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To enhance the poor sensing capabilities of traditional p-type metal oxide semiconductor sensors, a novel gas sensor was designed with Co3O4/CuO heterostructure modified by glutathione (GSH)-reduced gold (Au), which was characterized by different analyses. The experiments showed that the 0.5 wt.% Au–Co3O4/CuO gas sensor exhibited excellent sensing performance with a response value of up to 28.3 for 3 ppm NO2 at a relatively low operating temperature (1 0 0 ∘ C). Besides, it demonstrated a linear relationship between detection concentration and response value, displayed good selectivity for NO2, showcased stability and exhibited repeatability. Moreover, the sensor revealed the ability to resist humidity at the optimal temperature. Finally, we proposed a gas sensing mechanism to explain the enhanced NO2 detection performance of the sensor, attributed to the heterojunction structure between Co3O4/CuO and the catalytic properties of Au. This led to an increase in adsorbed oxygen, as confirmed by XPS characterization. Therefore, the 0.5 wt.% Au–Co3O4/CuO ternary nanocomposite gas sensor is deemed to be a highly effective sensing material that can be utilized to detect NO2 gas in real-life applications. Au-Co3O4/CuO ternary nanocomposites were successfully fabricated by a one-step hydrothermal method with a subsequent two-step sintering method. The experiments showed that the 0.5 wt% Co3O4/CuO gas sensor exhibited excellent sensing performance with a response value of up to 28.3 for 3 ppm NO2 at a relatively low operating temperature (100∘C). Thus, it is deemed to be a highly effective sensing material that can be utilized to detect NO2 gas for real-life applications. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO2) is a major pollutant that poses significant risks to sustainable human life. As a result, a growing focus has been placed on the development of highly selective and sensitive gas sensors for NO2. Traditional cutting-edge non-organic NO2 gas detectors often necessitate stringent production conditions and potentially harmful materials, which are not environmentally friendly, and these shortcomings have limited their widespread practical use. To overcome these challenges, we synthesized self-assembled peptide nanotubes (SPNTs) through a molecular self-assembly process. The SPNTs were then combined with SnO2 in varying proportions to construct NO2 gas sensors. The design of this sensor ensured efficient electron transfer and leverage the extensive surface area of the SPNTs for enhanced gas adsorption and the effective dispersion of SnO2 nanoparticles. Notably, the performance of the sensor, including its sensitivity, response time, and recovery rate, along with a lower detection threshold, could be finely tuned by varying the SPNTs content. This approach illustrated the potential of bioinspired methodologies, using peptide self-assemblies, to develop integrated sensors for pollutant detection, providing a significant development in environmentally conscious sensor technology. [ABSTRACT FROM AUTHOR]

The particle sizes of sensitive material have significant influence on the gas property. We reported at room temperature NO2 gas sensor using SnO2 particles of various size to investigate their impact on sensing performance in a wide concentration range, even at ppb level. Results showed that the gas response increases with the decrease of particle size, mainly attributed to the larger specific surface area of small size to absorb more target gas. The SnO2-40 nm exhibited the highest response to low concentrations of NO2 gas, reaching a value of 106 at 5 ppm, and it can detect trace amounts of NO2 with a detection limit of 100 ppb. The mechanism of gas sensing property is discussed, highlighting the relationship between small size and large specific surface area. This paper provides useful guideline for fabrication high-performance gas sensor with optimized particle sizes. [ABSTRACT FROM AUTHOR]

P-type spinel cobalt oxide (Co3O4) is widely used in the design and manufacture of chemical-resistant gas sensors due to its large specific surface area and high oxygen content. However, most current p-type Co3O4-based sensors exhibit weaknesses in gas susceptibility and high working temperature towards NO2 detection. In this work, we report a highly sensitive NO2 gas sensor based on Au-functionalized Co3O4 nanospheres. The Co3O4 nanospheres were fabricated by a hydrothermal method and then acted as a precursor for loading Au nanoclusters using glutathione (GSH) as a reducing reagent to obtain the composite material. The characterization results demonstrate that the introduction of Au doping significantly improved the chemical bonding state and microstructure of the composite material's surface. Compared to a pure Co3O4 sensor, the Au/Co3O4 nanohybrid with a weight percentage of 0.25% exhibited the highest response of 23.6 towards 20 ppm NO2 at 120 °C. Further investigation indicates that it also has good humidity resistance, preferable repeatablity and adequate linearity. The gas sensing performance can be predominantly attributed to the spherical structure of the composite materials, modulation of the nano-Schottky junction, and the special chemical properties of Au nanoclusters. [ABSTRACT FROM AUTHOR]

Cellulose nanofiber (CNF), a natural polymer material with a high specific surface area, is a potential candidate for gas sensors. Here, we report Au/SnO2 composites with excellent performance synthesized by a chemical precipitation method based on CNF-assisted synthesis, and a series of Au/SnO2 composites were prepared by adjusting the Au content. The sensitivity of the 1.5 wt.% Au/SnO2 sensor to a low concentration of 1 ppm NO2 was 53, nearly 17 times higher than that of pure SnO2 synthesized by CNF, under ultraviolet (UV) irradiation at a wavelength of 365 nm. The crystal structure of the composite was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), revealing that the composites had high crystallinity and particles reaching the nanoscale. Further experimental data showed that the CNF-assisted synthesis Au/SnO2 sensors had good selectivity, repeatability, and stability. Additionally, the sensor is able to maintain its excellent gas sensing performance even under varying humidity conditions. [ABSTRACT FROM AUTHOR]

Cellulose is a common natural polymer, and the surface of the nanocellulose has a large number of hydroxyl groups, which is possible used to precipitate metal salts to obtain the precursors, and then calcine to get the corresponding metal oxides. In this paper, tin dioxide (SnO2) nanoparticles were prepared with different amounts of nanocellulose by a low-temperature hydrothermal method (60°C) followed by calcination. The obtained material was verified to be impurity-free SnO2 nanoparticles by various types of physical phase analysis and morphological characterization. The SnO2 nanoparticles obtained from 50 mg nanocellulose exhibited a significantly improved sensing performance, and the response toward SO2 at 1 ppm was 4.68. In addition, multiple performance tests were conducted on the obtained gas sensor, and it was finally found to have a good gas sensitivity and an excellent selectivity. The repeatability and stability also presented preferable results. Additionally, the sensing mechanism was discussed. The prepared SnO2 sensor is promising for the detection of SO2 due to its high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

ZnSnO3 microspheres was compounded by hydrothermal method with sodium alginate (SA) as a crystal growth modifier, and the Au nanoparticles were decorated on the surface of ZnSnO3 microspheres by simple solution method and heat treatment process. The structure and morphology of the prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Under ultraviolet (UV) irradiation, the 0.2wt% Au/ZnSnO3@4g/L SA sensor could detect HCHO and reached a good response of 18.8 at 20 ppm, which was three times higher than the ZnSnO3 in the absence of Au. This sensor also performed an outstanding linearity within 5–20 ppm HCHO and satisfied repeatability. Moreover, the possible mechanism of the influence of Au on gas sensitivity is also proposed. [ABSTRACT FROM AUTHOR]

Since cobalt-containing spinel oxides have good prospects for the detection of toxic gases, they also have great potential for applications in the field of gas sensors. However, ZnCo2O4 -based gas sensors have the disadvantages of low response values and poor selectivity in formaldehyde detection. In this study, we attempted to prepare formaldehyde gas sensors by varying the addition of sodium citrate for hydrothermal synthesis of ZnCo2O4. During the fabrication process, it was found that an appropriate amount of sodium citrate content could produce ZnO on the surface of ZnCo2O4 , and that the gas sensitivity of ZnO-ZnCo2O4 to formaldehyde was better compared to that of pure ZnCo2O4. The sensor has a response rate of 17 at 20 ppm formaldehyde at 200°C. It also has good selectivity, repeatability, and stability. These results can provide foundational knowledge for the implementation of spinel oxide materials in the field of gas sensors. [ABSTRACT FROM AUTHOR]

This present study reported a high-performance gas sensor, based on In2O3/ZnO composite material modified by polypeptides, with a high sensibility to NO2, where the In2O3/ZnO composite was prepared by a one-step hydrothermal method. A series of results through material characterization technologies showed the addition of polypeptides can effectively change the morphology and size of In2O3/ZnO crystals, and effectively improve the sensing performance of the gas sensors. Due to the single shape and small size, In2O3/ZnO composite modified by polypeptides increased the active sites on the surface. At the same time, the gas sensing properties of four different ratios of polypeptide-modified In2O3/ZnO gas sensors were tested. It was found that the In2O3/ZnO-10 material showed the highest response, excellent selectivity, and good stability at room temperature under UV light. In addition, the response of the In2O3/ZnO-10 gas sensor showed a strong linear relationship with the NO2 gas concentration. When the NO2 gas concentration was 20 ppm, the response time was as quick as 19 s, and the recovery time was 57 s. Finally, based on the obtained experimental characterization results and energy band structure analysis, a possible gas sensing mechanism is proposed. [ABSTRACT FROM AUTHOR]