Ojha, B. / Aleksandrova, M. / Schwotzer, M. / Franzreb, M. / Kohler, H. (2023)

Sensing and Bio-Sensing Research, 2023, 100558, doi.org/10.1016/j.sbsr.2023.100558

Abstract

For a comparative study of the gas sensing performance to dissolved volatile organic compounds (VOCs), the SnO2-powders have been prepared using two different fabrication routes; the flame-spray-pyrolysis (FSP) and the sol-gel (SG) route; and were admixed with the same additive-powders (alumina, YSZ, and NASICON). The morphology of the two different SnO2/additive families were investigated by ESEM analysis and Energy-dispersive X-Ray Spectroscopy (EDS). Both SnO2/additive material families were separately deposited as thick-film-layers on two four-fold sensor-chips which were simultaneously thermo-cyclically operated in a measurement cell combined with a carrier gas probe, which enables sensing tests with evaporated VOCs (acetic acid, propionic acid, ethanol, acetone) dissolved in water. The resulting Conductance-over-Time-Profiles (CTPs) highlight better sensitivities of most of the FSP-layers to all the analytes compared to the SG-prepared layers. Furthermore, the CTP shapes of the FSP layers show clearly enhanced specificity representing the individual analyte components. This was interpreted to be the consequence of the extremely fine, scarcely agglomerated grain morphology of FSP-prepared powders and their very narrow grain size distribution which provide better conditions for enhanced gas specific surface reactions. Results promise a better chemical analysis capability of dissolved VOCs by numerical analysis of the CTP of FSP-prepared gas sensitive layers.

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