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61.
The syntheses of Co(AH2)2X2 (AH2 = 1-methyl-4, 4-dimercaptopiperidine, X = Cl Br, I, acetate, propanate, perchlorate, nitrate and sulphate), M(AH2) Cl2 (M = Cd, Zn) are described. According to IR and UV-visible data it seems most probable that the aminogem-dithiol (AH2) coordinates Co via both sulphur atoms, but Zn and Cd via one sulphur. A square pyramidal geometry about Co and a tetrahedral geometry about Zn and Cd are proposed. In no case has coordination via nitrogen been found. Strong X-H…N hydrogen bonds have been observed in most of these complexes. 相似文献
62.
Voltammetric Determination of Metronidazole Using a Sensor Based on Electropolymerization of α‐Cyclodextrin over a Carbon Paste Electrode 下载免费PDF全文
Arturo Hernández‐Jiménez Gabriela Roa‐Morales Horacio Reyes‐Pérez Patricia Balderas‐Hernández Carlos E. Barrera‐Díaz Margarita Bernabé‐Pineda 《Electroanalysis》2016,28(4):704-710
An electrochemical sensor for metronidazole (MTZ) was built via the surface modification of a carbon paste electrode (CPE) by a film obtained through electropolymerization of α‐cyclodextrin (CPEα‐CD). The CPEα‐CD was characterized by cyclic voltammetry (CV) and atomic force microscopy (AFM), by both techniques was demonstrated that the polymer film is coating the electrode surface. The electroreduction behaviour of MTZ in HClO4 media as a supporting electrolyte was studied by differential‐pulse voltammetric (DPV) technique. The DPV electrochemical process was observed to be diffusion controlled and irreversible. Under optimal conditions, the peak current was proportional to MTZ concentration in the range of 0.5 to 103.0 μM with a detection limit of 0.28±0.02 μM. The method was successfully applied to quantify of MTZ in pharmaceutical formulations. In addition, this proposed MTZ sensor exhibited good reproducibility, long‐term stability and fast current response. 相似文献
63.
Stereodivergent Aminocatalytic Synthesis of Z‐ and E‐Trisubstituted Double Bonds from Alkynals 下载免费PDF全文
Dr. Leyre Marzo Javier Luis‐Barrera Dr. Rubén Mas‐Ballesté Dr. José Luis García Ruano Dr. José Alemán 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16467-16477
A highly diastereoselective synthesis of trisubstituted Z‐ or E‐enals, which are important intermediates in organic synthesis, as well as being present in natural products, is described using different alkynals and nucleophiles as starting materials. Diastereocontrol is mainly governed by the appropriate catalyst. Therefore, those reactions controlled by steric effects, such as the Jørgensen–Hayashi's catalyst, give access to E isomers, and those catalysts that facilitate hydrogen bonding, such as tetrazol‐pyrrolidine Ley's catalyst, allow the synthesis of Z isomers. A stereochemical model based on DFT calculations is proposed. 相似文献
64.
Cover Picture: Stereodivergent Aminocatalytic Synthesis of Z‐ and E‐Trisubstituted Double Bonds from Alkynals (Chem. Eur. J. 46/2016) 下载免费PDF全文
65.
J. E. Carrera-Crespo Marina E. Rincón F. González E. Barrera Ignacio González 《Journal of Solid State Electrochemistry》2016,20(10):2713-2723
Decoration of TiO2 nanotube films (TiO2 nanotube arrays (TNAs)) with CdS nanoparticles has been pursued for a broad range of applications that goes from solar cells to biological sensors. In most synthesis methods, the scale-up of devices has been challenging due to the poor contact at the chalcogenide/oxide interface. In this work, we validate the electrochemical/thermal/chemical route as a superior strategy to sensitize TNAs with CdS nanoparticles when compared with conventional methods. The process consisted of (i) electrodeposition of cadmium on TNAs to ensure strong bonding between TiO2 and Cd precursor particles, (ii) air annealing of Cd-decorated TNAs to thermally oxidize cadmium to cadmium oxide, and (iii) total sulfurization of cadmium oxide to obtain CdS in an hexagonal phase matching that of TNAs. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses indicated the complete transformation of cadmium precursor particles into CdS and a good surface coverage of the internal/external walls of TNAs. When compared to samples prepared by successive ionic layer adsorption and reaction (SILAR), electrochemical impedance spectroscopy data revealed the improvement of the electrical properties of the TNA matrix due to the sulfurization process and a lower contact resistance at the CdS/TNA interface. These improvements explain the superior photoelectrochemical response of CdS/TNA photoelectrodes obtained by the electrochemical/thermal/chemical route. 相似文献
66.
Igor A. Sedov Timur I. Magsumov Erin Hart Ashley M. Ramirez Sarah Cheeran Maribel Barrera Melissa Y. Horton Anisha Wadawadigi Olivia Zha Xin Y. Tong William E. AcreeJr. Michael H. Abraham 《Journal of solution chemistry》2017,46(12):2249-2267
A gas chromatographic headspace analysis method was used to experimentally determine gas-to-liquid partition coefficients and infinite dilution activity coefficients for 29 liquid organic solutes dissolved in triethylene glycol at 298.15 K. Solubilities were also determined at 298.15 K for 23 crystalline nonelectrolyte organic compounds in triethylene glycol based on spectroscopic absorbance measurements. The experimental results of the headspace chromatographic and spectroscopic solubility measurements were converted to gas-to-triethylene glycol and water-to-triethylene glycol partition coefficients, and molar solubility ratios using standard thermodynamic relationships. Expressions were derived for solute transfer into triethylene glycol by combining our measured experimental values with published literature data. Mathematical correlations based on the Abraham model describe the observed partition coefficient and solubility data to within 0.16 log10 units (or less). 相似文献
67.
68.
This article reports the preparation and characterization of europium-doped zirconium oxide (ZrO2:Eu3+) formed by homogeneous precipitation from propoxyde of zirconium [Zr(OC3H7)4]. The alkoxide sol gel process is an efficient method to prepare the zirconium oxide matrix by the hydrolysis of alkoxide precursors followed by condensation to yield a polymeric oxo-bridged ZrO2 network. All compounds were characterized by thermal analysis and the X-ray diffractometry method. The thermoluminescence (TL) emission properties of ZrO2:Eu3+ under beta radiation effects are studied. The europium-doped sintered zirconia powder presents a TL glow curve with two peaks (Tmax) centered at around 204 and around 292 °C, respectively. TL response of ZrO2:Eu3+ as a function of beta-absorbed dose was linear from 2 Gy up to 90 Gy. The europium ion (Eu3+)-doped ZrO2 was found to be more sensitive to beta radiation than undoped ZrO2 obtained by the same method and presented a little fading of the TL signal compared with undoped zirconium oxide. 相似文献
69.
A. Cano P. Cañizares C. Barrera C. Sáez M.A. Rodrigo 《Electrochemistry communications》2011,13(11):1268-1270
In the search for new disinfection technologies for reused water, in this work the effect of current density on the disinfection capability, during the electrolyses with conductive diamond anodes of the effluent of a municipal wastewater treatment plant was evaluated. It was found that this electrolytic technology can disinfect completely for current densities ranging from 1.3 to 130 A m− 2, but the disinfection rate and chlorine speciation are significantly affected by particular current density applied. In order to avoid the occurrence of non desired species, the lower value of this range is proposed. In those conditions, complete disinfection can be obtained and hypochlorite and chloramines are the main species, not being produced chlorate, perchlorate or organo-chlorinates species. 相似文献
70.
Maria Bertília Oss Giacomelli Maria Carminati Lima Volnei Stupp Rui Miguel de Carvalho Júnior Jos Bento Borba da Silva Pilar Bermejo Barrera 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2151-2157
In this work, tetramethylammonium hydroxide (TMAH) was used to solubilize the DORM-1 dogfish muscle certified reference material as a model substance for the determination of As, Cd, Pb and Se by electrothermal atomic absorption spectrometry (ET AAS). The sample was mixed with a small amount of TMAH and heated to 60 °C for 10 min in a water bath. After dissolution, As and Se were determined using palladium and magnesium nitrates as a chemical modifier added in solution. For Cd and Pb, best results were obtained with a mixture of 250 μg of each of iridium and rhodium as permanent modifiers. In both cases, the calibration was performed with aqueous solutions in 0.2% v/v HNO3. The temperature program for each analyte was optimized using pyrolysis and atomization curves established with the fish reference material. The detection limits in dry samples and the characteristic mass values were: Cd 0.005 μg g−1 and 0.9 pg; Pb 0.04 μg g−1 and 7.6 pg; As 0.4 μg g−1 and 13 pg and Se 0.6 μg g−1 and 20 pg, respectively. Results from the determination of these elements in the DORM-1 certified fish reference material were within the 95% confidence interval of the certified values. 相似文献