Derivation of Cubic and Hexagonal Mesoporous Silica Films by Spin-coating
Abstract:By introducing spin-coating method to the evaporation induced self-assembly (EISA) process, a simple and reproducible route in controlling the mesophase of silica thin films has been developed for the first time in this work. When a comparatively solvent-rich Si-sol (The atomic ratio of TEOS : F127 : HCl : H2O : EtOH = 1 : 0.006 : 0.2 : 9.2 : 30) was used as coating solution, the mesophase of resultant silica films was selectively controlled by adjusting the spin-on speed. The cubic mesophase has been obtained… Show more
“…It is expected that the prepared TiO 2 microspheres have promising applications as photocatalysts in the treatment of oil spills and other waterborne pollutants in the sea or in lakes − because they can float on water surfaces for a long time. However, the ultrahighly dispersible TiO 2 nanoparticles prepared in this study will also be promising candidates for the fabrication of transparent photocatalytic and superhydrophilic films , as well as for the formation of electrode layers in dye-sensitized solar cells. , 7 SEM image of hollow TiO 2 microspheres calcined at 450 °C for 2 h (a) and photograph of calcined TiO 2 microspheres floating on water (b). …”
Section: Resultsmentioning
confidence: 99%
“…Extensive efforts have been made so far to synthesize TiO 2 nanoparticles. − However, controlling the size and shape is still very difficult and is quite different from that of other metal oxides. The preparation of stable suspensions free from mutual agglomeration is another important issue in the preparation of TiO 2 nanoparticles.…”
A new process for controlling the structure of TiO2 from hollow microspheres to highly dispersible nanoparticles has been developed by altering the concentration of tetrabutylammonium hydroxide (TBAH) in the solvothermal reaction of titanium isopropoxide. Robust and size-controllable hollow TiO2 microspheres, constructed by the assembly of 18 nm TiO2 nanoparticles, were synthesized at relatively high TBAH concentration. The diameters of hollow spheres, with a shell thickness of approximately 250 nm, were controlled to 1.5-4 microm by varying the concentration of TBAH in the range of 0.1-0.5 M. After calcination at 450 degrees C, the hollow microspheres were not appreciably deformed and were still floating on the surface of the water. However, highly dispersible TiO2 nanoparticles with an average diameter of 13 nm were obtained at a low TBAH concentration such as 9.2 mM. The colloidal particle size of TiO2 in an aqueous suspension at pH 2 was 12.5-13.5 nm, which indicates that the each nanoparticle is completely separated. The overall procedure is simple and highly reproducible, and large-scale synthesis is available at low cost.
“…It is expected that the prepared TiO 2 microspheres have promising applications as photocatalysts in the treatment of oil spills and other waterborne pollutants in the sea or in lakes − because they can float on water surfaces for a long time. However, the ultrahighly dispersible TiO 2 nanoparticles prepared in this study will also be promising candidates for the fabrication of transparent photocatalytic and superhydrophilic films , as well as for the formation of electrode layers in dye-sensitized solar cells. , 7 SEM image of hollow TiO 2 microspheres calcined at 450 °C for 2 h (a) and photograph of calcined TiO 2 microspheres floating on water (b). …”
Section: Resultsmentioning
confidence: 99%
“…Extensive efforts have been made so far to synthesize TiO 2 nanoparticles. − However, controlling the size and shape is still very difficult and is quite different from that of other metal oxides. The preparation of stable suspensions free from mutual agglomeration is another important issue in the preparation of TiO 2 nanoparticles.…”
A new process for controlling the structure of TiO2 from hollow microspheres to highly dispersible nanoparticles has been developed by altering the concentration of tetrabutylammonium hydroxide (TBAH) in the solvothermal reaction of titanium isopropoxide. Robust and size-controllable hollow TiO2 microspheres, constructed by the assembly of 18 nm TiO2 nanoparticles, were synthesized at relatively high TBAH concentration. The diameters of hollow spheres, with a shell thickness of approximately 250 nm, were controlled to 1.5-4 microm by varying the concentration of TBAH in the range of 0.1-0.5 M. After calcination at 450 degrees C, the hollow microspheres were not appreciably deformed and were still floating on the surface of the water. However, highly dispersible TiO2 nanoparticles with an average diameter of 13 nm were obtained at a low TBAH concentration such as 9.2 mM. The colloidal particle size of TiO2 in an aqueous suspension at pH 2 was 12.5-13.5 nm, which indicates that the each nanoparticle is completely separated. The overall procedure is simple and highly reproducible, and large-scale synthesis is available at low cost.
In this study, we explore the effect of nickel incorporation in Cu/fumed-SiO 2 catalyst for CO 2 reduction reaction. Two catalysts, Cu and CuNi supported on fumed silica were synthesized using a novel surface restricted combustion synthesis technique, where the combustion reaction takes place on the surface of the inert fumed-SiO 2 support. An active solution consisting of a known amount of metal nitrate precursors and urea (fuel) was impregnated on fumed silica. The catalyst loading was limited to 1 wt% to ensure localized combustions on the surface of fumed-SiO 2 by restricting the combustion energy density. The synthesized catalysts were tested for CO 2 hydrogenation reaction using a tubular packed bed reactor between temperature 50 C and 650 C, where Cu/SiO 2 showed high CO 2 conversion to carbon monoxide, and the addition of Ni further improved the catalytic performance and showed some tendency for methane formation along with CO. Moreover, both the catalysts were highly stable under the reaction conditions and did not show any sign of deactivation for $42 hours time on stream (TOS). The catalysts were characterized using X-ray diffractometer (XRD), scanning electron microscope/energy dispersive X-ray spectrometer (SEM/EDX), transmission electron microscope (TEM), and the Brunauer-Emmet-Teller (BET) surface area measurement technique to understand their structural properties and to assess the effect of CO 2 conversion reaction. In situ DRIFTS was also used to investigate the reaction pathway followed on the surface of the catalysts.
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