Fabrication and good ethanol sensing of biomorphic SnO2 with architecture hierarchy of butterfly wings

Using super-hydrophobic butterfly wings as templates, we developed an aqueous sol-gel soakage process assisted by ethanol-wetting and followed by calcination to fabricate well-organized porous hierarchical SnO2 with connective hollow interiors and thin mesoporous walls. The exquisite hierarchical architecture of SnO2 is faithfully replicated from the lightweight skeleton of butterfly wings at the level from nano- to macro-scales. On the basis of the self-assembly of SnO2 nanocrystallites with diameter around 7.0 nm, the interconnected tubes (lamellas), the fastigiated hollow tubers (pillars) and the double-layered substrates further construct the biomorphic hierarchical architecture. Benefiting from the small grain size and the unique hierarchical architecture, the biomorphic SnO2 as an ethanol sensor exhibits high sensitivity (49.8 to 50 ppm ethanol), and fast response/recovery time (11/31 s to 50 ppm ethanol) even at relatively low working temperature (170 degrees C).