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131.
Antonio S. Santos Arnaldo C. Pereira Maria D. P. T. Sotomayor César R. T. Tarley Nelson Durán Lauro T. Kubota 《Electroanalysis》2007,19(5):549-554
This work evaluated an amperometric biosensor based on multi‐wall carbon nanotubes (MWCNT), chemically modified with methylene blue (Met) and horseradish peroxidase (HRP), for detection of phenolic compounds. The dependences of the biosensor response due to the enzyme immobilization procedure, HRP amounts, pH and working potential were investigated. The amperometric response for catechol using the proposed biosensor showed a very wide linear response range (1 to 150 μmol L?1), good sensitivity (50 nA cm?2 μmol?1 L), excellent operational stability (after 300 determinations the response remained at 97%) and very good storage stability (lifetime>3 months). Based on all these characteristics, it is possible to affirm that the material is promising for phenol detection due to its good electrochemical response and enzyme stabilization. The biosensor response for various phenolic compounds was investigated. 相似文献
132.
Wagner B. De Almeida Hélio F. Dos Santos Patrick J. O'Malley 《Structural chemistry》1995,6(6):383-389
The potential energy surface (PES) for the herbicide diuron (DCMU), a photosystem II inhibitor, has been extensively investigated using the quantum-mechanical semiempirical molecular orbital methods AM1 and PM3 and molecular mechanics method. A detailed conformational search has been carried out which revealed the occurrence of four genuine minimum energy structures. The relative stability of the conformers and rotational barriers to conformational interconversion were evaluated using distinct theoretical approaches. The results showed that thetrans form of the diuron molecule is more stable than thecis form in all methods, and so it may possibly be the biologically active isomer. 相似文献
133.
The thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in Ac2O led to novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles and chiral (9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindoles were obtained on FVP. Starting from l-cysteine methyl ester (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazines were obtained as single stereoisomers. The thermolysis of (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazine-3-carboxylic acid in Ac2O gave 5-acetyl-2-phenyl-2,3-dihydrothiazole. The structures of methyl (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylate 1a and methyl (2R,4R)-N-chlorocarbonyl-2-(2-hydroxyphenyl)thiazolidine-4-carboxylate 9 were determined by X-ray crystallography. 相似文献
134.
Alvarez-Puebla RA dos Santos DS Blanco C Echeverria JC Garrido JJ 《Journal of colloid and interface science》2005,285(1):41-49
Illite clays are known to have a strong affinity for metallic pollutants in the environment and can be applied as low-cost adsorbents for industrial waste treatment. A crucial factor in the development of such applications, however, is the understanding of the chemical, mineralogical, and colloidal properties of these clays. It is also important to understand the mechanisms involved in the surface adsorption of metals by these adsorbants. In order to study the retention of transition metals on illite clays, we have applied surface characterization techniques such as FPIA, SEM-EDX, XRD, N2 (77 K) adsorption, and FTIR. In addition to these experimental techniques, we have also employed a theoretical model that accounts for the chemistry of transition metal ions, and considers the global retention process to be the sum of several single retention processes. This model adequately fits the experimental data and allows for the speciation of metal retention on illite surfaces. Between pH values of 2.53 and 3.01 the only adsorption processes are the electrostatic sorption of [Cu(H2O)6]2+, and the surface complexation of [Cu(H2O)6]2+ and [Cu(OH)(H2O)5]+ ions. Surface complexation of [Cu(OH)(H2O)5]+ ions increases with pH, overcoming [Cu(H2O)6]2+ retention, and thus contributing to the surface precipitation of Cu(OH)2. 相似文献
135.
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137.
Raul Aguayo Felipe Arias Alvaro Cañete Carolina Zuñiga Enrique A. Castro Paulina Pavez José G. Santos 《国际化学动力学杂志》2013,45(3):202-211
The reactions of the title compounds with phenoxides, secondary alicyclic (SA) amines, and pyridines, in 44 wt% ethanol–water, at 25°C and an ionic strength of 0.2 M, were subjected to kinetic and product studies. From analytical techniques (HPLC and NMR), two pathways were detected (nucleophilic attack at the phosphoryl center and at the C‐1 aromatic carbon) for the reactions of all the nucleophiles with the phosphate ( 2 ) and for the pyridinolysis of the thionophosphate ( 1 ). Only aromatic nucleophilic substitution was found for the reactions of 1 with phenoxides and SA amines. For the dual reactions, the nucleophilic rate constants (kN) were separated in two terms: $k_{\rm N}^{\rm P}$ and $k_{\rm N}^{{\rm Ar}}$, which are the rate constants for the corresponding electrophilic centers. The absence of a break in the Brønsted‐type plots for the attack at P is consistent with concerted mechanisms. The Brønsted slopes, βAr 0.32–0.71, for the attack at the aromatic C‐1, are in agreement with stepwise mechanisms where formation of a Meisenheimer complex is the rate‐determining step. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 202–211, 2013 相似文献
138.
In this paper we report a simple methodology for obtaining (+) trans - 1,2 - epoxylimonene (1b) in high purity (>99% HRGC) and reasonable quantity. The mixture of 1a and 1b in CH2Cl2 is stirred with 1M NaHSO3 in water. Under these conditions 1a is completely destroyed, while 1b is only partially destroyed. 相似文献
139.
dos Santos Poli Anne Karoline Hilário Rodrigo Barbosa Gama Adriana Medeiros Baldan Mauricio Ribeiro Gonçalves Emerson Sarmento 《Journal of Solid State Electrochemistry》2019,23(1):33-52
Journal of Solid State Electrochemistry - Polyaniline was electrosynthesized using three voltammetric cycles on carbon fiber felts annealed at 1400, 1600, 2000, and 2300 K. Felts and... 相似文献
140.
Benvenuti Jaqueline Capeletti Larissa Brentano Gutterres Mariliz dos Santos João Henrique Zimnoch 《Journal of Sol-Gel Science and Technology》2018,85(2):446-457
Journal of Sol-Gel Science and Technology - This study reports the development of a functional adsorbent synthesized by the molecular imprinting method in a sol–gel matrix. The adsorption... 相似文献