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101.
Miguel J. Dabdoub Claudio C. Silveira Eder J. Lenardo Palimcio G. Guerrero Jr. Luiz H. Viana Cristiane Y. Kawasoko Adriano C.M. Baroni 《Tetrahedron letters》2009,50(40):5569-5571
A new, short total synthesis of dihydroactinidiolide 1 is described using selenium carbenium ion-promoted carbon–carbon bond formation as the key step. Our synthetic strategy starts with a lactonization reaction between 1,3,3-trimethylcyclohexene 13 and α-chloro-α-phenylseleno ethyl acetate 14, affording the key intermediate, α-phenylseleno-γ-butyro lactone 15, which reacted via a selenoxide elimination to the target compound 1. 相似文献
102.
Red persistent luminescent diopside nanoparticles doped with Mn2+ and codoped with RE3+ (Eu2+, Dy3+) have been obtained by sol-gel method. The influence of codoping rare earth ions on the persistent luminescence was studied by wavelength-resolved thermally stimulated luminescence (TSL) measurements from 30 to 650 K after X-ray irradiation. From these first results, a mechanism of persistent luminescence is proposed. In this mechanism Mn2+ and Eu2+ act as TSL recombination centers, Mn3+ and Eu3+ being stable hole centers, whereas Dy3+ acts as a good electron trap giving rise to a TSL peak at high temperature. Finally, persistent luminescence was measured. Intensity and persistence of the red luminescence of CaMgSi2O6: Mn2+–Dy3+ are better than those of CaMgSi2O6: Mn2+ and CaMgSi2O6: Mn2+–Eu2+, which are in agreement with the results of TSL. 相似文献
103.
Oleg Lupan Vasile Postica Rainer Adelung Frédéric Labat Ilaria Ciofini Ulrich Schürmann Lorenz Kienle Lee Chow Bruno Viana Thierry Pauporté 《固体物理学:研究快报》2018,12(1)
A method for surface doping and functionalization of ZnO nanowires (NWs) with Pd (Pd/ZnO) in a one‐step process is presented. The main advantage of this method is to combine the simultaneous growth, surface doping, and functionalization of NWs by using electrochemical deposition (ECD) at relatively low temperatures (90 °C). Our approach essentially reduces the number of technological steps of nanomaterial synthesis and final nanodevices fabrication with enhanced performances. A series of nanosensor devices is fabricated based on single Pd/ZnO NWs with a radius of about 80 nm using a FIB/SEM system. The influence of Pd nominal composition in Pd/ZnO NW on the H2 sensing response is studied in detail and a corresponding mechanism is proposed. The results demonstrate an ultra‐high response and selectivity of the synthesized nanosensors to hydrogen gas at room temperature. The optimal concentration of PdCl2 in the electrolyte to achieve extremely sensitive nanodevices with a gas response (SH2) ≈ 1.3 × 104 (at 100 ppm H2 concentration) and relatively high rapidity is 0.75 µM. Theoretical calculations on Pd/ZnO bulk and functionalized surface further validated the experimental hypothesis. Our results demonstrate the importance of noble metal presence on the surface due to doping and functionalization of nanostructures in the fabrication of highly‐sensitive and selective gas nanosensors operating at room temperature with reduced power consumption. 相似文献
104.
105.
Dinis F. Silva Alexandre M. Viana Isabel Santos-Vieira Salete S. Balula Luís Cunha-Silva 《Molecules (Basel, Switzerland)》2022,27(5)
An effective and sustainable process capable of simultaneously execute desulfurization and denitrogenation of fuels is in fact an actual necessity in the refinery industry. The key to achieve this goal is the parallel oxidation of sulfur and nitrogen compounds present in fuels, which is only achieved by an active and recovered catalyst. A novel heterogeneous catalyst was successfully prepared by the encapsulation of an imidazolium-based polyoxometalate (POM) into a ZIF-8 framework ([BMIM]PMo12@ZIF-8). This composite material revealed exceptional catalytic efficiency to concurrently proceed with the oxidative desulfurization and denitrogenation of a multicomponent model fuel containing various sulfur and nitrogen compounds. A complete removal of all these compounds was achieved after only one hour and the catalyst system was able to be reused for ten consecutive cycles without loss of efficiency. In fact, an ionic liquid POM was incorporated in the ZIF-8 for the first time, and this composite compound was originally applied as a catalyst for simultaneous oxidative desulfurization and denitrogenation processes. 相似文献
106.
107.
Eloisa Cordoncillo Purification Escribano F. Javier Guaita Clotilde Philippe Bruno Viana Clement Sanchez 《Journal of Sol-Gel Science and Technology》2002,24(2):155-165
Sol-gel matrices have been investigated for some years as potential matrices for rare earth luminescence. Sm3+, Eu3+, Dy3+, Er3+ and Tm3+ optical properties in siloxane-zirconium hybrid matrices prepared at room temperature have been investigated. Even if luminescence efficiency is governed by non-radiative relaxation linked to hydroxyl groups, in these matrices, rare earth fluorescence is always observed but lifetimes and quantum yields are dependent on the elaboration procedure. Eu3+ is used as a probe of the local surrounding around the dopant and the emission and decay profiles measurements in rare earth doped and undoped matrices are presented. 相似文献
108.
109.
Di Muccio A Pelosi P Attard Barbini D Generali T Girolimetti S Stefanelli P Leonelli A Amendola G Vergori L Viana Fresquet E 《Journal of chromatography. A》1999,833(1):19-34
The method studied uses a combination of a solid-matrix dispersion partition (SMDP) followed by high-performance size-exclusion chromatography on a minicolumn (HPmSEC) of 7.8 mm I.D. for the separation of pyrethroid (PYR) residues from fatty material. The solid-matrix dispersion extraction is carried out by absorbing a fat solution onto an Extrelut-3 cartridge (filled with a macroporous diatomaceous material) and extracting the PYR residues with acetonitrile. Up to 1 g of fatty material can be extracted with 15 ml acetonitrile. The small amount (mean +/- S.D. = 12.4 +/- 5.9 mg) of fatty material which is eluted into the acetonitrile is further removed by HPmSEC. PYR pesticide residues are collected in a 2-ml fraction between 7 and 9 ml, the column being washed up to 24 ml. The two techniques used in series allow a better removal of fat, a greater input of sample and a lower consumption of solvent compared to the sole SEC on macrocolumns, and a lower limit of determination compared to the sole SEC on minicolumns. Recoveries of 9 PYR out of the 14 investigated residues from soya oil were in the range 66-83% at spiking levels ranging 0.49-2.57 mg/kg, while for 6 PYR residues tested at spiking levels in the range 0.13-0.53 mg/kg the recoveries were in the range 80-111%. Recovery of fluvalinate and permethrin could not be calculated due to interferences from soya oil, while lambda-cyhalothrin, esfenvalerate and tralomethrin gave low recovery. The final extract contains small amount (mean +/- S.D. = 2.4 +/- 0.9 mg) of lipid residue and is not completely free from interferences. 相似文献
110.
Juliana?B.?Silva Cristina?F.?Diniz Ana?P.?P.?Viana Nelcy?D.?S.?MohallemEmail author 《Journal of Sol-Gel Science and Technology》2005,35(2):115-122
Composites of cobalt ferrite particles dispersed in a silica matrix (CoFe2O4/SiO2) were prepared by the sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica and metallic nitrates as precursors of ferrite. Samples of SiO2 and CoFe2O4/SiO2 were prepared in monolithic shape, dried at 110∘C, treated at various temperatures and their characteristics were compared. After the thermal treatment, the surface area of the silica matrix decreased, above 700∘C it densified, and above 1100∘C it crystallized. The same heat treatment in the composite led to the crystallization of CoFe2O4 particles in the SiO2 matrix and the increase in particle size, with the consequent increase in magnetization. The presence of particles in the matrix reinforced its structure, avoiding large changes in surface area and porosity and in the structure of the matrix after high temperature thermal treatment. 相似文献