Nucleation and growth of molecular

In both cases, the Au nanoparticles behave as molecular crystals in respect that they can be dissolved, precipitated, and redispersed in solvents without change in properties. The first method is based on a reduction process carried out in an inverse micelle system. The second synthetic route involves vaporization of a metal under vacuum and co-deposition of the atoms with the vapors of a solvent on the walls of a reactor cooled to liquid nitrogen temperature (77 K). Nucleation and growth of the nanoparticles take place during the warm-up stage. This procedure is known as the solvated metal atom dispersion (SMAD) method. 

The term binary homogeneous nucleation is used to describe the formation of particles from two different gas-phase compounds such as sulfuric acid and water such nucleation can occur when their individual concentrations are significantly smaller than the saturation concentrations needed for nucleation of the pure compounds. It is believed that in the atmosphere, formation of particles from low-volatility gases occurs not by condensation of a single species but rather by the formation and growth of molecular clusters involving at least two, and as described shortly, probably three or more different species. 

In the case of co-deposition nucleation and growth of metal nanoparticles are influenced by the process of a polymer matrix formation from deposited low-molecular fragments (TFE) of PTFE. At the initial stages the deposited... 

Molecular sieve particles grown from unstirred gels contain (6-15 nm) voids, some are sharply faceted typically most of these voids are located in the small, iron-rich crystallites near the center of the FeZSM-5 particle (Figure 3) (15, 16). Many of the facets of these voids are rounded during steam treatment, the voids also provide sites for the nucleation and growth of second phase particles. Hydrothermal treatments for 1, 2 or 4 h at 550 °C of the unstirred samples produces second phase particles, 2 to 6 nm diameter, whereas steaming at 700 °C for 4 h results in particles... 

Bonafede, S. J. and Ward, M. D. (1995). Selective nucleation and growth of an organic polymorph by ledge-directed epitaxy on a molecular crystal substrate. / Am. Chem. Soc., 117, 7853-61. [93]... 

We have recently developed methods where nucleation and growth of cocrystals are directed by the effect of the cocrystal components on reducing the solubility of the molecular complex to be crystallized. The supersaturation, a, with respect to cocrystal is derived from the difference in chemical potential between the cocrystal components in the supersaturated solution state and in the solid state and is given by... 

At sufficiently high supersaturation and very low temperature, the frequency of molecular collisions within the gas phase is great enough to cause homogeneous nucleation and growth of powder-like product. Up to the present, CVD has been an important technique for manufacturing superfine powders as discussed in Section 3.7.1, or surface modification of functional powders as shown in Figure 6.7. 

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