Zeolite Modified Vanadium Pentoxide Sensors for the Selective Detection of Volatile Organic Compounds
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Zeolite Modified Vanadium Pentoxide Sensors for the Selective Detection of Volatile Organic Compounds David C. Pugh1, Ivan P. Parkin1 Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ
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ABSTRACT Exposure to volatile organic compounds can lead to asphyxiation, pneumonia like conditions, comas, seizures and irreversible lung, kidney and central nervous system damage. Volatile organics are additionally extremely flammable and explosive, making their early detection in the immediate environment increasingly important. Metal oxide semiconductor (MOS) gas sensors present a potential technology to detect such gases. Metal oxide semiconducting (MOS) gas sensors represent a cheap, robust and sensitive technology for detecting volatile organic compounds. An array of five thick film MOS gas sensors was fabricated, based on vanadium pentoxide inks. Production took place using a commercially available screen printer, a 3 x 3 mm alumina substrate containing interdigitated electrodes and a platinum heater track. V2O5 inks were modified using zeolite beta, zeolite Y, mordenite & ZSM5 admixtures. Sensors were exposed to three common reducing gases, namely acetone, ethanol, and toluene, and a machine learning technique was applied to differentiate between the different gases. Sensors produced strong responses to all gases. Zeolite modified sensors were found to increase the responsiveness of the sensors compared to umodified V2O5 in a number of cases. Machine learning techniques were incorporated to test the selectivity of the sensors. A high level of accuracy was achieved in determining the class of gas observed. INTRODUCTION Previous research on V2O5 as a gas sensing material has focused on the use of nanofibres[1] and nanorods[2]. These are thin film sensors that show responses to ethanol and other species with hydroxyl functional groups. The response of these sensors is quite low (R0/R ≈ 1.5 to 100 ppm of ethanol) when compared with other more conventional gas sensitive semiconductors, such as WO3 and SnO2. The purpose of this study was to investigate the influence of zeolite admixtures in V2O5 sensors, and to use an array of zeolite modified sensors in combination with machine learning techniques to identify specific classes of gas at various concentrations. EXPERIMENT Vanadium pentoxide was used, as supplied by BDH Chemicals (Product code: 30565). All zeolites were supplied by zeolyst. Zeolite beta (CP 811E-75), zeolite Y (CVB 600) and ZSM-5 (CVB 2802) were supplied in their protonated form. Mordenite (CVB 2802) was supplied as NH4-Mordenite. This was converted to H-Mordenite as described by Bordiga et.al.[3] HMordenite was heated to 675°C for one hour.
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All sensors were produced by screen printing metal oxide inks onto 3 x 3 mm alumina substrate tiles, containing
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