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Author: search.filters.author.Jadsadapattarakul, DamrongsakSubject: search.filters.subject.[0 1 0] Preferred orientation

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    Improved selectivity, response time and recovery time by [0 1 0] highly preferred-orientation silicalite-1 layer coated on SnO2 thin film sensor for selective ethylene gas detection
    (2010-01-29)
    Jadsadapattarakul, Damrongsak
    ;
    Thanachayanont, Chanchana
    ;
    Nukeaw, Jiti
    ;
    Sooknoi, Tawan
    In this work, sensing response, response time and recovery time for selective ethylene gas detection were improved by coating a layer of [0 1 0] highly preferred-orientation silicalite-1 polycrystals on SnO<inf>2</inf> thin film sensors. The sensors were prepared by primarily depositing SnO<inf>2</inf> on borosilicate glass substrates using ultrasonic spray pyrolysis technique. Conventional and [0 1 0] preferred orientations of silicalite-1 layers were then directly coated on the SnO<inf>2</inf> thin film sensors by hydrothermal crystallization technique with different gel compositions. The silicalite-1/SnO<inf>2</inf> thin film sensors were calcined at 550 °C in dry air. The crystal structure and surface morphology of SnO<inf>2</inf> and silicalite-1 layers were characterized by XRD and SEM techniques. XANES and TPR were used to verify oxidation state and reduction temperature of the SnO<inf>2</inf> thin film sensors, respectively. The interaction of C<inf>2</inf>H<inf>4</inf> and H<inf>2</inf>O with silicalite-1 was determined by TPD. The sensing performances, such as selectivity, dynamic range, response time and recovery time were evaluated for the C<inf>2</inf>H<inf>4</inf> and H<inf>2</inf>O. The results showed that the incorporated silicalite-1 layers readily improve the C<inf>2</inf>H<inf>4</inf> selectivity and dynamic range by preferential adsorption of C<inf>2</inf>H<inf>4</inf> molecules on the silicalite-1 filtering layers. The response time and recovery time for the [0 1 0] highly preferred-orientation silicalite-1/SnO<inf>2</inf> thin film sensor (t<inf>90%</inf>, 14 and 144 s) were shorter than those of the conventional one (t<inf>90%</inf>, 25 and 208 s). It is suggested that the [0 1 0] preferred-orientation silicalite-1, with a pore direction perpendicular to SnO<inf>2</inf> thin film surface, can accelerate the molecular diffusion and reduce the diffusion pathway of ethylene to the sensing film. © 2009 Elsevier B.V.