0000000000126083
AUTHOR
Mercedes Alvaro
Design of stable mixed-metal MIL-101(Cr/Fe) materials with enhanced catalytic activity for the Prins reaction
[EN] This work highlights the benefit of designing mixed-metal (Cr/Fe) MOFs for enhanced chemical stability and catalytic activity. A robust and stable mixed-metal MIL-101(Cr/Fe) was prepared through a HF-free direct hydrothermal route with Fe(3+)content up to 21 wt%. The incorporation of Fe(3+)cations in the crystal structure was confirmed by(57)Fe Mossbauer spectrometry. The catalytic performance of the mixed metal MIL-101(Cr/Fe) was evaluated in the Prins reaction. MIL-101(Cr/Fe) exhibited a higher catalytic activity compared to MIL-101(Cr), improved chemical stability compared to MIL-101(Fe) and a higher catalytic activity for bulky substrates compared to MIL-100(Fe).In situinfra-red sp…
Gold Nanoparticles Supported on Nanoparticulate Ceria as a Powerful Agent against Intracellular Oxidative Stress
Ceria-supported gold nanoparticles are prepared exhibiting peroxidase activity and acting as radical traps. Au/CeO2 shows a remarkable biocompatibility as demonstrated by measuring cellular viability, proliferation, and lack of apoptosis for two human cell lines (Hep3B and HeLa). The antioxidant activity of Au/CeO2 against reactive oxygen species (ROS) is demonstrated by studying the cellular behavior of Hep3B and HeLa in a model of cellular oxidative stress. It is determined that Au/CeO2 exhibits higher antioxidant activity than glutathione, the main cytosolic antioxidant compound, and its CeO2 carrier. Overall the result presented here shows the potential of implementing well-established …
Nano-Jewels in Biology. Gold and Platinum on Diamond Nanoparticles as Antioxidant Systems Against Cellular Oxidative Stress
Diamond nanoparticles (DNPs) obtained by explosive detonation have become commercially available. These commercial DNPs can be treated under Fenton conditions (FeSO(4) and H(2)O(2) at acidic pH) to obtain purer DNP samples with a small average particle size (4 nm) and a large population of surface OH groups (HO-DNPs). These Fenton-treated HO-DNPs have been used as a support of gold and platinum nanoparticles (≤2 nm average size). The resulting materials (Au/HO-DNP and Pt/HO-DNP) exhibit a high antioxidant activity against reactive oxygen species induced in a hepatoma cell line. In addition to presenting good biocompatibility, Au/HO- and Pt/HO-DNP exhibit about a two-fold higher antioxidant …
A novel photochemical 1,4-acyl migration in enol esters. The photolysis of enol acetates of 3-phenylpropiophenones
Abstract Photolysis of the enol acetates 1a,b gives the 1,4-diketones 4a,b by a mechanism involving a primary homolytic carbonyl—oxygen bond cleavage, followed by 1,2-hydrogen shift and in cage recombination.
Tunability by alkali metal cations of photoinduced charge separation in azacrown functionalized graphene.
A modified graphene oxide containing aza-9-crown-3 ether units covalently anchored has been prepared; aqueous suspensions of this material in the presence of Li(+), Na(+) and K(+) cations exhibit enhanced electrochemical response, enhanced photoinduced charge separation and longer lifetimes, facts that can be attributed to stabilization of electrons on graphene oxide by the nearby alkali metal cation-azacrown complexes.
Ship-in-a-Bottle Synthesis of a Large Guest Occupying Two Y Zeolite Neighbour Supercages: Characterisation and Photocatalytic Activity of the Encapsulated Bipyrylium Ion
In a series of papers we reported the ship-in-a-bottle synthesis, photochemical properties and photocatalytic applications of 2,4,6-triphenylpyrylium cation (TP ) encapsulated inside the cavities of large pore zeolites Y and Beta. 2] The identity of encapsulated TP was then confirmed spectroscopically, particularly by the match of the IR spectra of the encapsulated organic material and that of the tetrafluoroborate solid of TP (TPBF4). In addition, the electrochemical response of zeolite Y encapsulated TP (TP@Y) consisted of a reversible single reduction process taking place at the same redox potential as that measured for TPBF4 solutions. Encapsulation of TP has a dramatic influence on its…
Study of Redox Processes in Zeolite Y-Associated 2,4,6-Triphenylthiopyrylium Ion by Square Wave Voltammetry
The electrochemical responses of 2,4,6-triphenylthiopyrylium ion (TTP+) in solution and attached to zeolite Y (TTP@Y) are described using cyclic and square wave voltammetries upon immersion of zeolite-modified polymer film electrodes in MeCN (LiClO4, Et4NClO4, and BuN4PF6 electrolytes) and aqueous (LiNO3, NaNO3, and KNO3 electrolytes) media. The electrochemistry of TTP@Y in contact with Bu4NPF6/MeCN is identical to that of TTP(BF4) in solution, with reduction processes at −0.25, −0.74, and −1.36 V vs SCE, and oxidation steps at +0.85 and +1.11 V. This response differs from those obtained for TTP@Y in Et4NClO4/MeCN and LiClO4/MeCN electrolytes. In contact with aqueous electrolytes, TTP@Y dis…
Electrochemistry of Mesoporous Organosilica of MCM-41 Type Containing 4,4′-Bipyridinium Units: Voltammetric Response and Electrocatalytic Effect on 1,4-Dihydrobenzoquinone Oxidation
The electrochemistry of a novel organic−inorganic material in which 4,4‘-bipyridinium units (BP) are covalently attached to the walls of a periodic mesoporous organisilica (PMO) of the MCM-41 type is described. The pristine material (BP@PMO), having its internal space completely filled by the cetyltrimethylammonium structure-directing agent, is almost electrochemically silent. In contrast, the extracted material obtained after removal of the structure-directing agent (BP@PMO-ex) exhibits two reduction peaks at −0.36 and −0.75 V vs AgCl/Ag in contact with aqueous electrolytes. BP@PMO-ex shows a remarkable electrocatalytic effect on the oxidation of 1,4-dihydrobenzoquinone (H2Q) that is studi…
Synthesis of a Hydrothermally Stable, Periodic Mesoporous Material Containing Magnetite Nanoparticles, and the Preparation of Oriented Films
Magnetite nanoparticles modified covalently with triethoxysilane having a quaternary dicetyl ammonium ion are used together with tetraethylorthosilicate as building blocks to prepare a mesoporous material. Cetyltrimethylammonium bromide is used as a structure-directing agent under conditions typically used for mesoporous MCM-41 silicas. The resulting mesoporous material (MAG-MCM-41), containing up to 15 wt % of magnetite is characterized by transmission electron microscopy (TEM), isothermal gas adsorption, and X-ray diffraction. In contrast to siliceous MCM-41, mesoporous MAG-MCM-41 exhibits a remarkable hydrothermal stability. The magnetic properties of MAG-MCM-41 are characterized by DC a…
Spontaneous doping and magnetic properties of polyacetylene and polypropyne synthesized in situ in Ni-exchanged mordenite and mesoporous MCM-41
Upon polymerisation of acetylene and propyne inside the channels of Ni2+-exchanged mordenite and mesoporous MCM-41 spontaneous doping and formation of antiferromagnetic NiO clusters are observed to various extents. The population of polarons present in the final polymer/zeolite composite: (i) is higher for polyacetylene than for polypropyne; (ii) increases with polymerisation temperature in the range 100 to 335 °C; (iii) increases with the C content; and (iv) is higher for mordenite than for MCM-41 under the same conditions. The use of Ni(0),H+-mordenite for polymer formation enhances the polaron population of the resulting polymer by over one order of magnitude. Doped polyacetylene encapsu…