Sensors functionalized conducting polymer

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

PNA strand, resulting in an increase of the electrochemical signal (SWV peak current) as a result of probe-target hybridization. The PNA-functionalized conductive polymer sensor allowed for a detection limit of approximately 10 nM, and the feasibility for single-nucleotide mismatch detection was also demonstrated. 

Solid-state ion sensors with conducting polymers as sensing membranes have also proved useful in some applications. Of particular importance are the pH sensors based on polyaniline that can be also applied in non-aqueous solutions. Polypyrrole-based sensors for nitrate also show great promise for water analysis. However, in addition to these two excellent examples, a large number of functionalized conducting polymers have been synthesized already, and these materials may offer unique possibilities for fabrication of durable, miniaturized ion sensors. 

A.D. Aguilar, E.S. Forzani, X.L. Li, N.J. Tao, L.A. Nagahara, I. Amlani, and R. Tsui, Chemical sensors using peptide-functionalized conducting polymer nanojunction arrays, Appl. Phys. Lett., 87, 193108 (2005). 

Utilizing these functionalized conducting polymers, a solar cell, an electrochromic device, a chemical luminescent material, a sensor, a polymer battery, etc. can be constructed, in which the functionality is attributed to the incorporated functional molecule. 

Incorporation of the latter ions into the polymer can be controlled by varying the electrochemical paramets [164] and these systems could be used as modified electrodes in sensors and actuators. Redox processes in these phthalocyanine-functionalized conducting polymer electrodes are found to be accompanied by a change in the pH of the electrolyte solution and therefore these polymers are useful for the preparation of pH modulator electrodes [168]. 

Reisberg, S Dang, L.A., Nguyen, Q.A. et al. (2008) Label-free DNA electtochemical sensor based on a PNA-functionalized conductive polymer. Talanta, 76 (1), 206-210. Chumbimuni-Torres, K.Y., Wu, J., Clawson, C. et al. (2010) Amplified potentiomet-ric transduction of DNA hybridization using ion-loaded liposomes. Analyst, 135 (7), 1618-1623. 

Consequent ], the next generation of amperometric enzyme electrodes has to be based on immobilization techniques which are compatible with microelectronic mass-production processes and easy to miniaturize. Additionally, the integration of all necessary sensor components on the surface of the electrode h to prevent the leaking of enzymes and mediators simultaneously improving the electron-transfer pathway from the active site of the enzyme to the electrode surface. In this communication, functionalized conducting polymers electrochemically deposited on the electrode sur ce are investigated with respect to their possibilities for Ae modification of dectrodes and the covalent attachment or entrapment of sensor compon s. 

The discovery of inherently conducting polymers also provided a class of materials that would feed the imagination of Scientists and Engineers in pursuit of Intelligent Material Systems and Structures. No other class of materials possess the inherent properties necessary to function as sensors, information processors and actuators, as well as the possibility of providing an energy conversion system. 

Other applications of conductive polymers in chemical and biological sensors include a building of electrical connection between different elements of these devices6 or electrical connection and mediators of electron transfer between enzyme and electrode26,27 or between electrocatalytically active functional groups or incorporated nanoparticles and electrode,28 as a filter,29 as matrix for immobilization of enzymes or even as a combination of many of these functions.26 The requirements for materials for these applications are very specific and will not be analyzed here. 

Sensor technologies are developed using principles of physical and chemical sciences and their interrelationships. Some examples are fiber-optic-based, semiconductor-based, conducting polymer-based, mechanical, electrochemical, calorimetric, and colorimetric sensors. In this section these sensor technologies are discussed with respect to their functions, advantages, capabilities, and requirements. 

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