Abstract Metal-incorporated SAPO-34 catalysts were prepared by one-step hydrothermal method. Effects of various parameters including the types of metal ions, Cu2+ sources, structure directing agents (SDAs), hydrothermal temperature and time on catalyst activity of the metal-incorporated SAPO-34 catalysts were investigated. Three types of metal-incorporated SAPO-34 catalysts (Cu/SAPO-34, Fe/SAPO-34 and Mn/SAPO-34) were successfully obtained. Compared with Fe/SAPO-34 and Mn/SAPO-34 catalysts, Cu/SAPO-34 catalyst revealed complete cubic-like microstructure, wide active temperature window and high conversion rate in selective catalytic reduction (SCR) of nitric oxide. After defined Cu2+ was the favorable active site of SAPO-34 catalyst, the effects of four Cu2+ sources on SCR performance were further investigated, and found Cu2+ sources did not produce significant influence on nitric oxide conversion rates. SDAs determined the formation of Cu/SAPO-34 catalyst, and the Cu/SAPO-34 catalyst adopting tetraethylenepentamine (TEPA) as SDA could maintain higher crystal integrity and active sites, which were in favor of the SCR reaction. Moreover, hydrothermal temperature and time had great influences on the formation of Cu/SAPO-34 catalyst. When the hydrothermal temperature was higher than 150 oC and the hydrothermal time was longer than 3 days, the Cu/SAPO-34 catalyst with a cubic-like structure and high catalyst activity could be obtained.

Abstract WO3 nanorods were synthesized via a simple hydrothermal approach. Their microstructure and morphology were analyzed with x-ray diffraction, scanning electron microscope and x-ray photoelectron spectroscopy. The effects of reaction temperature, reaction time, and citric acid concentration, on the gas-sensing performance of WO3 nanorods were investigated. The optimized response value of WO3 sensor to ethanol gas (100 ppm) was 26.48, with a response time of 1 s under a low operating temperature (160 °C). The recovery capability and stability of the gas sensor were tested and discussed. Additionally, the working principle of WO3 sensor was proposed. In comparison to the sensors published by previous researchers, the WO3 sensor has shown great potential.

Bi2MoO6 nanosheets were synthesized by a hydrothermal method. Morphology and structure of the Bi2MoO6 nanosheets were analyzed by SEM, XRD, N2 adsorption techniques and XPS. Gas-sensing properties of the as-prepared Bi2MoO6 sensors were also systematically investigated. The results showed the reaction temperature greatly affected the morphology and structure of as-prepared Bi2MoO6 nanosheets. When the reaction temperature reached 170 ºC, the morphology of the Bi2MoO6 nanosheets tended to regular, and pure Bi2MoO6 nanosheets were obtained. The operating temperature determined the gas-sensing properties of the Bi2MoO6 sensor. At this optimal operating temperature of 300 ºC, the sensitivity of the Bi2MoO6 sensor towards 20 ppm nitrogen oxide (NO) reached a maximum of 3.13. With the increase of the nitrogen oxide (NO) concentration, the sensitivity of the Bi2MoO6 sensor also rapidly increased, and displayed an almost linear relationship between them. Additionally, the Bi2MoO6 sensor demonstrated excellent selectivity with respect to several typical interfering gases.

Star-shaped PbS nanomaterials are synthesized by a hydrothermal method. Morphology and structure of the PbS nanomaterials are analyzed by SEM, HRTEM and XRD. Gas-sensing properties of the as-prepared PbS sensor are also systematically investigated. The results show star-shaped PbS nanostructure consists of four symmetric arms in the same plane and demonstrate good crystallinity. With the increase of ethanol concentration, the sensitivity of the PbS sensor significantly increases and demonstrates an almost linear relationship at the optimal operating temperature of 400 ºC. Moreover, the fast response-recovery towards ethanol is also observed, which indicates its great potential on ethanol detection.