Solution-based route

Particularly desirable among film deposition processes are solution-based techniques, because of the relative simplicity and potential economy of these approaches. However, the covalent character of the metal chalcogenides, which provides the benefit of the desired electronic properties (e.g., high electrical mobility), represents an important barrier for solution processing. Several methods have been developed to overcome the solubility problem, including spray deposition, bath-based techniques, and electrochemical routes, each of which will be discussed in later chapters. In this chapter, a very simple dimensional reduction approach will be considered as a means of achieving a convenient solution-based route to film deposition. 

Solution-based synthetic strategies for one-dimessional nano-structures by Wang and Li (2006). Recent progress in the solution-based routes to prepare onedimensional nano-structures are reviewed. The role of crystal structure in the determination of the growth behaviour of the nano-crystals is underlined. 

One of the chapters of this handbook has already made an in-depth discussion on luminescence of rare earth doped nanomaterials, presented by Liu and Chen (2007b). So in this chapter, we will focus on the chemical synthesis technology of inorganic rare earth nanomaterials, especially on the versatile solution-based routes, and recent discoveries and milestones in the synthesis and properties studies are systemically reviewed. The general physical synthesis routes, such as MOCVD, PLD, magnetron sputtering, would not be specifically mentioned in our chapter. 

Rare-earth nanomaterials find numerous applications as phosphors, catalysts, permanent magnets, fuel cell electrodes and electrolytes, hard alloys, and superconductors. Yan and coauthors focus on inorganic non-metallic rare-earth nanomaterials prepared using chemical synthesis routes, more specifically, prepared via various solution-based routes. Recent discoveries in s)mthesis and characterization of properties of rare-earth nanomaterials are systematically reviewed. The authors begin with ceria and other rare-earth oxides, and then move to oxysalts, halides, sulfides, and oxysulfides. In addition to comprehensive description of s)mthesis routes that lead to a variety of nanoforms of these interesting materials, the authors pay special attention to summarizing most important properties and their relationships to peculiar structural features of nanomaterials s)mthesized over the last 10-15 years. 

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Andre and co-workers have utilised kneading and neat grinding in the investigation of solvate and salt formation involving the small heterocycles dioxane, morpholine or piperazine and the API 4-aminosahcylic add. In particular, the use of mechanochemical approaches has led to the simple formation of solvate and salt forms that were otherwise obtained using more complex solution-based routes. 

The application of mechanochemistry for the construction of metal-ligand bonds can significantly improve the synthesis of porous MOFs, a class of materials with increasing technological importance. Different materials have been synthesized such as (HKUST-1) obtained by neat grinding or LAG of copper(II) acetate monohydrate with benzene-1,3,5-tricarboxylic acid that has shown comparable BET surface area to that of samples obtained by conventional solution-based routes [14]. Another example concerns a porous interpenetrated mixed ligand MOF Zn2(fma)2(bipy), prepared mechanochemically from Zn(0Ac)2 2H20, fumaric acid, and 4,4-bipyridine [15]. 

CZTS is composed of abundant and non-toxic elements and has a 1.45-1.51 eV band gap with a high optical absorption coefficient (> 104 cm ), which makes it suitable for solar cell absorber layers. CZTS also shows promising thermoelectric properties, with ZT values of up to 0.36 at 700 K. Control of the materials composition has been shown to be fundamental for optimization of its functional properties. Solution processed CZTS absorber layers have provided photovoltaic efficiencies much higher than those obtained by vacuum-deposition techniques. This may be attributed to the better control of the composition and crystal-phase homogeneity by solution processing. Therefore, solution based routes for the preparation of solar absorber materials and solar cells are moving more and more into focus of scientific and industrial research. 

Schwartz, R. W. Reichert, T. L. Clem, P. G. Dimos, D. Liu, D. 1997. A comparison of diol and methanol-based chemical solution deposition routes for PZT thin film fabrication. Int. Ferro. 18(l-4) 275-286. 

Much the most important polycarbonate in commercial terms is made from 2,2-di(4-hydroxyphenyl)propane, commonly known as bisphenol A. This polymer was discovered and developed by Farbenfabriken Bayer [92], The synthesis and properties of this and many other polycarbonates were described by Schnell in 1956 [93], The polymer became available in Germany in 1959, and was given the trade name Makrolon by Bayer (in the USA, Merlon from Mobay). General Electric (GE) independently developed a melt polymerisation route based on transesterification of a bisphenol with DPC [94], Their product, Lexan, entered the US market in 1960. The solution polymerisation route using phosgene has since been displaced by an interfacial polymerisation. 

Table 6.6 summarizes photocatalytic water splitting properties of various mixed oxides prepared from two different processes, solid-state reaction (SSR) and solution based Pechini-type polymerizable complex routes [56,57,120-122], Ba5Ta40i5 prepared... 

Workers at Sphinx [24] have published a synthetic route to a series ofhighly functionalized biphenyl compounds. The key reactions in this sequence are the biaiyl Stille and/or Suzuki couplings to form the biphenyl nucleus and the use of Mitsunobu chemistry to attach the variable side chains (Fig. 2). The illustrated route utilizes a solution-based diaryl coupling followed by on-resin Mitsunobu reactions. Although the diaiyl coupling proceeds on solid phase, this group s desire to maximize resin loading prompted them to implement the former route. 

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. 

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. 

PPV samples prepared by solution based sulfonium precursor routes were found to be polycrystalline. PPV thin films prepared by CVP, however, show a structure that is dependent... 

Another example concerns the immobilization of a biocatalyst—the enzyme glucose oxidase (GOD)—to the silica nanotubes [4]. GOD was immobilized, on both the inside and outside surfaces, via the aldehyde silane route. These GOD-nanotubes (60 nm diameter) were dispersed into a solution containing 90 mM glucose and also the components of the standard dianisidine-based assay for GOD activity. A GOD activity of 0.5 0.2 units per milligram of nanotubes was obtained. These studies also showed that protein immobilized via the Schiff base route is not leached from the nanotubes, where GOD activity ceased when the nanotubes were filtered from the solution. 

The sol-gel method is a low temperature synthesis route for complex oxides [42]. It can be used to make complex functional oxide nanowires inside the pores of templates. In addition to the sol-gel method precursor-based solution deposition routes can also be used for nanostructure formation [43]. In both cases a postdeposition high temperature anneal (>500-600 °C) is needed to form the required stoichiometric phase. Due to the requirement of a high temperature anneal, alumina templates are used as the polycarbonate membranes decompose at a much lower temperature. For chemical solution deposition the membrane is dipped directly into the precursor solution. For sol-gel growth generally the required sol is prepared and the template is put into the sol for a required period (e.g. 0.5-1 h). After removing the membrane from the sol it is dried and then annealed at higher temperature before the required phase is formed. A schematic of the sol-gel route is shown in Figure 21.10. 

At the start of the 1990s the only available aqueous solution-based pulmonary delivery systems were the nebulizers that had their routes in technology developed at the turn of the nineteenth century. From a patient perspective, nebulizer therapy is time consuming, equipment costs are high, and cleaning and maintenance can be problematic from a pharmaceutical perspective, nebulizers exhibit poor delivery efficiency and high variability [22], However, nebulizers... 

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