Synthesis of Ag-Loaded ZnCo₂O₄ Hierarchical Nanospheres With Improved Isoprene Sensitivity

Isoprene is a typical biomarker in human exhaled breath and can be used to diagnose chronic liver disease (CLD). However, its stable alkene structure hinders easy detection on metal–oxide–semiconductor (MOS) sensor because of the low sensitivity. Herein, we reported a surface modification strategy to boost the isoprene sensitivity of ZnCo2O4. To expound it, ZnCo2O4 hierarchal nanospheres (HNSs) were prepared by a solvothermal route and then decorated with Ag nanoparticles via a photoreduction method. Benefiting from the outstanding spillover effect of Ag as well as the increased oxygen vacancy, the obtained Ag/ZCo2O4 HNSs showed superior isoprene-sensing performance to the bare ZnCo2O4 HNSs, especially of higher sensitivity (5.9 versus 1.3 for 1000-ppb isoprene at 260 °C) and better selectivity (Sisoprene/ammonia: 3.3 versus 1.2). Besides, the Ag/ZnCo2O4 sensor also showed the low limit of detection (LOD) (5 ppb) and good stability. These features make the Ag/ZnCo2O4 sensor a promising candidate for human breath analysis. The results of first principal calculations reveal that the improved isoprene sensitivity and selectivity of Ag/ZnCo2O4 HNSs can be attributed to the enhanced isoprene absorption on ZnCo2O4 HNSs after Ag decoration.