排序方式: 共有97条查询结果,搜索用时 31 毫秒
1.
Grumelli DE Forzani ES Morales GM Miras MC Barbero CA Calvo EJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2349-2355
The sulfonation of polyaniline (PANI) films by nucleophilic addition of sulfite ion has been controlled through the polymer oxidation state under electrochemical control. The process was monitored by in situ electrochemical quartz crystal microbalance (EQCM), and the polymer oxidation was accomplished by electrode potential steps in sulfite aqueous solutions. The nucleophilic addition of sulfite to PANI only takes place on the oxidized polymer. From the ratio of added mass to the injected charge, the degree of sulfonation has been obtained with a yield as high as 50%. It has been observed that the ion-exchange mechanism during the oxidation-reduction process in the resulting sulfonated polymer is analogous to the polymer produced by electrophilic sulfonation of polyaniline or by copolymerization of aniline with aminosulfonic acids, unlike the ionic exchange observed for unmodified PANI. 相似文献
2.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Lisheng D Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Shuchen Z Zhong Yuanyuan 《Physical review letters》1993,71(21):3417-3420
3.
Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
4.
Teixeira-Neto É Leite CA Cardoso AH Medeiros da Silva MC Braga M Galembeck F 《Journal of colloid and interface science》2000,231(1):182-189
Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press. 相似文献
5.
6.
7.
Frederico F. Martins Dr. Ángel Sánchez-González Jose Lanuza Dr. Haralampos N. Miras Prof. Xabier Lopez Dr. Nuno A. Bandeira Dr. Adrià Gil 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(35):8977-8984
Phosphoester hydrolysis is an important chemical step in DNA repair. One archetypal molecular model of phosphoesters is para-nitrophenylphosphate (pNPP). It has been shown previously that the presence of molecular metal oxide [Mo7O24]6− may catalyse the hydrolysis of pNPP through the partial decomposition of polyoxomolybdate framework resulting in a [(PO4)2Mo5O15]6− product. Real-time monitoring of the catalytic system using electrospray ionisation mass spectrometry (ESI-MS) provided a glance into the species present in the reaction mixture and identification of potential catalytic candidates. Following up on the obtained spectrometric data, Density Functional Theory (DFT) calculations were carried out to characterise the hypothetical intermediate [Mo5O15(pNPP)2(H2O)6]6− that would be required to form under the hypothesised transformation. Surprisingly, our results point to the dimeric [Mo2O8]4− anion resulting from the decomposition of [Mo7O24]6− as the active catalytic species involved in the hydrolysis of pNPP rather than the originally assumed {Mo5O15} species. A similar study was carried out involving the same species but substituting Mo by W. The mechanism involving W species showed a higher barrier and less stable products in agreement with the non-catalytic effect found in experimental results. 相似文献
8.
9.
10.
McGlone T Vilà-Nadal L Miras HN Long DL Poblet JM Cronin L 《Dalton transactions (Cambridge, England : 2003)》2010,39(48):11599-11604
Two titanium embedded polyoxometalates with unprecedented structural features are presented: a monotitanium containing tungstoantimonate Na(13)H(3)[TiO(SbW(9)O(33))(2)]·33 H(2)O featuring a {Ti=O}(2+) moiety (1) and a hexatitanium containing tungstoarsenate K(6)[Ti(4)(H(2)O)(10)(AsTiW(8)O(33))(2)]·30 H(2)O containing a {Ti(4)(H(2)O)(10)}(16+) moiety (2). Both compounds have been fully characterised by single crystal X-ray diffraction, elemental analysis, IR and TGA. 1 is constructed from two α-B-{Sb(III)W(9)O(33)} fragments linked by five sodium cations and an unprecedented square pyramidal Ti(O)O(4) group with a terminal Ti=O bond, and 2 exhibits a Krebs-type structure composed of two {AsTiW(8)O(33)} fragments, where one W(VI) centre has been substituted for a Ti(IV) centre in each, fused together via a belt of four additional Ti(IV) centres. This system represents the tungsten Ti-incorporated polyoxoanion with one of the highest Ti:W ratios so far reported. Additionally, 2 could also be isolated as an n-tetrabutylammonium salt and has been further characterised by electrochemistry and electrospray ionisation (ESI) MS studies. Due to the unique nature of these systems, both have been fully investigated using DFT calculations yielding highly interesting results. Structure 1 has been optimised with five sodium atoms in the belt position, which in addition to reducing the high charge of the cluster influence a stabilisation of the antimony lone pairs. Electrostatic potential calculations highlight the high electronegativity of the terminal oxygen on the titanium centre, enhancing real potentiality as a reactive site for catalysis. 相似文献