Natural fuel assisted biogenic synthesis of ZnO nanoparticles: Evaluation of crystallite size, optical band gap and gas sensing ability

Abstract

Biogenic combustion approach has been used to synthesize ZnO nano particles utilizing grape juice as bio-ingredient. The prepared sample is subjected to heat-treatment at 350°C and 450°C. XRD patterns revealed that the phase is changed from Zn(OH)₂ to ZnO with the heat treatment showing the improvement in the crystallinity. The average crystallite size of ZnO nanoparticles heat-treated at 350°C and 450°C is found to be 9 and 17 nm. The presence of different functional groups has been identified by FTIR analysis. The optical band gap of heat-treated ZnO nanoparticles is in between 3.19 and 3.11 eV. The particle size of the heat-treated (450°C) ZnO nanoparticles estimated from SEM micrograph is found to be 25.3 nm and is very close to the crystallite size. The elemental analysis established the stoichiometry of ZnO nanoparticles. The sensor films fabricated from heat treated ZnO nanoparticles show good sensor response towards CO₂ gas detection. The response times of all the produced sensors vary between 9 and 31 seconds, whereas the restoration times range from 11 to 64 seconds.