RESUMO
How to achieve high sensing of Cr2O3-based sensors for harmful inorganic gases is still a challenge. To this end, Cr2O3 nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr2O3-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr2O3-based sensor to realize highly sensitive detection of trace H2S gas. At 170 °C, Cr2O3-600 exhibits a high response of 42.8 to 100 ppm H2S gas, which is 3.45 times larger than that of Cr2O3-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr2O3 material. In addition, the Cr2O3-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.
RESUMO
Response and recovery time to toxic and inflammable hydrogen sulfide (H2S) gas are important indexes for metal oxide sensors in real-time environmental monitoring. However, large-scale production of ZnO-based sensing materials for fast response to ppb-level H2S has been rarely reported. In this work, hierarchically porous hexagonal ZnO hollow tubule was simply fabricated by zinc salt impregnation and subsequently calcination using absorbent cotton as the template. The influence of calcination temperature on the corresponding morphology and sensing properties is also explored. The hollow tubules calcined at 600 °C are constructed from abundant cross-linked nanoparticles (â¼20 nm). Its Brunauer-Emmett-Teller surface area is 31 m2·g-1 and the meso- and macroporous sizes are centered at 35 and 115 nm, respectively. The sensor with a lower detection limit of 10 ppb exhibits a fast response speed of 29 s toward the 50 ppb H2S rather than those of the reported intrinsic and doped ZnO-based sensing materials. Furthermore, the sensor shows a wide linear range (10-1000 ppb), good reproducibility, and stability. Such excellent trace ppb-level H2S performances are mainly related to the inherent characteristics of hierarchically porous hollow tubular structure and the surface-adsorbed oxygen control type mechanism.
RESUMO
Most of the reported ternary oxides based sensors have not been realized to detect ppb-level H2S till now. In this work, Zn2SnO4 hierarchical quasi-microspheres were prepared through a facile surfactant-free hydrothermal method followed by calcination in air atmosphere. The quasi-microspheres are composed of nanosheets with the thickness of 100 nm and octahedra with the average size of 0.63 µm, respectively. The sensor fabricated from such Zn2SnO4 hierarchical quasi-microspheres shows excellent selective response to H2S at 133 °C with the lowest detection limit of 1 ppb. The gas response exhibits good linear relationship in the concentration range of 1-1000 ppb. Such outstanding H2S sensing property might be attributed to its porous structure, the synergistic effect of the two typical building blocks and the surface adsorbed oxygen, and the possible sensing mechanism is also discussed.
RESUMO
In the title polymeric compound, [Cd(C(9)H(12)O(4))(C(10)H(8)N(2))](n), the Cd(II) atom is located on a twofold rotation axis and is coordinated by two 4,4'-bipyridine ligands and two 2,2-dimethyl-cyclo-pentane-1,3-dicarboxyl-ate ions. The carboxyl-ate ion and the N-heterocycle both function as bridges to link adjacent Cd(II) atoms to result in the formation of a layer structure parallel to (010). The mid-point of the central C-C bond of the 4,4'-bipyridine ligand is located on an inversion center. In the crystal, the carboxyl-ate ion is disordered over a twofold rotation axis in respect of its methyl group and the cyclo-pentane ring.