Research article Influence of Ta 2 O 5 on polyaniline surface for liquid petroleum gas sensing applications Aashis S. Roy Department of Materials Science, Gulbarga University, Gulbarga, India Ameena Parveen Department of Physics, Government First Grade College, Gulbarga, India Ambika Prasad Department of Materials Science, Gulbarga University, Gulbarga, India, and Koppalkar R. Anilkumar Department of Physics, S.S. Margol College, Gulbarga, India Abstract Purpose – The purpose of this paper is to study the sensitivity and selectivity properties of polyaniline/tantalum pentoxide (PANI/Ta 2 O 5 ) composite to liquid petroleum gas (LPG). Design/methodology/approach – Polyaniline/tantalum pentaoxide (PANI/Ta 2 O 5 ) composites were synthesized by in situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is the novel polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The composites were characterized by FTIR, XRD and SEM. Temperature dependence conductivity of the composites shows thermally activated behaviour. Sensitivity and selectivity of the composites are studied. Findings – The PANI/ Ta 2 O 5 composites of 20 wt% and 30 wt% are showing maximum change in resistance against time when compared to pure PANI and other polyaniline composites when exposed to LPG. The 20wt % composites show maximum sensitivity of 83% to LPG. The selectivity studies reveals that LPG could be sensed better when compared to oxyacetylene and other test gases. Practical implications – Selectivity studies have been carried out and the sensor proved to be better than metal oxides sensors. Social implications – The sensing material is of low cost. Originality/value – To the best of the authors’ knowledge, studies on Ta 2 O 5 -based gas sensor have not been reported previously. Keywords Sensors, Gases, Liquefied petroleum gas, Polymerisation, Polyaniline/tantalum pentaoxide, Sensitivity, Selectivity, Oxyacetylene gas Paper type Research paper Introduction Gas sensors based on semiconducting metal oxides have attracted the attention of environmentalist and many other researchers. Hydrocarbon gases, including liquid petroleum gas (LPG) find useful applications, as a clean source of energy at both the domestic and industries. However, the explosive nature of LPG makes requirement of reliable and efficient gas sensors indispensable (Ihokura and Watson, 1994; Vlachos et al., 1996; Korotcenkov, 2007; Korotcenkov et al., 2003, 2004; Pagnier et al., 2000; Gupta et al., 2005; Dewan et al., 2007; Haridas et al., 2008; Madhusudhana Reddy and Chandorkar, 1999). Major constituents of LPG include butane (70-80 percent), propane (5-10 percent) and propylene, butylene, ethylene and methane (1-5 percent). Conductometric metal oxide semiconductor thin films are the most promising devices among solid state chemical sensors, due to their small dimensions, low cost, low power consumption, and high compatibility with microelectronic processing. It is widely accepted that the key process in the response of the semiconductors to reducing gases involves the modulation of the concentration of adsorbed oxygen species such as O 22 and O 2 . Although many different oxides have been investigated for their gas sensing properties but commercially available gas sensors are made mainly of SnO 2 in the form of thick films, porous pellets, or thin films. The effects of the microstructure, namely, the ratio of surface area to volume, grain size, and pore size of the metal oxide particles, as well as the film thickness of the sensor are well recognized. Lack of long term stability has until today prevented wide applications of this type of sensor. The most recent research has been devoted towards nanostructured oxides, since reactions at grain boundaries and complete depletion of carriers in the grains can strongly modify the material transport properties. Unfortunately, the high temperature required for the surface reactions to take place induces a grain growth by coalescence and prevents the achievement of stable materials (Comini et al., 2002). The current issue and full text archive of this journal is available at www.emeraldinsight.com/0260-2288.htm Sensor Review 32/2 (2012) 163–169 q Emerald Group Publishing Limited [ISSN 0260-2288] [DOI 10.1108/02602281211209455] 163