Ion-selective electrodes with stable and reproducible internal solid contact based on nanoparticles of polyaniline and plasticized poly(vinyl chloride)

Tom Lindfors*

*Korresponderande författare för detta arbete

    Forskningsoutput: KonferensbidragPosterVetenskaplig


    The poster presents all-solid-state ion-selective electrodes (ISE) with a stable and reproducible internal solid contact (SC). The SC consists of a plasticized PVC membrane, which contains 5 or 20% (v/v) of polyaniline (PANI) dispersion with the mean particle size of 8 nm [1]. The SC layer is thus in principle similar to the membranes used in the "single-piece" concept from 1995 [2]. The outer membrane was a conventional K+-selective ion-selective membrane (ISM). The main principles of the electrode concept and some experimental results will be highlighted in the poster. A similar ISE concept focusing on different aspects was recently reported by Grekovich et al. [3] and Paciorek et al. [4,5].

    The presentation focuses on the following aspects:
    - The ES form of the PANI dispersion has an extremely good pH stability between pH 2-12, as well as long-term stability at pH 7.5 (measured with UV-vis spectroscopy over two months)
    - PANI does not dissolve in the outer PVC membrane resulting in well-defined contacts
    - The interface between the inner solid contact layer and the outer PVC membrane is mechanically stable
    - PANI does not influence the selectivity and redox activity of the outer PVC membrane
    - The electrical conductivity of the inner contact can be tuned
    - All membrane components are mixable and electropolymerization can be avoided
    - Impedance measurements shows that the capacitive contribution at the solid contact | substrate interface is considerably decreased by 20% PANI

    Lately, many sensor groups have adapted the SC concept [6], which is based on electrically conducting polymers (CP). It is often only assumed that the internal contact has a good long-term stability and no attention has been paid to direct monitoring of the stability of the contact, for example, with spectroscopic techniques [7]. It is, however, well-known that the CPs can undergo oxidation and reduction processes, which may cause considerable changes in their electrical con-ductivities. In preparing SC electrodes with good long-term stability, it is therefore highly im-portant to monitor the stability of the SC layer.

    The chemistry of PANI is more complex than for most other CPs. This fact has in some cases resulted in device concepts that have not been optimal. A key factor in the application of PANI in ISEs is to understand how the pH stability of the electrically conducting emeraldine salt (ES) form can be tuned [8]. The ES form has very good environmental stability and can be prepared as thin intractable films, soluble processable materials and dispersions.

    [1] Ormecon GmbH, Germany
    [2] J. Bobacka, T. Lindfors, M. McCarrick, A. Ivaska and A. Lewenstam, Anal. Chem. 1995, 67, 3819
    [3] A.L. Grekovich, N.N. Markuzina, K.N. Mikhelson, M. Bochenska and A. Lewenstam, Electroanalysis, 2002, 14, 551-555
    [4] R. Paciorek, P.D. van der Wal, N.F. de Rooij and M. Maj-Żurawska, Electroanalysis, 2003, 15, 1314
    [5] R. Paciorek, P. Bieganowski and M. Maj-Żurawska, Sensors and Actuators B, 2005, 108, 840
    [6] A. Cadogan, Z. Gao, A. Lewenstam, A. Ivaska, D. Diamond, Anal. Chem., 1992, 64, 2496
    [7] T. Lindfors and A. Ivaska, Anal. Chem., 2004, 76, 4387
    [8] T. Lindfors and L. Harju, Synth. Met., submitted
    StatusPublicerad - 2007
    MoE-publikationstypO2 Other
    EvenemangDevelopment and Application of Chemical Sensors - Zürich, Schweiz
    Varaktighet: 28 juni 200729 juni 2007


    KonferensDevelopment and Application of Chemical Sensors


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