Porosity controlled 3D SnO2 spheres via electrostatic spray: Selective acetone sensors

Abstract

Tailoring of semiconducting metal oxides (SMOs) nanostructures with high porosity is of importance for enhanced gas sensing performance. Hierarchically-assembled SMOs possess high surface area but often suffer from low porosity. Here, bimodal pore-loaded hierarchical SnO2 (PH-SnO2) spheres were successfully synthesized via electrostatic spraying method (e-spraying) combined with colloidal templating route using polystyrene beads. The resulting porous PH-SnO2 spheres were used as sensing layers for detection of acetone, which exhibited about 20 % enhanced response compared with hierarchical SnO2 (H-SnO2) spheres without pores. In addition, e-spraying is a fascinating technique for uniform catalytic functionalization through a simple dispersion of catalytic nanoparticle (NPs) in the e-spraying solution to improve the sensing performance. As a result, the Pt-functionalized PH-SnO2 (Pt-PH-SnO2) spheres showed dramatically improved acetone detection capability with a response (R-air/R-gas) of 44.83 at 5 ppm as compared to PH-SnO2 spheres (R-air/R-gas= 6.61) as well as superior selectivity. In this work, the unique combination of e-spraying and PS templating route paves the way for robust and facile synthetic method for bimodal pore loaded 3D hierarchical SMOs, and demonstrates the feasibility for application in exhaled breath sensors.