Dual engineering of helical SnO2 nanostructures and Co2+/Co3+ valence state for ultra-selective acetone detection

Acetone (CH 3 COCH 3 ) is a key biomarker for non-invasive diagnosis and real-time monitoring of diabetes mellitus, motivating the development of sensing platforms capable of highly sensitive, selective, and humidity-robust detection. Here, we report Co 3 O 4 -decorated SnO 2 nanohelices (CSNHs) synthesized via sequential glancing-angle deposition (GLAD) as a structurally and electronically engineered framework for high-performance acetone sensing. The optimized 2-nm-thick CSNHs achieve an ultrahigh response of 859.8 to 50 ppm acetone at 350 °C—an 8-fold enhancement over pristine SnO 2 nanohelices—along with excellent repeatability (coefficient of variation, CV ≤ 5%) and ultralow theoretical detection limits of 14 ppt (dry) and 175 ppt at 80% relative humidity. Structural analysis and finite element method (FEM) simulations reveal that the helical SnO 2 architecture provides extensive inflection points and structural bottlenecks, enabling frequent gas–surface collisions and pronounced modulation of double Schottky barriers. X-ray photoelectron spectroscopy (XPS) analysis confirms that Co 3 O 4 nanoparticle decoration forms p–n heterojunctions and induces interfacial charge transfer, partial Co 3+ to Co 2+ reduction, and oxygen-vacancy generation, thereby enriching chemisorbed oxygen species and facilitating oxygen spillover onto SnO 2 . These synergistic structural and catalytic effects collectively endow CSNHs with exceptional acetone sensing capabilities, offering a promising route toward next-generation breath-based diagnostics. • Co 3 O 4 -decorated SnO 2 nanohelices were fabricated via sequential GLAD. • The sensor exhibits a high response of 859.8 to 50 ppm acetone. • Ultralow detection limits of 14 ppt (dry) and 175 ppt (80% RH) were demonstrated. • Helical geometry maximizes gas-surface collision frequency via FEM analysis. • XPS confirms Co 3+ to Co 2+ reduction facilitates oxygen vacancy formation.