The layered 2-D materials, such as molybdenum disulfide (MoS ₂ ), are among the most promising candidates for detecting H ₂ S gas at very low concentrations.

The stacking 2D materials, such as molybdenum disulfide (MoS₂), are among the most promising candidates for detecting H₂S gas. Herein, we designed a series of novel nanocomposites consisting of MoS₂ and ZnCo₂O₄. These materials were synthesized via a simple hydrothermal method. The microstructure and morphology of nanocomposites were studied by different characteristics such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy. These nanocomposites were used as gas sensors, and the highest response (6.6) toward 10 ppm of H₂S was detected by the gas sensor of MZCO-6 (having MoS₂ contents 0.060 g) among all other tested sensors. The response value (R_a/R_g) was almost three times that of pure ZnCo₂O₄ (R_a/R_g = 2). In addition, the sensor of MZCO-6 exposed good selectivity, short response/recovery time (12/28 s), long-term stability (28 days), and a low detection limit (0.5 ppm) toward H₂S gas at RT. The excellent performance of MZCO-6 may be attributed to some features of MoS₂, such as stack structure, higher BET and surface area and active sites, a synergistic effect, etc. This simple fabrication sensor provides a novel idea for detecting H₂S gas at RT.

Real-time sensing of hydrogen sulfide (H₂S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene Ti₃C₂T_x, Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and H₂S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Ti₃C₂T_x/NiCo₂O₄-based gas sensor detected the highest response (16) toward 10 ppm H₂S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Ti₃AlC₂, WS₂, and MoSe₂/NiCo₂O₄). The MXene Ti₃C₂T_x/NiCo₂O₄ sensor showed excellent responses, minimum limits of detection (0.1 ppm H₂S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward H₂S and butane were accredited to p–p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing H₂S and butane at the lowest concentration to prevent different gas-exposure-related diseases.

To take full advantage of lab-on-fiber technologies for gas sensing, we propose a reflective Fabry-Perot interferometer (FPI) CO ₂ gas sensor composed of the functional material (polyhexamethylene biguanide, PHMB) and a single-mode fiber (SMF)-hollow core capillary (HCC) structure. The theoretical analysis of the FPI cavity mode in the PHMB film is discussed. The experiment results show a maximum sensitivity of 286 pm/ppm in the low concentration region of 0-1000 ppm detection range and a high sensitivity of 6.88 pm/ppm in the atmosphere CO ₂ concentration range (200-600 ppm). The response time of the CO ₂ sensor is about 10 min. Repeated experiments show that the sensor has good sensing stability and a high selectivity for CO ₂ gas. In addition, the sensitivity of our CO ₂ sensor is stable to temperature changes. Moreover, the results of monitoring the real in-door atmosphere verify the repeatability and desirable sensing performance of our sensor. This reflective lab-on-fiber CO ₂ sensor has a concise structure, low cost, and high sensitivity possessing more possibilities in various and complex applications.