Synthesis of SnO2 quantum dot sensitized LaFeO3 for conductometric formic acid gas sensors

Quantum dots (QDs) with small size are also expected to improve sensing properties of complex metal oxides semiconductors. Herein, SnO2 QDs was adopted to dope and sensitize LaFeO3 for formic acid (HCOOH) gas sensing. In detail, SnO2 QDs was pre-synthesized by a solvothermal reaction and dispersed with LaFeO3 sol-gel precursor followed by calcination treatment. Characterization results found that SnO2 QDs doping enabled LaFeO3 become porous, which was beneficial for the diffusion of gas molecular. The sensing properties of composites of LaFeO3 doped with different amounts of SnO2 QDs were investigated and compared with that of pure LaFeO3 and LaFeO3/SnO2 composites. SnO2 QDs doping largely improve the sensitivity of LaFeO3 to HCOOH. The sensor based on LaFeO3 doped with 2.5 wt% SnO2 QDs exhibited much better sensing performance to HCOOH, and a high response value of 31.5–100 ppm HCOOH and a low detection limit of 1 ppm can be reached at 210 ℃. Its high HCOOH sensing properties might be contributed to the formation of heterojunctions between SnO2 QDs and LaFeO3 and the small size of SnO2 QDs. This work confirms the advantages of QDs sensitization in semiconductor gas sensing.