Journal of Materials Science and Engineering 5 (2011) 271-276 Development of Tungsten Oxide Based Gas Sensor for Ethanol Vapor Detection Lim Guatwei, Tan Xian-ju, Chan Choongyew, Ang Gaiktin and Abu Bakar Mohamad Zailani School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang, Malaysia Received: August 11, 2010 / Accepted: August 27, 2010 / Published: March 10, 2011. Abstract: In this work, tungsten oxide (WO 3 ) powder with average grain size of 50 nm was prepared using modified Nishide-Mizukami sol-gel method. The powder was characterized using X-Ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with transmission electron microscopy (TEM). The ethanol vapor sensing properties were investigated at different operating temperatures and gas concentrations. The WO 3 pellet ethanol sensor exhibited excellent sensitivity to ethanol vapor with maximum sensitivity value of 29 at low temperature which is 200 °C. It was shown that the WO 3 pellet can be reliably used to monitor high concentration of vapor above 1,500 ppm. This study demonstrated the possibility of utilizing WO 3 pellet as a sensor element for the detection of ethanol vapor. Key words: Sol-gel, WO 3 , catalytic gas sensor. 1. Introduction Nowadays, a lot of volatile organic compound (VOC) sensors have been developed and some are commercially available. However, the sensitivity of the sensors is still not at a satisfactory level. Much attention had been given to semiconductor gas sensors based on metal oxides due to its advantages of reliability, low price, structural simplicity and easy implementation [1-3]. Semiconductor material such as WO 3 is particularly attractive because of its promising electrical properties which enable it to be used as gas sensing applications. Various techniques have been used to prepare pure WO 3 films such as chemical vapor deposition [4], sol-gel [5], sputtering [6], screen-printing [7-8], and so on. A few research groups had devoted their investigation to WO 3 for gas sensing application. They had been showing that WO 3 has outstanding sensitive Corresponding author: Abu Bakar Mohamad Zailani, associated professor, research fields: process safety and modeling, environmental. E-mail: chmohdz@eng. usm.my. properties to mainly nitrogen oxides (NO x ), ammonia (NH 3 ), and ozone (O 3 ). Most of them were focused on the NO x gas sensing properties and study of sensing to other gases such as VOCs was rare [9]. Until recent years, Kanda and Maekawa had developed WO 3 thick films for detecting VOCs [6]. In 2007, screen printed WO 3 films were also fabricated for detecting ethanol and acetone vapor [7-8]. Nevertheless, research about the detection of VOCs using WO 3 is still lacking and this sensing material is still being studied and exploited at present time. In this paper, the sensitivity of the pure WO 3 (by a modified Nishide-Mizukami sol-gel method) [5] correspond to the ethanol concentrations and working temperatures were investigated. 2. Experiment 2.1 Pellet Sensor Fabrication The materials were prepared through the sol-gel route which was suggested by Nishide and Mizukami [5]. However, the experiment was modified in such a