ARTICLE Copyright © 2012 by American Scientific Publishers All rights reserved. Printed in the United States of America Journal of Nanoengineering and Nanomanufacturing Vol. 1, pp. 1–9, 2012 (www.aspbs.com/jnan) Specific H 2 S Gas Sensor Based on Metal Nanoparticles, Sulfur and Nitrogen/Single-Walled Carbon Nanotube-Modified Field Effect Transistor Shirin Nasresfahani 1, 3 , Mohammad Mahdi Doroodmand 2, 3, * , Mohammad Hossein Sheikhi 1, 3 , and Ahmad Reza Ghasemi 1, 3 1 School of Electrical and Computer engineering, University of Shiraz, Shiraz, Iran 2 Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran 3 Nanotechnology Research Center, Shiraz University, Shiraz, Iran ABSTRACT A novel hydrogen sulfide (H 2 S) sensor is fabricated using commercial metal oxide field effect transistor (MOSFET), individually modified with Fe or Ag-doped single-walled carbon nanotubes (SWCNTs). In this study, integrated circuit (IC: BS250) was selected as selective probe for H 2 S detection. For this purpose, plastic cover on the surface of drain was drilled to bare the drain surface, followed by modification with nitrogen and sulfur-doped SWCNTs by chemical vapor deposition (CVD) process. The CVD-synthesized SWCNTs were then electrochemically modified with Ag or Fe nanoparticles. Accordance to the figures of merit, fabricated sensor was linear from 150 to 920 parts per billion (ppb). Detection limit was also 85 ppb. Relative standard deviation (RSD) for five replicate analyses was 3.26%. Based on 90% of maximum response (t 90 , response time was ∼52 s. Calibration sensitivity was measured to 0.30 mV/ppb. No interference was observed, when introducing at least 500 folds of interferences such as vapors of H 2 O, HCl, HClO 4 , HNO 3 , HIO 4 , gaseous species like O 2 , H 2 , CO, CO 2 , NO 2 , hydrocarbons such as C 2 H 2 , CH 4 and also volatile orgasmic compounds (VOCs) to 400 ppb of H 2 S solution. Reliability of the sensor was also evaluated via determination of the amounts of H 2 S in different industrial samples. KEYWORDS: H 2 S Gas Sensor, Field Effect Transistor, Carbon Nanotubes, Metal Nanoparticles. 1. INTRODUCTION Hydrogen sulfide (H 2 S) is a colorless, bad smelling and poisonous gas. It is generated in sewage, coal and natural gas processing and petroleum industries. Owning to the highly toxicity of H 2 S, 1 this gas produces severe effects on the nervous system at low concentration. Also at higher concentrations, H 2 S causes life threatening. 1 Therefore, quantitative detection of H 2 S gas ranging from a few parts per billion (ppb) to the hundred parts per million (ppm) is of great important for both oil and natural gas industries and human safety. Exciting detection of H 2 S rely mainly on electrochemical 2–4 and metal oxide semiconductor devi- ces. 5–11 While there are commercially a number of sensing devices, drawbacks of existing H 2 S sensors including high operating temperatures, low selectivity, cross sensitivity ∗ Author to whom correspondence should be addressed. Email: doroodmand@shirazu.ac.ir Received: Accepted: problems and high cost, making them inappropriate for environmental monitoring. 10–12 Over the last decade, one-dimensional nanostructures such as carbon nano- tubes (CNTs) have been attracted substantial attention because of their unique structural, electronic, optical, thermal and mechanical properties. 12–15 Chemical sensors based on CNTs offer high sensitivity and low power consumption. 16–19 This is due to the fact that, CNTs have nano-sized morphology and high aspect ratio, which make them suitable for high sensitive and rapid gas adsorption of gaseous species. Interaction between carbon nano- structures and any gas molecules causes significant change in the electrical properties of CNTs. One of the most interesting transduction systems, employed during the last years, is the “Metal-Oxide- Semiconductor Field Effect Transistor” (MOSFET). Since then, many theoretical and experimental studies have described the performance of the FETs. FETs are adopted to provide physical/chemical changes into an electrical sig- nal. They have been used as detection system in potentio- metric sensors. 20 However in accordance with the literature review, few studies have been focused on CNT-based field J. Nanoeng. Nanomanuf., 1, 1–9, 2012 2157-9326/2012/1/001/009 doi:10.1166/jnan.2012.1020 1