Glassy carbon surface

Utilization of resonance effects can facilitate unenhanced Raman measurement of surfaces and make the technique more versatile. For instance, a fluorescein derivative and another dye were used as resonantly Raman scattering labels for hydroxyl and carbonyl groups on glassy carbon surfaces. The labels were covalently bonded to the surface, their fluorescence was quenched by the carbon surface, and their resonance Raman spectra could be observed at surface coverages of approximately 1%. These labels enabled assess to changes in surface coverage by C-OH and C=0 with acidic or alkaline pretreatment [4.293]. 

FIGURE 2-13 STM image of an electrochemically activated glassy-carbon surface. (Reproduced with permission from reference 46.)... 

Mori E, Rajeshwar K (1989) The kinetics of electrocrystaUization of tellurium and cadmium telluride at the glassy carbon surface. J Electroanal Chem 258 415-429 Cowache P, Lincot D, Vedel J (1989) Cathodic codeposition of cadmium telluride on conducting glass. J Electrochem Soc 136 1646-1650... 

Several methods have been applied to treat and activate glassy carbon surfaces for use as an electrode. The simplest one uses... 

Figure 4, Differential pulse voltammetry of a freshly polished, activated glassy carbon surface (a) and a digital simulation of the DPV (b). The pulse frequency vas2 Hz with an amplitude of 10 mV. The DC scan rate was 2 mV s...

Figure 5. X-ray photoelectron survey spectrum (a) of an o-phenylenedlamlne derlvatlzed glassy carbon surface. High resolution C Is and N Is spectra of a derlvatlzed surface (b) and surface which was derlvatlzed following reduction with lilAlH to destroy surface o-qulnone functional groups (c). The spectrum were signal averaged for 90 min (a) and 20 min (b and c) and smoothed prior to display.

The film formed during the blank test was left on the glassy carbon surface. Upon addition of further mercury nitrate, 20-50 til of a 5 g/1 solution were... 

For cases in which the NPs are not soluble in the supporting electrolyte in which they will be examined, it is possible to solvent-cast a thin film of the NPs on the electrode surface followed by evaporation [44] or to directly apply an insoluble gel containing the NPs [45]. In a related approach, films of anionic Prussian Blue NPs that had been synthesized in a solution containing chitosan (a cationic glucosamine polymer) were drop-cast onto glassy carbon surfaces, giving very stable... 

The cathodic stability of the AsFe anion was studied on a glassy carbon surface, and a reduction process was found at 1.15 V vs Li °... 

Table 4.3. They vary with the electrode material and with the tetraalkylammonium cation used. Early workers used mercury electrodes but mercury may be involved in the overall reaction. Glassy carbon is generally favoured as the electrode material. Reproducibility of data depends critically on methods used for cleaning the glassy carbon surface [33].

More recently, Engel and Olesik have also concluded that formic acid is a good modifier for carbon dioxide in SFC. The results they obtained on porous glassy carbon stationary phases with 1.5% (w/w) formic acid in CO2 (16) showed that formic acid was effective because of its strong H-bond donor and very weak H-bond acceptor characteristics higher concentrations of formic acid (3%), however, were found to polymerize on the porous glassy carbon surface (17). 

Figure IB. SEM of an 02 rf plasma treated glassy carbon electrode y500 magnification. The right side of the glassy carbon surface was protected and so exhibits the structure of an untreated electrode. (Reproduced from Ref. 33. Copyright 1981, American Chemical Society.)...

Figure 8. Carbon, Cls, spectra. Key a, from a polyvinyl alcohol homopolymer reference sample b, a spectrum of a modified glassy carbon surface corresponding to Fig. 7, spectrum e and c, the difference spectrum obtained by subtracting b from a, magnified 2X- (Reproduced, with permission, from Ref. 22. Copyright 1981, Pergamon Press.)...

Figure 10. Laser Raman spectra of Tokai glassy carbon surfaces. Key A, as polished B, following a 3-min 02 rf plasma treatment and C, following reduction with LiAlHk. (Reproduced, with permission, from Ref. 132.)...

These results indicate that the properties of the redox polymers, such as redox potentials and spectroscopic properties, can be varied systematically and, more importantly, can be predicted from those observed for mononuclear model compounds. As an example of the transfer of photochemical properties from monomeric analogues to the corresponding polymers, the photochemical behavior of the redox polymer [Ru(bpy)2(PVP)sCl]Cl will be considered. This polymer contains one metal center for every five-monomer units. Photolysis of a thin layer of this material on a glassy carbon surface leads to a change in the redox potential of the material from about 650 to 850 mV (See Figure 4.17) [32]. The voltammetric process affected is associated with a metal-center-based Ru(ll/m) redox process. By analogy to the behavior observed for the mononuclear species [Ru(bpy)2(py)Cl]+ (py = pyridine),... 

Figure 41. Spectroelectrochemistry of a film of Co(4-TCPyP) on a glassy carbon surface, in aqueous solution, showing (a) the Ru(III)Ru(III)Ru(III)/Ru(III)Ru(III)Ru(II) in the range from 0.12 to 0.42 V. (b) The Co(III/II) reduction in the range from —0.06 to 0.12 V. (c) Cyclic voltammograms of a Co(4-TCPyP) modified glassy carbon electrode in 0.5 M KNO3 aqueous solution. Inset. Plot of the peak current intensities as a function of the scan rate.

Electrochemical impedance measurements were also used to detect the hybridization of DNA on Si/Si02 chips and great emphasis has been put by Cloarec et al. [112] on the immobilization of single strands on the substrates in order to obtain reproducible sensors. The adsorption of dsDNA and nucleotides on a glassy carbon surface has also been evaluated by electrochemical impedance spectroscopy by Oliveira Brett et al. [113,114]. 

A basic voltametric instrument consists of a cell, a potentiostat, and a recorder. Chemical reactions are caused by applying a potential to an electrode in a cell. The current, which flows under the experimental conditions, is monitored with the recorder. The cell generally consists of three electrodes placed in seawater (1) the working electrode, usually a hanging drop of Hg or a Hg-plated graphite or glassy-carbon surface (2) the reference electrode, made of either calomel or Ag wire anodized to form AgCl and (3) a counterelectrode made of pure Pt wire. 

Cytochrome c dynamics at gold and glassy-carbon surfaces monitored by... 

One typical example of this behavior is the voltammogram of the ferro/ferricyanide couple (test reaction) that at carbon electrodes is less reversible than at noble metal electrodes. The kinetics of the test reaction in 1 M aqueous KCl was used as the reference to compare its electrochemical behavior on different carbon electrodes [20]. This electrochemical reaction occurs via an outer sphere mechanism and its rate depends on the electrolyte composition and can be increased by appropriate treatment of carbon electrodes, for instance, by application of a high current potential routine to electrodes of carbon fibers. Similar results have been obtained with glassy carbon surfaces that had been pretreated at 500°C under reduced pressure. An alternative activation method is based on careful electrode surface polishing [6]. 

McDermott, M.T. and McCreery, R.L. (1994). Scanning tunneling microscopy of ordered graphite and glassy carbon surfaces electronic control of quinone adsorption. Langmuir, 10, 4307-14. 

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