Solution Based Methods

One of the most basic requirements in analytical chemistry is the ability to make up solutions to the required strength, and to be able to interpret the various ways of defining concentration in solution and solids. For solution-based methods, it is vital to be able to accurately prepare known-strength solutions in order to calibrate analytical instruments. By way of background to this, we introduce some elementary chemical thermodynamics - the equilibrium constant of a reversible reaction, and the solubility and solubility product of compounds. More information, and considerably more detail, on this topic can be found in Garrels and Christ (1965), as well as many more recent geochemistry texts. We then give some worked examples to show how... 

In general, there are two possibilities to prepare nanocarbon-supported metal(oxide) catalysts. The in situ approach grows the catalyst nanoparticles directly on the carbon surface. The ex situ strategy utilizes pre-formed catalyst particles, which are deposited on the latter by adsorption [94]. Besides such solution-based methods, there is also the possibility of gas phase metal (oxide) loading, e.g., by sputtering [95], which is used for preparation of highly loaded systems required for electrochemical applications not considered here. 

Using this novel solution-based method, we have been able to incorporate [C6H5CH2NH3][H2P04], BADP (77), an SHG-active material, into polymeric hosts such as poly(acrylamide) (PAA) and polyethylene oxide) (PEO) to produce transparent, colourless, low scattering SHG-active composites with excellent temporal stability. 

Three techniques have been described in the literature to prepare combinatorial libraries of fuel cell electrocatalysts solution-based methods [8, 10-14], electrodeposition methods [15-17] and thin film, vacuum deposition methods [18-21]. Vacuum deposition methods were chosen herein for electrocatalyst libraries in order to focus on the intrinsic activity of the materials, e.g., for ordered or disordered single-phase, metal alloys. 

Unlike solution based methods in which the sample is dissolved in an aqueous medium that usually includes some small percentage of mineral acid, in GDMS the sample is not a homogeneous liquid, but a solid, and can therefore take a number of forms (e.g., machined hollow cathodes, compacted disks, and dried solution residue). In the next section, cathode/anode geometry is discussed in the section presented here, an equally important but often overlooked issue, the physical form of the sample, is discussed. 

Furthermore, CNT-clay hybrid filler can also be used to prepare polymer nanocomposites by solution based method. Hydrophilic... 

In solvent casting or solution mixing, CNTs are first dispersed in a suitable solvent and then mixed with a polymer solution to obtain a suspension of nanotubes in the polymer. The mix is then poured into suitable die molds and the solvent is allowed to evaporate to leave behind nanocomposite film. Solution based methods offer advantages of lower viscosities which facilitate uniform mixing and dispersion. Ultrasonication or magnetic stirring is typically used to separate and disperse CNTs uniformly in different solvents or... 

Pure fluorite type Ce02 is obtained straightforwardly via solid state thermal decomposition or aqueous precipitation. In the recent years, novel s)mthetic routes and techniques have been applied for the synthesis of nanoceria. In this section, the synthesis through aqueous and nonaque-ous solution-based methods as well as the dry and post annealing routes toward ceria nanomaterials are illustrated with examples. And the related systems as well as the simulation works providing instructive results are also discussed. 

The formation of rare earth organic-inorganic hybrid nanostructure could be realized via nonaqueous or aqueous solution based methods. Later, the products could be converted into rare earth oxides by calcination in air. The nanostructures could be partially or mostly preserved. 

In summary, rare earth nanomaterials have shown a great potential of fheir optical and catalytic properties for applications in the medical, nanodevices, catalysis, and fuel cells. A number of productive synthesis routes have been developed toward various rare earth nanomaterials. Well-defined rare earfh compoimd based nanostructures have been extensively obtained via dry methods, aqueous solution based methods, as well as the nonaqueous solution based methods. The targets of obtaining pure phase, desired composition, controllable and uniform shapes and sizes, funed surface sfafus, and funcfionalizafion have been partially reached. 

The most generally used solution-based method to synthesize cocrystals is slow evaporation from solutions with equimolar or stoichiometric concentrations of cocrystal components.f Solvo-thermal methods are also reported in the literature, although less frequently. ° In this method, heat is used to dissolve stoichiometric amounts of both components, the solution is cooled, and the cocrystals are then allowed to nucleate and grow. These processes, however, suffer from the risk of crystallizing the single component phases, thereby reducing the possibility of isolating the multiple component crystalline phase. As a result... 

A large number of binary ceramics such as carbides, nitrides, and oxides have been obtained by the decomposition of metal-organic precursors. The following text presents some selected examples to demonstrate the promises and limitations of molecular precursor approach. A complementary account of the synthesis of metal oxide nanoparticles from solution-based methods is given in Chapter 12.03. 

Solution-based methods for OLED fabrication such as ink-jet printing... 

Recently, a solution-based method for photochemical preparation of polyfullerences has been discovered [81,82]. In the photopolymerization, carefully deoxygenated fullerene cluster solutions are used. As discussed in the previous section, Cjo and C70 form microscopic aggregates or clusters in room-... 

Current gold nanopaiticle solution based methods of biosensing are not limited strictly to this one type of nanopaiticle but can incorporate other particles as well. Peptide linked gold nanoparticle - quantum dot biosensors have been created by Chang et al., that rely on the ability of the gold nanoparticles to quench the photoluminescence of the quantum dots when in their close proximity bound state [26]. The method of sensing is also considered an on sensor since the default state of the particles is off (no luminescence), and it is converted to on (luminescence) once sensing takes place. 

To conclude, it is clear there is a strong dependence of the performance of synthetic hematite on the deposition technique. While methods such as spray pyrolysis and CVD consistently produce electrodes photoactive for water oxidation, solution-based methods such as sol-gel approaches have failed to produce especially photoactive hematite. This is certainly related to the quality of the prepared material in terms of crystallinity and impurity concentrations. Aqueous methods of preparing hematite typically pass through a phase containing iron hydroxide (e.g., akaganeite, lepidocrocite, or goethite) but primarily hematite is detected after at annealing at 500°C. However, it has been shown that at temperatures up to 800°C, a nonstoichiometric composition remains in hematite when prepared in this way... 

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