Ordered mesoporous NiFe_2O_4 with ultrathin framework for low-ppb toluene sensing

Highly sensitive and selective detection against specific target gases, especially at low-ppb （part per bil- lion） level, remain a great number of challenges in gas sensor applications. In this paper, we first present an ordered mesoporous NiFe204 for highly sensitive and selective detection against low-ppb toluene. A series of mesoporous NiFe204 materials were synthesized by templating from mesoporous silica KIT-6 and its framework thickness was reduced from 8.5 to 5 nm by varying the pore size of KIT-6 from 9.4 to 5.6 nm, accompanied with the increase of the specific surface area from 134 to 216 m^2 g^-1. The ordered mesoporous NiFe2O4 with both ultrathin framework of 5 nm and large specific surface area of up to 216 m^2 g^-1 exhibits a highest response （Rgas/Ralr-1 = 77.3） toward 1,000 ppb toluene at 230℃ and is nearly 7.3 and 76.7 times higher than those for the NiFe204 replica with thick framework and its bulk counter- part respectively, which also possesses a quite low limit of detection （〈2 ppb）, and good selectivity.

Highly sensitive and selective detection against specific target gases,especially at low-ppb(part per billion)level,remain a great number of challenges in gas sensor applications.In this paper,we first present an ordered mesoporous NiFe_2O_4 for highly sensitive and selective detection against low-ppb toluene.A series of mesoporous NiFe_2O_4 materials were synthesized by templating from mesoporous silica KIT-6 and its framework thickness was reduced from 8.5 to 5 nm by varying the pore size of KIT-6 from 9.4 to 5.6 nm,accompanied with the increase of the specific surface area from 134 to 216 m^2g^(-1).The ordered mesoporous NiFe_2O_4 with both ultrathin framework of 5 nm and large specific surface area of up to 216 m^2g^(-1)exhibits a highest response(R_(gas)/R_(air)-1=77.3)toward 1,000 ppb toluene at 230℃ and is nearly 7.3 and 76.7 times higher than those for the NiFe_2O_4 replica with thick framework and its bulk counterpart respectively,which also possesses a quite low limit of detection(<2 ppb),and good selectivity.