Application of composites of graphene derivatives and conducting polymers in solid-state electrochemical sensors

We report the incorporation of few-layer graphene (< 3 monolayers), graphene oxide (GO), reduced graphene oxide (RGO) or exfoliated graphite in electrically conducting polyaniline (PANI) and poly(3,4-ethylenedioxythiophene) matrices [1-6]. The composite films were used either as such in electrochemical solid-state sensor applications [6] or as buried ion-to-electron transducer layers in polymeric solid-contact ion-selective electrodes (SC-ISEs) aimed for trace analysis and applications within health diagnostics [7, 8]. In both the two- and three-electrode cell [5, 9], the composite materials had very good potential cycling stability in aqueous electrolyte solutions for at least 10000 cycles with only minor degradation (6%), which is beneficial for obtaining high signal stability in electrochemical sensors.

It is shown that SC-ISE having the transducer made of a composite consisting of few-layer graphene and PANI had a detection limit of only 5x10(-9) M Ca(2+) (0.2 ppb; parts per billion) [7]. In addition to the hydrophobicity of graphene, the transducer makes use of the synergistic effect of PANI and graphene resulting in increased redox capacitance which is crucial for obtaining good long-term signal stability. Moreover, the presentation discusses shortly the relationship of the graphene barrier properties and the reproducibility of the standard potential of electrochemical sensors. This is one of the key issues in the fabrication of conditioning- and calibration-free devices.

References
[1] A. Österholm, T. Lindfors, J. Kauppila, P. Damlin, and C. Kvarnström, Electrochim. Acta, 83, 463-470, (2012)
[2] T. Lindfors, A. Österholm, J. Kauppila, and M. Pesonen, Electrochim. Acta, 110, 428-436, (2013)
[3] T. Lindfors, A. Österholm, J. Kauppila, and R.E. Gyurcsányi, Carbon, 63, 588-592, (2013)
[4] T. Lindfors and R.-M. Latonen, Carbon, 69, 122-131, (2014)
[5] T. Lindfors, Z. Boeva, and R.-M. Latonen, RSC Adv., 4, 25279-25286, (2014)
[6] Z.A. Boeva, K.A. Milakin, M. Pesonen, A.N. Ozerin, and V.G. Sergeyev, T. Lindfors, RSC Adv., 4, 46340-46350, (2014)
[7] Z.A. Boeva and T. Lindfors, manuscript in preparation
[8] T. Lindfors, L. Höfler, G. Jagerszki, and R.E. Gyurcsányi, Anal. Chem., 83, 4902-4908, (2011)
[9] T. Lindfors, Electroanalysis, in press, (2015)