Electrode templated

Above, the oxygen electrode template printed on transfer film. Below, lay the film emulsion side down on the circuit board, and secure the film to the circuit board. 

Dissolution of the membrane material exposes arrays of cylinders that are attached at one end to a conductive electrode. Template synthesis can be used to prepare size-monodisperse particles or cyhndrical wires that are up to 50 pm in length and 15 ran to 5.0 pm in diameter. Template synthesis is the most popular method for preparing nanostructures of various materials using electrodeposition. Its primary disadvantage is that commercial templates are usually less than 50 pm in thickness and this places an upper limit on the length of the nanowires that can be obtained. 

Fig. 37.6 Scanning electron micrographs showing the surface of electrode templates fabricated from (A) c-axis-ori-ented YBa2Cu307-s film, (B) /c-axis-oriented YBa2Cu3-O7-S film, and (C) a-axis-oriented YBa2Cu307-s film. All superconductor films were supported on MgO(lOO) substrates and were —1500 A thick.

Fig. 37.7 AFM images acquired for a series of high-Jc electrode templates onto which polypyrrole was electro-chemically deposited. (A) A c-axis-oriented YBa2Cu307-s thin film (B) Pt (C) an a/c mixed axis-oriented YBa2Cu307-5 film. Polymer films were grown in all cases by potential steps to 1.2 V vs. SCE for 2 s using a solution composed of 0.10 M Et4NBp4 and 0.14 M pyrrole in acetonitrile. (Adapted from Ref. 11.)...

Chemical and electrochemical techniques have been applied for the dimensionally controlled fabrication of a wide variety of materials, such as metals, semiconductors, and conductive polymers, within glass, oxide, and polymer matrices (e.g., [135-137]). Topologically complex structures like zeolites have been used also as 3D matrices [138, 139]. Quantum dots/wires of metals and semiconductors can be grown electrochemically in matrices bound on an electrode surface or being modified electrodes themselves. In these processes, the chemical stability of the template in the working environment, its electronic properties, the uniformity and minimal diameter of the pores, and the pore density are critical factors. Typical templates used in electrochemical synthesis are as follows ... 

Recently, another template-based technique for preparation of metallic nanoparticles on electrode surfaces was described [18]. This technique does not need any nanomanipulation by STM or AFM. It is based on reduction... 

Electrochemical template-controlled sjmthesis of metallic nanoparticles consists of two steps (i) preparation of template and (ii) electrochemical reduction of metals. The template is prepared as a nano structured insulating mono-layer with homogeneously distributed planar molecules. This is a crucial step in the whole technology. The insulating monolayer has to possess perfect insulating properties while the template has to provide electron transfer between electrode and solution. Probably, the mixed nano-structured monolayer consisting of alkylthiol with cavities which are stabilized by the spreader-bar approach [19] is the only known system which meets these requirements. 

Gold electrodes coated by nanostructured self-assembled monolayer of TMPP and Cl2 are used as template for in situ synthesis of metallic nanoparticles (Figure 2). 

The second class of materials, which we will consider herein are carbons with a highly ordered porosity prepared by a template technique [15-18]. The pores are characterized by a well-defined size determined by the wall thickness of the silica substrate used as substrate for carbon infiltration. They can be also interconnected, that is very useful for the charge diffusion in the electrodes. Figure 1 presents the general principle of the carbon preparation by a template technique, where the silica matrix can be, for example, MCM-48 or SBA-15. 

The pores of the silica template can be filled by carbon from a gas or a liquid phase. One may consider an insertion of pyrolytic carbon from the thermal decomposition of propylene or by an aqueous solution of sucrose, which after elimination of water requires a carbonization step at 900°C. The carbon infiltration is followed by the dissolution of silica by HF. The main attribute of template carbons is their well sized pores defined by the wall thickness of the silica matrix. Application of such highly ordered materials allows an exact screening of pores adapted for efficient charging of the electrical double layer. The electrochemical performance of capacitor electrodes prepared from the various template carbons have been determined and are tentatively correlated with their structural and microtextural characteristics. 

Prussian blue-based nano-electrode arrays were formed by deposition of the electrocatalyst through lyotropic liquid crystalline [144] or sol templates onto inert electrode supports. Alternatively, nucleation and growth of Prussian blue at early stages results in nano-structured film [145], Whereas Prussian blue is known to be a superior electrocatalyst in hydrogen peroxide reduction, carbon materials used as an electrode support demonstrate only a minor activity. Since the electrochemical reaction on the blank electrode is negligible, the nano-structured electrocatalyst can be considered as a nano-electrode array. 

E. Braun, Y. Eichen, U. Sivan, and G. Ben-Yoseph, DNA-templated assembly and electrode attachment of a conducting silver wire. Nature 391, 775-778 (1998). 

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