Sensors and Actuators B 203 (2014) 647–654 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo ur nal home page: www.elsevier.com/locate/snb Quartz crystal microbalance VOCs sensor based on dip coated polyaniline emeraldine salt thin films Zaher Ihdene a , Ahmed Mekki a,c,∗ , Boualem Mettai a , Rachid Mahmoud a,∗∗ , Boudjema Hamada b , Mohamed M. Chehimi c,∗ ∗ ∗ a Ecole Militaire Polytechnique, BP 17, Bordj El Bahri, Alger 16111, Algeria b Laboratoire de Synthèse Pétrochimique, Université M’Hamed Bougara de Boumerdès, Boumerdès 35000, Algeria c Univ Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR CNRS 7086, 15 rue J-A de Baïf, 75013 Paris, France a r t i c l e i n f o Article history: Received 3 February 2014 Received in revised form 7 July 2014 Accepted 9 July 2014 Available online 19 July 2014 Keywords: VOCs sensing QCM Polyaniline-emeraldine salts Masse sensitive sensors a b s t r a c t Quartz crystal microbalance (QCM) technique has been used to detect a number of aromatic volatile organic compounds (VOCs) vapors widely used in research and industrial fields. Detection was based on dip coated polyaniline emeraldine salts (PANI-ES) thin films doped with three different acids, i.e. hydrochloric acid (HCl), dodecylbenzene sulfonic acid (DBSA) and 1,5-naphtalene disulfonic acids (1,5-NDSA)) on AT-cut 10 MHz QCM electrode. Frequency change was recorded upon adsorption and desorption of (VOCs) on PANI films. It was found that frequency shifts varied linearly with both vapor concentration in part per million (ppm) and film thickness in nanometer (nm). Frequency changes are assumed to be mainly due to electrostatic interactions established between vapor molecules and dopant agents within PANI-ES films. Particularly, PANI-DBSA films were found to be highly sensitive (∼7 Hz/ppm), selective to para-xylene (over toluene and benzene) and have a limit of detection of 3 ppm. Interestingly, the films exhibit excellent recovery within less than 3 min. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Nowadays, various environmental agencies have classified volatile organic compounds (VOCs) and air borne odorous spices as potent toxic chemical agents, owing to their serious effect resulted on air quality and consequently human health by causing nerve diseases and even death. Their wide use in many workspaces, manufacturing units and facilities such as laboratories, hospitals and food industry have induced a great attention and enforced an imperative task for the development of monitoring and early warning systems. Therefore, many features like portability, field- deployability, robustness, and low cost are required to be taken ∗ Corresponding author at: Ecole Militaire Polytechnique, BP 17, Bordj El Bahri, Alger 16111, Algeria. Tel.: +213 550573460. ∗∗ Corresponding author. ∗ ∗ ∗ Corresponding author. Present address: Institut de Chimie et des Matériaux Paris Est – Equipe Systèmes Polymères Complexes, UMR 7182 CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, 94320 Thiais, France. E-mail addresses: mekki ahmedkarim@yahoo.fr, ahke0405@gmail.com (A. Mekki), rachid mahm@yahoo.fr (R. Mahmoud), chehimi@univ-paris-diderot.fr (M.M. Chehimi). into account to design such system. Furthermore, it should yield fast and sensitive identification of an unknown sample on loca- tion, and it should function autonomously. Thus, in the last few decades, efforts were focused on the development of sensors with more selectivity and reproducibility for on-line monitoring and in situ detection of VOCs. Hence, a number of varieties of chemical sensors were investigated, including electrochemical sensor [1–3], semiconductor sensors [4–6], quartz crystal microbalances (QCM) [7–10], surface acoustic wave (SAW) sensors [11–13], optical-fiber sensors [14–16], fluorescent systems [17], microcapacitors [18] and so on. A typical configuration for a chemical sensor includes a sorbent coating which interacts with the target analyte, and the resultant physical change in the coating is subsequently exploited for ease of recording or display. Thus, the sensitivity and selectiv- ity of chemical sensor is critically governed by the sorbent coating type. In fact a large number of sorbent materials, especially poly- mers [19] have been investigated as sensing coatings as well as preconcentration layers. Amongst the various tested polymers, the utilization of conducting polymers as sensitive layers in gas sen- sors is becoming a promising approach. Polypyrrole was one of the first polymers used in gas sensor for detection of alcohols and other organic vapors [20–22]. Recently, the researchers are http://dx.doi.org/10.1016/j.snb.2014.07.030 0925-4005/© 2014 Elsevier B.V. All rights reserved.