Table of Contents Author Guidelines Submit a Manuscript
International Journal of Electrochemistry
Volume 2011, Article ID 508126, 8 pages
http://dx.doi.org/10.4061/2011/508126
Review Article

New Developments in Electrochemical Sensors Based on Poly(3,4-ethylenedioxythiophene)-Modified Electrodes

Department of Analytical Chemistry and Instrumental Analysis, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Polizu 1-7, 011061 Bucharest, Romania

Received 2 February 2011; Accepted 14 March 2011

Academic Editor: Bengi Uslu

Copyright © 2011 Stelian Lupu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

There is a growing demand for continuous, fast, selective, and sensitive monitoring of key analytes and parameters in the control of diseases and health monitoring, foods quality and safety, and quality of the environment. Sensors based on electrochemical transducers represent very promising tools in this context. Conducting polymers (CPs) have drawn considerable interest in recent years because of their potential applications in different fields such as in sensors, electrochemical displays, and in catalysis. Among the organic conducting polymers, poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives have attracted particular interest due to their high stability and high conductivity. This paper summarizes mainly the recent developments in the use of PEDOT-based composite materials in electrochemical sensors.

1. Introduction

The improvement of life quality is one of the most important objectives of global research efforts pursued by the international research community. It is a common fact that the quality of life is closely linked to the control of diseases and health monitoring, foods quality and safety, and quality of the environment. A continuous, fast, selective, and sensitive monitoring of key analytes and parameters is required in the above-mentioned fields. Sensors based on electrochemical transducers represent very promising tools in this context. The integration of technological developments, and in particular of a new generation of smart and composite materials interacting with their surrounding, is bringing huge potential for the development of new sensors based on chemically modified electrodes (CMEs), allowing a greater security and safety of the peoples.

2. Electrochemical Transducers

An important application of the CMEs lies in the design of electrochemical (bio)sensors. A (bio)sensor is a device consisting of a (bio)active substance, such as an inorganic or polymeric catalyst, an enzyme, an antibody, a tissue or a microorganism, which can specifically recognize species of interest, in intimate contact with a transducer. The transducer converts the (bio)chemical signal into an electronic signal. Many forms of transducers have been developed, such as potentiometric and amperometric electrodes, optoelectronic detectors, field-effect transistors, and thermistors. Among these, the electrochemical devices (potentiometric, amperometric, voltammetric, and impedance transducers) have been widely studied. These electrochemical transducers use the powerful features of the corresponding electrochemical methods, for example, potentiometry, amperometry, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). In the case of potentiometric sensors a local equilibrium is set up at the sensor interface, and the electrode potential is measured. For amperometric sensors, a potential is applied to drive the electrode reaction, and the resulting current is measured. In cyclic voltammetry, the electrode potential is scanned linearly using a triangular potential waveform, and the current is measured. CV provides useful information on the thermodynamics of redox processes, on the kinetics of heterogeneous electron transfer reactions, and on coupled chemical reactions. The measured current is used for the quantification of the analyte. EIS is a nondestructive steady-state technique that provides quantitative information about the relaxation phenomena over a wide range of alternative current (AC) frequencies and the resistive and capacitive properties of materials. The equivalent circuits fitted to the impedance curves are useful in the characterization of the electrochemical systems. EIS is currently used to investigate the charge transport and adsorption processes in various types of electrochemical sensors.

During the last two decades, the area of electrochemical sensors has greatly benefited from the development of nanotechnology, which has enabled the production of microelectrodes (MEs). MEs have critical dimensions less than the scale of a diffusion layer, and they have enabled the measurements of fast electron transfer kinetics into previously inaccessible domains of time, space, and media [13]. MEs can operate at an ionic strength level comparable with that present in real samples. The most used MEs geometries are disk, sphere, hemisphere, and band shapes. MEs can be also wired in parallel with each microelectrode acting diffusionally independent, resulting in a signal which is typically thousands of times larger. This device, called array, can contain several MEs in both regular and random distributions [38]. The MEs arrays have been proved to be useful in electroanalysis [9]. Recently, a unique design with an arrangement of interdigitated array electrodes (IDEs) has received a lot of attention. In this design, at least one generator electrode is placed closed to a collector electrode. More interesting are arrangements consisting in several generator electrodes placed side by side with collector electrodes in an interdigitated manner. The operation mode of IDEs is based on the generation of electroactive species by a potential excitation at the generator electrodes followed by the diffusion of these species across the thin-layer gap, due to the concentration gradient, to the collector electrodes where they react electrochemically. The reactant species at the collector electrodes can diffuse back to the generator electrodes. This operation mode is called redox cycling and makes the measured currents at both the generator and collector electrodes extremely high. The very small distance between generator and collector electrodes allows a very high percentage of the generated species to be collected at the collector electrodes. Another important feature of these devices is the steady-state current that can be achieved by holding the collector electrodes at a fixed potential while sweeping the potential at the generator electrodes. In the case of a band gap width in the scale of nanometers, it is expected that the device will behave as an electrochemical sensor having the characteristics of both nanoelectrodes and interdigitated array electrodes. The IDEs can detect in this way ultratrace amounts of analytes within a small space [10] and also unstable electrochemical intermediates [11]. Several papers dealing with the characteristic of bare, unmodified, IDEs have appeared in the last decade [1214]. These studies have provided information on the effect of the electrode size and spacing on the current collection efficiency and redox cycling.

3. Conducting Polymer-Modified Electrodes

The use of electroactive polymers represents an important development in the preparation of modified electrodes. Electroactive polymers present several advantages over monomolecular layers, for example, (i) the electrochemical responses for polymer films are more clearly observed than those of immobilized monomolecular layers; (ii) multilayer films of polymers can undergo a larger number of oxidation state turnovers than monolayer films, which implies that the redox sites in multilayer films have an enhanced stability; (iii) the presence on the electrode surface of a large number of redox mediator molecules yields a high reaction rate between mediator substrate, resulting in an enhancement of the electrocatalytic efficiency of the modified surface; (iv) the polymer films can incorporate different electroactive species in order to obtain well-defined microstructures on electrode surfaces. Thanks to these advantages and since the electroactive polymers are technically easier to attach at the electrode surfaces than covalently bonded reagents are, polymeric coating has become a popular technique of electrode modification.

The electroactive polymers may be classified into redox polymers, electronically conducting polymers, and ion exchange polymers.

Conducting polymers (CPs) conduct electricity via delocalized metal-like band structures. The interest in CPs has started in the late 1970s, and since then much attention has been devoted to the preparation, characterization, and application of these polymers [1517]. These polymeric films exhibit good adhesion and electrical contact to the electrode surface. Thin films of CPs deposited on the electrode surface can be electrochemically cycled between the neutral, for example, the insulating state, and the oxidized, for example, the conducting state. Also, thicker films of CPs can be obtained in the oxidized, conducting state and then can be removed from the electrode surface to yield free-standing, electrically conducting films. The oxidation of the insulating polymer is referred to as a “doping” process by analogy with the doping of inorganic semiconductors. The neutral polymer can be converted into an ionic complex that consists of a polymeric cation (or anion) and a counterion, which is the reduced form of the oxidizing agent (or the oxidized form of the reducing agent). The use of an oxidizing agent corresponds to a p-type doping process and that of a reducing agent to an n-type doping process. In the case of oxidation, for example, removal of an electron from the polymeric chain, a so-called “polaron” is formed [18]. The polaron is a radical ion (spin 1/2) associated with a lattice distortion. When a second electron is removed from the polymer chain, a so-called “bipolaron” is formed. A bipolaron is defined as a pair of charge (spinless) associated with a strong local lattice distortion. This class of polymers includes polypyrrole, polyaniline, polythiophene, and relevant derivatives.

The functioning of a large part of CMEs is based on electrocatalysis. The electrooxidation or reduction of an analyte at a bare electrode surface occurs at much more positive or negative potentials than expected on the basis of thermodynamics, respectively, which means that an overpotential is required by the electrode reaction. In Figure 1 the basic idea of decreasing or eliminating this overpotential by an immobilized mediator catalyst is depicted. The analyte (substrate) diffuses from the bulk of the solution to the electrode surface, where the oxidized form of the mediator (Mox) oxidizes it by a purely chemical reaction. The electrode is maintained at a potential positive enough to assure that the oxidized form Mox is the stable state of the mediator. Then, the reduced form Mred is rapidly reoxidized to the active form Mox. By this approach, the oxidation of the substrate takes place at a potential that is between the thermodynamic value of the substrate oxidation and that of the redox mediator.

508126.fig.001
Figure 1: Electrocatalysis at modified electrode. M: mediator, S: substrate.

The decrease of the electrode potential at which oxidation or reduction actually occurs may improve the analytical performance. By decreasing the detection potentials, possible improved detection limits and selectivity may be obtained because of the lower noise level. Furthermore, electrode processes that occur at potentials near those of solvent breakdown, or even beyond this limit, can be shifted to a useful potential value.

3.1. PEDOT-Inorganic Composite-Modified Electrodes

In recent years, a considerable progress has been made with developing modified electrodes, for instance, based on redox and conducting polymers [19, 20]. The electrode surface can be deliberately modified by different procedures, such as adsorption, electroadsorption, chemical bonding, and electropolymerization of various chemical species. Modification of the electrode surface can also be an important aid in obtaining greater selectivity and sensibility. Conducting polymers (CPs) have drawn considerable interest in recent years because of their potential applications in different fields such as in sensors, electrochemical displays, and in catalysis [16, 17]. Among the organic conducting polymers, poly(thiophene) and its derivatives, such as poly(3,4-ethylenedioxythophene), (PEDOT), have attracted particular interest because these compounds appeared to be the most stable organic conducting polymers currently available [2128]. Conducting polymers can be deposited as dense modifying layers on common electrode substrates, which is of importance to the development of many technologies, including electrochemical sensors technology. Conducting organic polymers also constitute a category of materials showing suitable reversible redox chemistry. On the other hand, considerable interest has been also devoted to the preparation and characterisation of polynuclear transition metal hexacyanoferrates by virtue of their characteristics which include electrochromic properties [29], ability to mediate redox reactions [3033]. The transition metal hexacyanoferrates represent an important class of insoluble mixed valence compounds. A large number of inorganic films have been prepared both chemically and electrochemically onto various electrode substrates. However, their low stability, especially in alkaline solutions, remains a central problem for the application of any metal hexacyanoferrate film-modified-electrode in electroanalysis. The extraordinary properties of both CP and metal hexacyanoferrates have been exploited in the preparation of electrodes modified with bilayer structures consisting of conducting polymers and iron(III) hexacyanoferrate (Prussian blue, PB) [3441]. The presence of organic conducting polymers in the bilayer films increases the stability of PB, resulting in enhanced electrochemical responses. Prussian Blue (iron(III)hexacyanoferrate(II), PB) has been extensively studied for modification of conducting polymers [35, 4245]. The use of PEDOT and PB for the preparation of the composite materials is based on the appealing properties of each component, such as the excellent stability of the PEDOT layer in aqueous solution and its doped state [4649], and the electrocatalytic activity of PB [5052]. It is important to note that, in the potential region where the composite materials are electrochemically active, the PEDOT organic component is in its conducting state, while the PB inorganic component displays its good electrocatalytic activity. As a consequence, a synergistic effect is obtained, and the composite material displays new electrochemical properties. These composite coatings are prepared by a two-step method. In the first step, the organic layer is deposited through the electrochemical polymerization of the corresponding monomer in the presence of the ferric hexacyanoferrates anions. In the second step, the in situ formation of PB within the PEDOT matrix is achieved via potentiodynamic methods in Fe3+ containing aqueous solution. Both forms of PB, for example, soluble and insoluble, can be deposited by this procedure [53, 54]. Another approach consists in the use of a mixture of ferric and ferrous hexacyanoferrates [5559] or iron (III) chloride and ferricyanide [60]. These composite materials showed appealing properties for various applications in capacitors and electrochemical sensors. The incorporation of ferric hexacyanoferrates within the PEDOT matrix was also investigated in respect of the development of new electrochemical sensors [6164].

3.2. PEDOT-Metal-Nanoparticles Composite-Modified Electrodes

Metal nanoparticles-based composite materials have attracted a great deal of interest due to their unique electrochemical, optical, and catalytic properties and their potential use in electrochemical sensors and biosensors [6572]. Noble metal nanoparticles (NPs) were incorporated into conducting polymers using various preparation procedures in order to improve their analytical performances [73]. To this purpose, chemical and electrochemical methods have been developed for ex situ or in situ NPs preparation. The incorporation of NPs in conducting polymers has been achieved by self-assembly of chemically presynthesized NPs onto self-assembled monolayers (SAMs) [74], electrochemical deposition of chemically pre-synthesized NPs onto previously synthesized polymer films [75], electrochemical polymerization of the appropriate monomer in the presence of chemically pre-synthesized NPs [73], and layer-by-layer intercalation of the inorganic NPs into conducting polymer composite coatings [67, 76]. In this area, PEDOT has been quite extensively studied for NPs incorporation into polymeric films [77, 78], mainly due to its excellent stability and the possibility to prepare the corresponding PEDOT polymer matrix through electrochemical polymerization of the 3,4-ethylenedioxythiophene (EDOT) monomer in aqueous solution [7984]. Another approach consists in the use of ultrasounds for NPs preparation [85]. This new preparation procedure resulted in homogeneous size distribution within the range 5–17 nm. The use of ultrasounds in the electropolymerisation of conducting polymers on various substrates and the preparation of sonogel-based electrochemical sensors has been also reported [8692]. Recently, a great deal of interest has been also devoted to the in situ preparation of Pt nanoparticles [9398]. In this case, the in situ preparation of Pt nanoparticles has been achieved via electrochemical methods, and in particular potentiostatic deposition at a fixed potential value which is sufficiently negative to assure reduction of the appropriate precursors to metallic states. However, this latter approach for in situ electrodeposition of NPs onto conducting polymers layers has not reached yet the full analytical potential being currently under investigation by various research groups.

4. Conducting Polymers-Modified Microelectrode Arrays

Due to the unique features of the microelectrodes arrays, the modification of the surfaces of these devices has been also the subject of several studies. For instance, the generator-collector operation mode has been exploited in the study of the diffusion of electroactive species within a thin film deposited onto the surface of microelectrodes arrays [99102]. The modification of interdigitated microelectrodes with conducting polymers allowed the preparation of new miniaturized pH electrochemical sensors [103106]. Other microelectrodes arrays modified with inorganic films [107], organic polymers [108], inorganic-organic composite materials [109], and enzymes [110] were recently reported. Despite the benefits of the microelectrodes arrays, the modification of these devices with composite organic-inorganic materials has not been fully investigated. Based on the electrochemical properties of microelectrodes and interdigitated microelectrodes arrays as well as the selectivity and electrocatalytic activity of coatings consisting of composite organic-inorganic materials, there is a niche topic of research that can be exploited in order to combine these challenging properties for the design of new electrochemical microsensors.

5. Conclusions

The interest in electrochemical sensors based on PEDOT is still growing thanks especially to the new composite materials that have been recently developed. The composite materials are prepared via in situ formation of the inorganic component within the conducting polymer coating. New properties induced by the combination of a conducting polymer and a mixed valence compound were reported. The electrochemical behavior of these composite materials is based mainly on the redox reaction of the inorganic component. The incorporation of noble metal nanoparticles within conducting polymers matrix can improve the analytical performances of the electrochemical sensors and affords the electrochemical detection of analytes that usually are determined by using enzymes-based biosensors. The electrochemical microsensors based on microelectrode arrays can be used in multianalyte electrochemical sensing of biologically active compounds and potential hazardous compounds, which are key analytes for life quality control. It can be sought that the final application of these new electrochemical sensors will be the in situ study of real matrices, which implies only minor manipulation of the matrix. Therefore, the applications of these electrochemical microsensors to biomedical, foods, and environmental analysis are very promising in respect of qualitative and quantitative determination of specific analytes of interest, as well as analytes that, for different reasons, are dangerous to health.

Acknowledgment

Financial support from the Romanian Ministry of Education, Research and Youth (Grant no. 2 CEEX 06-1143/25.07.2006) is gratefully acknowledged.

References

  1. D. E. Williams, Microelectrodes: Theory and Applications, M. I. Montenegro, M. A. Queiros and J. L. Daschbach, Eds., Kluwer Academic Publishers, Dordrecht, The Netherlands, 1991.
  2. R. M. Wightman and D. O. Wipf, Electroanalytical Chemistry, vol. 15 of A. J. Bard, Ed., Marcel Dekker, New York, NY, USA, 1989.
  3. C. Amatore, Physical Electrochemistry: Principles, Methods and Applications, I. Rubenstein, Ed., Marcel Dekker, New York, NY, USA, 1995.
  4. S. Fletcher and M. D. Horne, “Random assemblies of microelectrodes (RAM electrodes) for electrochemical studies,” Electrochemistry Communications, vol. 1, no. 10, pp. 502–512, 1999. View at Google Scholar · View at Scopus
  5. M. Pagels, C. E. Hall, N. S. Lawrence et al., “All-diamond microelectrode array device,” Analytical Chemistry, vol. 77, no. 11, pp. 3705–3708, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  6. B. J. Seddon, Y. Shao, and H. H. Girault, “Printed microelectrode array and amperometric sensor for environmental monitoring,” Electrochimica Acta, vol. 39, no. 16, pp. 2377–2386, 1994. View at Google Scholar · View at Scopus
  7. T. J. Davies, S. Ward-Jones, C. E. Banks et al., “The cyclic and linear sweep voltammetry of regular arrays of microdisc electrodes: fitting of experimental data,” Journal of Electroanalytical Chemistry, vol. 585, no. 1, pp. 51–62, 2005. View at Publisher · View at Google Scholar · View at Scopus
  8. T. J. Davies and R. G. Compton, “The cyclic and linear sweep voltammetry of regular and random arrays of microdisc electrodes: theory,” Journal of Electroanalytical Chemistry, vol. 585, no. 1, pp. 63–82, 2005. View at Publisher · View at Google Scholar · View at Scopus
  9. O. Ordeig, J. Del Campo, F. X. Muñoz, C. E. Banks, and R. G. Compton, “Electroanalysis utilizing amperometric microdisk electrode arrays,” Electroanalysis, vol. 19, no. 19-20, pp. 1973–1986, 2007. View at Publisher · View at Google Scholar · View at Scopus
  10. P. Ugo, L. M. Moretto, and F. Vezzà, “Ionomer-coated electrodes and nanoelectrode ensembles as electrochemical environmental sensors: recent advances and prospects,” ChemPhysChem, vol. 3, no. 11, pp. 917–925, 2002. View at Publisher · View at Google Scholar · View at Scopus
  11. M. V. Mirkin, H. Yang, and A. J. Bard, “Borohydride oxidation at a gold electrode,” Journal of the Electrochemical Society, vol. 139, no. 8, pp. 2212–2216, 1992. View at Google Scholar · View at Scopus
  12. O. Niwa, M. Morita, and H. Tabei, “Electrochemical behavior of reversible redox species at interdigitated array electrodes with different geometries: consideration of redox cycling and collection efficiency,” Analytical Chemistry, vol. 62, no. 5, pp. 447–452, 1990. View at Google Scholar · View at Scopus
  13. M. Paeschke, U. Wollenberger, C. Köhler, T. Lisec, U. Schnakenberg, and R. Hintsche, “Properties of interdigital electrode arrays with different geometries,” Analytica Chimica Acta, vol. 305, no. 1–3, pp. 126–136, 1995. View at Publisher · View at Google Scholar · View at Scopus
  14. K. Ueno, M. Hayashida, J. Y. Ye, and H. Misawa, “Fabrication and electrochemical characterization of interdigitated nanoelectrode arrays,” Electrochemistry Communications, vol. 7, no. 2, pp. 161–165, 2005. View at Publisher · View at Google Scholar · View at Scopus
  15. R. J. Waltman and J. Bargon, “Electrically conducting polymers: a review of the electropolymerization reaction, of the effects of chemical structure on polymer film properties, and of applications towards technology,” Canadian Journal of Chemistry, vol. 64, no. 1, pp. 76–95, 1986. View at Google Scholar
  16. J. Roncali, “Conjugated poly(thiophenes): synthesis, functionalization, and applications,” Chemical Reviews, vol. 92, no. 4, pp. 711–738, 1992. View at Google Scholar · View at Scopus
  17. J. Roncali, “Synthetic principles for bandgap control in linear π-conjugated systems,” Chemical Reviews, vol. 97, no. 1, pp. 173–205, 1997. View at Google Scholar · View at Scopus
  18. J. L. Brédas and G. B. Street, “Polarons, bipolarons, and solitons in conducting polymers,” Accounts of Chemical Research, vol. 18, no. 10, pp. 309–315, 1985. View at Google Scholar · View at Scopus
  19. R. W. Murray, “Chemically modified electrodes,” in Electroanalytical Chemistry, A. J. Bard, Ed., vol. 13, Marcel Dekker, New York, NY, USA, 1984. View at Google Scholar
  20. R. W. Murray, Ed., Molecular Design of Electrode Surfaces, vol. 22, Wiley, New York, NY, USA, 1992.
  21. M. Dietrich, J. Heinze, G. Heywang, and F. Jonas, “Electrochemical and spectroscopic characterization of polyalkylenedioxythiophenes,” Journal of Electroanalytical Chemistry, vol. 369, no. 1-2, pp. 87–92, 1994. View at Google Scholar · View at Scopus
  22. H. Yamato, M. Ohwa, and W. Wernet, “Stability of polypyrrole and poly(3,4-ethylenedioxythiophene) for biosensor application,” Journal of Electroanalytical Chemistry, vol. 397, no. 1-2, pp. 163–170, 1995. View at Google Scholar · View at Scopus
  23. D. Iarossi, A. Mucci, L. Schenetti et al., “Polymerization and characterization of 4,4'-Bis(alkylsulfanyl)-2,2'-bithiophenes,” Macromolecules, vol. 32, no. 5, pp. 1390–1397, 1999. View at Google Scholar · View at Scopus
  24. B. Ballarin, F. Costanzo, F. Mori et al., “Electropolymerization and characterization of poly[4,4'-bis(butylsulphanil)-2,2'-bithiophene],” Electrochimica Acta, vol. 46, no. 6, pp. 881–889, 2001. View at Publisher · View at Google Scholar · View at Scopus
  25. B. Ballarin, R. Seeber, D. Tonelli et al., “Electrosynthesis and characterization of alkylester-substituted polythiophenes,” Synthetic Metals, vol. 88, no. 1, pp. 7–13, 1997. View at Google Scholar · View at Scopus
  26. B. Ballarin, R. Seeber, L. Tassi, and D. Tonelli, “Electrochemical synthesis and characterisation of polythiophene conducting polymers functionalised by metal-containing porphyrin residue,” Synthetic Metals, vol. 114, no. 3, pp. 279–285, 2000. View at Google Scholar
  27. S. Lupu, A. Mucci, L. Pigani, R. Seeber, and C. Zanardi, “Polythiophene derivative conducting polymer modified electrodes and microelectrodes for determination of ascorbic acid. Effect of possible interferents,” Electroanalysis, vol. 14, no. 7-8, pp. 519–525, 2002. View at Publisher · View at Google Scholar · View at Scopus
  28. S. Lupu, F. Parenti, L. Pigani, R. Seeber, and C. Zanardi, “Differential pulse techniques on modified conventional-size and microelectrodes. Electroactivity of poly[4,4'-bis(butylsulfanyl)-2,2'-bithiophene] coating towards dopamine and ascorbic acid oxidation,” Electroanalysis, vol. 15, no. 8, pp. 715–725, 2003. View at Publisher · View at Google Scholar · View at Scopus
  29. P. J. Kulesza, M. A. Malik, M. Berrettoni et al., “Electrochemical charging, countercation accommodation, and spectrochemical identity of microcrystalline solid cobalt hexacyanoferrate,” Journal of Physical Chemistry B, vol. 102, no. 11, pp. 1870–1876, 1998. View at Google Scholar · View at Scopus
  30. D. M. Zhou, H. X. Ju, and H. Y. Chen, “Catalytic oxidation of dopamine at a microdisk platinum electrode modified by electrodeposition of nickel hexacyanoferrate and Nafion®,” Journal of Electroanalytical Chemistry, vol. 408, no. 1-2, pp. 219–223, 1996. View at Google Scholar · View at Scopus
  31. A. A. Karyakin, E. E. Karyakina, and LO. Gorton, “On the mechanism of H2O2 reduction at Prussian Blue modified electrodes,” Electrochemistry Communications, vol. 1, no. 2, pp. 78–82, 1999. View at Google Scholar · View at Scopus
  32. N. Totir, S. Lupu, E. M. Ungureanu, and N. Iftimie, “Electrochemical behaviour of dopamine at a Prussian Blue modified electrode,” Revista de Chimie, (Bucuresti) (English edition), vol. 2, no. 1-2, pp. 23–27, 2001. View at Google Scholar
  33. N. Totir, S. Lupu, E. M. Ungureanu, M. Giubelan, and A. Ştefǎnescu, “Electrochemical behaviour of ascorbic acid on Prussian Blue modified electrodes,” Revue Roumaine de Chimie, vol. 46, no. 10, pp. 1091–1096, 2001. View at Google Scholar · View at Scopus
  34. K. Ogura, N. Endo, M. Nakayama, and H. Ootsuka, “Mediated activation and electroreduction of CO on modified electrodes with conducting polymer and inorganic conductor films,” Journal of the Electrochemical Society, vol. 142, no. 12, pp. 4026–4032, 1995. View at Google Scholar · View at Scopus
  35. S. Lupu, C. Mihailciuc, L. Pigani, R. Seeber, N. Totir, and C. Zanardi, “Electrochemical preparation and characterisation of bilayer films composed by Prussian Blue and conducting polymer,” Electrochemistry Communications, vol. 4, no. 10, pp. 753–758, 2002. View at Publisher · View at Google Scholar · View at Scopus
  36. S. Lupu, “Electrochemical detection of ascorbic acid and dopamine using poly-(3,4-ethylenedioxythiophene) /prussian blue films on platinum,” Revue Roumaine de Chimie, vol. 50, no. 3, pp. 213–217, 2005. View at Google Scholar · View at Scopus
  37. S. Lupu, “Electrochemical detection of ascorbic acid using prussian blue/poly-(3,4-ethylenedioxythiophene) films on platinum,” Revue Roumaine de Chimie, vol. 50, no. 3, pp. 207–211, 2005. View at Google Scholar · View at Scopus
  38. S. Lupu, “Electrochemical study of prussian blue/poly-(3,4-ethylenedioxythiophene) composite films,” Revue Roumaine de Chimie, vol. 50, no. 3, pp. 201–205, 2005. View at Google Scholar · View at Scopus
  39. S. Lupu, C. Lete, M. Marin, and N. Totir, “Electrochemistry of metal hexacyanoferrates and conducting polymers bilayer structures deposited on conventional size electrodes and ultramicroelectrodes. I. conventional size modified electrodes,” Revue Roumaine de Chimie, vol. 53, no. 7, pp. 539–546, 2008. View at Google Scholar · View at Scopus
  40. S. Lupu, C. Lete, M. Marin, and N. Totir, “Electrochemistry of metal hexacyanoferrates and conducting polymers bilayer structures deposited on conventional size electrodes and ultramicroelectrodes. II. modified ultramicroelectrodes,” Revue Roumaine de Chimie, vol. 53, no. 7, pp. 547–552, 2008. View at Google Scholar · View at Scopus
  41. S. Lupu, C. Lete, M. Marin, N. Totir, and P. C. Balaure, “Electrochemical sensors based on platinum electrodes modified with hybrid inorganic-organic coatings for determination of 4-nitrophenol and dopamine,” Electrochimica Acta, vol. 54, no. 7, pp. 1932–1938, 2009. View at Publisher · View at Google Scholar · View at Scopus
  42. M. Nakayama, M. Iino, and K. Ogura, “In situ FTIR studies on Prussian blue (PB)-, polyaniline (PAn)- and inner PB|outer PAn film-modified electrodes,” Journal of Electroanalytical Chemistry, vol. 440, no. 1-2, pp. 125–130, 1997. View at Google Scholar · View at Scopus
  43. R. Koncki and O. S. Wolfbeis, “Composite films of Prussian Blue and N-substituted polypyrroles: fabrication and application to optical determination of pH,” Analytical Chemistry, vol. 70, no. 13, pp. 2544–2550, 1998. View at Google Scholar · View at Scopus
  44. P. J. Kulesza, K. Miecznikowski, M. A. Malik et al., “Electrochemical preparation and characterization of hybrid films composed of Prussian blue type metal hexacyanoferrate and conducting polymer,” Electrochimica Acta, vol. 46, no. 26-27, pp. 4065–4073, 2001. View at Publisher · View at Google Scholar
  45. A. Lisowska-Oleksiak, A. P. Nowak, and V. Jasulaitiene, “Poly(3,4-ethylenedioxythiophene)-Prussian Blue hybrid material: evidence of direct chemical interaction between PB and pEDOT,” Electrochemistry Communications, vol. 8, no. 1, pp. 107–112, 2006. View at Publisher · View at Google Scholar
  46. S. Zhang, J. Hou, R. Zhang, J. Xu, G. Nie, and S. Pu, “Electrochemical polymerization of 3,4-ethylenedioxythiophene in aqueous solution containing N-dodecyl-β-d-maltoside,” European Polymer Journal, vol. 42, no. 1, pp. 149–160, 2006. View at Publisher · View at Google Scholar · View at Scopus
  47. C. Kvarnström, H. Neugebauer, S. Blomquist, H. J. Ahonen, J. Kankare, and A. Ivaska, “In situ spectroelectrochemical characterization of poly(3,4-ethylenedioxythiophene),” Electrochimica Acta, vol. 44, no. 16, pp. 2739–2750, 1999. View at Publisher · View at Google Scholar · View at Scopus
  48. L. Adamczyk, P. J. Kulesza, K. Miecznikowski, B. Palys, M. Chojak, and D. Krawczyk, “Effective charge transport in poly(3,4-ethylenedioxythiophene) based hybrid films containing polyoxometallate redox centers,” Journal of the Electrochemical Society, vol. 152, no. 3, pp. E98–E103, 2005. View at Publisher · View at Google Scholar · View at Scopus
  49. N. Rozlosnik, “New directions in medical biosensors employing poly(3,4-ethylenedioxy thiophene) derivative-based electrodes,” Analytical and Bioanalytical Chemistry, vol. 395, no. 3, pp. 637–645, 2009. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  50. F. Li and S. Dong, “The electrocatalytic oxidation of ascorbic acid on prussian blue film modified electrodes,” Electrochimica Acta, vol. 32, no. 10, pp. 1511–1513, 1987. View at Google Scholar · View at Scopus
  51. R. Koncki, “Chemical sensors and biosensors based on Prussian blues,” Critical Reviews in Analytical Chemistry, vol. 32, no. 1, pp. 79–96, 2002. View at Publisher · View at Google Scholar · View at Scopus
  52. F. Ricci and G. Palleschi, “Sensor and biosensor preparation, optimisation and applications of Prussian Blue modified electrodes,” Biosensors and Bioelectronics, vol. 21, no. 3, pp. 389–407, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  53. S. Lupu, “In situ electrochemical preparation and characterization of PEDOT-Prussian blue composite materials,” Synthetic Metals, vol. 161, no. 5-6, pp. 384–390, 2011. View at Publisher · View at Google Scholar
  54. S. Lupu and N. Totir, “The optimization of the electrochemical preparation of pedot-prussian blue hybrid electrode material and application in electrochemical sensors,” Collection of Czechoslovak Chemical Communications, vol. 75, no. 8, pp. 835–851, 2010. View at Publisher · View at Google Scholar
  55. A. Lisowska-Oleksiak and A. P. Nowak, “Metal hexacyanoferrate network synthesized inside polymer matrix for electrochemical capacitors,” Journal of Power Sources, vol. 173, no. 2, pp. 829–836, 2007. View at Publisher · View at Google Scholar · View at Scopus
  56. A. Lisowska-Oleksiak and A. P. Nowak, “Impedance spectroscopy studies on hybrid materials consisting of poly(3,4-ethylenedioxythiophene) and iron, cobalt and nickel hexacyanoferrate,” Solid State Ionics, vol. 179, no. 1–6, pp. 72–78, 2008. View at Publisher · View at Google Scholar · View at Scopus
  57. M. Wilamowska and A. Lisowska-Oleksiak, “Hybrid electrodes composed of electroactive polymer and metal hexacyanoferrates in aprotic electrolytes,” Journal of Power Sources, vol. 194, no. 1, pp. 112–117, 2009. View at Publisher · View at Google Scholar · View at Scopus
  58. A. P. Nowak, M. Wilamowska, and A. Lisowska-Oleksiak, “Spectroelectrochemical characteristics of poly(3,4-ethylenedioxythiophene)/ iron hexacyanoferrate film-modified electrodes,” Journal of Solid State Electrochemistry, vol. 14, no. 2, pp. 263–270, 2010. View at Publisher · View at Google Scholar · View at Scopus
  59. A. Lisowska-Oleksiak, A. P. Nowak, M. Wilamowska, M. Sikora, W. Szczerba, and CZ. Kapusta, “Ex situ XANES, XPS and Raman studies of poly(3,4-ethylenedioxythiophene) modified by iron hexacyanoferrate,” Synthetic Metals, vol. 160, no. 11-12, pp. 1234–1240, 2010. View at Publisher · View at Google Scholar · View at Scopus
  60. V. Noël, H. Randriamahazaka, and C. Chevrot, “Composite films of iron(III) hexacyanoferrate and poly(3,4-ethylenedioxythiophene): electrosynthesis and properties,” Journal of Electroanalytical Chemistry, vol. 489, no. 1, pp. 46–54, 2000. View at Publisher · View at Google Scholar · View at Scopus
  61. V. S. Vasantha and S. M. Chen, “Electrochemical preparation and electrocatalytic properties of PEDOT/ferricyanide film-modified electrodes,” Electrochimica Acta, vol. 51, no. 2, pp. 347–355, 2005. View at Publisher · View at Google Scholar · View at Scopus
  62. A. I. Melato, L. M. Abrantes, and A. M. Botelho do Rego, “Fe(CN) incorporation on Poly(3,4-ethylenedioxythiophene) films: preparation and X-ray Photoelectron Spectroscopy characterization of the modified electrodes,” Thin Solid Films, vol. 518, no. 8, pp. 1947–1952, 2010. View at Publisher · View at Google Scholar · View at Scopus
  63. A. Michalska, A. Gałuszkiewicz, M. Ogonowska, M. Ocypa, and K. Maksymiuk, “PEDOT films: multifunctional membranes for electrochemical ion sensing,” Journal of Solid State Electrochemistry, vol. 8, no. 6, pp. 381–389, 2004. View at Publisher · View at Google Scholar · View at Scopus
  64. M. Ocypa, A. Michalska, and K. Maksymiuk, “Accumulation of Cu(II) cations in poly(3,4-ethylenedioxythiophene) films doped by hexacyanoferrate anions and its application in Cu2+- selective electrodes with PVC based membranes,” Electrochimica Acta, vol. 51, no. 11, pp. 2298–2305, 2006. View at Publisher · View at Google Scholar · View at Scopus
  65. S. Guo and S. Dong, “Biomolecule-nanoparticle hybrids for electrochemical biosensors,” Trends in Analytical Chemistry, vol. 28, no. 1, pp. 96–109, 2009. View at Publisher · View at Google Scholar · View at Scopus
  66. I. Willner, B. Willner, and E. Katz, “Biomolecule-nanoparticle hybrid systems for bioelectronic applications,” Bioelectrochemistry, vol. 70, no. 1, pp. 2–11, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  67. C. Zanardi, F. Terzi, B. Zanfrognini et al., “Effective catalytic electrode system based on polyviologen and Au nanoparticles multilayer,” Sensors and Actuators, B, vol. 144, no. 1, pp. 92–98, 2010. View at Publisher · View at Google Scholar · View at Scopus
  68. S. Xu, G. Tu, B. Peng, and X. Han, “Self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres for fabrication of a mediatorless biosensor,” Analytica Chimica Acta, vol. 570, no. 2, pp. 151–157, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  69. J. Wang, “Nanoparticle-based electrochemical DNA detection,” Analytica Chimica Acta, vol. 500, no. 1-2, pp. 247–257, 2003. View at Publisher · View at Google Scholar · View at Scopus
  70. X. Luo, A. Morrin, A. J. Killard, and M. R. Smyth, “Application of nanoparticles in electrochemical sensors and biosensors,” Electroanalysis, vol. 18, no. 4, pp. 319–326, 2006. View at Publisher · View at Google Scholar · View at Scopus
  71. C. M. Welch and R. G. Compton, “The use of nanoparticles in electroanalysis: a review,” Analytical and Bioanalytical Chemistry, vol. 384, no. 3, pp. 601–619, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  72. F. W. Campbell and R. G. Compton, “The use of nanoparticles in electroanalysis: an updated review,” Analytical and Bioanalytical Chemistry, vol. 396, no. 1, pp. 241–259, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  73. F. Terzi, C. Zanardi, V. Martina, L. Pigani, and R. Seeber, “Electrochemical, spectroscopic and microscopic characterisation of novel poly(3,4-ethylenedioxythiophene)/gold nanoparticles composite materials,” Journal of Electroanalytical Chemistry, vol. 619-620, no. 1-2, pp. 75–82, 2008. View at Publisher · View at Google Scholar · View at Scopus
  74. L. Zhang and X. Jiang, “Attachment of gold nanoparticles to glassy carbon electrode and its application for the voltammetric resolution of ascorbic acid and dopamine,” Journal of Electroanalytical Chemistry, vol. 583, no. 2, pp. 292–299, 2005. View at Publisher · View at Google Scholar · View at Scopus
  75. A. Nirmala Grace and K. Pandian, “Pt, Pt-Pd and Pt-Pd/Ru nanoparticles entrapped polyaniline electrodes—a potent electrocatalyst towards the oxidation of glycerol,” Electrochemistry Communications, vol. 8, no. 8, pp. 1340–1348, 2006. View at Publisher · View at Google Scholar · View at Scopus
  76. K. Karnicka, M. Chojak, K. Miecznikowski et al., “Polyoxometallates as inorganic templates for electrocatalytic network films of ultra-thin conducting polymers and platinum nanoparticles,” Bioelectrochemistry, vol. 66, no. 1-2, pp. 79–87, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  77. S. S. Kumar, J. Mathiyarasu, and K. L. Phani, “Exploration of synergism between a polymer matrix and gold nanoparticles for selective determination of dopamine,” Journal of Electroanalytical Chemistry, vol. 578, no. 1, pp. 95–103, 2005. View at Publisher · View at Google Scholar · View at Scopus
  78. K. M. Manesh, P. Santhosh, A. Gopalan, and K. P. Lee, “Electrocatalytic oxidation of NADH at gold nanoparticles loaded poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) film modified electrode and integration of alcohol dehydrogenase for alcohol sensing,” Talanta, vol. 75, no. 5, pp. 1307–1314, 2008. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  79. F. Sundfors and J. Bobacka, “EIS study of the redox reaction of Fe(CN)63/4 at poly(3,4-ethylenedioxythiophene) electrodes: influence of dc potential and cOx:cRed ratio,” Journal of Electroanalytical Chemistry, vol. 572, no. 2, pp. 309–316, 2004. View at Publisher · View at Google Scholar · View at Scopus
  80. L. Pigani, A. Heras, Á. Colina, R. Seeber, and J. López-Palacios, “Electropolymerisation of 3,4-ethylenedioxythiophene in aqueous solutions,” Electrochemistry Communications, vol. 6, no. 11, pp. 1192–1198, 2004. View at Publisher · View at Google Scholar · View at Scopus
  81. R. Hass, J. García-Cañadas, and G. Garcia-Belmonte, “Electrochemical impedance analysis of the redox switching hysteresis of poly(3,4-ethylenedioxythiophene) films,” Journal of Electroanalytical Chemistry, vol. 577, no. 1, pp. 99–105, 2005. View at Publisher · View at Google Scholar · View at Scopus
  82. A. Zykwinska, W. Domagala, B. Pilawa, and M. Lapkowski, “Electrochemical overoxidation of poly(3,4-ethylenedioxythiophene)-PEDOT studied by means of in situ ESR spectroelectrochemistry,” Electrochimica Acta, vol. 50, no. 7-8, pp. 1625–1633, 2005. View at Publisher · View at Google Scholar · View at Scopus
  83. A. I. Melato, A. S. Viana, and L. M. Abrantes, “Different steps in the electrosynthesis of poly(3,4-ethylenedioxythiophene) on platinum,” Electrochimica Acta, vol. 54, no. 2, pp. 590–597, 2008. View at Publisher · View at Google Scholar · View at Scopus
  84. L. Chen, C. Yuan, H. Dou, BO. Gao, S. Chen, and X. Zhang, “Synthesis and electrochemical capacitance of core-shell poly (3,4-ethylenedioxythiophene)/poly (sodium 4-styrenesulfonate)-modified multiwalled carbon nanotube nanocomposites,” Electrochimica Acta, vol. 54, no. 8, pp. 2335–2341, 2009. View at Publisher · View at Google Scholar · View at Scopus
  85. L. M. Cubillana-Aguilera, M. Franco-Romano, M. L. A. Gil, I. Naranjo-Rodríguez, J. L. Hidalgo-Hidalgo De Cisneros, and J. M. Palacios-Santander, “New, fast and green procedure for the synthesis of gold nanoparticles based on sonocatalysis,” Ultrasonics Sonochemistry, vol. 18, no. 3, pp. 789–794, 2011. View at Publisher · View at Google Scholar · View at PubMed
  86. Y. Wei, Y. Li, N. Zhang, G. Shi, and L. Jin, “Ultrasound-radiated synthesis of PAMAM-Au nanocomposites and its application on glucose biosensor,” Ultrasonics Sonochemistry, vol. 17, no. 1, pp. 17–20, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  87. MA. Del, I. Naranjo-Rodríguez, J. M. Palacios-Santander, L. M. Cubillana-Aguilera, and J. L. Hidalgo-Hidalgo-de-Cisneros, “Study of the responses of a sonogel-carbon electrode towards phenolic compounds,” Electroanalysis, vol. 17, no. 9, pp. 806–814, 2005. View at Publisher · View at Google Scholar · View at Scopus
  88. J. M. Palacios-Santander, L. M. Cubillana-Aguilera, M. Cocchi et al., “Multicomponent analysis in the wavelet domain of highly overlapped electrochemical signals: resolution of quaternary mixtures of chlorophenols using a peg-modified Sonogel-Carbon electrode,” Chemometrics and Intelligent Laboratory Systems, vol. 91, no. 2, pp. 110–120, 2008. View at Publisher · View at Google Scholar · View at Scopus
  89. A. Et Taouil, F. Lallemand, J. Y. Hihn, J. M. Melot, V. Blondeau-Patissier, and B. Lakard, “Doping properties of PEDOT films electrosynthesized under high frequency ultrasound irradiation,” Ultrasonics Sonochemistry, vol. 18, no. 1, pp. 140–148, 2011. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  90. A. Et Taouil, F. Lallemand, J. Y. Hihn, and V. Blondeau-Patissier, “Electrosynthesis and characterization of conducting polypyrrole elaborated under high frequency ultrasound irradiation,” Ultrasonics Sonochemistry, vol. 18, no. 4, pp. 907–910, 2011. View at Publisher · View at Google Scholar · View at PubMed
  91. A. Et Taouil, F. Lallemand, L. Hallez, and J.-Y. Hihn, “Electropolymerization of pyrrole on oxidizable metal under high frequency ultrasound irradiation. Application of focused beam to a selective masking technique,” Electrochimica Acta, vol. 55, no. 28, pp. 9137–9145, 2010. View at Publisher · View at Google Scholar
  92. B. Lakard, L. Ploux, K. Anselme et al., “Effect of ultrasounds on the electrochemical synthesis of polypyrrole, application to the adhesion and growth of biological cells,” Bioelectrochemistry, vol. 75, no. 2, pp. 148–157, 2009. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  93. Y. Liu, M. Yang, Z. Zheng, and B. Zhang, “In situ synthesis of Pt nanoparticles in hyperbranched thin film for electrocatalytic reduction of dioxygen,” Electrochimica Acta, vol. 51, no. 4, pp. 605–610, 2005. View at Publisher · View at Google Scholar · View at Scopus
  94. F. Maillard, E. R. Savinova, and U. Stimming, “CO monolayer oxidation on Pt nanoparticles: further insights into the particle size effects,” Journal of Electroanalytical Chemistry, vol. 599, no. 2, pp. 221–232, 2007. View at Publisher · View at Google Scholar · View at Scopus
  95. C. W. Kuo, C. Sivakumar, and T. C. Wen, “Nanoparticles of Pt/HxMoO3 electrodeposited in poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) as the electrocatalyst for methanol oxidation,” Journal of Power Sources, vol. 185, no. 2, pp. 807–814, 2008. View at Publisher · View at Google Scholar · View at Scopus
  96. S. Patra and N. Munichandraiah, “Electrooxidation of methanol on pt-modified conductive polymer PEDOT,” Langmuir, vol. 25, no. 3, pp. 1732–1738, 2009. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  97. V. Zin, B. G. Pollet, and M. Dabalà, “Sonoelectrochemical (20 kHz) production of platinum nanoparticles from aqueous solutions,” Electrochimica Acta, vol. 54, no. 28, pp. 7201–7206, 2009. View at Publisher · View at Google Scholar · View at Scopus
  98. L. Y. Bian, Y. H. Wang, J. B. Zang, J. K. Yu, and H. Huang, “Electrodeposition of Pt nanoparticles on undoped nanodiamond powder for methanol oxidation electrocatalysts,” Journal of Electroanalytical Chemistry, vol. 644, no. 1, pp. 85–88, 2010. View at Publisher · View at Google Scholar · View at Scopus
  99. I. A. Arkoub, C. Amatore, C. Sella, L. Thouin, and J. S. Warkocz, “Diffusion at double microband electrodes operated within a thin film coating. Theory and experimental illustration,” Journal of Physical Chemistry B, vol. 105, no. 37, pp. 8694–8703, 2001. View at Publisher · View at Google Scholar · View at Scopus
  100. C. Amatore, C. Sella, and L. Thouin, “Diffusional cross-talk between paired microband electrodes operating within a thin film: theory for redox couples with unequal diffusion coefficients,” Journal of Physical Chemistry B, vol. 106, no. 44, pp. 11565–11571, 2002. View at Publisher · View at Google Scholar
  101. C. Amatore, C. Sella, and L. Thouin, “Effects of chemical environment on diffusivities within thin Nafion® films as monitored from chronoamperometric responses of generator-collector double microband assemblies,” Journal of Electroanalytical Chemistry, vol. 547, no. 2, pp. 151–161, 2003. View at Publisher · View at Google Scholar · View at Scopus
  102. S. Lupu, “The electrochemical features of sol-gel monoliths and films incorporating Cu(II)-cyclam complexes,” Revue Roumaine de Chimie, vol. 50, no. 11-12, pp. 967–974, 2005. View at Google Scholar · View at Scopus
  103. B. Lakard, G. Herlem, M. De Labachelerie et al., “Miniaturized pH biosensors based on electrochemically modified electrodes with biocompatible polymers,” Biosensors and Bioelectronics, vol. 19, no. 6, pp. 595–606, 2004. View at Publisher · View at Google Scholar · View at Scopus
  104. B. Lakard, O. Segut, S. Lakard, G. Herlem, and T. Gharbi, “Potentiometric miniaturized pH sensors based on polypyrrole films,” Sensors and Actuators, B, vol. 122, no. 1, pp. 101–108, 2007. View at Publisher · View at Google Scholar · View at Scopus
  105. O. Segut, B. Lakard, G. Herlem et al., “Development of miniaturized pH biosensors based on electrosynthesized polymer films,” Analytica Chimica Acta, vol. 597, no. 2, pp. 313–321, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  106. A. E. Musa, F. J. Del Campo, N. Abramova et al., “Disposable miniaturized screen-printed pH and reference electrodes for potentiometric systems,” Electroanalysis, vol. 23, no. 1, pp. 115–121, 2011. View at Publisher · View at Google Scholar
  107. O. Ordeig, C. E. Banks, F. J. Del Campo, F. X. Muñoz, and R. G. Compton, “Electroanalysis of bromate, iodate and chlorate at tungsten oxide modified platinum microelectrode arrays,” Electroanalysis, vol. 18, no. 17, pp. 1672–1680, 2006. View at Publisher · View at Google Scholar · View at Scopus
  108. A. Berduque, G. Herzog, Y. E. Watson et al., “Development of surface-modified microelectrode arrays for the electrochemical detection of dihydrogen phosphate,” Electroanalysis, vol. 17, no. 5-6, pp. 392–399, 2005. View at Publisher · View at Google Scholar · View at Scopus
  109. S. Lupu, F. J. del Campo, and F. X. Muñoz, “Development of microelectrode arrays modified with inorganic-organic composite materials for dopamine electroanalysis,” Journal of Electroanalytical Chemistry, vol. 639, no. 1-2, pp. 147–153, 2010. View at Publisher · View at Google Scholar · View at Scopus
  110. R. Solná, E. Dock, A. Christenson et al., “Amperometric screen-printed biosensor arrays with co-immobilised oxidoreductases and cholinesterases,” Analytica Chimica Acta, vol. 528, no. 1, pp. 9–19, 2005. View at Publisher · View at Google Scholar · View at Scopus