Scanning electrochemical microscope SECM

Alternatively, a higher rate of mass transport in steady-state measurements with a larger UME can be obtained by using it as a tip in the scanning electrochemical microscope (SECM). The SECM has typically been employed for probing interfacial ET reactions [29]. Recently, micropipettes have been used as SECM probes (see Section IV.B below) [8b,30]. Although the possibility of probing simple and assisted IT at ITIES by this technique was demonstrated, no actual kinetic measurements have yet been reported. 

Perhaps the most important experimental progress made recently in electrochemistry was the introduction of a scanning electrochemical microscope (SECM). Tsionsky et al. have used SECM to study also the rate of ET across a lipid monolayer at the water-benzene interface [48,49]. The presence of the monolayer decreased the rate of ET, being the decrease more significant for longer hydrocarbon chains and larger lipid concentration in solution. It was thus concluded that the ET reaction does not occur at defect sites in the lipid monolayer. 

The scanning electrochemical microscope (SECM) consisted of a positioning system from Marzhauser (Wetzlar, Germany), a bipotentiostat CH701 (CH Instruments, Austin, TX, USA) and a homemade control software. 

A third screening method for arrays of electrocatalysts was recently introduced by Hillier and coworkers [15, 29, 30]. Using a scanning electrochemical microscope (SECM), a microelectrode tip is moved over an electrocatalyst array. The resulting electrochemical feedback currents are measured and used to generate an activity map of the electrocatalyst library. This method does not require individual electronic addressability for each electrocatalyst... 

Light emission by ECL at scanning electrochemical microscope (SECM) tips is also under current development [68], Bard and coworkers have demonstrated that ECL can be generated at SECM tips when [(bpy)3Ru]2+ is used as... 

Treutler, T.H., and G. Wittstock. 2003. Combination of an electrochemical tunneling microscope (ECSTM) and a scanning electrochemical microscope (SECM) Application for tip-induced modification of self-assembled monolayers. Electrochim. Acta 48 2923-2932. 

Fig. 18 Scanning electrochemical microscope (SECM) surface images of bare gold electrode top) and AcMn5b modified gold electrode bottom) containing 5 mM ferrocyanide as redox mediator in phosphate buffer. Reproduced with permission from [76]...

The conception of the electrochemical robotic system was based on earlier instrumental developments aiming at the design of scanning electrochemical microscopes (SECM),79-81 however using a rather coarse positioning system and hence exhibiting limited scanning resolution. 

Y Selzer, I Turyan, D Mandler. Studying heterogeneous catalysis by the scanning electrochemical microscope (SECM) the reduction of protons by methyl viologen catalyzed by a platinum surface. J Phys Chem B 103 1509-1517, 1999. 

K Borgwarth, C Ricken, DG Ebling, J Heinze. Surface characterization and modification by the scanning electrochemical microscope (SECM). Ber Bun-senges Phys Chem 99 1421-1426, 1995. 

An alternative electrochemical approach to the measurement of fast interfacial kinetics exploits the use of the scanning electrochemical microscope (SECM). A schematic of this device is shown in Fig. 14 the principle of the method rests on the perturbation of the intrinsic diffusive flux to the microelectrode, described by Eq. (34) above. A number of reviews of the technique exist [109,110]. In the case of the L-L interface, the microelectrode probe is moved toward the interface once the probe-interface separation falls within the diffusion layer, a perturbation of the current-distance response is seen, which can be used to determine the rate of interfacial processes, generally by numerical solution of the mass-transport equations with appropriate interfacial boundary conditions. The method has been... 

Other dual electrode systems that operate at steady state and show similar shielding and collection effects include microelectrode arrays and the scanning electrochemical microscope (SECM). With microelectrode arrays (Section 5.9.3), one monitors diffusion between two neighboring electrodes. In a similar way, one can use the SECM (Section 16.4) to study diffusion between an ultramicroelectrode tip and substrate electrode. In both of these systems, convective effects are absent and the time for interelectrode transit is governed by the distance between the electrodes. 

Sufficient results can be obtained from scanning electrochemical experiments. By the use of the scanning electrochemical microscope (SECM) the electrochemical properties of catalytic materials can be achieved with high spatial resolution... 

M.H.T. Frank and G. Denuault, Scanning electrochemical microscope (SECM) study of the relationship between proton concentration and electronic charge as a fimction of ionic-strength during the oxidation of polyaniline. J. Electroanal. Chem., 379, 399 (1994). 

In addition to the techniques that have already been mentioned, with which to investigate photocatalytic reactions, including laser flash photolysis and EPR, there are several others that can yield very useful information. These include the slurry electrode technique, the use of biased electrodes or photoelectrodes, the scanning electrochemical microscopic (SECM) technique, and the Langmuir-Blodgett (LB) film technique. These will be discussed briefly. 

Fig. 1 Schematic diagram of the scanning electrochemical microscope (SECM).

Among other advances, the nanostructuration of electrochemically synthesized conducting polymers has raised a lot of interest. To achieve this, one of the most straightforward and common way is the use of a scanning electrochemical microscope (SECM). Since the pioneering work of Bard, several authors have refined the conditions, improving the resolution. Heinze et al. used a PMMA matrix to confine more cleanly the electrodeposition of PPy [24], and in a further work, they could deposit micropatterns of poly(dimethoxybithiophene) with the help of electrocatalysis by a ruthenium complex, obtaining well-defined plots [25,26]. 

Tiny cells [18] or ultramicroelectrodes [19-29], e.g., in scanning electrochemical microscopes (SECM, [28]), are used in other concepts. Ultramicroelectrodes are mainly used in systems where diffusion from or to the electrode is dominant. Rq reduces rapidly with decreasing electrode radius r and depends finally only on electrolyte conductivity, independent of radius or shape in steady state diffusion regime [22, 30,31]. 

Mandler D, Meltzer S, Shohat I (1996) Microelectrochemistry on surfaces with the scanning electrochemical microscope (SECM). Isr J Chem 36(1) ... 

To probe for pinholes in the electrophoretic paint insulation, the carbon nanofiber electrodes are tested with a scanning electrochemical microscope (SECM, see Chapter 12)... 

Electrochemical Atomic Force Microscope (EC-AFM) AND Scanning Electrochemical Microscope (SECM) in Dimethylformamide... 

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