Synthesis of novel porous ZnO octahedrons and their improved UV-light activated formaldehyde-sensing performance by Au decoration

Light-illumination assistance has emerged as an important strategy to develop metal oxide semiconductor (MOS) based gas sensor with low working temperature. Here, we report a facile and reliable sacrificial template method for novel ZnO porous octahedrons (POHs), in which ZnC2O4 center dot 2H(2)O solid octahedrons were pre-synthesized through a simple precipitation reaction at room temperature and then used as sacrificial template for ZnO POHs. Au-decorated ZnO POHs were also prepared by introducing Au species in the precipitation step. The two kinds of POHs are about 2-4 mu m in size and constructed by a great number of loosely stacked nanoparticles with the size about 30-50 nm. Numerous nanometer-sized pores are in situ created in the POHs during the decomposition of oxalate sacrificial template. Under the UV-light (similar to 365 nm) irradiation, the sensor fabricated with Au-decorated ZnO POHs exhibits an enhanced response towards formaldehyde at room temperature as compared with pure ZnO POHs. Besides of higher response, the Au/ZnO sensor also exhibits a good linearity within 50-800 ppm formaldehyde, as well as good selectivity and repeatability, demonstrating its promising application in formaldehyde detection. The UV-light activated gas-sensing mechanism is also discussed.