Sensors and Actuators B 222 (2016) 280–289 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo u r nal homep age: www.elsevier.com/locate/snb Electrochemically growth of Pd doped ZnO nanorods on QCM for room temperature VOC sensors Sadullah Öztürk a,∗ , Arif Kösemen b,c , Zühal Alpaslan Kösemen d , Necmettin Kılınc ¸ e,f , Zafer Ziya Öztürk b , Michele Penza g a Fatih Sultan Mehmet Vakif University, Faculty of Engineering, 34080 Istanbul, Turkey b Gebze Technical University, Department of Physics, 41400 Gebze, Kocaeli, Turkey c Mus Alparslan University, Department of Physics, 49100 Mus, Turkey d TUB ˙ ITAK UME Optics Laboratory, 41470 Gebze, Kocaeli, Turkey e Nigde University, Mechatronics Engineering Department, 51245 Nigde, Turkey f Nigde University, Nanotechnology Application & Research Center, 51245 Nigde, Turkey g ENEA, C.R. Brindisi, Materials and New Technologies Unit, SS. 7, Appia, km 714, 72100 Brindisi, Italy a r t i c l e i n f o Article history: Received 11 May 2015 Received in revised form 31 July 2015 Accepted 18 August 2015 Available online 20 August 2015 Keywords: Gas sensor ZnO Nanorods Electrochemical deposition Pd doping VOCs QCM a b s t r a c t Pristine and various palladium (Pd) doped ZnO nanorods have been synthesized on the quartz crystal microbalance (QCM) for volatile organic compound (VOCs) sensors at room temperature. The doping concentrations were varied from 0 mol% to 2.5 mol% by using electrochemical deposition method. The diameters of the fabricated nanorods were in the range of 100–200 nm, and were increased with Pd doping. The tested VOCs included alcohols (ethanol, methanol, isopropyl), ester (ethyl acetate), aromatic (toluene, xylene), ketone (acetone) and chloroform in the different concentrations. The results indicated that the sensitivity of the sensing materials was enhanced with the increasing Pd doping concentrations except for the acetone and chloroform. The undoped ZnO nanorod sensor showed higher sensor response against to acetone and chloroform while exposing high concentration of two analytes due to the absorb- ing/adsorbing mechanism. All undoped and Pd doped nanorods sensors showed the highest sensitivity to xylene. © 2015 Published by Elsevier B.V. 1. Introduction Volatile organic compounds (VOCs) are carbon-based organic compounds known as indoor/outdoors air pollutants from BTEXs (benzene, toluene, and xylenes), aldehydes, ketones and chlo- rinated hydrocarbons, and may cause several health problems (i.e. with short term and long term effects) depending on the exposure times and concentrations of VOCS in the breathing atmo- sphere. Short term effects include eye, nose and throat irritations, headaches, dizziness and asthma symptoms, but long term effects are more dangerous and may cause cancer, and damages in liver, kidney and central nervous systems [1,2]. The sources of VOCs can be in various materials including building/construction materials, paints, aerosols, disinfectants, air fresheners and automotive parts [1,2]. The presence of highly dangerous effects on health, and their presence in every moment of our lives reveal the need to develop ∗ Corresponding author. E-mail address: sozturk@fsm.edu.tr (S. Öztürk). rapid, highly selective, sensitive and suitable gas sensing devices for real-time monitoring. Chemical gas sensors can be used for personal and public safety, industrial manufacturing, medical diagnosis, automotive industry and also indoor/outdoor air quality [3–5]. Typically, a chemical gas sensor consists of a sensitive layer and transducing element. The sensitive layer directly interacts with gas molecules (or analytes) in the ambient, and thus, the sensitivity of sensors is directly linked to the surface area that can be increased by using nanostructured materials. The transducing element converts electrochemical or chemical reactions realized on sensor surface area to observable physical quantities such as current, frequency and absorbance by interacting with the gas molecules and sensitive layer of the sen- sors [6–8]. Metals, metal oxides, polymers and organic materials can be used as the sensitive layer. Metal oxide materials are highly robust to physical and chemical deformation effects, but very sen- sitive to any physical and chemical changes in the environment, and thus have been used in gas sensors applications for more than 50 years starting with SnO 2 by Seiyama [9,10]. In semiconducting metal oxide materials, zinc oxide (ZnO) have been used in many http://dx.doi.org/10.1016/j.snb.2015.08.083 0925-4005/© 2015 Published by Elsevier B.V.