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111.
112.
Angela?I.?López-LorenteEmail author Rosaria?A.?Picca Javier?Izquierdo Christine?Kranz Boris?Mizaikoff Cinzia?Di?Franco Soledad?Cárdenas Nicola?Cioffi Gerardo?Palazzo Antonio?Valentini 《Mikrochimica acta》2018,185(2):153
Hybrids consisting of silver nanoparticles (in varying fractions) and of TiOx/ZnO were prepared via top-down ion beam sputtering (IBS) deposition on silicon substrates. The deposited nanomaterials were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. It is shown that such composites represent a viable substrate for use in both surface enhanced Raman spectroscopy (SERS) and surface enhanced infrared absorption spectroscopy (SEIRAS), as exemplarily shown for crystal violet as the model analyte. The C-H bending mode at about 1181 cm?1 and the C-N vibration at 1361 cm?1 observed in the SERS and SEIRAS spectra, respectively, have been used as analytical signal. The substrate consisting of TiOx NPs with 33% fraction of silver provides the strongest enhancement in SERS (up to 10,000-fold), while TiOx/AgNPs with thickness of 2 and 1 nm in ion beam sputtering, respectively, provides the best sensitivity in SEIRAS. The substrates also display photocatalytic activity as shown by the degradation of adsorbed crystal violet under ultraviolet irradiation. 相似文献
113.
Manuel Salmón Armando Cabrera Nieves Zavala Georgina Espinosa-Pérez Jorge Cárdenas Rubén Gaviño Raymundo Cruz 《Journal of chemical crystallography》1995,25(11):759-762
3,4,5-Trimethoxybenzyl alcohol was cyclooligomerized with a bentonite clay used as a catalyst. Results of the crystal structure analysis of the racemic (±) nonamethoxy[1,1,1]orthocyclophane trimer, C30H36O9, are described. The structure was determined by X-ray diffraction at 293 K and shown to belong to the triclinic space group P
. The compound possesses a distorted crown conformation with unusual C–H...O intermolecular interactions, and with a crystal packing not observed before in other related derivatives. The racemic mixture was also discriminated in its two enantiomeric isomers, using proton NMR and Eu(III) as a chiral shift reagent. 相似文献
114.
The steroidal delta- and gamma-iodo ketones 1 and 9 were converted to the cyclic hemiketals 3 and 10, by oxidation to the iodoso derivatives with m-CPBA. Spontaneous cyclization of the latter intermediates to the corresponding oxocarbenium ions, followed by stereoselective addition of water, rendered the hemiketals. Depending on the reaction conditions, the five-membered oxocarbenium ion derived from the gamma-iodo ketone 9 may add H(2)O or m-CPBA to give either the hemiketal or a Baeyer-Villiger type product 12, while the oxocarbenium derived from 1 gives exclusively the hemiketal. When the reaction was carried out in dry methanol, methyl ketals were formed. Use of this methodology allowed us to synthesize 6-oxa-5alpha-pregnanes with and without functionalization at C-19. 相似文献
115.
Gerardo M. Ramos Tombo Daniel Bellu 《Angewandte Chemie (International ed. in English)》1991,30(10):1193-1215
The modern agrochemical industry is searching, more intensively than ever, for new substances to combat pests (weeds, deleterious insects, plant pathogens, etc.). In the complex and costly selection and optimization process, state-of-the-art scientific methods are always needed. The aims of the interdisciplinary optimization are mainly the reduction of the rate of application of the new substance, an increase in the selectivity against the target organism, and the optimal ecological profile. If a promising crop protection compound is a racemate or a diastereoisomeric mixture, the chemist has a unique opportunity to contribute to this optimization process through the synthesis of enantiomerically pure isomers for testing purposes. If the single isomer proves to be biologically superior to the racemate, the development of an economical and ecologically sound process for the production of the single isomer presents an even greater challenge. The average price of a crop protection compound is much lower than that for a pharmaceutical product, and this fact imposes a severe limitation upon the flexibility of the chemist who is concerned with the synthesis and production of a stereochemically pure agrochemical. This forces the crop protection chemist to make full use of both his scientific and creative capabilities. Fortunately, parallel to the development of the above optimization aims of a modern and ecologically sound crop protection research, there has been a continuous and worldwide advance in the area of asymmetric synthesis. Due to the interplay of these two parallel efforts there has been a great accumulation of chemical, biological, and agronomical knowledge in recent years, which should have implications beyond merely the synthesis of enantiomerically pure agrochemicals. 相似文献
116.
Surfaces of soda-lime glass and borosilicate glass have been investigated by grazing incidence X-ray reflectivity (GIXR). Characteristic differences are obtained in dependence on the fabrication procedure, the composition and the cleaning procedure. Strong variation is recorded between the two soda-lime float glass surfaces while minor differences are analysed between the top and bottom side of borosilicate float glass. This is attributed to the reduced amount of tin diffused into the bottom side of the borosilicate glass surface. Different cleaning procedures generate characteristic changes on the glass surfaces which can be verified by GIXR. The results indicate that borosilicate float glass combines the merits of the good surface quality of float glass with the high chemical resistivity of borosilicate glass.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
117.
C2-symmetric bis(sulfonamide) ligands derived from trans-(1R,2R)-cyclohexane-1,2-diamine were synthesized and complexed with [Cp∗RhCl2]2 in situ and used in the ATH of aromatic ketones with aqueous sodium formate as the hydrogen source. The chiral secondary alcohols were obtained with 90-99% enantioselectivity and in 50-100% yield. Reductions in water were faster than those in isopropanol/KOH. 相似文献
118.
Godinez CE Zepeda G Mortko CJ Dang H Garcia-Garibay MA 《The Journal of organic chemistry》2004,69(5):1652-1662
We report a highly convergent synthesis for the preparation of molecular gyroscopes consisting of para-phenylene rotors linked by triple bonds to methyl-substituted triptycenes acting as pivots and encapsulating frames. The desired 1,4-bis[2-(2,3,6,7,12,13-hexamethyl-10-alkyl-9-triptycyl)ethynyl]benzenes were prepared from 2,3-dimethyl-1,3-butadiene using Diels-Alder cycloadditions and Pd(0)-catalyzed coupling as the key reactions. The main challenge in the synthesis came about in the preparation of 9-alkynyl-triptycenes by Diels-Alder reaction of benzynes and 9-alkynyl-2,3,6,7-tetramethylanthracenes. These reactions occurred with chemical yields and regioselectivities that were strongly influenced by steric and electronic effects of substituents at C10 of the anthracene core. Anthracenes with methyl, propyl, and phenyl substituents were utilized to complete the synthesis of their corresponding molecular gyroscopes, and their solid-state structures were determined by single-crystal X-ray diffraction analysis. Examination of these results indicated that, as expected, the bulky triptycyl groups encourage crystallization motifs that create more free volume around the phenylene rotor, as needed to facilitate fast gyroscopic motion in the solid state. 相似文献
119.
W. Bernd Schweizer Jack D. Dunitz Rolland A. Pfund Gerardo M. Ramos Tombo Camille Ganter 《Helvetica chimica acta》1981,64(8):2738-2740
Crystallographic and spectroscopic evidence for an intramolecular (OH … π)-interaction in anti9,10-10endo-hydroxy, 10exo-butyltricyclo [4.2.1.12.5]deca-3, 7-dien-9-one ( 1 ) is presented. 相似文献
120.
The effect of sulfonation on polysulfone regarding its electrical properties is studied and discussed. In addition to the effect of percentage of sulfonation, the thickness of thin films and the ultraviolet (UV) treatment also were evaluated and reported. The results indicate that percentage of sulfonation is the most important effect, even over thickness. As the sulfonation percentage was increased, better electrical performance (fill factor and power conversion efficiency) was obtained because the sulfonate groups impart a kind of vacancy into the polymer structure, showing comparable energy level to that of conventional poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).In addition, the UV treatment not only cleans the film's surface but also polarizes the polymeric's surface improving the polysulfone performance, which was 24% better, at least, respect to that obtained without UV treatment. The obtained results open the possibility to optimize sulfonated polysulfones that could be used in inverted hybrid perovskite solar cells. 相似文献