An insulating second filler tuning porous conductive composites for highly sensitive and fast responsive organic vapor sensor

Three-dimensional (3D) vapor grown carbon nanofiber (VGCF)/clay/silicon rubber (SR) (VCS) coated polyurethane (PU) foam composites were fabricated by a facile dip-coating method. The insulating clay sheets were used as second-phase fillers to tailor the conductive VGCF network in the 3D porous conductive composites. The optimized VCS-coated PU (VCS@PU) foam composites exhibited excellent mechanical elasticity and durability, outstanding acid and alkali resistance, and stable electrical conductivity. Interestingly, vapor response time of the VCS@PU foam composites was strongly dependent the clay content, e.g., from 250 to 15 s for 0 and 1.2 wt% clay, respectively. Furthermore, the VCS@PU foam composites showed good reproducibility and high responsivity (similar to 10(6) resistance change) for a series of solvents (e.g., n-hexane, carbon tetrachloride, and chloroform); and a low detection limit of 1 ppm for n-hexane vapor was achieved. The related mechanisms of highly efficient vapor sensing behaviors were proposed and discussed, and the clay sheets acted as insulating sites among the bridged VGCFs network, inducing rapid destruction of the conductive network when the SR swelled. This work paves a new way for design and development of advanced highly sensitive and fast responsive organic vapor sensors by using an insulating second filler to tune porous conductive structure.