A new theoretical formula for the absolute value of the interfacial energy of the solid−liquid interface has
been derived on the basis of the fundamental theory of interfacial energy described in J. Colloid
Interface
Sci.
1996, 181, 259; 1996, 183, 299. Namely, the intrinsic specific interfacial energy of a solid−liquid interface
without adsorption is given by γ = −N
σλkT ln x
(
∞
), where N
σ is the surface density of the surface monomers
of the solid, λ is the ratio of the number of open bonding sites of a surface monomer to that of a free monomer,
k is the Boltzmann constant, T is the absolute temperature, and x
(
∞
) is the solubility of the bulk solid in terms
of mole fraction of the monomers in the liquid phase against the total mole numbers of the solution components
including the solvent molecules. Here, “monomer” refers to the minimum subunit of the solid such as AgCl,
AgBr, etc. The formula has been collated to the experimental results of γ for AgCl, AgBr, and AgI, determined
by potentiometric measurement of the size-dependent solubilities of these silver halide particles with the
Gibbs−Thomson equation. The experimental results were in excellent agreement with the theoretical values
for the silver halides. Also, some fundamental problems were found to be involved in Tolman's theory for
size dependence of γ, and it has been deduced that γ must be independent of particle size, as has been
confirmed by experiment.
Holmium (Ho), one of the lanthanide elements, shows a high magnetic moment. Here we present a simple, yet highly potential approach for preparing polymer-based magnetic materials from a three-dimensional polymer network composed with poly(acrylic acid) and Ho showing trivalent nature. We have successfully prepared a magnetic polymer network that reacts directly to a magnet by three-dimensionally immobilizing Ho in the polymer matrix. The present method allowed a preparation of wide range of magnetic materials using polymeric scaffolds, e.g., polymer-grafted particles and cross-linked polymer gels. As a result of the high Ho content, these materials responded quickly to the magnet. The discovery of a method to prepare magnetic materials will provide flexibility in materials design and greatly expand the scope of application of magnetic materials.
A procedure to obtain monodisperse nanoparticles of cobalt(II)
hexacyanoferrate(III) was investigated. To prevent a reaction with
[Fe(CN)6]3–, Co2+ was stored
in the form of a citrate complex at pH 7.8. By lowering the pH to
3.4 by the addition of acid, part of the Co2+ was released
and reacted with [Fe(CN)6]3– to form
nuclei, followed by their growth via mass-transfer of Co2+ from the citrate complex to the solid. Here, gelatin was employed
as a protective colloid. The particles obtained were cubic and fairly
monodisperse. The mean particle size was typically 160 nm and varied
from 30 to 450 nm, depending on the reactant contents. The formation
mechanism associated with equilibrium shifts was supported by a calculated
estimation of free Co2+ on the basis of the equilibrium
relationships involved in the preparation system.
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