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Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V2O5 nanosheets operating at room temperature. The small thickness and porosity of the V2O5 nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH3) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V2O5 is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device’s performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chain.

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The Ag/Pd–ZnO nanoplates exhibit 47 folds enhancement response to hydrogen gas. This demonstrates the catalyst phenomenon of Ag/Pd nanoparticles on the hydrogen sensing performance.

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We have investigated the behavior of GeO2 at the temperature of 300 K and the pressure from 0 to 100GPa by using the molecular dynamics simulation (the model with 5499 atoms). The results show that the Ge-Ge, Ge-O bond distance increase but O-O bond distance decreases when increasing the pressure. We find that the peak splitting of Ge-Ge at high pressure corresponds with the Ge-O-Ge and O-Ge-O bond angles. We also find that O-Ge-O bond angle decreases, and Ge-O-Ge bond angle increases with pressure. The core-sharing-bond is major at ambient pressure, but fractions of edge and face-sharing-bonds increase with pressure.