CdS/WS2 composite increased the active sites for the gas-sensitive reaction. Additionally, the 2D morphology of CdS/WS2 and the heterojunction formed between WS2 and CdS contributed to the improved performance. Anti-humidity interference tests showed that the CdS/WS2 sample remained stable under real-time monitoring of NH3 at different ambient humidity values. This study paves the way for designing high-performance gas sensors operating at room temperature.

Structures and performances from nature provide ideas for humans to deal with energy and environmental crisis. Inspired from natural structures, bacterial cellulose nanofibers with a fine-meshed network were selected as the raw materials to design acetone gas sensors. Here, Fe 2 O 3 nanorods were successfully introduced on the surface of carbon nanofibers by a feasible hydrothermal catalytic carbonization at 120 °C. Lots of heterojunctions between the bacterial cellulose carbon nanofiber and the Fe 2 O 3 nanorod were constructed, resulting in high gas-sensing properties to acetone vapor. At room temperature, the response of Fe 2 O 3 /bacterial cellulose carbon nanofiber composite (BCCF−Fe 2 O 3 ) to 5 ppm of acetone reached 2060% within 10 s. BCCF−Fe 2 O 3 showed high sensitivity and selectivity, ppb-level detection limit (100.7 ppb), nice long-term stability (30 days), low energy consumption (1.4 μW), and good anti-humidity performance in acetone detection. To our surprise, BCCF− Fe 2 O 3 had realized ultrasensitive exhaled acetone detection within 16 s, proving an effective and inexpensive strategy for diabetic noninvasive diagnosis.

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