On optimization of electrospun SnO2-ZnO nanofibers for low concentration ethanol sensing

One dimensional (1-D) nano-structures are expected to be the most suitable candidates for analyte sensing, owing to their high surface area to volume ratio. In the present work, SnO2-ZnO composite solutions with different viscosity have been synthesized and thickness of electrospun nanofibers is optimized to obtain uniformly distributed nanofibers without formation of bead-like structures. The nanofibers in the range of 75 to 250 nm have been successfully deposited on Interdigitated gold electrode (IDGE) for ethanol analyte sensing. The effect of the fiber width on the analyte sensing properties of the nanofibers has been studied to provide the optimum fiber thickness for ethanol sensing. The SnO2-ZnO nanofibers-based sensor, with the average fiber thickness 106.2 nm, has shown response of 41.66% towards 0.5 ppm ethanol with fast response time of 11 s. The crystallite size of the SnO2-ZnO composite is observed to 44.38 nm. The sensor has exhibited significant and appreciable selectivity towards ethanol as compared to other tested volatile organic compounds (VOCs). The crystallographic structure, valence states analysis and surface morphological analysis has been provided using XRD, XPS and FESEM characterization. The formation of n–n heterojunction further enhances the response of the sensor and the ethanol analyte sensing mechanism based on redox reaction at the surface and heterojunction interface is also presented.