Selectively enhanced sensing performance for oxidizing gases based on ZnO nanoparticle-loaded electrospun SnO2 nanotube heterostructures

In this work, we present gas sensors based on ZnO nanoparticle-loaded electrospun SnO2 nanotube (ZnO/SnO2) n-n heterostructures (HSs) synthesized by electrospinning combined with facile thermal decomposition. The sensing properties of the pristine SnO2 nanotubes (NTs) and ZnO/SnO2 HSs were investigated toward the representative oxidizing (NO2) and reducing (H-2, CO) gases. Results show that the as-prepared ZnO/SnO2 HSs exhibit selectively enhanced and diminished sensing performances for oxidizing and reducing gases, respectively. These phenomena are closely associated with the modulation of the local depletion layer on the surface of SnO2 nanoparticles (NPs) caused by charge transfer at the heterojunctions due to work function difference. A modified grain boundary-controlled sensing mechanism is proposed to describe charge transport in sensing layers based on the contact potential barriers between nanoparticles. Our study indicates that the selection of material system and their synergism are keys to the effective design of gas sensors with semiconducting metal oxide HSs.