Electrochemical template synthesis

Yu, N. R, and L. J. Gao. 2009. Electrodeposited Pb02 thin film on Ti electrode for application in hybrid supercapacitor. Electrochemistry Communications 11 220-222. Ferret, R, T. Brousse, D. Belanger, and D. Guay. 2009. Electrochemical template synthesis of ordered lead dioxide nanowires. Journal of the Electrochemical Society 156 A645-A651. 

Martin [21] proposed a mechanism for the growth of the nanostructures prepared by the hard-template method. However, the mechanism is insufficient in explaining the growth of partially filled nanotubes by an electrochemical template synthesis [36]. Recently, Lee and coworkers [37] investigated the electrochemical... 

FIGURE 13.13 PPy microrods formed by electrochemical template synthesis in the reduced (a) and oxidized (b) states. Reprinted with permission from [108]. Copyright 2011 Elsevier. 

The electrochemical template synthesis of MPc is a complicated multistep process. This is confirmed by the isolation and mass-spectrometric identification of a series of intermediate products in NiPc synthesis, which could be formed according to Scheme 2-36. 

Most of our work has focused on polypyrrole, poly(3-methylthiophene), and polyaniline. These polymers can be synthesized via oxidative polymerization of the corresponding monomer. This can be accomplished either electrochemically [10,12,42] or by using a chemical oxidizing agent [43-45]. We have adapted both of these approaches so that they can be used to do template synthesis of conductive polymers within the pores of our nanoporous template membranes. The easiest way to do electrochemical template synthesis is to coat a metal film onto one surface of the membrane and then use this film to electrochemically synthesize the desired polymer within the pores of the membrane [12]. Chemical template synthesis can be accomplished by simply immersing the membrane into a solution of the desired monomer and its oxidizing agent [9,16,44]. 

Accordingly, this chapter is meant to show the current state of the art and novel techniques for preparing controllable nanostructures as well as detailed mechanisms for electrochemical growth. Utilizing this information, it is hoped that it can serve as a template in its own right for scientists to create future nanostructured materials through electrochemical template synthesis. 

Silicon nanowires were fabricated for the first time by electrochemical template synthesis at room temperature by J. Mallet and coworkers (Mallet et al. 2008). This innovative, cheap, and simple process consists of electroreduction of Si ions using a nonaqueous solvent and insulating nanoporous membranes with average pore diameters from 400 to 15 nm which fix the nanowires diameters... 

Figure 2. Electrochemical template-controlled synthesis of nanoparticles on nanostructured monolayer. The size of nanoparticles depends on the reduction charge and can be adjusted easily. (Reprinted from Ref [18], 2005, with permission from Wiley-VCH.)...

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

Li N.C., Martin C.R. A high-rate, high-capacity, nanostructured Sn-based anode prepared using sol-gel template synthesis. J Electrochem. Soc.2001 148(2) A164-70. 

Template reactions between malonaldehydes and diamines in the presence of copper(II), nickel(II) or cobalt(II) salts yield neutral macrocyclic complexes (equation 15).99-102 Both aliphatic102 and aromatic101 diamines can be used. In certain cases, non-macrocyclic intermediates can be isolated and subsequently converted into unsymmetrical macrocyclic complexes by reaction with a different diamine (Scheme ll).101 These methods are more versatile and more convenient than an earlier template reaction in which propynal replaces the malonaldehyde (equation 16).103 This latter method can also be used for the non-template synthesis of the macrocyclic ligand in relatively poor yield. A further variation on this reaction type allows the use of an enol ether (vinylogous ester), which provides more flexibility with respect to substituents (equation 17).104 The approach illustrated in equation (15), and Scheme 11 can be extended to include reactions of (3-diketones. The benzodiazepines, which result from reaction between 1,2-diaminobenzenes and (3-diketones, can also serve as precursors in the metal template reaction (Scheme 12).101 105 106 The macrocyclic complex product (46) in this sequence, being unsubstituted on the meso carbon atom, has been shown to undergo an electrochemical oxidative dimerization (equation 18).107... 

Electrochemical reduction of Ni(taab)2+ [taab = (20), see p. 231] occurs in two one-electron steps, to complexes formulated as [Nim(taab)] + and [Niu(taab)]°. The relationship between the annulene taab and the two-electron reduction product, the porphyrin-like taab2-, is discussed.102 The preparation of macrocycles of type (87) by a template synthesis requires a minimum ring size of x = y = 3 and depends upon the strong complexing of the metal ion at the pH of the reaction, otherwise the metal hydroxide precipitates. The NiL(C104)2,nH20 (n = 0, 1, or 2) species have been prepared for x = 3, y = 4.479... 

Ruvl(0)2(L)]2 + 2649d being reported. The chemical and electrochemical interconversion of these products has been achieved, and the oxidative activity of Ruv analogues assessed.26496 The template synthesis of [Ru(L)(OH2)] (C104)2 (L = 464) has been reported although the exact nature of this product is unknown.26511 Reaction of [Ru2(OAc)4Cl] with LH2 (LH2 = 465) in ethanol yields the... 

The substitution of 3,6-dioxaoctane-l,8-diamine for 3,6-diazaoctane-1,8-diamine in a template synthesis with 2,6-diacetylpyridine on iron(II) yields the mixed donor macrocycle (127). This molecule also forms a seven-coordinate iron(II) complex [Fe(L)(NCS)2] (L = 127). This blue high-spin complex (room temperature magnetic moment = 5.44 BM) exhibits an electronic spectrum and electrochemical behaviour which indicate that the complex of the mixed donor oxygen-containing macrocycle stablizes the -I- 2 oxidation state to a greater extent than the same complex of the corresponding macrocyclic pentamine. The seven-coordinate high-spin iron(TT) complex [Fe(L)(H,0),] (L = 128) of the related macrocycle (128) is formed by the condensation of 2,9-di-(l-methylhydrazino)-l,10-phenanthroline with 2,6-diacetylpyridine in the presence of fresh FeClj HjO. The X-ray crystal structure of this complex clearly shows that the iron(II) atom is coplanar with the macrocyclic donor set. 

K. Jackowska, A. T. Biegunski, and M. Tagowska, Hard template synthesis of conducting polymers a route to achieve nanostructures, J. Solid State Electrochem., 12, 437-443 (2008). 

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