Quantum-sized ZnO nanoparticles synthesized in aqueous medium for toxic gases detection

► Quantum-sized ZnO nanoparticles are synthesized in aqueous medium. ► ZnO is used to detect toxic gases in the atmosphere. ► ZnO sensing material has high sensitivity to NO2 at operating temperature of 290 °C. ► ZnO based sensor exhibits high selectivity to CO and CH4. ► The intrinsic sensing of ZnO arises from stoichiometric defects.