Synthesis and Characterisation of ZnO–Ag Thin Films and Their use as Ammonia Sensors

Abstract

This study involves the preparation of colloidal silver (Ag) nanoparticle solution using Turkevich method. Specifically, the solution is mixed with the zinc nitrate hexahydrate and hexamethylenetetramine solution with various volume ratios (e.g. 50, 70 and 90 AgNPs %V) to deposit zinc oxide (ZnO)–Ag thin films on glass substrates at 350 °C using chemical spray pyrolysis technique. Then, these thin films are used to measure the sensitivity of ammonia (NH3) at room temperature (30 °C–32 °C). The thin films formed by this technique have been characterised by the following measurements: FE-SEM, XDR, AFM and EDXA; whereas, AFM, UV-Visible spectrophotometer and FT-IR spectrophotometer have been used to characterise the prepared Ag nanoparticles. The average size of ZnO–Ag nanoparticles formed on glass substrates is within the range of 68.93–86.64 nm, whereas the average size of Ag nanoparticles formed through Turkevich method is 48.9 nm. The XRD measurements show the wurtzite hexagonal and face centred cubic crystal structure of ZnO and Ag, respectively. The thin film that contains 50 %V of Ag has the highest gas sensitivity (69%). The high sensitivity of the ZnO–Ag sensor at room temperature is an indicator of the high efficiency of NH3 gas sensing.