SnO₂ nanowire gas sensors for detection of ppb level NOx gas

Until now, SnO₂ nanowires have been directly grown on alumina substrates with Au or Au-coated Pt electrodes by a thermal evaporation method using Sn or SnO₂ powders under vacuum. However, in this study, SnO₂ nanowires were successfully synthesized on the Pt phase of an alumina substrate by a thermal evaporation method using dibutyltin oxide [DBTO, (C₄H₉)₂SnO] even at atmospheric pressure, resulting in nanowire networks between the Pt phases. Ar with 1% O₂ was used as carrier gas with a flow rate of 100 mL/min at 900 °C (heating rate of 25 °C/min). The SnO₂ nanowires consisted of straight and branched nanowires, and exhibited a SnO₂ phase with a tetragonal structure. Both the DBTO and evaporation temperature play an important role on the synthesis of SnO₂ nanowires at atmospheric pressure. The SnO₂ nanowire sensor fabricated by an evaporation method showed a sensor response of ~ 500 for 0.05 ppm of NO₂, being ~ 10 times greater than that of a SnO₂ nanoparticle sensor. Furthermore, the SnO₂ nanowire sensor showed excellent repeatability and selectivity for NO₂ in the presence of SO₂, Cl₂, and H₂S.