Enhanced interfacial charge-transfer-driven acetone sensing using hierarchical bolt-shaped ZnO@Au heterostructures

Miniaturized volatile organic compound (VOC) sensors capable of low-temperature operation are essential for next-generation environmental monitoring and diagnostic healthcare. In this study, we report the synthesis of distinct ZnO architectures-ranging from low-dimensional nanorods and microrods to complex, hierarchical hollow-core bolt-shaped microstructures-via a scalable, template-free colloidal chemical route. These controlled geometrical variations enabled a systematic evaluation of the influence of size, porosity, and surface architecture on the acetone-sensing performance. The hollow-core bolt-shaped ZnO microstructures exhibited superior sensing behavior, attributed to their high surface area and accessible internal voids that facilitate efficient diffusion and adsorption–desorption of acetone molecules. To achieve state-of-the-art performance, the ZnO microstructures was functionalized with ultra-fine, non-agglomerated Au nanoparticles. The resulting ZnO@Au heterostructures exhibit a synergistic enhancement originating from the interplay between electronic and chemical sensitization. Specifically, the formation of Schottky barriers at the Au–ZnO interface induces a robust interfacial charge redistribution, significantly thickening the electron depletion layer. Consequently, the heterostructure-based sensor yielded a five-fold enhancement in response toward 200 ppm acetone relative to pristine ZnO. This work provides a mechanistic framework for the design of hybrid chemiresistive architectures, highlighting the critical role of interfacial engineering and hierarchical diffusion pathways in next-generation VOC detection. • Developed template free route to develop hierarchical bolt-shaped structures. • Hollow core architectures enhance sensing by reducing gas diffusion resistance. • Au-ZnO Schottky junctions induce charge redistribution and extend depletion layer. • Noble-metal spillover and barrier modulation enhance oxygen ionosorption on ZnO. • Achieved five-fold response enhancement to 200 ppm at low operating temperature.