P-N Heterojunction formation: Metal Sulfide@Metal Oxide Chemiresistor for ppb H2S Detection from Exhaled Breath and Food Spoilage at Flexible Room Temperature.

The development of a portable, low-cost sensor capable of accurately detecting H2S gas in exhaled human breath at room temperature is highly anticipated in the fields of human health assessment and food spoilage evaluation. However, achieving outstanding gas sensing performance and applicability for flexible room-temperature operation with parts per billion H2S gas sensors still poses technical challenges. To address this issue, this study involves the in situ growth of MoS2 nanosheets on the surface of In2O3 fibers to construct a p-n heterojunction. The In2O3@MoS2-2 sensor exhibits a high response of 460.61 to 50 ppm of H2S gas at room temperature, which is 19.5 times higher than that of the pure In2O3 sensor and 322.1 times higher than that of pure MoS2. The In2O3@MoS2-2 also demonstrates a minimum detection limit of 3 ppb and maintains a stable response to H2S gas even after being bent 50 times at a 60° angle. These exceptional gas sensing properties are attributed to the increase in oxygen vacancies and chemisorbed oxygen on In2O3@MoS2-2 nanofibers as well as the formation of the p-n heterojunction, which modulates the heterojunction barrier. Furthermore, in this study, we successfully applied the In2O3@MoS2-2 sensor for oral disease and detection of food spoilage conditions, thereby providing new design insights for the development of portable exhaled gas sensors and gas sensors for evaluating food spoilage conditions at room temperature.

Edge-enriched MoS2 nanosheets modified porous nanosheet-assembled hierarchical In2O3 microflowers for room temperature detection of NO2 with ultrahigh sensitivity and selectivity.

Nitrogen dioxide (NO2) is one of the most hazardous toxic pollutants to human health and the environment. However, deficiencies of low sensitivity and poor selectivity at room temperature (RT) restrain the application of NO2 sensors. Herein, the edge-enriched MoS2 nanosheets modified porous nanosheets-assembled three-dimensional (3D) In2O3 microflowers have been synthesized to improve the sensitivity and selectivity of NO2 detection at RT. The results show that the In2O3/MoS2 composite sensor exhibits a response as high as 343.09-5 ppm NO2, which is 309 and 72.5 times higher than the sensors based on the pristine MoS2 and In2O3. The composite sensor also shows short recovery time (37 s), excellent repeatability and long-term stability. Furthermore, the response of the In2O3/MoS2 sensor to NO2 is at least 30 times higher than that of other gases, proving the ultrahigh selectivity of the sensor. The outstanding sensing performance of the In2O3/MoS2 sensor can be attributed to the synergistic effect and abundant active sites originating from the p-n heterojunction, exposed edge structures and the designed 2D/3D hybrid structure. The strategy proposed herein is expected to provide a useful reference for the development of high-performance RT NO2 sensors.