Biomedical Engineering Reference
In-Depth Information
4.3 FUNCTIONALIZATION OF IONIC LIQUIDS FOR
EASE IMMOBILIZATION
With the development of the synthesis of ILs, the price of ILs
has been greatly decreased. However, considering the economic
criteria, the ease of separation and increasing the recycle
times, the immobilization of ILs on the solid supports is highly
desirable. The immobilization process transferred the desired
properties of ILs to the solid supports. And more important,
to date, difficulties in effective immobilization of generic ILs on
the electrode substrate have greatly hindered research on the
electrocatalysis of ILs. It was reported that the ILs can be bound
to a surface by either covalent bonds or noncovalent
interactions between the ILs and the surface. Mehnert
et al. have first proposed the concept of silica-supported ILs
catalysis, where the ILs immobilized on the Si/SiO
2
surface
was functionalized with alkyl siloxane appendages (Fig. 4.3)
[24, 44]. Similarly, ionic species were immobilized on the surface of
mesoporous nanostructured silicas by Moreau et al. (Fig. 4.4) [45].
Lee and coworkers [46] have proposed a method to immobilize
ILs on gold surface, which was based on self-assembly with
imidazolium ions bearing alkyl thiol (Fig. 4.5a). Interestingly,
simply by anion exchange, the wettability of gold surface could
be facilely controlled (Fig. 4.5b). Huck et al. developed IL based
polyelectrolyte brushes, which were anchored on Au surface
via thiol initiator, e.g., BrC-(CH
)
2
COO(CH
)
SH. Further by ion
3
2
6
exchange with ferricyanide ions ([Fe(CN)
) as redox probes,
CV measurements of the modified brushes showed the typical
electrochemical response corresponding to a surface-confined
electroactive species and the redox counterions, as ferricyanide
species form stable ion pairs with the quaternary ammonium
groups of the brush (Fig. 4.6) [47]. In a noncovalent way, Mao
et al. have reported that ILs could be directly immobilized on
the glassy carbon electrode (GC) by casting and observed the
electrocatalytic activity toward ascorbic acid (AA) and the
capability to facilitate direct electron transfer of horseradish
peroxidase (HRP) (Fig. 4.7) [48]. Dong et al. have reported
]
3
-
6
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