Sensors and Actuators B 135 (2009) 541–551 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Application of sensor arrays based on thin films of conducting polymers for chemical recognition of volatile organic solvents A.L. Kukla a,∗ , A.S. Pavluchenko a , Yu.M. Shirshov a , N.V. Konoshchuk b,1 , O.Yu. Posudievsky b,1 a V.E. Lashkarev Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, prospekt Nauki 45, Kiev 03028, Ukraine b L.V. Pisarzhevsky Institute of Physical Chemistry, National Academy of Sciences of Ukraine, prospekt Nauki 31, Kiev 03028, Ukraine article info Article history: Received 9 May 2008 Received in revised form 22 September 2008 Accepted 22 September 2008 Available online 2 October 2008 Keywords: Conducting polymer Chemiresistor Sensor array Chemical image recognition abstract The use of thin conducting polymer films (polyaniline, polypyrrole and poly-3-methylthiophene doped with ordinary mineral acids or monovalent anions, as well as heteropolyacids of Keggin type or corre- sponding heteropolyanions) as sensitive layers in the sensor arrays for chemical recognition of volatile organic analytes is investigated. The discrimination ability of various sensor subsets is evaluated by sta- tistical analysis of the data retrieved from responses of 20 different polymer sensors to the vapors of nine volatile organic solvents. An approach for constructing optimal sensor array is developed and the method for systematic selection of separate sensors from the given set to achieve the required analyte recognition reliability is proposed. © 2008 Published by Elsevier B.V. 1. Introduction Conducting organic polymers (COP) of polypyrrole, polythio- phene, polyindol, polyaniline and polyfuran families are widely used as sensitive materials for conductometric polymer sensors. Vast amount of publications is available on this subject, many of them summarized in the recent reviews [1–4]. These works, in par- ticular, describe main chemical transformations taking place during polymerization and consider the mechanisms of interaction of the adsorbed molecules with polymers, affecting the electroconduc- tive properties of the latter. A list of comparative responsiveness of various conducting polymers such as polypyrrole, polyaniline, poly(3,4-ethylene-dioxythiophene) towards different analytes may be found in [3]. A number of applications for various conduct- ing polymers in the chemical sensors are given in [4]; the work is focused, particularly, on their sensitivity to various inorganic ions and organic molecules as well as to gases. The work [5] demon- strates the use of polythiophene-based copolymers as promising materials for detection of some organic solvents by means of conductance measurements. Numerous applications of the COPs for creation of various electronic noses for monitoring mainly ∗ Corresponding author. Tel.: +38044 525 2332; fax: +38044 525 1827. E-mail addresses: kukla@mail.ru (A.L. Kukla), posol@inphyschem-nas.kiev.ua (O.Yu. Posudievsky). 1 Tel.: +38044 525 6672; fax: +38044 525 6216. foods, drinks and beverage quality are described in the review [6]. The main advantages of conducting polymers are the possibil- ity of working at room temperatures and simplicity of technology of their obtaining that significantly simplifies design of COP-based devices and allows to use them in portable instruments. Limitations of COP sensors operation are conditioned by insufficient repro- ducibility of produced sensitive layers, their sensitivity to moisture, temporal drift of specific conductivity and susceptibility to poison- ing [3,6]. Despite these drawbacks, some successful applications in chemical sensing have been reported [7–10]. Detention of COP in vapors of volatile organic compounds could alter the electron state of polymers chains, the number and distribution of charges in polymer chains that influence on conductivity along them, inter- chain charge carrier hopping and electrostatic interaction with counter-ions. Any of these factors or their combination can lead to the change of specific conductivity of the material [11–15]. Known approaches to directed synthesis of COP with required proper- ties mainly consist in modifying of polymer structure by inclusion of various functional groups into polymer chain and use of vari- ous dopants which result in selectivity and sensitivity changes in the COP-based sensors [3–6]. Manipulation of the polymer char- acteristics may also be performed by changing conditions of their preparation [6,8]. At the same time as indicated in [3], the main difficulties in advancement of the practical COP-based gas mixture analyzers are comprised in the absence of well-founded criteria for both evalua- 0925-4005/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.snb.2008.09.027