Indirectly monitoring halitosis via the detection of hydrogen sulfide (H2S) biomarkers using gas sensors is a newly emerging technique. However, such H2S sensors are required with critically high selectivity and sensitivity, as well as a ppb-level detection limit, which remains technologically challenging. To address such issues, here, we have developed highly sensitive and selective H2S sensors with NiO/WO3 nanoparticles (NPs), which have been synthesized by firstly hydrolyzing WO3 NPs and subsequently decorating with NiO NPs in a hydrothermal process. Theoretically, the NiO/WO3 NPs assist in forming a thicker electron depletion layer, adsorbing more oxygen species O2 – to oxidize H2S and finally release more electrons. Beneficially, 2.1 wt % NiO/WO3 NPs show high sensitivity to H2S (R a/R g = 15031 ± 1370 @ 10 ppm, 100 °C), which is 42.6-fold higher than that of the pristine WO3 NPs (R a/R g = 353 ± 5.6 @ 10 ppm, 100 °C). Further, the H2S sensor shows ppb-level detection limit (R a/R g = 4.95 ± 2.9 @ 0.05 ppm, 100 °C) and high selectivity. Practically, NiO/WO3 NP sensor prototype has been employed to detect the simulated exhaled halitosis compared with that of gas chromatography, revealing a close concentration of H2S. Our investigation offers an experimental base in future intelligent medical applications.

No abstract

Ammonia (NH 3 ) sensors proposed for the simultaneous exhalation diagnosis, environmental pollution monitoring, and industrial leakage alarm require high flexibility, selectivity, stability, humidity tolerance, and wide-concentration-range detection; however, technical challenges still remain. Herein, twistable and water-tolerant paper-based sensors integrated over surgical masks have been developed for NH 3 detection at room temperature, via decorating specially designed ternary nanocomposites (ternary-NCs) on the commercial filter paper. The NCs consist of a multiwalled carbon nanotube framework with a polypyrrole nanolayer and are further loaded with Pt nanodots. Benefiting from the synergy effect of ternary components, the ternary-NCs exhibit an ultrasensitive response to 5 ppb−60 v/v% NH 3 and present high selectivity confirmed by the theory calculations. Remarkably, the filter-paper-based sensors possess outstanding stability against twisting 0−1080°, along with excellent cuttability and foldability. Critically, such paper-based sensors can be integrated over surgical masks for simulated exhaled diagnosis and display superior water tolerance even being immersed in water for 24 h. Practically, the detecting accuracy of the filter-paper-based sensor toward the simulated exhaled NH 3 , environmental NH 3 pollution, and industrial NH 3 leakage is validated using ion chromatography.

Novel mesoporous NiO nanocuboids (M-NiO NCs) enriched with surface multichannel pathways have been achieved to sensitively detect 3H-2B biomarkers for real-time monitoring of Listeria monocytogenes.

The advanced PdCo NW sensors developed for the detection of hydrogen at a wide temperature range showed excellent low-temperature stability.

The newly emerged gas sensing detection of 3-hydroxy-2-butanone (3H-2B) biomarker is deemed as an effective avenue to indirectly monitor Listeria monocytogenes (LM). However, 3H-2B sensing materials requiring critically high sensitivity and selectivity, and ppblevel detection limit, remain challenging. Here, we report the advanced gas sensors built with bismuth vanadate microdecahedron (BiVO 4 MDCD) {010} facets selectively decorated with Pd nanoparticles (Pd NPs, Pd-{010}BiVO 4 MDCDs) for boosted detection of the 3H-2B biomarker. Meanwhile, BiVO 4 MDCDs with overall facets are randomly deposited with Pd NPs (Pd-BiVO 4 MDCDs). Comparatively, Pd-{010}BiVO 4 MDCD sensors show 1 order of magnitude higher response toward the 3H-2B biomarker at 200 °C. Further, Pd-{010}BiVO 4 MDCD sensors enable to detect as low as 0.2 ppm 3H-2B and show best selectivity and stability, and fastest response and recovery. Density functional theory calculations reveal a lower adsorption energy of 3H-2B onto Pd-{010}BiVO 4 MDCDs than those of pristine and Pd-BiVO 4 MDCDs. The extraordinary Pd-{010}BiVO 4 sensing performance is ascribed to the Pd NP-assisted synergetic effect of the preferential adsorption of 3H-2B target molecules, accumulated sensing agent of ionic oxygen species, and concentrated catalysts on the {010} facets. This strategy offers rapid and noninvasive detection of LMs and is thus of great potential in the upcoming Internet of Things.

No abstract

Hydrogen sensing simultaneously endowed with fast response, high sensitivity and selectivity are highly desired in detecting hydrogen leakages such as in those hydrogen-driven vehicles and space rockets. Here, hydrogen sensing...