Electrochemical patterning

CoRRY, C.E. 1985. Spontaneous polarization associated with porphyry sulfide mineralization Geophysics, 50, 1020-1034. Govett, G.J.S. 1976. Detection of deeply buried and blind sulfide deposits by measurement of H and conductivity of closely spaced surface soil samples. Journal of Geochemical Exploration, 6, 359-382. Govett, G.J.S. Atherden, P.R. 1987. Electrochemical patterns in surface soils -detection of blind mineralization beneath exotic cover, Thalanga, Queensland, Australia. Journal of Geochemical Exploration, 28, 201-218. 

Equation (4) is thus a time-dependent boundary condition to Eqs. (6, 7), which, supplemented by the remaining boundary conditions (which also involve external constraints resulting from the operation mode of the experiment, s.b.) and possibly by the incorporation of convection, form the most basic Ansatz for modeling patterns of the reaction-transport type in electrochemical systems. However, so far, there are no studies on electrochemical pattern formation that are based on this generally applicable set of equations. Rather, one assumption was made throughout that proved to capture the essential features of pattern formation in electrochemistry and greatly simplifies the problem it is assumed that the potential distribution in the electrolyte can be calculated by Laplace s equation, i.e. Poisson s equation (6) becomes ... 

Assuming, in addition, that the capacitance of the electrode is independent of ij>DL, an assumption, which also has been made so far in simulations of electrochemical pattern formation, the differential charge conservation law at the interface (Eq. (4)) becomes [26]... 

The intramolecular electron exchanges among the different metal sites of polynuclear /3-diketonate-metal complexes are a matter of intrinsic interest, especially as far as the stabilization of mixed-valent oxidation states is concerned " . Obviously, the pertinent electrochemical pattern, while becoming richer and richer, also tends to become more... 

Govett, G.J.S. and Atherden, P.R., 1987. Electrochemical patterns in surface soils - detection of blind mineralisation beneath exotic cover, Thalanga, Queensland, Australia. J. Geochem. Explor., 28 201-221. 

Before the model discussed above was published, tha-e were three other suggestions of how to model spatiotemporal dynamics in electrochemical systems. The first attempt at a theoretical description of electrochemical pattern formation came from Jome. His model is based on a chemical instability in the reaction mechanism and only takes into account the concentrations of the reacting species as dependent variables, not the potential. This, of course, means that the model is not applicable to any of the systems exhibiting an electrical instability. This includes the examples treated by Jome, namely, anion reduction reactions or cation reduction in the presence of SCN . Meanwhile, both oscillators are unanimously classified as NDR oscillators [see Section n.2.(ii)] and hence their spatiotemporal description requires a different approach. 

An important result of the theoretical description of the electrochemical patterns discussed above was that the distance between the working electrode and the equipotential surface has an important impact on the pattern formation, or more precisely, on the range of the spatial coupling. In view of this knowledge, it is to be expected that electrode configurations different from this parallel arrangement of two equipotential surfaces affect the dynamics in a different way. An experimental setup often employed in electrochemical experiments is the use of a Haber-Luggin... 

Particular emphasis is given to the patterning of quasi ID nanowire and bicontinuous gyroid arrays, both of which are of particular interest for device applications. The first study of these highly ordered electrochemically patterned semiconductor arrays used in a real device application is described in a dye-sensitized bulk heterojunction solar cell. 

Addition of protic acids to the solution of Ni(II) complexes triggered significant changes in their electrochemical patterns. For instance, upon addition of a strong acid ( HCIO ) the first reduction of [ Ni is... 

The most important data for our study are the first reduction and the first oxidation potentials. The general electrochemical pattern is presented in Fig. 48.2. 

Muller, A.-D. Muller, R Hietschold, M., Electrochemical pattern formation in a scanning near-field optical microscope. Applied Physics A Materials Science Processing 1998, 66, S453-S456. 

Torbensen, K., K. Malmos, F. Kanoufi, C. Combellas, S. U. Pedersen, and K. Daasbjerg. Using time-resolved electrochemical patterning to gain fundamental insight into aryl-radical surface modification. Chem. Phys. Chem. 13, 2012 3303-3307. 

Other important feature of triarylamine-zinc porphyrin dendrimers is the intramolecular energy transfer from the triarylamine moieties to the zinc porphyrin unit. Interestingly, zinc porphyrin fluorescence emission takes place with higher quantum yield upon excitation in the triarylamine moieties UV absorption bands than upon direct excitation of the ZnTPP unit. Similar antenna effect has been previously reported for a series of carbazole-porphyrin dendrimers [132] encompassing up to 21 redox centers. Their electrochemical pattern is strongly dependent on the way the carbazole are structured along the dendrimer branches and connected to the porphyrin core. 

Patel, A. N., McKelvey, K., and Unwin, P. R. 2012. Nanoscale electrochemical patterning reveals the active sites for catechol oxidation at graphite surfaces. J. Am. Chem. Soc. 134 20246-20249. 

On the oxidation side, the behavior of the folly desymmetrized catenanes 6 and 9 is particularly interesting from the viewpoint of molecular machines and it is the only one here discussed. Their electrochemical patterns are very similar and consist of three oxidative processes (for 6 " see Fig. 9.5a) the first two (Fig. 9.5c) are assigned to the two consecutive monoelectronic TTF oxidations [12], while the third one is ascribed to the oxidation of the DON unit. The first and second TTF oxidations exhibit the same features observed for a previously studied catenane [13, 14] and can be interpreted as follows after the TTF " oxidation, the electron donor ring circumrotates with respect to the electron accepting ring, delivering the DON unit into its cavity. 

Pavlovic E, Lai RY, Wu TT, Ferguson BS, Sun R, Plaxco KW, Soh HT (2008) Mitmrfluidic device architecture for electrochemical patterning and detection of multiple DNA sequences. Langmuir 24 1102-1107... 

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