Detection, conducting polymers

One early program carried out at AUied-Signal, Inc. proposed the use of conductive polymers in remotely readable indicators (210). Conductivity changes induced in the conductive polymer could be read externally and the history of the sample known. Systems designed to detect time—temperature, temperature limit, radiation dosage, mechanical abuse, and chemical exposure were developed. 

B. Fabre, S. Burlet, R. Cespuglio, and G. Bidan, Voltammetric detection of NO in the rat brain with an electronic conducting polymer and Nafion bilayer-coated carbon fibre electrode. J. Electroanal. Chem. 426, 75-83 (1997). 

T.-Y. Lee and Y.-B. Shim, Direct DNA hybridization detection based on the oligonucleotide-functionahzed conductive polymer. Ainal. Chem. 73, 5629—5632 (2001). 

Studies by Heinze etal. on donor-substituted thiophenes or pyrroles [33] such as methylthio (= methylsulfonyl) or methoxy-substituted derivatives provide further clear evidence for this reaction pathway. They found, for instance, that 3-methylthiothiophene or 3-methoxythio-phene (2) undergo a fast coupling reaction. However, deposition processes or insoluble film formation could not be detected in usual experiments with these compounds, even at high concentrations. Similarly, the corresponding 3,3 -disubstituted bithiophenes (2a) do not polymerize, but the anodic oxidation of 4,4 -disubstituted bithiophenes (2c) produces excellent yields of conducting polymers. 

GC material was widely modified with conducting (or nonconducting) polymers in order to obtain an improved surface for DNA adsorption and detection. The initial approaches were performed by the physical attachment of nylon or nitrocellulose membranes on GC electrodes [51]. As explained, these membranes were extensively used in classical DNA analysis due to their well-known adsorption properties [33]. Other approaches were performed by the direct adsorption of the polymeric film on the GC surface. Finally, polymeric films were electrochemically grown on the GC substrate. These conducting polymers are particularly promising for the adsorption, but also for inducing electrical signals obtained from DNA interactions. 

Boyle A, Genies EM, Lapkowski M. Application of electronic conducting polymers as sensors— polyaniline in the solid-state for detection of solvent vapors and polypyrrole for detection of biological ions in solutions. Synth Met 1989 28 C769-C774. 

Carvalho, E. R., Consolin Filho, N., Venancio, E. C., Osvaldo, N. O., Jr., Mattoso, L. H. C., and Martin-Neto, L. (2007). Detection of brominated by-products using a sensor array based on nanostructured thin films of conducting polymers. Sensors 7, 3258-3271. 

Potentiometric Sensors Inthe field of ion-selective electrodes, considerable progress has been achieved in the last few years. By buffering the primary ions concentration on a low level in the internal solution, ionic fluxes in the membrane are affected [424-426]. Thus, primary ion leakage into sample solution is hindered, resulting in a tremendous shift of detection limits to lower values for Pb +-selective electrodes, the detection limit up to 10 M level has been achieved for internal solution electrodes [424, 427] and below 10 M for all-solid-state electrodes with conducting polymer solid... 

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. 

Lower detection limits for Ca21. Cd24. Ag. K+, Na, I. and OO4 ion-selective electrodes were demonstrated when concentrations were reduced in the internal filling solutions 26 A future improvement will come when the ionophore is dissolved in a conductive polymer in direct electrical contact with a metal conductor.27 This electrode entirely omits the inner filling solution. 

Polyacetylene prepared by the Shirakawa route pyrolyses on heating, before showing any detectable crystal melting point. At the same time, it is insoluble in all known solvents. For these reasons it is essentially unprocessable. Until recently it has seemed to be a general rule that all conducting polymers were insoluble, which follows naturally from the conjugation of the double bonds along the chain which results in chain stiffness. 

Moreover, 0.5-pm diameter MIP beads have been prepared for chronoamperometric determination of morphine [204]. These beads were synthesized by thermo-radical precipitation polymerization of the MAA functional monomer, TRIM cross-linker, AIBN initiator and morphine template in the ACN solution. Then the beads were immobilized in a film of the PEDOT conducting polymer, electropolymerized onto the ITO electrode. The morphine detection with the use of the resulting chemosensor was much more sensitive to morphine (41.63 pA cm 2 mM for the morphine concentration range of 0.1-2 mM) than to morphine analogues. LOD for morphine was 0.3 mM. 

Solid-state ISEs with conducting polymers are also promising for low-concentration measurements [60,63,74], even below nanomolar concentrations [60,74], which gives rise to optimism concerning future applications of such electrodes. In principle, the detection limit can be improved by reducing the flux of primary ions from the ion-selective membrane (or conducting polymer) to the sample solution, e.g., via com-plexation of primary ions in the solid-contact material. For example, a solid-state Pb2+-ISEs with poly(3-octylthiophene) as ion-to-electron transducer coated with an ion-selective membrane based on poly(methyl methacrylate)/poly(decyl methacrylate) was found to show detection limits in the subnanomolar range and a faster response at low concentrations than the liquid-contact ISE [74]. 

Conducting polymers have been studied as potentiometric ion sensors for almost two decades and new sensors are continuously developed. The analytical performance of solid-state ion sensors with conducting polymers as ion-to-electron transducer (solid-contact ISEs) has been significantly improved over the last few years. Of particular interest is the large improvement of the detection limit of such solid-contact ISEs down to the nanomolar level. Further optimization of the solid contacts as well as the ion-selective membranes will most certainly extend the range of practical applications. 

IgG (rabbit) Homogeneous immunoassay competition between free and GOD-labelled IgG for surface-bound antibody Amperometric detection of H2O2 produced from glucose channelled through surface conducting polymer-bonded HRP -0.35 V 0.5-2.0 [xgml-1 0.33 [xgml-1 Darain et al. [79]... 

M.J.A. Shiddiky, D.-S. Park and Y.-B. Shim, Detection of polymerise chain reaction fragments using a conducting polymer-modified screen-printed electrode in a microfluidic device, Electrophoresis, 26 (2005) 4656-4663. 

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