Metal salts Nanosize

In the nanowater pools (called nano reactors), nanosized metals and metallic salts can be conveniently synthesised. In the case of synthesis of metals, metal ions from their salts are reduced by different agents like sodium borohydride, ascorbic acid etc. Metallic salts are generally prepared by exchange reactions. The addition or mixing can be done in two ways. 

As delineated in the Introduction, numerous research groups have focused on the preparation and application of transition metal nanoparticles in the zerovalent form during the last two decades but, parallel to this development, research in the area of nanosized metal oxides has also increased. The areas of application of metal oxide nanoparticles range from catalysis [4] to semiconductors (e.g., ZnO, ZnS, CdSe) [5]. In the area of heterogeneous catalysis, many different preparative methods have been described [4], Other methods are based on the hydrolysis of transition metal salts in microemulsions [3-8], These and other approaches have been reviewed and will not be specifically treated here. Rather, the main focus is on the author s own research. 

The Miilheim electrochemical method of producing R4N+X -stabUized transition metal colloids is a viable alternative to the traditional chemical process. The preparation of aqueous colloidal solutions of nanosized transition metal oxides or multimetal oxides (1-3 nm) is possible by an unusually simple procedure, namely hydrolysis of the corresponding metal salts under basic conditions in the presence of water-soluble stabiUzers. High concentrations (0.1-0.5 M) are usually possible, which is crucial for industrial applications. In many cases an in situ method for immobUization on a soUd carrier such as carbon black is possible in the absence of a stabUizer. In the rare case of IrO, the colloidal soluhon (2nm) is stable for... 

A survey of the literature has revealed that many of the various methods reported for the preparation of metal nanopartides are applicable to a number of metals across the Periodic Table. For example, salt reduction using main group hydride-reducing agents has been used for the preparation of many metals in nanosized form (not only those cited in this subchapter). It is not the goal here to provide a directory of all reports of nanopartides syntheses, but rather to provide examples of the principal types of preparative methods that can be used. 

As a solution-based materials synthesis technique, the microemulsion-mediated method [10-18] offers the unique ability to effect particle synthesis and particle stabilization in one step. The solubilized water droplets serve as nanosize test tubes, thus limiting particle growth, while the associated surfactant films adsorb on the growing particles, thereby minimizing particle aggregation. The purpose of this chapter is to review the literature on the microemulsion-mediated synthesis of metal hydroxides and oxides the definition of a metal is extended here to include the semimetal silicon. Since metal oxides are frequently produced by decomposing metal salts, aspects of the literature on microemulsion-derived metal salts are also considered. In principle, any previously established aqueous precipitation chemistry can be adapted to the microemulsion synthesis technique. Accordingly,... 

The tiny water meniscus on the AFM tip was used as a nanosized electrochemical cell, in which metal salts can be dissolved. 

Similar structures usually consist of metals or semiconductors, as in the case of QDs. Although the synthesis of these multicomponent nanosized materials is based on techniques similar to those employed for monocomponent materials, important experimental changes should be adopted [34]. For example, in the case of bimetallic nano-objects, if the synthesis starts from metal salts, the order in which the components are reduced constitutes one of the most important synthetic variables. The simplest method consists of the contemporary reduction of two different metal salts. Alternatively, by performing the reduction of the two metals in two subsequent steps, the second reduction generates a coating on the surface of the first metal. Some authors [156,159] suggest that intimate contact between nano-objects of different composition, as in the bicomponent nanosized material system reported in Fig. 6.14d, may induce properties very similar to those of true alloys of the... 

Two procedures for the formation of nanosized particles within these films are employed. The first procedure combines the principles of colloid chemistry, selforganization and the growth of monolayers. The formation of nanosize particles is performed in the presence of stabilization agents and components forming LBFs. Chemical and photochemical reduction of metal salts in aqueous solutions can cause particle formation. The resulting layers act as specific templates. This approach is also of interest in studies of biomineralization, including studies using the sol-gel method. 

Polyimide layers are suitable matrix for incorporation of metal, salts, chromophores as nanoscale particles to obtain of nanocomposite materials. It was discussed the possibility of use polyimides in materials chemistry and nanomateiials, one of these applications is the use for making biomedical implants for neurology, ophthalmology, biosensor device and chips which are a powerful tool in clinical diagnostics. Another important trend is use in electronics and optoelectronics such as dielectric substrates and intermediate barrier layers, creating nanocomposite films with various nanosized particles such as dyes, metal, dielectric and other clusters. 

Ancient colored glasses contained nanoparticles of Au and Cu. How were these synthesized i.e., what metal salts were used, along with other experimental conditions required to yield nanosized metal clusters) ... 

Chemical precipitation of metal from a solution of a soluble salt may also be used to form metallic powders. In this procedure, a reducing agent such as sodium borohydride is added to an aqueous metal salt, MX (Eq. 14). A mixture of aqueous products will be produced in addition to the reduced metal, since sodium borohydride also reacts exothermically with water to yield borax, Na2B207. As we will see in Chapter 6, this is the most widely used procedure for the synthesis of nanoparticulate metals, from the reduction of metal salts confined within nanosized entrainer molecules. 

---