Page 281 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 4 CONTROL OF NANOSTRUCTURE OF MATERIALS
4.6.2 Assembling and patterning of particles collectives) [9], survey of Japanese name of SAM [9],
introduction of self-assembling pattering of particles
Particle collectives can be used for photonic crystals using a functional template [11].
and the like by producing two- or three-dimensional
particle structures on a micron- or nanosized scale (1) Liquid-phase pattering
based on preparation of bulky colloid crystals (opal Liquid-phase pattering is capable of arrangement,
structure), formation of a particle deposition layer on alignment, and patterned integration of fine particles
the board surface, and patterning of particle collec- in only the specified region on the patterned self-
tives in an arbitrary shape. Examples include two- assembled mono-layer by the chemical reaction and
dimensional pattering of a particle monolayer, electrostatic interaction between the nano-/micropar-
two-dimensional pattering of particle multilayers with ticles and the functional group at its surface after
a controlled number of layers, and fine particle wiring forming it on the board (Fig. 4.6.9) [14–16].
with straight and curved particle alignments. This method realizes particle monolayer patterning
Since photonic properties with the band gap (Fig. 4.6.10(a)), straight/curved particle wiring (Fig.
obtained from particle collectives in an fcc (hcp) 4.6.10(b–d)), and precise arrangement of single parti-
structure are restricted, preparation of particle collec- cles [14]. In the particle monolayer patterning, a self-
tives with other crystal structures (periodical struc- assembled mono-layer with an octadecyl group is
ture) is necessary. New technology for preparing prepared all over the surface of a silicon board. The
nanomicro structures with full command of design in specified area exposed to the emission of ultraviolet
three-dimensional space is required for advanced light by use of photo masking is converted into a
photonic crystals and other new functions. For exam- silanol group and used as a template (Fig. 4.6.9).
ple, high-order structures have been prepared by mak- The surface of the silica particles is also modified
ing spherical particle collectives and its patterning with a carboxyl group by converting the cyano group
and integration. at the end of the self-assembled mono-layer into a
The following section describes the “two-solution carboxyl group and then the patterned self-assembled
method” for particle assembling and patterning, mono-layer is immerged in water dispersed with these
which uses a thin organic membrane called the self- particles for a few minutes. In water with a pH of
assembled mono-layer as a template. It makes use of about 7, the amino group has a positive zeta potential
“liquid-phase pattering” in colloid solutions, the “dry- and the carboxyl group has a negative zeta potential.
ing patterning” process of drying the colloid solution In this way, the particles are integrated in only the
and the interface between two kinds of solutions. amino group region of the board for patterning using
In describing this process, references are made to the electrostatic effect between the particles and the
other studies: Liquid-phase pattering [1–6], drying board (Fig. 4.6.10) [14].
patterning [1], preparation and patterning of a self-
assembled mono-layer [7, 8], details of the two-solu- (2) Drying patterning
tion method and the structure, defects, evaluation of The solution drying process has advantages in that the
the forming mechanism [9, 13], thermodynamic fcc (hcp) structure and closest packing structure are
explanation of self-assembling phenomena (formation easily obtained by use of the contraction and menis-
of a self-assembled mono-layer, formation of particle cus force of colloid solution. Figure 4.6.11 shows the

Ultraviolet emission
exposure

Electrostatic interactions

Silicon substrate
Octadecyl group Silanol group Amino group

OH CN COOH
Silica particle

Figure 4.6.9
Liquid phase pattering using the self-assembled mono-layer.

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