SnO ₂ -ZnO-Fe ₂ O ₃ tri-composite based room temperature operated dual behavior ammonia and ethanol sensor for ppb level detection

In this paper, we present a novel room temperature (RT) operated SnO2-ZnO-Fe2O3 based tri-composite analyte sensor with dual behavior having detection ability of up to ∼1 ppb with a substantial % response (R) to detect ammonia and ethanol vapors. The tri-composite is synthesized via a sol-gel spin coating technique and characterized using X-ray diffraction (XRD) for structural analysis. Fourier transform infrared spectroscopy (FTIR) and Raman results are used to confirm tri-composite formation. Further, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) results are used for examining the detailed surface morphology and structural and topographical characteristics of the tri-composite. The sensing characteristics are monitored from 1 ppb to 50 ppm for ammonia detection and 1 ppb to 25 ppm for ethanol detection at RT (∼27 °C) under ∼45% relative humidity (RH) conditions. This dual sensing behavior (based on change in resistance under ammonia and ethanol exposure) of the sensor is used to differentiate and detect the presence of ammonia (resistance decreases) and ethanol (resistance increases) with high %R within a few seconds. In addition, the sensor showed excellent sensing characteristics under moist conditions (up to 85% RH) and outstanding reproducibility, and was found to be highly stable, selective and specific towards the target analytes. This work not only reports a RT operated ppb level ammonia and ethanol sensor, but also explores the novel SnO2-ZnO-Fe2O3 tri-composite along with a scientific approach towards multi-composite nanostructures to develop analyte sensors.