Structural, morphological and sensing properties of layered polyaniline nanosheets towards hazardous phenol chemical Hyung-Kee Seo a,1 , Sadia Ameen b,1 , M. Shaheer Akhtar c,1 , Hyung Shik Shin b,n a Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA b Energy Materials & Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea c New & Renewable Energy Material Development Center (NewREC), Chonbuk National University, Jeonbuk, Republic of Korea article info Article history: Received 15 September 2012 Received in revised form 17 October 2012 Accepted 18 October 2012 Available online 20 November 2012 Keywords: Layered nanosheets I–V characteristics Phenol Chemical sensor Electrochemical impedance spectroscopy abstract Reliable sensing properties towards hazardous phenol chemical were detected by the novel working electrode of layered polyaniline (PANI) nanosheets. The layered PANI nanosheets were synthesized by the chemical polymerization of aniline monomer in the presence of hydrochloric acid and ammonium persulphate at 5 1C. The morphological, structural, optical, electrical and electrochemical properties of layered PANI nanosheets were extensively studied. The electrochemical behavior of layered PANI nanosheets based electrode was demonstrated by the electrochemical impedance spectroscopy (EIS) and cyclovoltametry (CV) measurements. The layered PANI nanosheets electrode showed reasonably good electrocatalytic activity towards the detection of phenol chemical, which resulted from the high redox current and low R CT . The current–voltage (I–V) characteristics were used to elucidate the sensing parameters of the fabricated phenol chemical sensor with layered PANI nanosheets electrode. The fabricated phenol chemical sensor with layered PANI nanosheets electrode significantly attained the high sensitivity of  1485.3 mA mM 1 cm 2 and the detection limit of 4.43 mM with correlation coefficient (R) of 0.9981 and short response time (10 s). & 2012 Elsevier B.V. All rights reserved. 1. Introduction Phenol and phenolic compound are widely used chemicals in plastics, fertilizers, paints, rubber, adhesives, paper and soap indus- tries [1]. It is also used as an antiseptic, a topical anesthetic for sore throat lozenges and sprays as a skin exfoliant [2]. The excess concentration of phenol and phenolic compounds is an issue of environmental concern due to their toxicity and persistence or high adsorptive nature in the environment [3]. Phenol if ingested in excess by human body could cause nausea, vomiting, sweating, diarrhea, excessive salivation and headache [4]. The acute exposure to phenol and its derivatives might also cause gastrointestinal irritation, cardiovascular, central nervous system and respiratory effects [2,5]. The detection, identification and the quantification of phenol and its compounds are very important for clean environ- ment. For the detection of phenol, several analytical techniques like gas chromatography [6], high performance liquid chromatography [7], capillary electrophoresis [8] and spectrophotometry [9] are used so far. The major drawbacks of these analysis methods are time-consuming, complex to perform and not easy to operate under in-situ monitoring which limits the practical applications. Electrochemical methods are the most adopted technique due to the advantages associated with its high sensitivity, greater selectivity, time efficiency, and reproducibility [10]. A unique organic p-type semiconductor polymer, polyaniline (PANI) is highly searched polymer due to its unique acid–base chemistry, stable electrical conduction, high-environmental stability and ease of fabrication [11–13]. Importantly, PANI possesses the typical conjugated bonds in the polymer skeleton which could be responsible for the charge conduction due to the generation of polarons or bipolarons [14]. The variable conductivity makes PANI as promising material for the specific application of electronics, optoelectronic, electrochemical, electrochromic, photovoltaic and sensing devices [15]. Moreover, the presence of the reactive –NH- groups in the polymer chain (PANI), positioned on either side by phenylene rings imparts the chemical flexibility to the system and improves the processibility to a large extent. PANI nanomaterial shows the versatility of nanostructures in the form of nanofibers, nanorods, nanowires and nanoflakes with high surface/volume ratio and low diffusional resistance [16]. Various PANI nanostructures display the improved optical, structural, electronic and electrical properties which might act as useful candidate for the application in electrochemical, electrochromic, biosensors and chemical sensors devices [17–18]. Recently, PANI nanomaterials have gained a great attention in the field of sensors including gas sensor, biosensor and chemical sensors [19]. In context of PANI based sensors, Kukla et al. prepared PANI thin films for detecting ammonia [20]. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta 0039-9140/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.talanta.2012.10.089 n Corresponding author. Fax: þ82 63 270 2306. E-mail address: hsshin@jbnu.ac.kr (H.S. Shin). 1 Authors contributed equally to this work. Talanta 104 (2013) 219–227