Controllable synthesis and gas response of biomorphic SnO2 with architecture hierarchy of butterfly wings

Well-organized porous hierarchical SnO2 with connective hollow interiors has been synthesized by using butterfly wings as templates via an aqueous sol–gel soakage process followed by calcination. The biomorphic porous hierarchy was constructed by a layer of flexural wall that was assembled by SnO2 nanocrystallites with diameter of around 7.0 nm. The wall thickness was tunable under the control of the impregnants concentration as well as the immersing time. The biomorphic SnO2 showed good sensing to ethanol and formaldehyde, due to its small nanocrystalline building blocks and unique porous hierarchical architecture. More interestingly, the response was found to be controllable and dependent on the wall thickness. The response decreased with the increase of wall thickness, which should be ascribed to the increasing difficulty of gas diffusion to the inner of the walls.