Biomedical Engineering Reference
In-Depth Information
5
µ
m
P1
IPMC
5
µ
m
P1
IPMC
FIGURE 3.9
Two schematic diagrams showing different preparation processes. Top left: A
schematic shows initial compositing process; top right: its top-view SEM micrograph. Bottom
left: A schematic shows surface electroding process; bottom right: its top-view SEM micro-
graph where platinum is deposited predominantly on top of the initial Pt layer.
The initial compositing process requires an appropriate platinum salt such as
Pt(NH
3
)
4
HCl in the context of chemical reduction processes similar to the processes
evaluated by a number of investigators, including Takenaka et al. (1982) and Millet
et al. (1989). The principle of the compositing process is to metalize the inner surface
of the material (usually, in a membrane shape, Pt nanoparticles) by a chemical-
reduction means such as LiBH
4
or NaBH
4
. The ion-exchange polymer is soaked in
a salt solution to allow platinum-containing cations to diffuse through via the ion-
exchange process. Later, a proper reducing agent such as LiBH
4
or NaBH
4
is
introduced to platinize the materials by molecular plating.
As can be seen in figures 3.10 and 3.11, the metallic platinum particles are not
homogeneously formed across the material but concentrate predominantly near the
interface boundaries. It has been experimentally observed that the platinum partic-
ulate layer is buried a few microns deep (typically 1-10
m) within the IPMNC
surface and is highly dispersed. A TEM image of the near-boundary region of an
IPMNC strip on the penetrating edge of the IPMNC shows a functional particle
density gradient where the higher particle density is toward the surface electrode.
The range of average particle sizes was found to be around 40-60 nm.
µ
