Electro-deposition approach

Ion implantation (qv) has a large (10 K/s) effective quench rate (64). This surface treatment technique allows a wide variety of atomic species to be introduced into the surface. Sputtering and evaporation methods are other very slow approaches to making amorphous films, atom by atom. The processes involve deposition of a vapor onto a cold substrate. The buildup rate (20 p.m/h) is also sensitive to deposition conditions, including the presence of impurity atoms which can faciUtate the formation of an amorphous stmcture. An approach used for metal—metalloid amorphous alloys is chemical deposition and electro deposition. 

In a different approach (112), mercury and silver were electro-deposited on the electrodes when a potential of 0.1 V was applied. However, Hg(II) can be deposited with no voltage applied without interference from silver, but with less reproducibility. Reversibility can be achieved by immersing the crystal in 1 1 mixture of 0.01 M ammonium peroxydlsulfIde and 0.01 M HNO3 for 5 min. 

One approach to dramatically increase the electrical conductivity of CNT yams is to apply a metal coating on the pure CNT yams. Randeniya et al. (2010) reported a composite yam with high electrical conductivity by self-fuelled electro-deposition of metal nanoparticles onto a dry-spun CNT yam. Cu-CNT and Au-CNT composite yams prepared by this method had metal-Uke electrical conductivities (2-3 x 10 S/m). However, the tensile strength of the composite yams was 30-50% lower than that of the original CNT yam. 

Nucleation — Stochastic approach to nucleation — Spatial distribution of clusters — Figure. Experimental (histograms) and theoretical (lines) distribution of the distances between first (a), second (b) and third (c) neighbor silver crystals electro chemically deposited on a glassy carbon electrode [iii-v]... 

Separation of Metals by Electrolysis.—The complete separation of one metal from another is important in quantitative electro-analysis the circumstances in which such separation is possible can be readily understood from the preceding discussion of simultaneous deposition of two metals. The conditions must be adjusted so that the discharge potentials of the various cations in the solution are appreciably different. If the standard potentials differ sufficiently and there are no considerable deposition overvoltages, complete separation within the limits of analytical accuracy is possible this is, of course, contingent upon the metals not forming compounds or solid solutions under the conditions of deposition. Since the concentration of the ions of a deposited metal decreases during electrolysis, the deposition potential becomes steadily more cathodic, and may eventually approach that for the deposition of another metal. For example, if the ionic concentration is reduced to 0.1 per cent of its original value, the potential becomes 3 X 0.0295 volt more cathodic for a bivalent metal and 3 X 0.059 volt for a univalent metal, at ordinary... 

Another intriguing approach to electrocatalysis involves the use of underpotential-deposited monolayers and submonolayers of foreign metal adatoms on metal substrates. Such layers afford unique electronic and morphological surface properties, not usually achievable with pure metal or alloys. Underpotential-deposited layers have been found to have high catalytic activity for such reactions as H2 generation, 02 reduction, and certain electro-organic reactions. 

Recently, Fabre et al. [31] and Freund et al. [7, 8] used electro-chemically deposited, self-doped, boronic-acid-substituted, conducting polymers for saccharide and fluoride detection. Freund et al. prepared a potentiometric sensor for saccharides using self-doped PABA [7, 8]. The transduction mechanism in that system is reportedly the change in pKa of polyaniline that accompanies complexation, and the resulting change in the electrochemical potential. Sensors produced with this approach exhibit reversible responses with selectivity to various saccharides and 1,2-diols (Figure 3.22) that reflect their binding constants with phenylboronic acid observed in bulk solutions. The sensitivity... 

DPN is not restricted to gold surfaces or to thiol deposition. Metal salts have been used as inks, and the native oxide layer of silicon has been used as the substrate. By applying a potential difference between the AIM tip and the substrate, it is possible to deposit material electro-chemicafly, reducing metallic ions in the one-dimensional electrochemical cell that is established in the meniscus and leading to the deposition of metal nanostructures. Polymeric structures may also be fabricated using electrochemical approaches. ... 

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