Biomedical Engineering Reference
In-Depth Information
500
µ
m
100
µ
m
500
µ
m
50
µ
m
FIGURE 3.12
Various surface micrographs of IPMNCs using different techniques of chem-
ical plating and placing electrodes on the boundary surfaces.
and reduction occurs, as well as ultrasonic cleaning and chemical cleaning by acid
boiling (HCl or HNO
3
-low concentrates).
The second step is to incorporate the ion-exchanging process using a metal com-
plex solution such as tetra-amine platinum chloride hydrate as an aqueous platinum
complex ([Pt(NH
3
)
4
]Cl
2
or [Pt(NH
3
)
6
]Cl
4
) solution. Although the equilibrium condition
depends on the types of charge of the metal complex, such complexes were found to
provide good electrodes. The immersion and stirring time is typically more than 1 h.
The third step (initial platinum compositing process) is to reduce the platinum
complex cations to metallic state in the form of nanoparticles by using effective
reducing agents such as an aqueous solution of sodium or lithium borohydride (5%)
at favorable temperature (i.e., 60
°
C). Platinum black-like layers deposit near the
surface of the material.
The final step (surface electroding process) is intended to effectively grow Pt
(or other novel metals, a few microns of thickness) on top of the initial Pt surface
to reduce the surface resistivity. Therefore, an additional amount of platinum is plated
by the following process on the deposited Pt layer:
1.
Prepare a 240-ml aqueous solution of the complex ([Pt(NH
3
)
4
]Cl
2
or
[Pt(NH
3
)
6
]Cl
4
) containing 120 mg of Pt and add 5 ml of the 5% ammonium
hydroxide solution (pH adjustment).
