共查询到20条相似文献,搜索用时 750 毫秒
1.
Lovelock KR Ejigu A Loh SF Men S Licence P Walsh DA 《Physical chemistry chemical physics : PCCP》2011,13(21):10155-10164
The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 μm Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied. 相似文献
2.
本综述首先简单介绍了扫描电化学显微镜的基本概况,尤其是不同的工作模式. 其次,有针对性地介绍了SECM的不同工作模式在氧还原和水解析氧反应相关研究中的应用. 最后,对扫描电化学显微镜未来在新能源转换存储系统研究领域的应用进行了展望. 相似文献
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In this paper, we describe a novel method for measuring the forward heterogeneous electron-transfer rate constant (kf) through the thiol monolayer of gold monolayer protected clusters (MPCs) in solution using scanning electrochemical microscopy (SECM). Applying the equations for mixed mass-transfer and electron-transfer processes, we develop a new formula using only the diffusion coefficient and the tip radius and use it as part of a new method for evaluating SECM approach curves. This method is applied to determine the electron-transfer rates from a series of SECM approach curves for monodisperse hexanethiol MPCs and for polydisperse hexanethiol, octanethiol, decanethiol, dodecanethiol, and 2-phenyethylthiol gold MPCs. Our results show that as the alkanethiol length increases the rate of electron transfer decreases in a manner consistent with the previously proposed tunneling mechanism for the electron transfer in MPCs. However, the effective tunneling coefficient, Beta, is found to be only 0.41 A-1 for alkanethiol passivated MPCs compared to typical values of 1.1 A-1 for alkanethiols as self-assembled monolayers on two-dimensional gold substrates. Similar SECM approach curve results for Pt and Au MPCs indicate that the electron-transfer rate is dependent mostly on the composition of the thiol layer and not on differences in the core metal. 相似文献
5.
《Electrochemistry communications》2002,4(1):67-71
The construction and characterisation of ring–disk (RD) microelectrodes suitable for use in scanning electrochemical microscopy (SECM) is reported. Such RD electrodes are proposed as probes for novel generator–collector SECM experiments. In this case, the interaction of both the reactants and products with the substrate under investigation can be followed simultaneously from a single approach curve to the substrate. Examples of such approach curves to conducting and insulating substrates are given to demonstrate the potential of this new mode of SECM operation. 相似文献
6.
《Electrochemistry communications》2007,9(10):2617-2621
Scanning electrochemical microscopy (SECM) still lacks reliable means for performing constant-distance imaging experiments. We demonstrate, for the first time, that the same negative alternating current (AC) feedback can be observed on approach to an insulator and an unbiased conductor at optimal experimental conditions. This leads to a novel constant-distance imaging mode. To perform AC-SECM imaging, only minor modifications of the existing SECM set-up were necessary. The new constant-distance AC-SECM imaging was conducted to provide topographical information not affected by variations in sample conductivity and reactivity. Furthermore, simultaneous AC and DC SECM measurements were carried out to demonstrate that both topographical and chemical information could be revealed. 相似文献
7.
Scanning electrochemical microscopy (SECM) has been performed in the restricted space of nanolitre droplets with a robust and easy-to-handle coaxial electrode assembly centring a Pt microdisk in a circular Ag electrode. Straightforward and reproducible fabrication of the specially designed probe tips was achieved by using Tollens reaction to chemically deposit a uniform and well-adhering layer of silver on the body of a glass-insulated Pt microdisk electrode. The suitability of the novel dual-electrode SECM tip for measurement in small volumes was evaluated by imaging an array of four Pt band microelectrodes in 500 nL electrolyte. 相似文献
8.
对扫描电化学显微镜(Scanning Electrochemical Microscope,SECM)的发展及其在界面电化学中的研究应用进行了评述。介绍了SECM的工作原理以及常用的操作模式,并对SECM在液/液界面、固/液界面等方面的应用进行了总结。 相似文献
9.
Szunerits S Knorr N Calemczuk R Livache T 《Langmuir : the ACS journal of surfaces and colloids》2004,20(21):9236-9241
This work establishes the compatibility of surface plasmon resonance imaging (SPR-i) with the visualization of localized electropolymerization. The "writing" of polypyrrole and polypyrrole-oligonucleotide patterns onto thin gold films is demonstrated using scanning electrochemical microcopy (SECM), while an optical method, SPR-i, simultaneously detected the formed micropatterns. The combination of these two methods, SECM/SPR-i, has the advantage of not only controlling the patterning process but also providing unique information on the micropattern formation. The influence of the pulsing time and the monomer concentration on the spot size and its characteristics has been investigated in detail using SPR-i. Fluorescence microscopy and atomic force microscopy have also been used to support the data obtained by SPR-i. 相似文献
10.
扫描电化学显微镜是一种在检测样品表面物理形貌的同时能提供丰富的电化学信息的扫描探针技术,由于超微电极的引入,它可以高时空分辨率地探究各类样品的物理形貌和电化学性能之间的构效关系. 随着现代纳米科技的不断发展,扫描探针的尺寸也逐渐从亚微米发展到纳米级别. 与此同时,高效优选各类氧反应和氢反应电催化材料,明晰其电化学反应过程和性能是二十一世纪绿色新能源转换存储系统(如可再生燃料电池、金属空气电池等)的重要研究方向. 本文首先概括了可应用于扫描电化学显微镜的纳米级扫描探针的制备及发展,之后着重介绍了近四年纳米尺度扫描电化学显微镜在电催化氧反应和氢反应研究中的一些最新研究进展. 最后以点窥面,对未来纳米尺度扫描电化学显微镜的未来发展趋势作了展望. 相似文献
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MAO Bing-Wei MU Ji-Qian ZHUO Xiang-Dong FENG Zu-De YAN En-Rou PAN Guo-Bin XIE Zhao-Xiong REN BinState Key Laboratory for Physical Chemistry of the Solid Surface Chemistry Department Xiamen University Xiamen Fujian China 《中国化学》1995,13(2):105-111
The development of the instrumentation of a scanning electrochemical microscopy (SECM) is presented. The core of the SECM sensing system is constructed based on piezobimorph scanners, a mechanical micropositioner of multi-dimensional adjustment and ultramicroelectrodes. The control of the electrochemical cell and the SECM system is realized by a battery powered bipoteniostat and analog control circuits respectively with the control of a microcomputer work station. The demonstrations of SECM experiments are given on both a standard IDA sample and a silver electrode. Discussions on the resolution and quality of SECM image are made. 相似文献
13.
Yuanshu Zhou Yasufumi Takahashi Takeshi Fukuma Tomokazu Matsue 《Current Opinion in Electrochemistry》2021
Scanning electrochemical microscopy (SECM) is a powerful technique that can provide chemical identity, quantification, and spatiotemporal information on biosurfaces. The ability of SECM for noninvasive and high-resolution electrochemical imaging has made it valuable for the study of cell phenotypes and functions. This review focuses on the latest advances of SECM technique for the biosurface imaging. The SECM measurements of different biomarkers, including oxygen consumption rate and enzyme activity of cell aggregates, redox state of cardiomyocytes, and bacterial metabolic activity, are introduced. The applicability of SECM on membrane permeability measurements, neurotransmitter measurements, and intracellular measurements is discussed. 相似文献
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Parthasarathy M Singh S Hazra S Pillai VK 《Analytical and bioanalytical chemistry》2008,391(6):2227-2233
The stomatal physiology, chlorophyll distribution and photosynthetic activity of somatic embryo (SE)- and seedling-derived
peanut plants grown in vitro (test tube-grown) and extra vitrum (soil-grown) are investigated using scanning electrochemical microscopy (SECM). This SECM
imaging is performed in two different feedback modes, corresponding to oxygen evolution and chlorophyll distribution. More
specifically, the oxygen evolution profiles of the in vitro leaves indicate important differences in leaf anatomy between the SE- and seedling-derived leaves. On the other hand, the
chlorophyll distribution images show individual stomata of size ca. 27 ± 5μm. Further studies on senescing (aged) leaves reveal
interesting voltammograms that vary widely over the stomatal complexes and the surrounding tissues, probably due to the release
of electroactive metabolites during chlorophyll breakdown when the leaves turn yellow. Thus, the present investigation could
open up new opportunities for characterizing botanical systems using electroanalytical techniques. In addition, it could provide
further insights into various areas of current relevance, including signal transduction, cell fate/differentiation and developmental
biology.
Schematic representation of SECM imaging used in this investigation. The SECM probe is a Pt UME disk (25 μm diameter) embedded
in an insulating glass sheath so that the ratio of the diameter of the death to that of the electrode surface (RG) is 7. RE denotes the reference electrode Ag/AgCl, sat. KCl and CE refers to the counter electrode, a Pt wire. Oxygen evolving from the leaf surface during photosynthesis diffuses into the
electrolyte (0.1 M KCl) and gets reduced at the Pt UME, biased to a potential of −0.5 V, at a diffusion-limited rate to produce
a change in the tip-current 相似文献
15.
Recent applications of scanning electrochemical microscopy (SECM) to studies of single biological cells are reviewed. This
scanning probe microscopic technique allows the imaging of an individual cell on the basis of not only its surface topography
but also such cellular activities as photosynthesis, respiration, electron transfer, single vesicular exocytosis and membrane
transport. The operational principles of SECM are also introduced in the context of these biological applications. Recent
progress in techniques for high-resolution SECM imaging are also reviewed. Future directions, such as single-channel detection
by SECM, high-resolution imaging with nanometer-sized probes, and combined SECM techniques for multidimensional imaging are
also discussed. 相似文献
16.
Most of SECM studies have been carried out in liquid or gel phases. A Severinghaus type, CO2 detecting potentiometric tip has been fabricated and used in gas phase SECM studies. The microcell tip is made without gas permeable membrane. Faster response, needed in SECM, was achieved by substituting the membrane with an air gap. The carbon dioxide concentration profile in the gas phase over a disc‐shaped colony of yeast has been detected with the new tip. Estimation of the carbon dioxide output of the fungi colony was attempted by fitting simulated curves to measured ones obtained with one dimensional (line) scans. 相似文献
17.
Zhang M Becue A Prudent M Champod C Girault HH 《Chemical communications (Cambridge, England)》2007,(38):3948-3950
Scanning electrochemical microscopy (SECM) has been used to image latent fingermarks enhanced by adsorption of gold nanoparticles onto which silver is chemically deposited, a process known as "multi-metal-deposition" (MMD). 相似文献
18.
This communication reports the findings of the investigation of the electrochemical (EC) oxidation of the important bimolecular guanosine (Gs) by scanning electrochemical microscopy (SECM) using carbon fiber ultramicroelectrodes (CF-UMEs) as the probe and substrate. The first attempt is to try to gain a steady-state voltammogram for EC oxidation of Gs at the CF-UME probe in aqueous buffer solutions with three different pH values. Experimental results indicate that due to serious adsorption of Gs on the CF-UME surface, an "S-shaped" steady-state voltammetric curve, which is required for SECM studies, cannot be obtained in aqueous solutions. To solve this adsorption problem, a series of experiments for studying the EC behavior of Gs in DMF are carried out. A well-defined "S-shaped" steady-state cyclic voltammogram (CV) could be achieved at the CF-UME in DMF containing 0.1M TBAPF6 as the supporting electrolyte. By combining several EC techniques, including cyclic voltammetry at glassy carbon (GC) macroelectrode and CF-UMEs, and chronoamperometry, the general chemical characteristics and EC behavior of Gs in DMF solution are studied. Furthermore, SECM detection of Gs*+, the radical cation of Gs electrogenerated in its first oxidation, is carried out by using feedback and tip generation/substrate collection modes in a nanogap configuration. Gs*+ has been electrochemically detected for the first time, with an estimated lifetime of =40 mus and E degrees = 1.55 V versus NHE for the Gs/Gs*+ couple. 相似文献
19.
Laforge FO Kakiuchi T Shigematsu F Mirkin MV 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10705-10710
Molecular partitioning and electron-transfer kinetics have been studied at the ionic liquid/water (IL/water) interface by scanning electrochemical microscopy (SECM). The ionic liquid C8mimC1C1N is immiscible with water and forms a nonpolarizable interface when in contact with it. Partitioning of ferrocene (Fc) across the IL/water interface was studied by SECM and found to be kinetically fast with a partition coefficient CIL/CW of 2400:1. The partition coefficient value was measured by SECM under quasi-steady-state conditions without waiting for complete solute equilibration. To investigate the kinetics of the electron transfer (ET) between aqueous ferricyanide and Fc dissolved in IL, a new approach to the analysis of the SECM current-distance curves was developed to separate the contributions of Fc partitioning and the ET reaction to the tip current. Several combinations of different aqueous and nonaqueous redox species were investigated; however, only the Fc/Fe(CN)63- system behaved according to the Butler-Volmer formalism over the entire accessible potential range. 相似文献
20.
Scanning electrochemical microscopy (SECM) was used for imaging of n-hexadecanethiol-modified Au surfaces. In these studies, small defects were observed in the monolayer when a submicrometer electrode was used as an SECM tip, although a cyclic voltammogram of a Au disk electrode showed that the surface of the Au was completely covered with n-hexadecanethiol. The dependence of the SECM images on the potential of the Au electrode was also examined. A comparison of the current at the Au electrode and the tip current in the SECM images showed that direct electron transfer through the monolayer was dominant, rather than electron transfer at the defects. The size of the defects was estimated from the tip current to be 1-100 nm, under the assumption that the defects were small compared to the SECM probe. 相似文献