Preparation of Nanostructures

Most of the electrochemical phenomena occur in size regimes that are very small. The effects of size on diffusion kinetics, electrical double layer at the interface, elementary act of charge transfer and phase formation have recently been reviewed by Petrri and Tsirlina [12]. Mulvaney has given an excellent account of the double layers, optical and electrochemical properties associated with metal colloids [11]. Special emphasis has been given to the stability and charge transfer phenomenon in metal colloid systems. Willner has reviewed the area of nanoparticle-based functionalization of surfaces and their applications [6-8]. This chapter is devoted to electrochemistry with nanoparticles. One of the essential requirements for electrochemical studies is that the material should exhibit good conductivity. 

This includes two classes of materials namely, semiconductors and metals. There have been excellent reviews on electrochemistry with semiconductor nanoparticles [18-20]. Here, we confine ourselves to electrochemical studies with metallic nanoparticles. 

Electrochemical studies with nanosized particles require them to be accessible to the electrode surface where the potential can be controlled. This can be accomplished either by using the metallic colloid along with an inert, planar electrode or by attaching the nanopartide onto a conducting matrix. Both these methods have been demonstrated in the literature [21-25]. In this section, some of the anchoring methods that are available for this purpose are briefly explained. A few other methods of preparation are explained wherever appropriate. 

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This review will examine some of the methods for the preparation of nanostructured titania catalysts with controlled phase and architecture. Specifically, analyses quasi-... 

A synthetic alternative to this is the chemical reduction of metal salts in the presence of extremely hydrophilic surfactants have yielded isolable nanometal colloids having at least 100 mg of metal per litre of water [105], The wide range of surfactants conveniently used to prepare hydrosols with very good redispersibility properties include amphiphilic betaines A1-A4, cationic, anionic, nonionic and even environmentally benign sugar soaps. Table 3.1 presents the list of hydrophilic stabilizers used for the preparation of nanostructured colloidal metal particles, and Table 3.2 shows the wide variety of transition metal mono- and bi-metallic hydrosols formed by this method [105,120],... 

Suslick, K.S., Hyeon, T., Fang, M., and Cichowlas, A., Sonochemical preparation of nanostructured catalysts, in Advanced Catalysts and Nanostructured Materials, Moser, W., Ed., Academic Press, San Diego, 1996, p. 197, chap. 8. 

Reetz, M.T., Quaiser, S.A., and Merk, C., Electrochemical preparation of nanostructured titanium clusters characterization and use in Mcmurry-type coupling reactions, Chem. Ben, 129, 741, 1996. 

Figure 6.4 The preparation of nanostructured materials in solution evolves from (a) the classic examples of suspension, dispersion, or emulsion polymerization, to the methods that include the covalent crosslinking of select domains within supramolecular polymer assemblies (b) core crosslinking of polymer micelles (c) shell crosslinking of polymer micelles (SCKs) (d) nanocages from core-eroded SCKs (e) shaved hollow nanospheres from outer shell/core-eroded vesicles.

In this brief overview, we will use selected examples to illustrate how nanotechnology impacts catalyst preparation and ways that catalytic reactions can be conducted. We will also discuss the impact of catalysis on nanotechnology using examples where catalysts are used to facilitate preparation of nanostructures and nanomaterials, and to produce motion in nanomachines. 

Given the importance of particle size to rate capabilities in Li+ batteries, preparation of nanostructures of Li+ insertion material for possible use as electrodes in Li+ batteries seemed like an obvious extension of our work on nanomaterials. The fact that these nanostructures can be prepared as high-density ensembles that protrude from a surface like the bristles of a brush (Fig, 2A) seemed particularly useful for this proposed application because the substrate surface could then act as a current collector for the nanostructured battery electrode material. 

Recently, great attention has been dedicated to the development of novel synthetic procedures for the preparation of nanostructured catalysts with superior activity and thermal stability to those currently available. 

Finally, the molecular approach, which has been adopted for many years by research groups in heterogeneous catalysis, appears to be a powerful concept to tackle the CVD preparation of nanostructures. 

The pulsed electrodeposition technique (PED) is a versatile method for the preparation of nanostructured metals and alloys [47]. In the last two decades PED has received much attention worldwide because it allows the preparation of large bulk samples with high purity, low porosity and enhanced thermal stability. 

This study shows the possibilities and specific feature of IR-pyrolysis for the formation of nanostructured carbon. In such way PAN, thermal transformations of which have been studied in detail [8-11], was chosen as the precursor for preparation of nanostructured carbon materials by carbonization of PAN and its composites with gadolinium chloride under non-coherent IR radiation. Specific action of IR-radiation on vibrational energy of PAN bands macromolecules allows one to decrease extremely time treatment and as a result to make simple, low energy and cost-effective pyrolitic method. 

The electrodeposition technology has proven to be the least expensive, effective, and readily adoptable method to deposit Ag substrates for reliable SERS substrates with good reproducibility. It allows the preparation of nanostructure patterns by controlling the amount of composition, deposition time, temperature, and applied potential. The SERS substrates prepared by electrodeposition were a good candidate for the fabrication of a reproducible substrate. In principle, most of the metals including Au [55], Cu [56], and Ag [57-59] can be electrodeposited from aqueous solutions. 

Upon the addition of CO or H2 in the presence of appropriate stabilizers, the controlled chemical decomposition of zerovalent transition metal complexes yields isolable products in multigram amounts [49]. The growth of metallic Ru particles from Ru(COT) (COD) (COT = cyclooctatetraene, COD = cycloocta-1,5-diene) with low-pressure dihydrogen was first reported by Ciardelli et al. [49a]. This material was, however, not well characterized, and the colloidal aspect of the ill-defined material seems to have been neglected in this work. Bradley and Chaudret [49b-l] have demonstrated the use of low-valent transition metal olefin complexes as a very clean source for the preparation of nanostructured mono- and bimetallic colloids. 

Below, we shall discuss the basic published results and summarise the experimental approaches that may permit the preparation of nanostructures on the chemically modified surfaces. In this section we are not going to consider the methods concerning remote actions on the surface. Among them, this can be an action with the needle of scanning tunnelling microscope, writing from different source of radiation over photo-, radiation-... 

Although it does not exhaust the entire range of porous materials, the list attempts to cover those that can be described in terms of extended porous structures and whose electrochemistry has been extensively studied. In addition, since 1990 there has been a growing interest in the preparation of nanostructures of metal and metal oxides with controlled interior nanospace, whereas a variety of nanoscopic poro-gens such as dendrimers, cross-linked and core-corona nanoparticles, hybrid copolymers, and cage supramolecules are currently under intensive research (Zhao, 2006). Several of such nanostructured systems will be treated along the text, although, for reasons of extension, the study in extenso of their electrochemistry should be treated elsewhere. 

Especially, the eco-friendly ionic liquids have obtained extensive attention in organic synthesis with the merits provided as above. The ionic liquids as the unusual green solvents are applied extensively in various organic synthesis reactions, such as Friedel-Crafts reactions, oxidation reactions, reduction reactions, addition reactions, C-C formation reactions, nucleophilic substitution reactions, esterifications, rearrangements, hydroformylations, and nitration reactions [7-14]. Besides, the ionic liquids also have applications in the extraction separation, the electrochemistry, and preparation of nanostructured materials, the production of clean fuel, environmental science, and biocatalysis. This chapter would present in detail the application of the ionic liquids as the unusual green solvents (also as dual green solvent and catalyst) for the alkylation and acylation. 

Facile preparation of nanostructured manganese oxides by hydrotreatment of commercial particles... 

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