Biology Reference
In-Depth Information
ing polymer [51]. Polypyrrole and polyaniline are considered nowa-
days the most promising conducting polymers for the development
of biosensor devices owing to their good biocompatibility, conduc-
tivity,andstability.Thecombinationofnanoengineered“smart”con-
ducting polymers with biomolecules and nanostructures, like metal
NPs and carbon nanotubes (CNTs), may generate conducting com-
positeswithnewandinterestingproperties,providinghighersensi-
tivity and stability ofthe immobilizedbiomolecules.
Nonconducting polymers
are polymeric binders (epoxy,
methacrylate,silicone,araldite)whichconfertotheconductingcom-
posite a certain physical, chemical, or biological stability, while the
electrical conductivity is provided by the conducting filler (micro or
nanoparticles of platinum, gold, graphite, carbon nanotubes, etc.).
Conducting composites
based on
nonconducting polymers
are
classified by the nature of the conducting material and the arrange-
ment of its particles (i.e., whether the conducting particles are dis-
persed in the polymer matrix or if they are grouped randomly in
clearly defined conducting and insulating zones).
The inherent electrical properties of the
conducting composite
dependonthenatureofeachofthecomponents,theirrelativequan-
tities, and their distribution. Micro and nanostructurated conduct-
ing particles are usually used as fillers in conducting composites:
the electrical resistance is determined by the connectivity of these
conductingmicroornanoparticlesinsidethenonconductingmatrix;
therefore,therelativeamountofeachcomponenthastobeassessed
to achieve optimal composition. A percolation curve [52], as shown
inFig.3.1,isarepresentationofthelogarithmicvariationoftheelec-
tricalresistanceofacompositeasafunctionofitsconductingphase
content. By constructing a percolation curve, it is possible to deter-
mine the minimum conductor content required to achieve certain
conductivity. This pointis known asthe percolation threshold.
Thecompositeacquiresparticularelectrochemicalfeaturesfrom
the nature of the conductive filler in the bulk.
The extensive range of unique properties inherent to metal
NPs, including electrical conduction, makes them very attractive
candidates for integration into polymers as NP-polymer compos-
ites. Embedding NPs into host polymers provides a means for
introducing a variety of properties to the polymer-based com-
