Search results for "poro"
showing 10 items of 1943 documents
X-ray analysis on the nanogram to microgram scale using porous complexes
2012
X-ray single-crystal diffraction (SCD) analysis has the intrinsic limitation that the target molecules must be obtained as single crystals. Here we report a protocol for SCD analysis that does not require the crystallization of the sample. In our method, tiny crystals of porous complexes are soaked in a solution of the target, such that the complexes can absorb the target molecules. Crystallographic analysis clearly determines the absorbed guest structures along with the host frameworks. Because the SCD analysis is carried out on only one tiny crystal of the complex, the required sample mass is of the nanogram–microgram order. We demonstrate that as little as about 80 nanograms of a sample …
Understanding the role of Ti-rich domains in the stabilization of gold nanoparticles on mesoporous silica-based catalysts
2018
3 Tablae, 14 Figures.-- Supplementary material.-- © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Visible light photocatalytic activity of macro-mesoporous TiO2-CeO2inverse opals
2018
Macro-mesoporous TiO2 inverse opal materials were synthesized and they were tested as photocatalysts under visible light irradiation. The influence of cerium oxide addition towards the Rhodamine B (RhB) photodegradation activity was evaluated. Structural, textural, spectral and surface properties of the TiO2-CeO2 inverse opal nanocomposites were studied by XRD, XPS, SEM, TEM, N2 adsorption-desorption, Diffuse Reflectance UV–vis and Photoluminescence spectroscopies. Compared to commercial TiO2 anatase, the macro-mesoporous TiO2 inverse opal exhibited six times higher kinetic rate constant in the RhB degradation under visible light irradiation. The good photocatalytic activity was related to …
The influence of the anatase nanoparticles boundaries on the titania activity performance
2014
Metal oxides structures, formed by ordered self-assembling of crystalline nanoparticles aggregates, are attracting growing attention in fields such as catalysis or solar cells. The properties of these structures are influenced not only by their morphology and nanoparticles composition but also by the assembled particles boundaries. In order to determine the influence of these boundaries on the structures properties, the present investigation has been devoted to study the characteristics of anatase nanoparticles boundaries in titania aggregates prepared by TiCl4 hydrolysis at low temperature. Proton magic angle spinning nuclear magnetic resonance and high resolution transmission electron mic…
Mesocrystalline anatase nanoparticles synthesized using a simple hydrothermal approach with enhanced light harvesting for gas-phase reaction
2018
Mesocrystalline TiO2 nanoparticles were synthesized using a hydrothermal approach. A simple two-step procedure at low temperature (<140 °C) allowed the nucleation of primary particles sized 2–4 nm and their subsequent assembly as almost spherical aggregates sized ≈20 nm. X-ray powder diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS) studies, and HRTEM studies confirmed anatase as the unique TiO2 crystalline phase. The mesocrystalline structure of the anatase aggregates was clearly evidenced by HRTEM and SAED results. The mesocrystalline nanopowders exhibit a mesoporous structure with a surface area and pore volume of 63.5 m2 g−1 and 0.22 cm3 g−1, respectively. Ultraviolet …
2018
We report a novel multi-step method for the preparation of ordered mesoporous titania scaffolds and show an illustrative example of their application to solar cells. The method is based on (monolayer) colloidal nanosphere lithography that makes use of polystyrene nanoparticles organised at a water–air interface and subsequently transferred onto a solid substrate. A titania precursor solution (titanium(IV) isopropoxide in ethanol) is then drop-cast onto the monolayer and left to “incubate” overnight. Surprisingly, instead of the expected inverse monolayer-structure, a subsequent calcination step of the precursor yields an ordered monolayer of hollow titania nanospheres with a wall thickness …
Tailoring the Structural, Optical, and Photoluminescence Properties of Porous Silicon/TiO2 Nanostructures
2015
The structural, optical, and photoluminescence properties of porous silicon (PSi)/titanium dioxide (TiO2) nanostructures were investigated. PSi structures consisting of macro- and mesoporous layers were fabricated by metal-assisted chemical etching, and then TiO2 was introduced inside the PSi matrix using the atomic layer deposition technique. We performed scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectroscopy, ellipsometry, and photoluminescence (PL) spectroscopy to characterize the prepared and annealed PSi/TiO2 nanostructures. TEM and Raman analyses revealed that TiO2 had a crystalline anatase stru…
Sol-gel derived anatase TiO2: morphology and photoactivity
1994
Abstract High-surface area TiO 2 (anatase) was prepared by the sol-gel method and characterized by various instrumental and analytical methods, including X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, porosimetry, specific surface area measurements, scanning electron microscopy, and titration of surface hydroxyl groups. The specimen was tested for photodegradation of phenol and nitrophenols carried out in aqueous suspension at pH = 3; photoactivity was compared with that of commercially available anatase TiO 2 . Results are discussed in terms of porosity, surface area, and availability and population of surface OH groups, consequent upon the particular method used for…
Anionic Organic Guests Incorporated in Zeolites: Adsorption and Reactivity of a Meisenheimer Complex in Faujasites
2005
Zeolites are suitable microporous hosts for positively charged organic species, but it is believed that they cannot adsorb organic anions. Pure Meisenheimer complex, derived from reduction of 2,4-dinitroaniline with NaBH4, was adsorbed inside faujasite cavities. Evidence for the internal incorporation of this negatively charged reaction intermediate comes from 1) XPS elemental analysis as a function of the depth of penetration into the particle, 2) the remarkable blue shift in lambda(max) of the Meisenheimer complex adsorbed on zeolite (ca. 470 nm) as compared to that in acetonitrile (580 nm) and 3) from the lack of reactivity with size-excluded hydride-acceptor reagents. Evidence is provid…