Colloidal diameter

Hydrodynamic radius of a colloidal particle (radius u = 7 h assumed) Colloid diameter (d = 2a = 2/ assumed throughout)... 

Fig. 9. 22 Absorption spectrum of ZnO colloids (diameter 29.3 A) in ethanol at different electrode potentials (reference electrode Ag/AgCl). The light was transmitted through an optically transparent electrode (indium tin oxide (ITO) layer on glass). Insert difference spectra between -0.6 and -0.95 V and -0.6 and -1.1 V. (After ref. [64])...

Polymer gel template Calculated porosity (vol.%) Specific surface area (m g- ) Pore diameter range (nm) Ti02 colloid diameter range (nm)... 

Stable colloidal dispersions of copper have been obtained in water by reduction of copper (II) with NaBH4 in the presence of PVPD, PVA, dextrin and PVME at 25 C [44, 45]. However, when high-molecular weight compounds such as polyethylene oxide, /8-cyclodextrin and PAA are used protective colloids do not form. The mean colloidal diameter depends on the properties of the applied polymer and is 50 A for PVPD and 150 A for PVA. In contrast, the mean diameter of copper particles obtained... 

Figure 4. Temperature dependence of the PNIPAM colloid diameter and turbidity. The diameter was determined using a commercial quasielastic light scattering apparatus (Malvern Zetasizer 4). The turbidity was measured for a disordered dilute dispersion of these PNIPAM colloids by measuring light transmission through a 1.0 cm pathlength quartz cell with a UV-visible-near IR spectrophotometer. Solids content of the sample in the turbidity experiment was 0.071%, which corresponds to a particle concentration of 2.49 x 10 spheres/cc. Also shown is the temperature dependence of the turbidity of this random colloidal dispersion. The light scattering increases as the particle becomes more compact due to its increased refractive index mismatch from the aqueous medium (76) (Adapted from ref 16).

FIGURE 3.21 Comparison of the predictions for the onset of destabilization, Cp (wt %) as a function of polymer size to colloid diameter ratio, with the data of Sperry et al. (1981) for polystyrene particles (4.3 x 10 cm and potential of -80 mV) in an aqueous solution of hydroxymethylcellulose with a molecular weight of 63,800 to 438,800 at an ionic strength of 0.01 M. Reprinted from Cast et al. (1983). Reproduced with permission from the Royal Society of Chemistry. 

The pore sizes of porous membranes by the sol-gel process can be controlled by colloidal diameters and firing temperature, since the pores are considered to be formed as spaces among packed colloidal particles, that is, interparticle pores. 

Figure 9.22 Absorption spectrum of ZnO colloids (diameter 29.3 A) in ethanol at different electrode potentials (reference electrode Ag/AgCI). The light was transmitted through...

The above picture of an easy mapping of the averaged trajectories of the colloids on a quasi-macroscopic description only held for amorphous structures, i.e., when the largest microscopic length scale was the colloidal diameter. In case the colloids formed some kind of structure, e.g., colloidal crystals or fractal structures, the situation was different. These internal structures brought in a different length scale that interfered with the averaging. We illustrate this in the case of a polycrystalline colloidal film [77]. 

In order to clarify the detailed character of the hydrodynamic interactions between colloids in SRD, Lee and Kapral [103] numerically evaluated the fixed-particle friction tensor for two nano-spheres embedded in an SRD solvent They found that for intercolloidal spacings less than 1.2 d, where d is the colloid diameter, the measured friction coefficients start to deviate from the expected theoretical curve. The reader is referred to the review by Kapral [30] for more details. 

The swelling equilibrium of small polymer colloids (diameters of 30-100 nm) with respect to the surface structure by analyzing different types of covalently bound surface stabilizing groups was studied by Antonietti et al. [54] in 1996. 

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