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• Synthesis of heterostructure NiO-ZnO nanodisks. • Utilization of NiO-ZnO nanodisks as gas sensor. • Fabrication of high sensitive and low-concentration sulfur dioxide gas sensor based on NiO-ZnO nanodisks. This paper reports the synthesis and characterization of NiO-ZnO nanodisks synthesized through a facile hydrothermal method. The morphological characterizations confirmed the formation of well-defined nanodisks in high density with an average thickness of 60 ± 5 nm. The x-ray diffraction analysis confirmed the well incorporation of the NiO into the matrix of ZnO crystal and the average crystallite size for the NiO-ZnO nanodisks was found to be 39.71 nm. The compositional analysis revealed the formation of pure NiO-ZnO nanostructures. The synthesized NiO-ZnO nanodisks were used as electrode materials to fabricate Sulfur dioxide (SO 2) gas sensors and the gas sensor response and recovery times were systematically analyzed with respect to the operating temperatures and the SO 2 gas concentration. The observed sensor gas response, response time and recovery time of the fabricated NiO-ZnO nanodisks based gas sensor were 16.25, 52 s and 41 s, respectively, towards 20 ppm SO 2 gas at an optimized temperature of 240 °C. Thus, it is believed that the NiO-ZnO nanodisks could be a promising candidate for the fabrication of efficient gas sensors towards toxic and hazardous gases. [ABSTRACT FROM AUTHOR]

Here, we reported the synthesis of pure CoSn(OH) 6 and Fe-doped CoSn(OH) 6 nanocubes for gas sensing application by hydrothermal method. The extensive characterizations determined the crystal structure, morphology and chemical composition of the samples, such as, XRD, SEM, XPS, etc. Compared with the pure CoSn(OH) 6 , the gas sensing performance of 5Fe-CoSn(OH) 6 to N-butyl alcohol is improved significantly. The 5Fe-CoSn(OH) 6 based sensor presented high gas response of 60.309 toward 30 ppm N-butyl alcohol at relatively low operating temperature of 200 °C. Moreover, the 5Fe-CoSn(OH) 6 based sensor also exhibited excellent stability, selectivity and humidity resistance to N-butyl alcohol. The gas sensing properties of 5Fe-CoSn(OH) 6 is greatly improved due to the large specific surface area, narrow band gap, sufficient oxygen vacancies and quickly separation efficiency of electrons-hole pairs. The results demonstrate that the doping of Fe3+ is an effective way to improve the gas sensing properties of CoSn(OH) 6 sensors to detect N-butyl alcohol. [Display omitted] • The pure CoSn(OH)6 and Fe-doped CoSn(OH)6 were successfully synthesized by a hydrothermal method. • The sensing properties of the pure CoSn(OH)6 and Fe-doped CoSn(OH)6 to N-butyl alcohol were investigated for the first time. • 5Fe-CoSn(OH)6 exhibits the most remarkable gas sensing performance to N-butyl alcohol at 200 ℃. • The doping of Fe3 + is a promising approach for achieving an excellent gas sensing performance for the development of CoSn(OH)6 gas sensors to detect N-butyl alcohol. [ABSTRACT FROM AUTHOR]

In this work, the pure and Ni-doped Bi 2 WO 6 are successfully synthesized by a one-step hydrothermal method. We apply the various techniques, such as X-ray diffraction (XRD), Scanning Electron Microscope (SEM),Transmission Electron Microscope (TEM), Ultraviolet–visible spectroscopy (UV–vis) and photo luminescence (PL) et al., to characterize the structure, morphology, chemical compositions, optical properties and crystal defects of the prepared samples. Compared with pure Bi 2 WO 6 and other Ni-doped Bi 2 WO 6 , the 4 at% Ni-Bi 2 WO 6 sensor exhibits the highest gas response (31.2), fast response-recovery characteristic, good stability and unique selectivity to 30 ppm n-butanol at 325 ℃. The enhanced gas sensing mechanism could be attributed to its unique hierarchical hydrangea-like structure, the large specific surface area, the low band gap energy, high electron separation efficiency and abundant oxygen vacancies. We have fabricated the pure Bi 2 WO 6 and Ni-doped Bi 2 WO 6 successfully. The as-fabricated 4 at% Ni-doped Bi 2 WO 6 gas sensor shows superior gas-sensing performance toward n-butanol. [Display omitted] • The pure and Ni-doped Bi 2 WO 6 were successfully synthesized by hydrothermal method and the 4 at% Ni-Bi 2 WO 6 exhibits hydrangea-like morphology with hierarchical structures. • The Ni-doped Bi 2 WO 6 gas sensor presented a largely enhanced gas sensing properties to n-butanol. • The 4 at% Ni-doped Bi 2 WO 6 gas sensor showed excellent gas sensing properties to n-butanol. • The introducing Ni into Bi 2 WO 6 can increase oxygen vacancies and improve high electron-hole pairs separation efficiency. [ABSTRACT FROM AUTHOR]

Abstract: We report a successful synthesis of ZnO nanoparticles, nanosheets and nanoflowers via a simple hydrothermal process, and investigate comprehensively their gas-sensing performances. Of all the nanostructures, nanoflowers are found to show the most superior gas-sensing properties, e.g., highest gas response, shortest response and recovery time, excellent selectivity, and good repeatability and stability, which are attributed to their unique three-dimensional hierarchical structures with the largest specific surface area arising from remarkable amount of petals and pores. Further, the sodium citrate is found to be the key to producing such unique flower-like architecture, which can be understood upon the nucleation and self-assembly of building blocks of ZnO. Such development of the hierarchical architectures may open up an avenue to further enhance the gas-sensing performances of ZnO nanostructures for the on-site detection of the gases of interest. [Copyright &y& Elsevier]

The Ni-SnO 2 /g-C 3 N 4 composite exhibits unique hierarchical structure, which presents the gas response of 142.5 toward 10 ppm acetone at 125 °C. [Display omitted] • Hierarchical Ni-doped SnO 2 /g-C 3 N 4 nanocomposites are successfully synthesized. • The highly ordered Ni-doped SnO 2 nanosheets in situ grew onto g-C 3 N 4 lamina. • Ni-doped SnO 2 /g-C 3 N 4 presented the gas response of 142.5 toward 10 ppm acetone at 125 °C. • Introduction of g-C 3 N 4 formed g-C 3 N 4 -SnO 2 heterojunction and resulted in sharp resistance change. • Doping of Ni produced more oxygen vacancies for SnO 2. The development of metal oxides semiconductor-based gas sensors for the accuracy detection of acetone in human exhaled breath is highly desirable for diabetes diagnosis. Herein, we use calcining and hydrothermal method to grow highly ordered Ni-doped SnO 2 nanosheets onto g-C 3 N 4 lamina. The prepared Ni-SnO 2 /g-C 3 N 4 composite presents high gas response of 142.5 (Resistance ratio, defined as S = R air /R gas) toward 10 ppm acetone at the optimized operating temperature of 125 °C, under the environment temperature of 25 °C, 80 %RH. Moreover, the Ni-SnO 2 /g-C 3 N 4 based senor also maintains fast response–recovery time, good stability and extraordinary humidity resistance for detecting acetone, including the theoretical detection limit (LOD) as low as 1.38 ppb. The greatly improved gas sensing properties of the Ni-SnO 2 /g-C 3 N 4 composite can be due to the highly ordered hierarchical structure, Ni dopant and SnO 2 /g-C 3 N 4 heterojunctions. We believe this novel Ni-SnO 2 /g-C 3 N 4 nanocomposite promises to be a potential gas sensing material for diabetes diagnosis. [ABSTRACT FROM AUTHOR]