Gas-sensing performance enhancement in ZnO nanostructures by hierarchical morphology

We report a successful synthesis of ZnO nanoparticles, nanosheets and nanoflowers via a simple hydrothermal process, and investigate comprehensively their gas-sensing performances. Of all the nanostructures, nanoflowers are found to show the most superior gas-sensing properties, e.g., highest gas response, shortest response and recovery time, excellent selectivity, and good repeatability and stability, which are attributed to their unique three-dimensional hierarchical structures with the largest specific surface area arising from remarkable amount of petals and pores. Further, the sodium citrate is found to be the key to producing such unique flower-like architecture, which can be understood upon the nucleation and self-assembly of building blocks of ZnO. Such development of the hierarchical architectures may open up an avenue to further enhance the gas-sensing performances of ZnO nanostructures for the on-site detection of the gases of interest.