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41.
dos Reis Lima Fernanda Maria Silva Saimon Moraes da Silva Freires André Goulart Marília Oliveira Fonseca Damos Flavio Santos de Cassia Silva Luz Rita 《Journal of Solid State Electrochemistry》2019,23(3):725-734
Journal of Solid State Electrochemistry - This paper reports the development of a photoelectrochemical platform based on indium tin oxide (ITO) electrode modified with carboxyl-functionalized... 相似文献
42.
43.
Silva AM Filipe P Seixas RS Pinto DC Patterson LK Hug GL Cavaleiro JA Mazière JC Santus R Morlière P 《The journal of physical chemistry. B》2008,112(37):11456-11461
In micellar solutions, one-electron reduction of (*)O 2 (-) radical-anions by 3-alkylpolyhydroxyflavones (FnH) with alkyl chains of n = 1, 4, 6, 10 carbons produces phenoxyl radicals ( (*)Fn) identical to those obtained by one-electron oxidation by (*)Br 2 (-) radical-anions or by repair of tryptophan radicals. In cetyltrimethylammonium bromide (CTAB), F1H localizes in the Stern layer, and alkyl chains of other FnH solubilize in the hydrophobic interior, interacting with cetyl tails. This interaction produces more compact micelles with lower intramicellar fluidity, as suggested by the increase in the pseudo-first-order rate constant of (*)Fn formation ( k 1) from approximately 390 s (-1) for n = 1 to 610 s (-1) for n = 10, leading to an intramicellar bimolecular rate constant of 1 x 10 (5) M (-1) s (-1). Additionally, (*)F1 and (*)F4 decay by intermicellar bimolecular reaction (2 k = 20 and 2 x 10 (5) M (-1) s (-1), respectively) whereas other (*)Fn radicals are stable over seconds due to increased localization with regards to the Stern layer. In contrast, the thick uncharged hydrophilic palisade layer and the compact hydrophobic core of Triton X100 micelles are responsible for a much higher microviscosity resulting in a decrease in k 1 from approximately 15.6 s (-1) for n = 1 to 9.6 s (-1) for n = 10. 相似文献
44.
Carvalho PN Rodrigues PN Alves F Evangelista R Basto MC Vasconcelos MT 《Talanta》2008,76(5):1124-1129
Determination of organochlorine pesticides (OCPs) in sediments implicates extraction of these compounds from the matrix, which is difficult owing to strong interaction among OCPs and different constituents of the sediments, particularly organic content. The method here described is a combination of microwave assisted extraction (MAE), headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), acting in selected-ion storage mode, or GC-electron capture detector (ECD, for routine analysis). Methanol was used as extracting solvent and aliquots of the MAE extracts (after inclusion of a step for sulfur elimination when required) were used to prepare aqueous solutions for HS-SPME. A complete automation of the SPME procedure increases the sample throughput, including standard addition for calibration purpose. The procedure has the advantage of exclude additional clean-up steps and pre-concentration before SPME. Application to reference sediments of different characteristics revealed absence of significant interferences from the matrix for alpha-lindane, gamma-lindane, aldrin, dieldrin, endrin, 4,4'-DDT, 4,4'-DDD, 4,4'-DDE, heptachlor, heptachlor epoxide and good sensitivity. Detection limits ranged from 0.005 to 0.11 ng of OCP per gram of dried sediment using GC-MS and from 0.01 to 0.26 ngg(-1) using GC-ECD. The linear response ranges embraced 5-6 orders of magnitude (up to 1000 ngg(-1)) in GC-MS, being narrower for GC-ECD. The method was successfully applied to sandy and muddy sediments from Portuguese rivers estuaries, enabling quantification of seven OCPs. The method resulted effective, relatively simple and fast, being suitable for routine monitoring of residues of OCPs from sediments of different grain size and organic matter content, which influence concentration, mobility and availability of contaminants. 相似文献
45.
Costa M Areias F Abrunhosa L Venâncio A Proença F 《The Journal of organic chemistry》2008,73(5):1954-1962
The reaction of salicylic aldehydes with malononitrile was reinvestigated, and the reaction pathway was followed by 1H NMR spectroscopy. A delicate control of the experimental conditions allowed the synthesis of 2-imino-2H-chromene-3-carbonitriles 1, (2-amino-3-cyano-4H-chromen-4-yl)malononitriles 2, 4-amino-5-imino-2,7-dimethoxy-5H-chromeno[3,4-c]pyridine-1-carbonitrile 12, and (4,5-diamino-1-cyano-1,10b-dihydro-2H-chromeno[3,4-c]pyridin-2-ylidene)malononitrile 13. Two novel 2-iminochromene dimers, with structures 8 and 9, were isolated and fully characterized. The activity of compound 8a on Aspergillus spp. growth and on ochratoxin A production was evaluated. The results of the bioassays indicate that compound 8a, applied at concentrations of 2 mM, totally inhibited the growth of the fungi tested. Ochratoxin A production by Aspergillus alliaceus was reduced by about 93% with a 200 microM solution of this compound. A moderate inhibitory effect was observed for the analogous structure 8b, and no inhibition was registered for compounds 2 and 1, used as synthetic precursors of the dimeric species 8. 相似文献
46.
Antônio Gomes dos Santos Neto Franciele de Matos Morawski Ana Caroline Ferreira Santos Cláudia Quintino da Rocha Roberto Batista de Lima Marília Oliveira Fonseca Goulart Clenilton Costa dos Santos Flávio Colmati Antônio Euzébio Goulart Santana Marco Aurélio Suller Garcia Auro Atsushi Tanaka 《Electroanalysis》2023,35(5):e202200390
Here, we report multiwalled carbon nanotubes (MWCNTs) functionalized with γ-cyclodextrins (γCD) as a novel electrochemical strategy for Rutin determination, showing superior performance than β-cyclodextrins (βCD) modified MWCNTs, suggesting an adequate environment for host-guest interactions. Under optimized conditions, the sensor showed a linear range of 39–975 nmol L−1 and a limit of detection of 7 nmol L−1. When tested with quercetin, catechin, and caffeine, the platform presented high selectivity with an interference response <10 %. The method was employed to quantify Rutin in spiked pharmaceutical and herbal extracts, providing recovery of 93–98.4 %. Also, HPLC-PDA confirmed the method‘s accuracy. 相似文献
47.
Vasconcelos F Cristol S Paul JF Tricot G Amoureux JP Montagne L Mauri F Delevoye L 《Inorganic chemistry》2008,47(16):7327-7337
The assignment of high-field (18.8 T) (17)O MAS and 3QMAS spectra has been completed by use of first-principles calculations for three crystalline sodium phosphates, Na 3P 3O 9, Na 5P 3O 10, and Na 4P 2O 7. In Na 3P 3O 9, the calculated parameters, quadrupolar constant ( C Q), quadrupolar asymmetry (eta Q), and the isotropic chemical shift (delta cs) correspond to those deduced experimentally, and the calculation is mandatory to achieve a complete assignment. For the sodium tripolyphosphate Na 5P 3O 10, the situation is more complex because of the free rotation of the end-chain phosphate groups. The assignment obtained with ab initio calculations can however be confirmed by the (17)O{ (31)P} MAS-J-HMQC spectrum. Na 4P 2O 7 (17)O MAS and 3QMAS spectra show a complex pattern in agreement with the computed NMR parameters, which indicate that all of the oxygens exhibit very similar values. These results are related to structural data to better understand the influence of the oxygen environment on the NMR parameters. The findings are used to interpret those results observed on a binary sodium phosphate glass. 相似文献
48.
Dr. Meng Liu Christy Y. Hui Dr. Qiang Zhang Jimmy Gu Dr. Balamurali Kannan Dr. Sana Jahanshahi‐Anbuhi Prof. Dr. Carlos D. M. Filipe Prof. Dr. John D. Brennan Prof. Dr. Yingfu Li 《Angewandte Chemie (International ed. in English)》2016,55(8):2709-2713
We report on a paper device capable of carrying out target‐induced rolling circle amplification (RCA) to produce massive DNA amplicons that can be easily visualized. Interestingly, we observed that RCA was more proficient on paper than in solution, which we attribute to a significantly higher localized concentration of immobilized DNA. Furthermore, we have successfully engineered a fully functional paper device for sensitive DNA or microRNA detection via printing of all RCA‐enabling molecules within a polymeric sugar film formed from pullulan, which was integrated with the paper device. This encapsulation not only stabilizes the entrapped reagents at room temperature but also enables colorimetric bioassays with minimal steps. 相似文献
49.
Perin Gelson Silva Cristian M. Borges Elton L. Duarte José E. G. Goulart Helen A. Silva Rafaela B. Schumacher Ricardo F. 《Research on Chemical Intermediates》2016,42(6):5873-5885
Research on Chemical Intermediates - We describe a simple and rapid method for selective synthesis of 4-thiomethyl-1,3-dioxolan-2-ones promoted by KF/Al2O3 using PEG-400 as solvent under microwave... 相似文献