Page 74 - Book Hosokawa Nanoparticle Technology Handbook

CHAPTER 2 STRUCTURAL CONTROL OF NANOPARTICLES

2.1 Structure construction and function applications of nanoparticles, the surface has often
been modified with different compounds to provide
adaptation of nanoparticles
special functions. The internal structure can be
simply classified into monolithic matrix and
Nanoparticles are designed and prepared with mole- core–shell construction. When the cores of particles
cule and particle structures that can exhibit functions would be empty or contain only medium, they can be
desired for applications. The size and shape of the called as the “hollow particles”. Second, each layer
prepared particles are primarily important in the of surface, shell and core has single phase, random
function adaptation. Further, the surface and internal multi-phases, or ordered multi-phases. When a cer-
structures are commonly composed of multi-layers tain phase in the multi-phases would be empty, the
and/or multi-phases containing multi-components to structure can be called “porous” (porous structure).
provide the desired functions. A certain phase dispersed in the layer is not neces-
sarily isolated, but sometimes spanned through the
2.1.1 Structures of nanoparticles layer. Such a percolated structure has much effect on
the properties of the layer. Third, each phase can be
Many case-studies have been reported on nanostruc- crystalline or non-crystalline (amorphous) in the
ture construction so far. Figure 2.1.1 shows typical molecular arrangement. Finally, the layers and
structures of nanocomposite particles. phases are assembled by utilizing covalent bonding,
First, the particle has a macrostructure consisting van der Waals force, electrostatic force, hydrogen-
of the surface and internal part. The molecules and bonding, and so on.
atoms in the surface layer are in the active state dif- The structures of nanoparticles are required to be
ferent from those in the bulk, even if the particle held permanently in some cases of application, but,
would be composed only of a single compound. in other cases, to be disassembled after playing a role
Although this surface property itself is useful in at the beginning stage of application. In the latter case,

Core-shell structure
Surface structure

Bonding mode: covalent bond, weak interaction, etc.

Dispersed structure

Monolithic random Random Ordered
dispersion multiphases multiphases

Crystalline, amorphous, self associated

Figure 2.1.1
Typical structures of composite nanoparticles.

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