No abstract

Zinc oxide (ZnO) nanoparticles modified with uniformly dispersed silver (Ag) nanoparticles (Ag-ZnO) were prepared in one step by calcining precursor electrospun nanofibers. The molar ratios of Ag to Zn in the precursor solutions were 0, 1, 3, and 5%. The microstructure of the Ag-ZnO sensor was characterized by scanning electron microscopy and transmission electron microscopy. The existence of metallic Ag was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy, and the gas sensing properties of Ag-ZnO were investigated. The results showed that the ZnO nanoparticles after Ag nanoparticles modification exhibited excellent gas sensing performance to ethanol and hydrogen sulfide (H 2 S). The optimal working temperature of the Ag-ZnO sensor significantly decreased for ethanol compared with pure ZnO. The 3% Ag-ZnO sensor exhibited the fastest response to ethanol with the response/recovery times of only 5 and 9 s, respectively. However, all the Ag-ZnO-based gas sensors showed a high response value to H 2 S, especially the 3% Ag-ZnO gas sensor exhibited a maximum response value of 298 at 10 ppm H 2 S. These results could be attributed to the spillover effect and electron sensitization effect of Ag nanoparticles, which led to more absorbed oxygen species and active sites, and thereby can further enhance the gas sensing performances of ZnO-based gas sensors.

No abstract

Light‐driven semiconductor gas sensors are attracting considerable research attention in the recent past. Among them, silver phosphate (Ag3PO4) material has excellent photocatalytic activities due to its high separation efficiency of electron‐hole pairs under visible light. Inspired by the above point of view, in this study, Ag3PO4 nanoparticles were successfully synthesized via simple precipitation method. The microstructure of Ag3PO4 nanoparticles were characterized by scanning electron microscopy (SEM). The crystalline phase and the composition of the elements and the chemical bonding states of the material were characterized by X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS), respectively. Then the gas sensing performance of Ag3PO4 to ammonia (NH3) was systematically explored at room temperature under the illumination of LED lamp and the same was compared with the dark condition as well. Interestingly, the response value to NH3 under LED lamp was 30 % higher than that of dark condition and the detection limit was found to be as low as 10 ppm at room temperature. This can be ascribed to the generation of more oxygen species under visible light, which benefitted for enhancing the gas sensing performance of the sensor. Surprisingly, Ag3PO4 sensor exhibited superior selectivity to NH3 under mixed target gases, which can be attributed to the lone pair electrons of NH3 that tend to coordinate the empty orbitals of silver atom.

No abstract