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An efficient sensor was developed for the simultaneous determination of gallic and folic acid in juice samples using an electrochemically pretreated carbon paste electrode. The electrode was characterized by CV and EIS. The electrochemical behavior of GA and FA was evaluated by CV and SWV. The electrode exhibited high electrocatalytic activity towards GA and FA due to high surface area. Under the optimized condition, linear plots in the ranges of 0.08–13 μM and 0.1 to 15 μM were obtained for GA and FA, respectively. The proposed method was successful for the simultaneous determination of GA and FA in juice samples with satisfactory recovery. 相似文献
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Yi Yang Xueyi He Penghui Zhang Yassin H. Andaloussi Hailu Zhang Zhongyi Jiang Yao Chen Shengqian Ma Peng Cheng Zhenjie Zhang 《Angewandte Chemie (International ed. in English)》2020,59(9):3678-3684
Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H3PO4, the COFs (H3PO4@COFs) realize an ultrahigh proton conductivity of 1.13×10?1 S cm?1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H3PO4@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm?2 and a maximum current density of 456 mA cm?2, which exceeds all previously reported COF materials. 相似文献
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Balibanu F Hailu K Eymael R Demco DE Blumich B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,145(2):246-258
The response of the spin system has been investigated by numerical simulations in the case of a nuclear magnetic resonance (NMR) experiment performed in inhomogeneous static and radiofrequency fields. The particular case of the NMR-MOUSE was considered. The static field and the component of the radiofrequency field perpendicular to the static field were evaluated as well as the spatial distribution of the maximum NMR signal detected by the surface coil. The NMR response to various pulse sequences was evaluated numerically for the case of an ensemble of isolated spins (1/2). The behavior of the echo train in Carr-Purcell-like pulse sequences used for measurements of transverse relaxation and self-diffusion was simulated and compared with the experiment. The echo train is shown to behave qualitatively differently depending on the particular phase schemes used in these pulse sequences. Different echo trains are obtained, because of the different superposition of Hahn and stimulated echoes forming mixed echoes as a result of the spatial distribution of pulse flip angles. The superposition of Hahn and stimulated echoes originating from different spatial regions leads to distortions of the mixed echoes in intensity, shape, and phase. The volume selection produced by Carr-Purcell-like pulse sequences is also investigated for the NMR-MOUSE. The developed numerical simulation procedure is useful for understanding a variety of experiments performed with the NMR-MOUSE and for improving its performance. Copyright 2000 Academic Press. 相似文献
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Schön P Degefa TH Asaftei S Meyer W Walder L 《Journal of the American Chemical Society》2005,127(32):11486-11496
The mechanism of charge propagation in "ion channel sensors" (ICSs) consisting of gold electrodes modified with a layer of charged proteins and highly charged redox-active marker ions in solution was investigated by electrochemical techniques, QCM and AFM. The study is based on seven proteins (concanavalin A, cytochrome c, glucose oxidase, lysozyme, thyroglobulin, catalase, aldolase, and EF1-ATPase) in combination with seven electroactive marker ions ([Fe(CN)6]3-, [Fe(CN)6]4-, [Ru(NH3)6]3+, mono-, di-, and trimeric viologens), as well as a series of suppressor and enhancer ions leading to the following general statements: (i) electrostatic binding of charged marker ions to the domains of the protein is a prerequisite for an electrochemical current and (ii) charge propagation through the layer consists of electron hopping along surface-confined marker ions into the pores between adsorbed proteins. It is further shown that (iii) marker ions and suppressor ions with identical charge compete for oppositely charged sites on the protein domain, (iv) electrostatically bound multilayers of marker or enhancer ions with alternating charge form on a charged protein domain, and (v) self-exchange and exergonic ET catalysis between adsorbed marker ions and marker ions in solution take place. In addition to fundamental insight into the mechanism of charge propagation, valuable information for the design, optimization, and tailoring of new biosensors based on the ICS concept is demonstrated by the current findings. 相似文献
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金属钯纳米颗粒/氮化钛复合材料对水中2,4-二氯苯酚的电催化氢化脱氯(英文) 总被引:2,自引:0,他引:2
随着社会经济的快速发展,含氯有机物,特别是含氯苯系物,在农业、化工和医药等领域的使用量逐年增多,而使用过程中不合理的排放和控制致使含氯苯系物对生态环境,特别是水体环境的污染日趋严重.含氯苯系物具有高致毒致癌性,易生物富集,且很难被完全降解矿化,已被国家环保局认定为优先控制污染物.常规的废水处理工艺,如吸附、氧化及生物降解等,效率不高,且具有二次污染风险.电催化氢化脱氯技术是一种新型特别针对废水中含氯有机污染物的处理工艺,是通过在阴极电解还原水,原位生成原子态氢,以进攻苯环上C.Cl键,通过C.Cl键断裂H原子取代,使含氯苯系物完全转化为苯系物,达到去毒去害化的目的,近年来越来越受到研究者的关注.在整个电催化氢化脱氯技术中,高效稳定的电催化剂合成是关键,决定着脱氯效率、脱氯动力学、产物选择性及能量的利用率.本文报道了一种简易、无需添加任何表面活性剂的湿式还原法制备金属钯/氮化钛(Pd/TiN)和金属钯/碳(Pd/C)复合材料.在该复合材料中,金属钯颗粒具有均一的纳米尺寸(约5.0 nm)和球状形貌,且均匀分布在TiN和C载体上.作为针对水体中代表性含氯苯系物2,4-二氯苯酚的电催化氢化脱氯反应催化剂,Pd/TiN所展现的活性和稳定性均优于TiN和Pd/C,这源于TiN载体的促进作用.当TiN与Pd复合时,相应形成的Pd-TiN界面可改变Pd表面的电子结构,进一步优化Pd产活性氢及其吸附活化2,4-二氯苯酚的性能,因而其催化氢化脱氯活性增加.阴极工作电压是该催化反应中一个重要操作参数,决定了电催化氢化脱氯的效率和最终产物的构成.实验表明,.0.80 V vs Ag/AgCl是最佳操作电压,此时2,4-二氯苯酚的电催化氢化脱氯效率最高,可达到93.27%,且可实现最大程度的2,4-二氯苯酚向苯酚转化.脱氯反应路径研究发现,在Pd/TiN催化剂上2,4-二氯苯酚脱氯反应路径为2,4-二氯苯酚→对位一氯苯酚,邻位一氯苯酚→苯酚,但Pd/TiN对邻位和对位的C.Cl键断裂基本没有选择性.本文提供了一种新的有效调控Pd材料电催化氢化脱氯性能的方法,可望用于其他氢化反应体系的高效催化剂的设计合成,同时可推动电催化氢化脱氯技术在环境污染修复中的应用. 相似文献
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Hierarchical chlorine-doped rutile TiO2 spherical clusters of nanorods: Large-scale synthesis and high photocatalytic activity 总被引:1,自引:0,他引:1
In this study, we report the synthesis of hierarchical chlorine-doped rutile TiO2 spherical clusters of nanorods photocatalyst on a large scale via a soft interface approach. This catalyst showed much higher photocatalytic activity than the famous commercial titania (Degussa P25) under visible light (λ>420 nm). The resulting sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy, 1H solid magic-angle spinning nuclear magnetic resonance (MAS-NMR) and photoluminescence spectroscopy. On the basis of characterization results, we found that the doping of chlorine resulted in red shift of absorption and higher surface acidity as well as crystal defects in the photocatalyst, which were the reasons for high photocatalytic activity of chlorine-doped TiO2 under visible light (λ>420 nm). These hierarchical chlorine-doped rutile TiO2 spherical clusters of nanorods are very attractive in the fields of environmental pollutants removal and solar cell because of their easy separation and high activity. 相似文献
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31P chemical shift of adsorbed trialkylphosphine oxides for acidity characterization of solid acids catalysts 总被引:1,自引:0,他引:1
Zheng A Huang SJ Chen WH Wu PH Zhang H Lee HK de Ménorval LC Deng F Liu SB 《The journal of physical chemistry. A》2008,112(32):7349-7356
A comprehensive study has been made to predict the adsorption structures and (31)P NMR chemical shifts of various trialkylphosphine oxides (R3PO) probe molecules, viz., trimethylphosphine oxide (TMPO), triethylphosphine oxide (TEPO), tributylphosphine oxide (TBPO), and trioctylphosphine oxide (TOPO), by density functional theory (DFT) calculations based on 8T zeolite cluster models with varied Si-H bond lengths. A linear correlation between the (31)P chemical shifts and proton affinity (PA) was observed for each of the homologous R3PO probe molecules examined. It is found that the differences in (31)P chemical shifts of the R3POH(+) adsorption complexes, when referring to the corresponding chemical shifts in their crystalline phase, may be used not only in identifying Br?nsted acid sites with varied acid strengths but also in correlating the (31)P NMR data obtained from various R3PO probes. Such a chemical shift difference therefore can serve as a quantitative measure during acidity characterization of solid acid catalysts when utilizing (31)P NMR of various adsorbed R3PO, as proposed in our earlier report (Zhao; et al. J. Phys. Chem. B 2002, 106, 4462) and also illustrated herein by using a mesoporous H-MCM-41 aluminosilicate (Si/Al = 25) test adsorbent. It is indicative that, with the exception of (TMPO), variations in the alkyl chain length of the R3PO (R = C(n)H(2n+1); n > or = 2) probe molecules have only negligible effect on the (31)P chemical shifts (within experimental error of ca. 1-2 ppm) either in their crystalline bulk or in their corresponding R3POH(+) adsorption complexes. Consequently, an average offset of 8 +/- 2 ppm was observed for (31)P chemical shifts of adsorbed R3PO with n > or = 2 relative to TMPO (n = 1). Moreover, by taking the value of 86 ppm predicted for TMPO adsorbed on 8T cluster models as a threshold for superacidity (Zheng; et al. J. Phys. Chem. B 2008, 112, 4496), a similar threshold (31)P chemical shift of ca. 92-94 ppm was deduced for TEPO, TBPO, and TOPO. 相似文献