Enhanced Acetone-Sensing Performance of a Bilayer Structure Gas Sensor Composed of a ZnO Nanorod Top Layer and a ZnFe2O4 Nanoparticle Decorated ZnO Nanorod Bottom Layer

In this study, we report a high-performance acetone gas sensor utilizing a bilayer structure composed of a ZnO nanorod top layer and a ZnFe2O4 nanoparticle-decorated ZnO nanorod bottom layer. ZnO nanorods were synthesized via a water-bath method, after which the ZnFe2O4 nanoparticle-decorated ZnO nanorods were prepared using a simple immersion and calcination method. SEM and TEM revealed the porous morphology of the samples and the formation of ZnO-ZnFe2O4 heterojunctions. XPS analysis demonstrated an increase in oxygen vacancy content with the introduction of ZnFe2O4 nanoparticles. Compared to pure ZnO nanorods, ZnFe2O4-decorated ZnO nanorods showed a 3.9-fold increase in response to 50 ppm acetone. Covering this layer with ZnO nanorods further increased the response by an additional 1.6 times, and simultaneously enhanced the selectivity to acetone. The top layer improves gas sensing performance by introducing heterojunctions with the bottom layer, partially blocking acetone gas at the bottom layer to facilitate a more complete reaction, and filtering ethanol interference.