共查询到20条相似文献,搜索用时 15 毫秒
1.
The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)2 and β‐Ni(OH)2 were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)2 → γ‐NiOOH and β‐Ni(OH)2 → β‐NiOOH, the process of OH? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH? adsorption process occurs as an elementary step in the former reaction and the H+ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
The concentration effect on a two‐dimensional (2D) self‐assembly of 4, 4′‐dihexadecyloxy‐benzophenon (DHB) has been investigated by scanning tunneling microscopy. The self‐assembly of DHB at the phenyloctane/graphite interface was concentration dependent. Under low concentration, the DHB molecules were adsorbed intactly on the graphite surface. With the increasing of concentration, one of side chains connecting the conjugated moiety stretched into the liquid phase. The coexistence of two self‐assembled structures was observed in a moderate concentration. The result indicated that the van der Waals interactions between the molecules and the graphite lattice were decreasing with the increasing concentration. After the samples were placed in ambient conditions over 24 h, a different self‐assembled structure was obtained on the gas/solid interface, in which the DHB molecules were adsorbed on the surface with only one of the side chains. Both the benzophenon core and the other side chain were extended to the gas phase. The results demonstrated that concentration played an important role in forming the 2D molecular self‐assembly and provided an efficient approach for the control of the DHB molecular nanostructure. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
The electrochemical stability of TiO2 nanoarchitecture fabricated in fluoride electrolyte presented in this paper is related to 2D and 3D geometries that present a shift from nanopores toward nanotubes. The fabrication conditions involve a 60 V applied voltage for 2 hours of anodizing in order to create the ordered structures, in a mixture of low‐water glycerol electrolyte and fluoride. With the use of different ultrasonication times, a variety of nanotubes/nanopores were observed. The surface interfacial aspects were investigated mainly by surface microscopy and hydrophilic/hydrophobic balance for the grown structures ultrasonicated at various periods of time. The electrochemical behavior of the nanotube‐structured surface was performed by potentiodynamic evaluation and electrochemical impedance spectroscopy in a simulated body fluid solution. As a most important result, all surface analysis and electrochemical data interpretation permitted the proposition of a model for elaboration of different nanostructures from nanopores to nanotubes. These different surface nanoarchitectures were obtained as a result of ultrasonication at various periods of time. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
A facile and eco‐friendly biosynthetic route for preparing Pd truncated octahedrons (PdTOs) using firmiana simplex leaf extract was reported without any chemical reducing agents. The information of reducing components, reduction process and time were obtained by ATR‐FTIR imaging, FTIR and UV–Vis spectroscopy, respectively. TEM image revealed that more than 75% of PdNPs were composed of PdTOs with an average diameter of 9.2 nm. HR‐TEM analysis demonstrated that a single PdTO consisted of the mix of {100} and {111} crystal planes. SAED and XRD pattern confirmed the well crystalline nature of fcc structured PdTOs. The model reactions of electro‐oxidation of methanol and reduction of p‐nitrophenol (p‐NP) were adopted to explore the effects of structure and size of PdNPs on the catalytic properties. In the electro‐oxidation of methanol, the forward‐scan peak current density (If) of PdTOs was 10.05 mA cm‐2, 6.3 times and 1.9 times of PdNPs‐0 and PdNPs‐4:1, illustrating its superior electro‐catalytic property to that of spherical PdNPs. In the p‐NP reduction reaction, the apparent rate constant (Ka) over PdTOs was 0.358 min‐1, higher than spherical PdNPs‐0 (0.08 min‐1) with the similar particle size and lower than the same spherical PdNPs‐4:1 (0.562 min‐1) and commercial Pd/C (0.415 min‐1), which all about half the size of PdTOs. It has been demonstrated that electro‐chemical oxidation of methanol was a structure‐sensitive reaction, while the reduction of p‐NP was mainly dependent on the particle size of PdNPs. 相似文献
5.
Nucleation and growth of Ge nanoclusters on the Si(111)‐(7 × 7) surface studied by scanning tunneling microscopy
下载免费PDF全文
![点击此处可从《Surface and interface analysis : SIA》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yongping Zhang Zhiqian Chen Guo Qin Xu Eng Soon Tok 《Surface and interface analysis : SIA》2015,47(2):222-226
Nucleation and growth of two‐dimensional Ge nanoclusters on the Si(111)‐(7 × 7) surface at elevated substrate temperatures have been studied using scanning tunneling microscopy. The uniformity of the Ge nanoclusters is improved with the increase of substrate temperature, and ordered Ge nanoclusters are formed on the faulted and unfaulted halves of (7 × 7) unit cell at substrate temperature of 200 °C. It is proposed that the Ge nanoclusters consist of six Ge atoms with three on top of the center adatoms and others on the rest atoms within one half of a unit cell. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
Cell‐Surface Engineering by a Conjugation‐and‐Release Approach Based on the Formation and Cleavage of Oxime Linkages upon Mild Electrochemical Oxidation and Reduction
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Abigail Pulsipher Debjit Dutta Wei Luo Prof. Muhammad N. Yousaf 《Angewandte Chemie (International ed. in English)》2014,53(36):9487-9492
We report a strategy to rewire cell surfaces for the dynamic control of ligand composition on cell membranes and the modulation of cell–cell interactions to generate three‐dimensional (3D) tissue structures applied to stem‐cell differentiation, cell‐surface tailoring, and tissue engineering. We tailored cell surfaces with bioorthogonal chemical groups on the basis of a liposome‐fusion and ‐delivery method to create dynamic, electroactive, and switchable cell‐tissue assemblies through chemistry involving chemoselective conjugation and release. Each step to modify the cell surface: activation, conjugation, release, and regeneration, can be monitored and modulated by noninvasive, label‐free analytical techniques. We demonstrate the utility of this methodology by the conjugation and release of small molecules to and from cell surfaces and by the generation of 3D coculture spheroids and multilayered cell tissues that can be programmed to undergo assembly and disassembly on demand. 相似文献
7.
Bilge Taner Pervin Deveci Zafer Üstündaǧ Selda Keskin Emine Özcan Ali Osman Solak 《Surface and interface analysis : SIA》2012,44(2):185-191
3‐Aminophenylcalix[4]pyrrole (3APCP) was grafted to a glassy carbon (GC) surface during the electrochemical oxidation process in 0.1 M tetrabutylammoniumtetra‐fluoroborate (TBATFB) containing acetonitrile solution. The presence of a surface film was confirmed electrochemically by comparing voltammograms of dopamine and ferricyanide redox probes at the bare and modified electrodes. Reflection‐absorption infrared spectroscopy (RAIRS), XPS, atomic force microscopy (AFM), ellipsometry and the contact angle measurements were also employed to characterize 3APCP film on GC electrode. RAIRS analysis revealed that calix[4]pyrrole was bonded to the glassy carbon surface via the etheric linkage. The stability of the modified GC electrode was also studied. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
8.
Yiming Wang Xiaofeng Pang Yuyu Zhang Hongzhi Wang 《Surface and interface analysis : SIA》2009,41(10):775-778
Chemical modifications on the surface of optical fibers have played an important role in the immobilization of biological recognition molecules. In this article, the specific goal was to characterize the covalent bond on the surface of optical fiber by scanning electron microscopy and energy dispersive X‐ray spectrometry (EDS) and chemical analysis after silanization. Optical fibers pretreated with hydrofluoric acid and piranha solution were silanized in the 3‐aminopropyltriethoxysilane solution, then microscopic components of silanized optical fibers were determined to validate the silanization. Results showed that carbon atom was measured with EDS, and the ratio of silicon and oxygen atom was 1:3.6 on its surface by calculation. Fluorescence experiments on the short silanized optical fiber segments indicated that the intensity of fluorescence was relatively weak and reached equilibrium after 3 h. Both methods, EDS and fluorescence test, were effective to characterize the covalent bond of different silanes and biological recognition molecules on the optical fibers for biosensor applications. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
The catalytic efficiency of ammonium dihydrogenphosphate was evaluated in the two heterogeneous forms of NH4H2PO4/MCM‐48 and NH4H2PO4/MCM‐41, as mesoporous catalysts, in the solvent free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones through one‐pot three‐component condensation of ethyl acetoacetate, an aryl aldehyde and urea. Different reaction parameters including catalytic efficacy, solvent effect, and urea concentration are considered. 相似文献
10.
《应用有机金属化学》2017,31(5)
A new, green and reusable nanomagnetic heterogeneous catalyst, namely Fe3O4@TiO2@O2PO2(CH2)NHSO3H, was synthesized and fully characterized using suitable techniques such as infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies, thermogravimetry, vibrating sample magnetometry and energy‐dispersive X‐ray spectroscopy. The applicability of the constructed heterogeneous core–shell catalyst as a promoter was successfully explored for the synthesis of 2‐amino‐4,6‐diphenylnicotinonitrile derivatives upon the reaction of a good range of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate. The desired products were obtained with good to high yields in short reaction times under solvent‐free conditions. The suggested mechanism offers an anomeric‐based oxidation route to the products in the final step of the synthetic pathway. 相似文献
11.
Christiane Ruff Katja Hr Bernhard Weckerle Peter Schreier Thorsten Knig 《Journal of separation science》2000,23(5):357-359
Isotope ratio monitoring gas chromatography‐mass spectrometry of the 2H/1H ratio by pyrolysis isotope ratio mass spectrometry (P‐IRMS) was used to analyze benzaldehyde originating from various sources. Based on the δ2HSMOW value of an authentic reference sample determined with an elemental analyzer (EA), the range of reproducibility and linearity was checked. Correct (EA related) and reproducible data were obtained for sample amounts >0.6 μg benzaldehyde (on column). In another series of experiments, the influence of sample preparation, i. e. simultaneous distillation‐extraction (SDE) was found to be negligible. The following ranges of δ2HSMOW values were determined for benzaldehyde using five types of samples, i. e. (i) synthetic (δ2HSMOW –78 to –85‰, ex benzal chloride; +420 to +668‰, ex toluene) and ‘natural’ (including ‘ex‐cassia’) references (δ2HSMOW –83 to –144‰); (ii) bitter almond oils (δ2HSMOW –113 to –148‰); (iii) fruits (δ2HSMOW –111 to –146‰); (iv) kernels (δ2HSMOW –115 to –188‰); and (v) leaves (δ2HSMOW –165 to –189‰). 相似文献
12.
《Journal of computational chemistry》2017,38(20):1780-1788
The (nitro)(N‐methyldithiocarbamato)(trimethylphospane)nickel(II), [Ni(NO2)(S2CNHMe)(PMe3)] complex catalyses efficiently the O‐atom transfer reactions to CO and acetylene. Energetically feasible sequence of elementary steps involved in the catalytic cycle of the air oxidation of CO and acetylene are proposed promoted by the Ni(NO2)(S2CNHMe)(PMe3)] ↔ Ni(NO2)(S2CNHMe)(PMe3) redox couple using DFT methods both in vacuum and dichloromethane solutions. The catalytic air oxidation of HC≡CH involves formation of a five‐member metallacycle intermediate, via a [3 + 2] cyclo‐addition reaction of HC≡CH to the Ni‐N = O moiety of the Ni(NO2)(S2CNHMe)(PMe3)] complex, followed by a β H‐atom migration toward the Cα carbon atom of the coordinated acetylene and release of the oxidation product (ketene). The geometric and energetic reaction profile for the reversible [Ni( ‐NO2)(S2CNHMe)(PMe3)] [Ni( ‐ONO)(S2CNHMe)(PMe3)] linkage isomerization has also been modeled by DFT calculations. © 2017 Wiley Periodicals, Inc. 相似文献
13.
A non‐optical force sensor that allows operation both in lateral (shear) and in vertical (tapping) force detection modes has been introduced for dynamic tip–sample distance regulation in scanning near‐field optical microscopy (SNOM) of biological samples. The sensor is based on a rectangular bimorph cantilever consisting of two thin piezoceramic layers bonded to a brass centre shim. One of the piezo layers serves as the probe dither and another as the responder of the sensed forces. The sensor is driven with a home‐made Q‐control electronics so that its sensitivity and bandwidth can be adjusted. The dynamics, characteristics and design considerations of the sensor are theoretically and experimentally discussed. Driving the bimorph cantilever at its eigenfrequency with appropriate force feedback allows one to obtain a quality factor (Q‐factor) up to 103 in water, suitable for different sample softness and imaging environments. The high sensitivity of the sensor is demonstrated both by shear force and by tapping mode imaging of soft biological samples in their natural state. Near‐field optical resolution of better than 100 nm on red blood cells in water has been obtained. The experimental results suggest that this SNOM sensor would be a promising set‐up for biological applications. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
14.
The efficient in‐situ reduction and cyclization reaction of aromatic aldehyde, 1,3‐cyclopentanedione (tetronic acid), and nitro‐compound under SnCl2·2H2O‐THF medium
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
An efficient in‐situ reduction and cyclization reaction for the synthesis of pyrazolo[4,3‐f]quinoline, pyrazolo[3,4‐f]quinoline, and pyrazolo[3,2‐f]quinoline derivatives directly form 5‐nitroindazole, 6‐nitroindazole and 5‐nitroindole in the presence of SnCl2·2H2O was reported. Compared to traditional synthetic methods, this approach has the advantages of stable reagents, easy obtaining raw material, and high yields. In this research, SnCl2·2H2O is the efficient reducing agent for the in‐situ reduction and cyclization reaction of nitro‐compound. In addition, this process provided an alternative approach for the synthesis of target compounds. 相似文献
15.
《Surface and interface analysis : SIA》2018,50(4):488-495
Graphene‐supported Si‐TiO2 (Si‐Ti‐GE) composites have been synthesized by a simple polymerization and sintering method. In the Si‐Ti‐GE composites, many small Si‐TiO2 particles are scattered on the graphene sheet, which can mitigate the agglomeration of the material and further reduce the particle size. The initial discharge capacities of Si‐TiO2, Si‐Ti‐GE‐1, Si‐Ti‐GE‐2, and Si‐Ti‐GE‐3 are 336.9, 337.2, 339.8, and 356.6 mAh g−1 at the current density of 200 mA g−1, respectively. The discharge rate capacities of TiO2, Si‐TiO2, and Si‐Ti‐GE‐3 composites retain 57.5%, 41.7%, and 82.1% at the current density from 100 to 400 mA g−1, respectively. Therefore, the introduction of graphene not only could facilitate the Li+ diffusion and electron transport but also could make better electrical conductivity. 相似文献
16.
High Sensitive Microsensor Based on Organic‐Inorganic Composite for Two‐Dimensional Mapping of H2O2 by SECM
下载免费PDF全文
![点击此处可从《Electroanalysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Danielle Diniz Justino Isabel Lourenço Torres Rita de Cássia Silva Luz Flavio Santos Damos 《Electroanalysis》2015,27(5):1202-1209
The present work describes the development of a selective, sensitive and stable sensing microsensor for scanning electrochemical microscopy (SECM) to measure H2O2 during electrochemical reduction of oxygen. The microsensor is based on graphene and Poly(3,4‐ethylenedioxythiophene) composite as support to iron (III) hexacyanoferrate (II) (PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor). The electrochemical properties of the PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The PEDOT/graphene/FeIII4[FeII(CN)6]3 microsensor showed an excellent electrocatalytic activity toward hydrogen peroxide (H2O2) reduction with a diminution of the overpotential of about 500 mV in comparison to the process at a bare gold microelectrode. The microsensor presented excellent performance for two dimensional mapping of H2O2 by SECM in 0.1 mol L?1 phosphate buffer solution (pH 7.0). Under optimized conditions, a linear response range from 1 up to 1000 µmol L?1 was obtained with a sensitivity of 0.08 nA L µmol?1 and limit of detection of 0.5 µmol L?1. 相似文献
17.
《应用有机金属化学》2017,31(10)
A heterogeneous material composed of MCM‐48/H5PW10V2O40 was produced and used as an efficient, eco‐friendly and highly recyclable catalyst for the one‐pot and multicomponent synthesis of 3,4‐dihydroquinoxalin‐2‐amine, diazepine‐tetrazole and benzodiazepine‐2‐carboxamide derivatives in aqueous media and at room temperature with high yields in short reaction times (40–60 min). The recoverable catalyst was easily recycled at least five times without any loss of catalytic activity. The structures of obtained products were confirmed using 1H NMR and 13C NMR spectra. 相似文献
18.
A novel Cu(OAc)2·H2O catalyzed coupling reaction of N‐substituted‐2‐iodobenzamides with malononitrile to afford N‐substituted‐3‐amino‐4‐cyano‐isoquinoline‐1(2H)‐ones is described. The reaction proceeded in DMSO at 90°C for 5 h in nitrogen without external ligands. 相似文献
19.
Theoretical Study on the Intermolecular Interactions between 1,1‐Diamino‐2,2‐Dinitroethylene and H2O
The density functional method was applied to the study of 1,1‐diamino‐2,2‐dinitroethylene (Fox‐7)/H2O dimer. All the possible dimers ( 1, 2 and 3 ), as well as the monomers, were fully optimized with the DFT method at the B3LYP/6‐311++G** level. The basis set superposition errors (BSSE) are 4.62, 4.07 and 3.45 kJ/mol, and the zero point energy (ZPE) corrections for the interaction energies are 7.94, 5.66 and 6.40 kJ/mol for 1, 2 and 3 , respectively. Dimer 1 is the most stable, judged by binding energy. After BSSE and ZPE corrections, the greatest corrected intermolecular interaction energy of dimer 1 was predicted to be ?29.36 kJ/mol. The charge redistribution mainly occurs on the adjacent N–H··· O atoms and N–O··· H atoms between submolecules. The oxygen in the nitro group acts as a moderate hydrogen acceptor as compared to water oxygen. Based on the statistical thermodynamic method, the standard thermodynamic functions, heat capacities (C0P), entropies (S0T) and thermal corrections to enthalpy (H0T), and the changes of thermodynamic properties on going from monomer to dimer over the temperature range 200.00‐700.00 K were predicted. It is energetically or thermodynamically favorable for Fox‐7 to bind with H2O and to form dimer 1 at room temperature. 相似文献
20.
The enzyme catechol-O-methyltransferase (COMT) plays an important role in the metabolism of catechol estrogens and degradation of the catecholamine neurotransmitters, such as epinephrine. Several analytical methods, mainly high-performance liquid chromatography with electrochemical amperometric detection, have been reported for the analysis of catecholamines and their metabolites in biological fluids. In this paper we report the relevance of controlling temperature in calibration procedures of metanephrine, an O-methylated product of catechol-O-methyltransferase, using epinephrine as substrate. The results at higher temperatures show shorter retention times of metanephrine, no undue band-broadening and increased electro signals. This study also showed that, despite different temperatures leading to similarly specific activities of recombinant human COMT as expected, there are additional advantages in flow analytical methods where good sensitivity, efficiency and selectivity is required, mainly in tissues with low levels of COMT activity. 相似文献