Biology Reference
In-Depth Information
flow systems. Additionally, the pastes are dissolved by some nonpo-
lar electrolytic solvents, leading to a deterioration of the signal. The
general degradation of these devices occurs quickly and has limited
their use to the research laboratory [18]. Unlike soft carbon paste,
rigid carbon polymer composites allow the design of different con-
figurations, and these materials are compatible with nonaqueous
solvents. Next section is focused in the preparation and properties
of rigidcarbon polymer composites.
3.3.2
Rigid Carbon-Polymer Composite
Rigid carbon-polymer composites are obtained by mixing a car-
bon filler (such as graphite or CNT) with nonconducting polymeric
binders (epoxy, methacrylate, silicone, araldite), obtaining a soft
paste that becomesrigid after a curing step.
Rigidcarbon-polymercompositesareinterestingalternativesfor
the construction of electrochemical (bio)sensors. The capability of
integrating various materials (including nanostructured particles
and biomolecules) is one of their main advantages. Some materi-
als which are incorporated within the composite result in enhanced
sensitivity and selectivity. The best composite components will give
the resulting material improved chemical, physical, and mechani-
cal properties. As such, it is possible to choose between different
binders and polymeric matrices and conductive fillers in order to
obtainabettersignal-to-noiseratio,alowernon-specificadsorption,
andimprovedelectrochemicalproperties(electrontransferrateand
electrocatalytic behavior). This incorporation is possible to be per-
formed either through a previous modification of one of the com-
ponent of the composite before its preparation or through physical
incorporation intothe composite matrix.
The electrical resistance is determined by the connectivity of
the conducting particles inside the nonconducting matrix; there-
fore, the relative amount of each composite component has to
be assessed to achieve optimal composition. Figure 3.2 shows
scanning electron micrographs of different carbon-based materi-
als based on the same conductive filler (graphite) but different
polymeric binders: (A) Araldite-M-graphite (73.2%), (B) Araldite-
CW2215-graphite (45.8%), (C) silicone-graphite (61.0%), (D)
