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Stability size-dependent

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. [Pg.367]

Cobalt shows a dramatic size dependence(JJ cJ that resembles the behavior of iron more so than that of vanadium or niobium. The smallest cluster to react is the trimer and the 5-9 atom clusters are significantly more inert than any of the larger clusters. Cobalt also has a significant dip in reactivity between 19 and 22. A theoretical calculation rationalized the onset in reactivity at the trimer to be associated with energetic stability of the products(29). [Pg.56]

Evaporation of the droplets is an issue on the surfaces, since the vapor pressure of the liquid increases as the droplet radius decreases, thereby making the droplets evaporate even in a saturated vapor environment. The droplet volume can be stabilized by using the WGM size-dependent absorption peaks in the droplets in a supersaturated environment, where droplets increase in size until absorption at a WGM resonance... [Pg.481]

There were many early experimental investigations of bluff-body stabilization. Most of this work [69] used premixed gaseous fuel-air systems and typically plotted the blowoff velocity as a function of the air-fuel ratio for various stabilized sizes, as shown in Fig. 4.56. Early attempts to correlate the data appeared to indicate that the dimensional dependence of blowoff velocity was different for different bluff-body shapes. Later, it was shown that the Reynolds number range was different for different experiments and that a simple independent dimensional dependence did not exist. Furthermore, the state of turbulence, the temperature of the stabilizer, incoming mixture temperature, etc., also had secondary effects. All these facts suggest that fluid mechanics plays a significant role in the process. [Pg.244]

The YBG equation is a two point boundary value problem requiring the equilibrium liquid and vapor densities which in the canonical ensemble are uniquely defined by the number of atoms, N, volume, V, and temperature, T. If we accept the applicability of macroscopic thermodynamics to droplets of molecular dimensions, then these densities are dependent upon the interfacial contribution to the free energy, through the condition of mechanical stability, and consequently, the droplet size dependence of the surface tension must be obtained. [Pg.18]

The largest portion of the monomer (>95%) is dispersed as monomer droplets whose size depends on the stirring rate. The monomer droplets are stabilized by surfactant molecules absorbed on their surfaces. Monomer droplets have diameters in the range 1-100 pm (103-105 nm). Thus, in a typical emulsion polymerization system, the monomer droplets are much larger than the monomer-containing micelles. Consequently, while the concentration of micelles is 1019-1021 the concentration of monomer droplets is at most 1012-1014 L 1. A further difference between micelles and monomer droplets is that the total surface area of the micelles is larger than that of the droplets by more than two orders of magnitude. The size, shape, and concentration of each of the various types of particles in the... [Pg.352]

Moreover, particle size can significantly affect the material properties of the nanoparticles and is important for their interaction with the biological enviromnent (e.g., as concerns their ability to pass fine capillaries or to leave the vascular compartment via fenestrations after intravenous administration). Particle sizing results are thus crucial parameters in the development and optimization of preparation processes as well as in the evaluation of dispersion stability. Particle sizing, however, has also been employed for other purposes for example, to evaluate the size dependence of the nanoparticle matrix properties [1] or to obtain additional information on the particle shape [2,3]. [Pg.2]

The method of laser ablation from a metal has been used to prepare nanoparticles dispersed in a solution [202-207]. Recently, colloidal gold nanoparticles in water having an average diameter of 5.5 nm were prepared by laser ablation at 1064 nm (800 mJ/cm ) from a gold metal plate [208]. The final nanoparticle size depends on the laser fluence and the stabilizer concentration (Fig. 17). [Pg.607]

Table 1 lists the atomization energies of the Na(3p)Arn clusters. The atomization energies found in the present work and those obtained by Tutein and Mayne are in very good agreement within 200 cm, whatever the cluster size. The size dependence of stabilities observed by Tutein and Mayne is confirmed. [Pg.377]

The factors that determine crystal size, a topic of particular relevance to this chapter, have been discussed to some extent in Section 3.4. There are two main factors that generally affect crystal size for any particular material the deposition mechanism and the deposition temperature. The hydroxide cluster mechanism is expected to give a crystal size similar to that of the original hydroxide cluster (with some growth possible as deposition proceeds). That size depends mainly on temperature, both because higher temperatures allow more grain growth and, possibly more important, lower temperatures kinetically stabilize very small nuclei in solution that are thermodynamically unstable. For example, in the hydroxide cluster mechanism, where crystal size is believed to be controlled mainly by the size of the Cd(OH)2 colloids, the relevant equilibria are... [Pg.355]

In Sections III and IV, we described droplet size dependencies of the ET and MT rates across microdroplet/water interfaces. Such experiments on single droplets are possible by the laser trapping spectroscopy-electrochemistry technique alone. Besides these experiments, the technique is also highly useful in controlling a reaction efficiency in microdroplets [99,100]. In this section, we describe electrochemically induced dye formation reactions across microdroplet/water interface and demonstrate control of the dye formation reaction yield in micrometer dimension. The effects of microenvironments and additives (surfactant or stabilizer) on dye formation reactions are also described. [Pg.207]


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See also in sourсe #XX -- [ Pg.192 ]




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