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排序方式: 共有289条查询结果,搜索用时 31 毫秒
101.
Alvaro M Cabeza JF Fabuel D Corma A García H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(13):3733-3738
An electrochemiluminescent cell has been developed that has an active layer consisting of ruthenium tris-bipyridyl encapsulated inside zeolite Y supercages. Operation of the cell requires the addition of polyethylene glycol as the solid electrolyte. The cell, which exhibits electrical conductivity behavior typical of a semiconductor, has an optimum operating voltage of 3 V. Ion exchange of sodium by cesium and vapor deposition of calcium metal inside the zeolite pores enhance the electrochemiluminescent efficiency of the cell by a factor of 4. 相似文献
102.
Ramiro-Manzano F Atienzar P Rodriguez I Meseguer F Garcia H Corma A 《Chemical communications (Cambridge, England)》2007,(3):242-244
We have developed a quasi-fractal colloidal crystal to localize efficiently photons in a very broad optical spectral range; it has been applied to prepare dye sensitized photoelectrochemical solar (PES) cells able to harvest very efficiently photons from the ultraviolet (UV) and the visible (VIS) regions of the solar spectrum. 相似文献
103.
104.
105.
José Avelino Silva Nuno Ratola Sara Ramos Vera Homem Lúcia Santos Arminda Alves 《Analytica chimica acta》2015
Vegetation (and pine needles in particular) has been widely used as an alternative to other conventional sampling devices to assess the atmospheric presence of semi-volatile organic contaminants (SVOCs). While most analytical procedures developed focus only on one or two chemical classes, this this work intends to establish a multi-component protocol to quantify brominated flame-retardants (BFRs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polynuclear aromatic hydrocarbons (PAHs) and one class of contaminant of emerging concern, the synthetic musks fragrances (SMCs). Pine needles extracts were obtained by ultrasonic solvents extraction (USE), and different cleanup approaches using solid-phase extraction (SPE) employing combinations of sorbents and solvents as well as gel permeation chromatography (GPC) were tested. SPE with alumina followed by GCP yielded the best results, with average recoveries over 80%. 相似文献
106.
107.
Pau Ferri Chengeng Li Reisel Millán Dr. Joaquín Martínez-Triguero Dr. Manuel Moliner Dr. Mercedes Boronat Dr. Avelino Corma 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19876-19883
The methanol-to-olefins reaction catalyzed by small-pore cage-based acid zeolites and zeotypes produces a mixture of short chain olefins, whose selectivity to ethene, propene and butene varies with the cavity architecture and with the framework composition. The product distribution of aluminosilicates and silicoaluminophosphates with the CHA and AEI structures (H-SSZ-13, H-SAPO-34, H-SSZ-39 and H-SAPO-18) has been experimentally determined, and the impact of acidity and framework flexibility on the stability of the key cationic intermediates involved in the mechanism and on the diffusion of the olefin products through the 8r windows of the catalysts has been evaluated by means of periodic DFT calculations and ab initio molecular dynamics simulations. The preferential stabilization by confinement of fully methylated hydrocarbon pool intermediates favoring the paring pathway is the main factor controlling the final olefin product distribution. 相似文献
108.
Sergio Rojas-Buzo Benjamin Bohigues Christian W. Lopes Dbora M. Meira Mercedes Boronat Manuel Moliner Avelino Corma 《Chemical science》2021,12(29):10106
The Lewis/Brønsted catalytic properties of the Metal–Organic Framework (MOF) nodes can be tuned by simply controlling the solvent employed in the synthetic procedure. In this work, we demonstrate that Hf-MOF-808 can be prepared from a material with a higher amount of Brønsted acid sites, via modulated hydrothermal synthesis, to a material with a higher proportion of unsaturated Hf Lewis acid sites, via modulated solvothermal synthesis. The Lewis/Brønsted acid properties of the resultant metallic clusters have been studied by different characterization techniques, including XAS, FTIR and NMR spectroscopies, combined with a DFT study. The different nature of the Hf-MOF-808 materials allows their application as selective catalysts in different target reactions requiring Lewis, Brønsted or Lewis–Brønsted acid pairs.The Brønsted/Lewis acid properties of Hf-MOF-808 can be tuned by simply controlling the solvent employed in its synthesis, with direct catalytic implications on the activity and selectivity of organic reactions sensitive to the active site nature. 相似文献
109.
Dihedral f-tilings by spherical parallelograms and spherical triangles were obtained in [3–5]. In this paper we extend these
results presenting the study of all dihedral f-tilings of the sphere S
2, whose prototiles are a spherical equilateral or isosceles triangle and a spherical isosceles trapezoid. The combinatorial
structure, including the symmetry group of each tiling, is given in Table 1. 相似文献
110.
Gianotti E Diaz U Coluccia S Corma A 《Physical chemistry chemical physics : PCCP》2011,13(24):11702-11709
Non-ordered organic-inorganic mesoporous hybrid materials with basic sites have been synthesized following a fluoride-catalysed sol-gel process at neutral pH and low temperatures that avoids the use of structural directing agents (SDAs). Proton sponges have been used as the organic builder of the hybrids, while the inorganic part corresponds to silica tetrahedra. The proton sponges are diamines that exhibit very high basicity and, after functionalization, have been introduced as part of the walls of the mesoporous silica by one-pot synthesis. Several hybrids with different organic loadings have been synthesized and characterized by gas adsorption, thermogravimetric and elemental analysis, solid state MAS-NMR and FTIR spectroscopy. These hybrids show high activity as base catalysts and can be recycled. 相似文献