Highly sensitive and selective dimethylamine sensors based on hierarchical ZnO architectures composed of nanorods and nanosheet-assembled microspheres

Hierarchical ZnO architectures composed of nanorods and nanosheet-assembled microspheres were successfully synthesized through a one-pot, cost-effective and environment-friendly hydrothermal process at low-temperature. X-ray diffraction and Raman spectroscopy indicated that the ZnO architectures are well-crystallized in a hexagonal wurtzite structure. Electronmicroscopy observations and N2 adsorption–desorption results confirmed that plenty of meso-pores imbed in the nanosheets and considerable interspaces exist among adjacent nanosheets. Photoluminescence analysis showed that abundant intrinsic defects (52.5% electron donor defects and 47.5% electron acceptor ones) are present on the ZnO crystal surfaces. X-ray photoelectron spectrometry revealed that a large mount of oxygen species (23.77%) chemisorbs on the surface of the as-prepared ZnO structures. The gas sensing property of the ZnO architectures displayed high response, fast response-recovery, good selectivity and long-term stability to 1–1000 ppm dimethylamine at 370 °C. Especially, even 1 ppm dimethylamine could be well detected with a high response value (S = 16.8). More interestingly, dimethylamine could be easily distinguished from a trimethylamine, methylamine or ammonia atmosphere with high selectivity. The high dimethylamine response is mainly attributed to the high contents of electron donor defects ( Z n i and V O ) on the ZnO surfaces.