ABSTRACT
In this work, hollow spherical Pt-loaded WO3/ZnO heterostructured composites were prepared by a chemical liquid phase synthesis method. The morphology, crystal structure and components of the composites were characterized by SEM, TEM, XRD, XPS, etc. The sensing performance for various gases was also tested. Compared with the pristine WO3 (S = 44@225 °C, 50 ppm) gas sensor, the gas sensor that is functionalized with 1 wt% Pt and 0.5 mmol ZnO (1Pt/WZ-2) has a high response of 842-50 ppm at a relatively low temperature of 100 °C for TEA, with a quick response/recovery time of 34/120 s, a lower detection limit of 50 ppb, and good selectivity and moisture resistance. This study provides a highly efficient synthesis method of composite materials for TEA gas detection and the sensitivity mechanism is also discussed in detail.
ABSTRACT
In recent years, metal-organic framework (MOF) derivatives have gradually become ideal materials for gas sensors due to their controllable composition, diverse structures and open metal sites. In this research, a simplified hydrothermal method was applied to successfully prepare MOF-derived α-Fe2O3 spindles, and an in situ reduction method was then utilized to deposit Pt, Pd and PtPd bimetallic nanoparticles (NPs) on the α-Fe2O3 spindles. The effects of noble metals Pt, Pd and PtPd on the gas-sensing properties of Fe2O3 were systematically examined. The PtPd/α-Fe2O3 sensor has enhanced gas-sensing performance for triethylamine (TEA), especially at PtPd content of 1.5 wt% and mass ratio of Pt : Pd = 90 : 10, where the response of the sensor to 100 ppm TEA at a lower temperature of 150 °C is 442, which is 34 times higher than that of the original α-Fe2O3 (response of 13). Additionally, the sensor demonstrated improved response/recovery properties and very respectable selectivity, repeatability, long-term stability within 30 days and lower detection limit (500 ppb) at 150 °C. Combining the results of XPS and O2-TPD, the enhanced gas-sensing properties of PtPd bimetallic-modified α-Fe2O3 over monometallic (Pt or Pd) modified α-Fe2O3 were analyzed, which can be attributed to the chemical and electronic sensitization of noble metals and the synergistic effect of the PtPd bimetallic NPs, resulting in more surface defects and enhanced oxygen adsorption capacity of the sensing material. This work provided an effective gas-sensing material for the low-temperature detection and analysis of triethylamine gas.
ABSTRACT
In this study, a straightforward two-step hydrothermal process was used to synthesize Fe-doped NiO nanomaterials. A number of characterization approaches were employed to explore the structure and morphology of the synthesized Fe-doped NiO. The as-prepared samples were multi-layered flower-like structures formed by nanoparticles, according to scanning electron microscopy and transmission electron microscopy studies. The findings of the study on gas sensing performance showed that the response of the 1.5 at % Fe-NiO sensor was nearly 100 times greater than that of the pure NiO sensor, and the lower limit of detection was greatly decreased (50 ppb). The 1.5 at % Fe-NiO sensor exhibited superior sensing performance for n-butanol. The incorporation of an appropriate amount of Fe into the NiO lattice modified the carrier concentration, which is the primary cause of the increased sensor performance of an appropriate amount of Fe-doped NiO. In addition, the density functional theory calculation method based on the first-principles theory was used to study the adsorption performance and electronic behavior of pure NiO and 1.5 at % Fe-NiO for n-butanol. The calculated results were consistent with the experimental results.
ABSTRACT
In this work, core-shell AuPd nanoparticles (NPs) sensitized Co3O4/ZnO@ZnO ellipsoid nanoparticles was successfully synthesized via a simple liquid phase synthesis method. SEM and TEM characterization results showed that the as-prepared samples have core-shell ellipsoid morphology and the size of the nanoparticles were uniform. Systematic gas sensing characterization was carried out to obtain the gas sensing property of AuPd NPs decorated Co3O4/ZnO@ZnO. It was found that the gas sensing property could be significantly enhanced after noble metal decoration with Au, Pd and AuPd NPs, respectively. The optimal gas sensing performance was achieved by AuPd NPs functionalized Co3O4/ZnO@ZnO based gas sensor. The maximum response reached 256-100 ppm toluene at 250 °C, which is 50 °C lower than pure ZnO. The detection limit of AuPd functionalized Co3O4/ZnO@ZnO was as low as 100 ppb. The enhanced sensing mechanism was mainly attributed to the synergistic effect of Au and Pd, which was detailly discussed in gas sensing mechanism part.
