Characterization of nanosized TiO 2 based H 2 S gas sensor G. N. Chaudhari Æ D. R. Bambole Æ A. B. Bodade Æ P. R. Padole Received: 28 May 2005 / Accepted: 28 September 2005 / Published online: 4 May 2006 Ó Springer Science+Business Media, LLC 2006 Abstract The present investigation deals with the fabri- cation of H 2 S gas sensor based on semiconducting oxi- de,TiO 2 . Among the various metal oxide additives tested, Al 2 O 3 is outstanding in promoting the sensing properties of nanosized TiO 2 based H 2 S gas sensor. XRD pattern of TiO 2 /Al 2 O 3 shows complete phase formation with anatase structure and grain growth 45 nm. The TiO 2 sensor loaded with 5 wt% Al 2 O 3 and 0.5 wt% Pd shows increase in sensitivity to H 2 S. The cross sensitivity of 0.5 wt% Pd:5 wt% Al 2 O 3 doped TiO 2 also checked for CO, LPG and H 2 gases. The highest sensitivity for low concentration of H 2 S was observed using TiO 2 based mixed Al 2 O 3 and Pd. The H 2 S sensor shows high sensitivity and undesirable cross sensitivity effect using TiO 2 /Al 2 O 3 /Pd as sensing materials. Introduction Metal-oxide semiconductors are extensively used as gas sensors due to their property, which changes their con- ductivity under gas exposures. TiO 2 seems to be one of the most interesting candidates for gas detection and has commercially been used as lambda sensor in exhaust pipes. Likewise, its sensing capability has been improved with the addition of foreign atoms such as Pt [1–3], Cu [4, 5], Cr [6] or Nb [7–9]. Hydrogen Sulfide is a toxic gas often produced in coal or natural gas manufacturing. The threshold limit value for Hydrogen sulfide is 10 ppm. When the concentration of H 2 S is higher than 250 ppm, it is dangerous to human body and may cause death. Reliable, low cost H 2 S consumption is in high demand for environmental safety and industrial control purposes. Numerous efforts have been directed to develop H 2 S gas sensors by mainly employing solid electrolytes such as alkali metal sulfates [10] by adding hydrophonic silica [11], ZrO 2 [12], CeO 2 [13] to the sensor element. It was also found that addition of as noble metal, Ag makes the material very sensitive to H 2 S [14]. Owing to extensive investigation, the properties of solid electrolyte H 2 S sensors are reaching the levels for practical applications [15]. On the other hand, electronic interaction between H 2 S and SnO 2 was first studied [16]. Thereafter, H 2 S sensing properties of semiconductor metal oxides such as CeO 2 [17] and SnO 2 [18] have been studied. However little was known about H 2 S sensing properties of other semiconductor metal oxide materials. In doped semiconducting oxides two types of sensiti- zation mechanisms have been proposed, viz chemical sensitization and electronic sensitization [19]. In chemical sensitization, the sensing gas molecule gets adsorbed at the sensor surface where it is dissociated or activated with the help of a dopant. This dissociated molecule at the sensor surface interacts with the semiconducting oxide. This will lead to a change in the conductivity at the sensor surface. On the other hand, electronic sensitization is followed by direct exchange of electrons between added dopant and the semiconductor surface. There is a change in the oxidation state of dopant on contact with sensing gas molecule due to electron exchange from dopant to oxygen which leads to a change in the conductivity of the sensor surface. G. N. Chaudhari (&) Æ D. R. Bambole Æ A. B. Bodade Æ P. R. Padole Gas Sensor and Thin Films Laboratory, Department of Chemistry, Shri Shivaji Science College, Amravati 444602, India e-mail: cgnroa@yahoo.com J Mater Sci (2006) 41:4860–4864 DOI 10.1007/s10853-006-0042-7 123