ALD-assisted synthesis of V2O5 nanoislands on SnO2 nanowires for improving NO2 sensing performance

Abstract

Anchoring nanoparticles on the surfaces of metal oxide nanosensors is a promising strategy to improve sensing performance. However, several issues regarding the surface coverage and uniform distribution of nanoislands over base sensing materials have yet to be resolved using conventional synthetic routes. Herein, we present a viable alternative for the decoration of V2O5 nanoislands on SnO2 nanowires: a new two-step process that combines atomic layer deposition (ALD) and successive thermal post-treatment. This process enables us to control the surface coverage of V2O5 nanoislands by varying the number of ALD cycles and to homogeneously disperse the nanoislands on the SnO2 nanowire surfaces. The NO2 response of the V2O5-decorated SnO2 sensor improved as the number of ALD-V2O5 cycles increased; the highest response, obtained by the sensor prepared with 50 ALD-V2O5 cycles, was more than 50 times greater than that of the pristine SnO2 nanowires. However, the sensing performance degraded beyond 50 ALD-V2O5 cycles as there was an oversupply of V2O5 nanoislands. Based on density functional theory calculations, we determined that V2O5 nanoisland loading is in competition with the exposed SnO2 surface to increase sensing performance, which implies that the surface coverage of V2O5 nanoislands must be precisely optimized.