Sol–gel derived (Sr,Ni)Al2O4 composites for benzene and toluene sensors

doi:10.1016/j.matlet.2007.04.033

Materials Letters

Volume 61, Issue 30, December 2007, Pages 5213-5216

https://doi.org/10.1016/j.matlet.2007.04.033 Get rights and content

Abstract

Strontium(II) added NiAl₂O₄ composites prepared by sol–gel technique was utilized for the detection of benzene and toluene vapors. XRD, SEM and BET measurements were employed to identify the structural phases, surface morphology and surface area. The (Sr,Ni)Al₂O₄ composites sintered at 900 °C were subjected to dc resistance measurements in the temperature range of 30–200 °C to study the benzene and toluene vapor detection characteristics. The maximum sensitivity of the composites was obtained at 150 °C. An increase in the sensitivity was observed with increase in benzene and toluene concentration from 100 to 5000 ppm at 150 °C. Among the different compositions, the (Sr,Ni)Al₂O₄ composites with higher strontium content (NiSA5) showed the best sensitivity towards benzene and toluene vapor detection.

Introduction

The increased concern about environmental protection has led to continuous expansion in searching for new volatile organic compounds (VOC) sensor materials [1]. Semiconducting oxides have emerged as economical sensors for monitoring toxic vapors than the other available organic and polymeric material comparatively [2], [3]. The sensitivity of these sensors to gases depends on the microstructure, which can be achieved by adopting special techniques of preparation or by doping impurities [4]. The sol–gel technique is considered as the most promising technique for the preparation of metal oxides [5], [6] and among the VOCs, benzene and its derivatives were confirmed to cause diversiform cancers [7]. The sensing behavior of benzene and toluene by metal oxides like SnO₂ [8], TiO₂ [9], doped ZnO [10] and WO₃ [11] focused our interest to utilize mixed metal composites containing metal aluminates for the above purpose. Though magnesium aluminate spinels were used as humidity sensors [12], [13] there are no literatures found regarding nickel aluminate and Sr(II) added nickel aluminates for the purpose of sensing VOCs. In the present paper the newly developed Sr(II) added nickel aluminate composites by sol–gel technique were investigated for their sensing behavior towards benzene and toluene vapor.

Section snippets

Experimental

Sr(II) added NiAl₂O₄ composites with the molar ratios of Ni:Sr (1.0:0.0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, 0.0:1.0) keeping the aluminium molar ratio as a constant were labeled as NiSA1, NiSA2, NiSA3, NiSA4, NiSA5 and NiSA6 respectively. The composites in the form of pellets were sintered at 900 °C for 5 h. The structural studies were carried out using a Philips X’pert diffractometer and the surface morphology was determined by a Leo-Jeol scanning electron microscope. The nitrogen

N₂ adsorption/desorption isotherms

The nitrogen adsorption/desorption isotherms of NiSA1, NiSA6 and NiSA5 (mixed metal composite with maximum sensitivity) were carried out. The large increase in the nitrogen adsorption for NiSA1 at the higher relative pressures (Fig. 1) indicates that it contains only a mesoporous character. While the nitrogen adsorption for NiSA5 and NiSA6 considerably increased at a low relative pressure indicating the formation of micropores in addition to the presence of mesopores. The composite NiSA1

Conclusion

A study on the benzene and toluene detection characteristics of Sr(II) added NiAl₂O₄ composites prepared by sol–gel technique has been carried out. It was observed that the sensitivity of the composites to benzene and toluene was higher at 150 °C, and was found to increase with benzene and toluene concentration. The increase in surface area and porosity with the formation of micropores makes the composite NiSA5 to be a good candidate for sensing applications as evidenced by its higher

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Sol–gel derived (Sr,Ni)Al2O4 composites for benzene and toluene sensors

Abstract

Introduction

Section snippets

Experimental

N2 adsorption/desorption isotherms

Conclusion

Sens. Actuators, B, Chem.

Sens. Actuators, B, Chem.

Mater. Lett.

Sens. Actuators, B, Chem.

Sens. Actuators, B, Chem.

Mater. Chem. Phys.

Sens. Actuators, B, Chem.

Sol–gel derived (Sr,Ni)Al₂O₄ composites for benzene and toluene sensors

N₂ adsorption/desorption isotherms