The interaction of carbon monoxide to Fe(III)(salen)-PEDOT:PSS composite as a gas sensor F. Arabloo a, *, S. Javadpour a, *, R. Memarzadeh b , F. Panahi c , M. Davazdah Emami a , M.H. Shariat a a Department of Materials Science & Engineering, Shiraz University, Shiraz, Iran b Department of Materials Science and Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran c Department of Chemistry, College of Sciences, Shiraz University, Shiraz, Iran A R T I C L E I N F O Article history: Received 7 March 2015 Received in revised form 15 April 2015 Accepted 29 April 2015 Available online xxx Keywords: Chemical sensor Fe(III)(salen) PEDOT:PSS Thin film Carbon monoxide A B S T R A C T PEDOT:PSS/Fe(salen) composite thin films were coated on glass pieces with interdigitated Au electrodes by spin coating method for CO gas sensing application. The metal complex doped PEDOT:PSS film was experienced by some common atmospheric gases to examine its identification ability for CO gas detection. The highest response factor (DR/R 0  100) and lowest response time were gained 31.32  0.88% and 38 s, respectively. An optimum level of doping (0.1 wt.% of Fe(salen)) was established for the highest sensitivity. The results showed that the sensor response was reproducible (RD < 2%) and fast recovery (5 s) in dry atmosphere and room temperature. The Fe(salen)-doped PEDOT:PSS was well characterized by different techniques such as UV–vis and FTIR spectroscopy. In addition, the surface topography of Fe(salen) doped PEDOT:PSS film was investigated using AFM. The results of this study can be helpful in selecting appropriate procedure for utilizing PEDOT:PSS/Fe(salen) composite for effective gas sensing applications. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction The significance of environmental gas monitoring is currently at the center of an intense theoretical and experimental studies and much research has focused on the development of suitable gas- sensitive materials [1]. Among greenhouse gases, carbon monox- ide is one of the hazardous gases that come out of car and truck exhausts, aeroplanes, as well as factories. CO is an odorless and colorless gas then has been called silent killer [2]. Recently, conducting polymers (CPs) have received much more attention due to their successful applications in various fields of chemical and biological sensors [2,3]. As they have very rapid response to the specific gases, they can be useful for gas sensing applications [4]. Among various CPs, Poly(3,4-ethylenedioxy) thiophene-poly(styr- enesulfonate) (PEDOT:PSS) has good film-forming property and high stability [5]. In earlier studies, researchers have tried that improve stability and conductivity of conductive polymers [2,4,6,7]. For instance, Polypyrrole functionalized with iron porphyrin have reversible and quite fast response toward CO and behaves as a sensor at room temperatures [8]. As well as, a morpholine doped PEDOT:PSS film acts as a CO sensor [6]. In addition, PEDOT:PSS thick films-modified electrodes have been used for sensing nitricoxide (NO) gas. Lin et al. [9] showed that the PEDOT:PSS film demonstrated the highest response to NO gas at room temperature and the response increased with increasing the PEDOT:PSS film thickness from 2.3 to 5.0 mm. In 2014, Hongxia and Ruiquan [10] investigated the behavior of SmBaCuMO 5+d (M = Fe, Co, Ni) toward NH 3 gas in room temperature. The results showed that maximum sensitivity of PANI/SmBaCuFeO 5+d (SBCF) was 4.68– 100 ppm NH 3 that it exhibited shortest response-recovery time, best selectivity and highest resistance sensitivity [10]. During the recent years, metal compounds doped in PEDOT:PSS also have wonderful results as CO gas adsorbents to improve selectivity of sensor [4]. Memarzahed et al. [4] tried to modify the gas sensing properties and selectivity of the polymer. Solutions of PEDOT/PSS and Co(salen) were produced by different concentrations of this dopant. An optimum level of doping (1 wt.% of Co(salen)) was established for the highest sensitivity. In their work, the sensitivity was increased from 12  0.05% to 22  0.05%. Moreover, the PEDOT: PSS was reported as a water-absorbing material. Several research- ers report the influence of environmental relative humidity (RH) on the optical and electrical properties. In 2013, Taccola et al. [11] fabricated the nanocomposite thin films from PEDOT:PSS and iron * Corresponding authors. E-mail addresses: f.arabloo69@yahoo.com (F. Arabloo), Sirus.Javadpour@shirazu.ac.ir (S. Javadpour). http://dx.doi.org/10.1016/j.synthmet.2015.04.019 0379-6779/ ã 2015 Elsevier B.V. All rights reserved. Synthetic Metals 209 (2015) 192–199 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.else vie r.com/locat e/synme t