Hierarchical porous SnO2 topologically transferred from tin oxalate for fast response sensors to trace formaldehyde

To avoid the destruction of hierarchical porous (HP) structures during fabrication process of sensors, a novel integration of materials synthesis and sensors manufacture was successfully realized by introducing the topological transformation approach (TTF) on basis of a facile, low-cost, conventional process including screen printing and calcination. By employing this method, HP-SnO₂ micro-rods assembled by nanoparticles were prepared in situ on the co-planar sensors´ surface. The as-prepared HP-SnO₂ sensor exhibits not only fast response (~4.3 s), which is one-tenth of response time of the commercial one, but also high sensitivity (Ra/Rg = 3.86) to formaldehyde at 1 ppm.