Au Decorated ZnO hierarchical architectures: Facile synthesis, tunable morphology and enhanced CO detection at room temperature

Abstract

A highly selective and sensitive gas sensing material was prepared by decorating gold (Au) nanoparticles on zinc oxide (ZnO) nanostructure. First, zinc oxide architectures were synthesised through facile one-pot hydrothermal synthesis route by using zinc acetate as the metal precursors, ethanolamine as the organic Lewis base and water as the reaction medium. The versatile zinc oxide architectures such as (i) nanostars (ZNS), (ii) marigold flower (ZMF), (iii) nanorods assembled flower (ZNF) and (iv) nanorods (ZNR) were successfully synthesised by the controlled variation of the reaction medium mole ratio. The crystal structure and morphological evaluation of the as prepared material were investigated in detail by several analytical techniques, and the findings are consistent with each other. The carbon monoxide (CO) sensing ability of the as prepared materials was carried out at different sensing temperature (Ts≤300°C) and at different gas concentration (5–1000ppm). Gas sensing study clearly shows that the sensor responses are found to be morphology and surface area dependent. Among all the zinc oxide nanostructures, nanostars exhibits excellent sensitivity (SR∼31 toward 5ppm) at the optimized sensing temperature of 275°C. Further, to improve the sensing characteristics and to reduce the operating temperature, different wt% of gold nanopartilces were decorated on the surface of zinc oxide nano-stars by solution impregnation technique. Surface decoration of only 3wt% gold nanoparticles incorporated zinc oxide nanostars exhibits enhanced sensing response (SR ∼15 toward 50ppm) at 35°C with an excellent response (ΓRES ∼8s) and recovery (ΓREC ∼15s) time. Sensor also posses excellent selectivity toward CO compare to other interfering gases such as methanol, ethanol, acetone and hydrogen.