Diamond electrodes surface modification

Kondo, T., Honda, K., Tryk, D.A. and Fujishima, A. (2005) Covalent modification of single-crystal diamond electrode surfaces. J. Electrochem. Soc. 152, E18-E23. 

Chemical modification of diamond electrode surfaces has also been accomplished by the reduction of diazonium salts, as discussed previously. Kuo et al. showed that substituted phenyl groups can be covalently attached to hydrogen-terminated, boron-doped diamond electrodes during the electrochemical reduction of substituted phenyl diazonium salts in acetonitrile (see Fig. 3) [51]. Diamond electrodes were modified with nitrophenyl, nitroa-zobenzene and trifluoromethyl phenyl ad-molecules, and all showed strong XPS signals for surface nitrogen (N Is, 402 eV)... 

The development of diamond catalysts involved special two-stage treatment of the diamond nanopowder surface, the so-called modifications. Figure 1 gives the schematic of the reception of electrode materials. As is seen from the schematic, the hydrogen electrode was make from special heat-treated treatment in the hydrogen environment [6]. 

Duo, I. (2003) Control of electron transfer kinetics at boron-doped diamond electrodes by surface modification, PhD Thesis, Ecole Polytechnique Federale Lausanne. 

In the following chapters of this textbook, different aspects of electrochemical research on carbon materials will be discussed in detail, including carbon electrodes in different applications (fuel cells, molecular electronics, sensing, etc.) using various methods (surface modification, carbon paste, carbon fiber, etc.), and electrochemistry of different carbon materials (graphene, HOPG, carbon nanotube, diamond, etc.). 

Diamond OTEs are also useful for studying the electrochemical and optical properties of important biomolecules, like cytochrome c. We recently reported that boron-doped microcrystalline diamond thin film electrodes are quite responsive for horse heart cytochrome c, exhibiting a very active and stable cyclic voltammetric response without any pretreatment or surface modification [119,124]. Heterogeneous electron-transfer... 

The other major electrochemical modification approach has been that in which aromatic diazonium salts in an electrolyte solution are reduced at a diamond electrode this leads to the formation of an aryl radical, which can then attach to the diamond surface [74], This work is based on a series of papers in which the same technique was applied to the surface modification of glassy carbon and highly ordered pyrolytic graphite (HOPG) [75-78]. This approach may also be quite fruitful for tbe covalent modification of diamond surfaces, if the attachment is as robust as it is on glassy carbon surfaces. 

For the APTES modification, the surfaces were characterized by recording the CVs for the Fe(CN)6 redox couple (Fig. 9.9). From the variation of AEp, it was found that the ET behavior was nearly reversible at the hydrogen-terminated diamond electrode... 

The highly attractive characteristics of conductive diamond electrodes continue to bring attention. Recently, it has also become clear that the possibilities for chemical modification can take advantage of these fundamental characteristics and build upon them, imparting novel selectivity and catalytic activity. The possible applications are as diverse as those for all other types of electrodes, because diamond can be a useful substrate for all. Moreover, all of the modification techniques that have been worked out over the past several years for other surfaces, such as carbon and gold, can now be transplanted onto diamond. Now is just the beginning of the blossoming of this field. 

As the simplest and most effective surface structure modification, we are interested in surface oxidation treatment. There are two important merits in the surface oxidation treatment of the diamond electrode. First, surface oxidation treatment changes the electrochemical character of diamond electrodes by means of electrostatic interactions between the electrode surface and redox ions. Second, surface oxidation treatment facilitate the subsequent functionalization of diamond electrodes. Actually, surface functional groups, which are introduced onto the diamond electrode by the surface oxidation treatment, facilitate the introduction of many kinds of functional materials. 

These results indicate that, by use of surface oxidation and subsequent APTES treatment, any enzymes that contain an amino group can be immobilized onto a diamond electrode in the same way. In other words, any desired type of catalytic activity can be introduced to diamond by use of the modification scheme mentioned above. One additional important point is that these modifications do not decrease the well known advantages of the diamond electrode for electrochemical detection. This fact promises to increase the number of potential applications of the diamond electrode. 

We have focused on the surface modification of diamond electrodes in order to improve their electrochemical properties. Surface modification at the atomic level is a well known phenomenon, in that the electrochemical properties of the electrodes are found to be quite sensitive to the chemical termination on the surface. For example, the electrochemical responses to several different redox... 

However, the peak was somewhat more clearly defined for the BDD electrode than for the GC electrode. It also has been observed that there is a slight adsorption of either reactant or product, as evidenced by a slight change in the background voltammogram. The results presented in this work have shown that it is very promising to use diamond electrodes for cysteine detection, without the use of mercury or surface modification. 

Chemical modification of diamond surfaces is a ripe area for research. Much can be learned about (1) how to control the electrode reaction kinetics and mechanisms at diamond through alterations of the surface chemistry and (2) using such modified surfaces as platforms for sensors and other devices based on the material. 

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