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 ZnCo 2 O 4 . To expound it, ZnCo 2 O 4 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/ZCo 2 O 4 HNSs showed superior isoprene-sensing performance to the bare ZnCo 2 O 4 HNSs, especially of higher sensitivity (5.9 vs 1.3 for 1000 ppb isoprene at 260 °C) and better selectivity (S isoprene/ammonia : 3.3 vs 1.2). Besides, the Ag/ZnCo 2 O 4 sensor also showed low limit of detection (5 ppb) and good stability. These features make the Ag/ZnCo 2 O 4 sensor a promising candidate for human breath analysis. The results of first principle calculations reveal that the improved isoprene sensitivity and selectivity of Ag/ZnCo 2 O 4 HNSs can be attributed to the enhanced isoprene absorption on ZnCo 2 O 4 HNSs after Ag decoration.