Metallic colloidal morphology

A new method for the size- and morphology-selective preparation of metal colloids using tetraalkylammonium carboxylates of the type NR4 R C02 (R = octyl, R = alkyl, aryl, H) both as the reducing agent and as the stabilizer [Eq. (4)] was reported by Reetz and Maase [42]. 

The methods used for the synthesis of metal NPss in colloidal solution are very important as they control the size and shape of NPs, which in turn affects their properties. Moreover, successful utilization of NPs in biological assays relies on the availability of nanomaterials in desired size, their morphology, water solubility and surface functionality, Several reviews on the synthesis of nanoparticles are available [93], Some reviews dedicatedly covered the synthesis of gold nanoparticles [109,127,140], Synthesis methods of CG (and other metal colloids) can arbitrarily be divided into following two major categories ... 

In summary, our results have demonstrated that a colloidal monolayer can be used as a flexible template to create ordered nano-structured arrays. Combining it with other techniques, a series of ordered nano-structured arrays with centimeter size could be easily fabricated on many different substrates. These nano-structured arrays are of surface roughness on the nano- and micro-scales, or similar to the microstructure of lotus leaves. Our results have demonstrated that such micro/nano-structured arrays, not only of insulators and semiconductors but also of metals, display morphology-dependent wettability. Significant enhancement of both hydrophobicity and hydrophilicity can be achieved by fabricating special surface micro/nano-structure on any material. This means that we can also realize tunable and controllable wettability of surface of any material by designing the proper surface structure. From this study, it can thus be expected that the nano-devices based on our nano-structured arrays would be waterproof and self-cleaning, in addition to their special device functions. 

The general characteristics of metal colloidal dispersions are weU understood even though the mechanisms by which such metallic particles are formed in the colloidal state aic not This is easily understood if one recognises the complexity of the processes [1] involved in nucleation, growth and coagulation. In order to understand fully and control the preparation, these three steps of course have to be studied individually. Water purity, trace impurities, concentration, cleanliness of the reaction vessel and other factors all have a significant effect on the size and morphology of the particles [1,2] and therefore need to be controlled. 

S. Sanchez-Cortes, J. V. Gatcia-Ramos and G. Morcillo, Morphological Study of Metal Colloids Employed... 

We found recently that the viscosity (//vac) of the colloidal thiolate precursor is a key parameter in controlling the shape of the nanoproducts in the solventless method [8]. Uniform nanowires, rods, or spheres could be made from the corresponding precursors that came from the solutions with different viscosities. The viscosity is a measure of the polymerization of the metal-thiolate complexes. Accordingly, the precursor with the highest viscosity produces nanowires (Fig. 20.5 a), and with decreases in the viscosity, the product morphology changes to rods (Fig. 20.5b) and then spheres (Fig. 20.5c). 

Despite the fact that the hydrolysis of the ferric ion is exceedingly sensitive to various experimental parameters (temperature, pH, etc.), hematite (a-Fe203) and akageneite ((3-FeOOH) were apparently the first reasonably uniform colloidal metal (hydrous) oxides dispersions reported in the literature, as already indicated in the introduction. Since then, this family of compounds has been the most extensively investigated, with specific emphases on particle uniformity, composition, and morphology. 

Colloidal sulfide, selenide, telluride, phosphide, and arsenide semiconductor particles are prepared by the controlled precipitation of appropriate aqueous metal ions by H2S, H2Se, H2Te, PH3, and AsH3, respectively. Colloids are stabilized, typically, by sodium poly-phosphate. A large number of experimental parameters determine the size, size distribution, morphology, and chemical composition of a semiconductor particles in a given preparation. Concentrations, rates, and the order of addition of the reagents the counterions selected ... 

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