Highly responsive n-butanol gas sensor based on double-shell ZnO hollow microspheres

• A scalable technique incorporating a homogeneous spherical carbon template was used to fabricate D-ZnO sensing materials. • The nesting effect of the double-shell structure and the exposure of multiple active surface sites enhanced the gas-sensitive properties of the materials. • The D-ZnO sensor enables detection of ppb grade n-butanol at 240 °C. The fabrication of gas sensors based on metal oxide semiconductors (MOS) with high sensitivity and low detection limits is a crucial research domain. Modulation of microstructural features is a critical strategy to enhance gas sensing performance, owing to its controllability and inherent design flexibility. The double-shell structure amplifies active surface sites and nested effects, further heightening gas-sensor interaction for escalated adsorption efficiency and reaction rates. In this paper, we fabricated hierarchical double-shell ZnO hollow microsphere (D-ZnO) sensors via a scalable technique, incorporating uniformly spherical carbon templates. These D-ZnO-based sensors demonstrated a high response (32.42) to 100 ppm n-butanol and achieved a low detection limit (DL) of 96 ppb at the optimized temperature of 240 °C. Such excellent gas sensing performance of D-ZnO can be attributed to the unique spatial structure of hierarchical double-shell for the modulation of gas diffusion pathways and collision frequency.