Diversiform metal oxide-based hybrid nanostructures for gas sensing with versatile prospects

Monitoring and detection of triethylamine (TEA) gas are indispensable to environmental and human safety. However, TEA gas sensor suffers from low response. Herein, unique nanosized-Pt-decorated hierarchical ZnO microspheres were prepared. Compared with pristine ZnO microspheres and Pt-c-ZnO (Pt nanoparticles deposited on commercial ZnO), the obtained Pt-ZnO exhibited the best TEA gas sensing behaviors, in terms of lower working temperature (200 °C), better selectivity and long-term stability. Notably, the response value of Pt-ZnO sensor towards 100 ppm TEA was up to 242, which was 50 and 16-fold higher than those of pristine ZnO and Pt-c-ZnO sensor, respectively. The superior properties were attributed to structural advantages as well as the synergistic effect between Pt and ZnO. The sensing mechanism was thoroughly clarified by the electron-sinker effect of Pt. It was further corroborated by Kelvin probe and density function theory (DFT) simulation. Moreover, higher surface adsorption oxygen activity and lower TEA adsorption energy of this optimal sample were demonstrated by temperature programmed desorption (O2-TPD) and DFT simulation. Based on the aforementioned advantages, Pt-ZnO becomes a satisfactory candidate for TEA gas sensors. Significantly, this work opens a new avenue for the understanding the mechanism for performance enhancement under.

Triethylamine gas sensor based on Pt-functionalized hierarchical ZnO microspheres

Herein, Bi2WO6-x nanosheets with tunable Bi quantum dots and oxygen vacancies have been synthesized by a facile hydrothermal treatment combining in-situ redox reaction route, which exhibited the highly enhanced activity for selective oxidation of aromatic alcohols to carbonyl compounds in aqueous medium under visible-light irradiation for the first time. Results revealed that the highly enhanced activity of this photocatalyst was mainly attributed to the synergetic effect of Bi quantum dots and oxygen vacancies, which resulted in the narrowed energy band gap by inducing the formation of defect state level below the conduction band, the enhanced light-harvesting ability and the improved separation efficiency of photocharges. Meanwhile, this photocatalyst also displayed excellent durability owing to the strong interaction between Bi quantum dots and robust Bi2WO6-x nanosheets against significant deactivation caused by either the leaching of Bi quantum dots or the structural collapse of Bi2WO6-x nanosheets, showing its good potential in practical applications.

Bi2WO6-x nanosheets with tunable Bi quantum dots and oxygen vacancies for photocatalytic selective oxidation of alcohols

We report the Ru doping effect on the gas-sensing properties of SnO2 nanofibers for acetone detection in this paper. For this purpose, pure and 1, 2, 3 mol% Ru-doped SnO2 nanofibers were prepared through electrospinning technique combined with calcination treatment. The fibrous microstructure of these nanofibers were maintained and the grain size of the SnO2 nanoparticals were decreased from 9.2 nm (pure) to 5.1 nm (3% Ru-doped) after Ru doping. In order to confirm that Ru doping is an effective way to improve the gas sensing properties of the SnO2-based gas sensor, the gas sensing properties of the sensors based on pure and Ru doped SnO2 nanofibers were investigated systematically. The results showed that the response to 100 ppm acetone of 2 mol% Ru-doped SnO2 nanofibers was 118.8, which was 12 times higher than that of pure SnO2 nanofibers. In the end, the role of Ru in the gas sensing mechanism of SnO2 nanofibers was analyzed according to the results of the X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS).

High-performance acetone gas sensor based on Ru-doped SnO2 nanofibers

Synthesis and application of Fe3O4/FeWO4 composite as an efficient and magnetically recoverable visible light-driven photocatalyst for the reduction of Cr(VI)

Tetragonal zircon BiVO4 (P-BiVO4) were grown on fluorine-doped tin oxide (FTO) glass via hydrothermal method. The cathodic photocurrent and Mott-Schottky analysis indicate that the tetragonal zircon BiVO4 is a p-type semiconductor. Inductively coupled plasma (ICP) analysis and X-ray photoelectron spectrum showed that there are Bi vacancies and interstitial oxygen exist in the crystal, which are the origin of the p-type conductivity. The flat band potential of the P-BiVO4 is about 1.33 V (vs Ag/AgCl) inferred from Mott-Schottky plots. Combining with diffuse reflection spectrum and valence band X-ray photoelectron spectrum, the calculated conduction band value of the P-BiVO4 is about 0.06 V vs RHE, slightly higher than the reduction potential of hydrogen. However, the P-BiVO4 exhibit hydrogen production activity under Xe light irradiation even though its conduction band level is not negative enough. This can be attributed to the hot carrier processes in p-type semiconductors.

Photocatalytic hydrogen evolution on P-type tetragonal zircon BiVO4

Morphology-tunable C–N/SnO2-based hierarchical microspheres with good gas sensitivity for triethylamine (TEA) have been fabricated via facile electrospinning and a subsequent calcination process. The reaction temperature and modifying calcining technology played a dominant role for the morphological evolution from precursor fibers to microspherical shapes and the formation of C–N-decorated SnO2 phase composition. C–N/SnO2/ZnO composites with tunable crystallinity, microstructure, and gas-sensing performance were strictly dependent on the added amount of Zn element. Fascinatingly, the constructed C–N/SnO2/ZnO/Au composites can not only precisely regulate the crystal size, dispersion status, loading position, and content of Au nanoparticles but also display excellent gas-sensing properties with ultrasensitivity and high selectivity under various temperature detections. The response of C–N/SnO2/ZnO/Au composites can reach up to approximately 1970, calculated to be 121.6 and 23.6 times for 50 ppm TEA molecule...

Novel Construction of Morphology-Tunable C-N/SnO2/ZnO/Au Microspheres with Ultrasensitivity and High Selectivity for Triethylamine under Various Temperature Detections.

One-step single-spinneret electrospinning synthesis of 1D fibrous hierarchical structure can not only prevent the agglomeration or restacking of fibers or particles and enlarge surface active area but also promote the directional migration of electrons in materials and achieve effective regulation of resistances. Herein, tunable SnO2 and SnO2/ZnO fibrous hierarchical structures with in situ growth of monodisperse spherical-like particles on surface provide a new sight for adjusting component distribution, surface absorption and chemical reaction, electronic transmission path, and electron transfer efficiency. Compared with SnO2 porous fibers and SnO2 hierarchical structures, the optimal SnO2/ZnO sensors exhibit superior gas-sensing response value of 366-100 ppm ethanol at 260 °C as well as excellent gas selectivity and long-term stability, in which the enhanced gas-sensing mechanism is primarily derived from multilevel effective heterojunctions with unique interface electronic effects. Especially, these SnO2-based sensors can achieve favorable linear relationship of the response and gas concentration for sensitive trace detection in cosmetics for the first time, providing a new strategy to design composite materials for quantitative analysis of volatiles in the cosmetics evaluation process.

Wang Gang

Papers

Photocatalytic hydrogen evolution on P-type tetragonal zircon BiVO4

Novel Construction of Morphology-Tunable C-N/SnO2/ZnO/Au Microspheres with Ultrasensitivity and High Selectivity for Triethylamine under Various Temperature Detections.

Multilevel Effective Heterojunctions Based on SnO2/ZnO 1D Fibrous Hierarchical Structure with Unique Interface Electronic Effects.

ZIF-8 derived hexagonal-like α-Fe 2 O 3 /ZnO/Au nanoplates with tunable surface heterostructures for superior ethanol gas-sensing performance

Construction of SnS2/ZIF-8 derived flower-like porous SnO2/ZnO heterostructures with enhanced triethylamine gas sensing performance