Structure–Property Control through Sulfur Incorporation into Multicomponent Core–Shell Superstructures for the Detection of 1-Hexanol and Nonanal

Incorporating sulfur into multicomponent core–shell superstructures (CSs) offers a powerful strategy for tailoring their chemical composition, defect structure, and interfacial charge-transfer behavior. Herein, we report sulfur-tuned CSs (CSs-1, 0.12 wt %; CSs-2, 0.24 wt %; CSs-3, 0.36 wt %) composed of nanoscale ZnO, ZnS, Ta 2 O 5, and SiO x that form heterogeneous architectures enabling precise modulation of interfacial chemistry and charge transfer. Increasing the sulfur content promotes progressive ZnS formation, which enlarges the ZnO/ZnS nanoparticle domains from 20–30 nm to 37–52 nm. Upon exposure to volatile organic compounds (VOCs), the direction and magnitude of band bending depend on the donor/acceptor nature of the analyte and the local oxide–sulfide composition. At low sulfur content (0.12 wt %), the shell remains predominantly oxide-rich, with ZnO/Ta 2 O 5 domains and limited sulfur states, resulting in a strong positive contact potential difference (CPD) response toward nonanal (+1100 mV) due to electron withdrawal from an electron-deficient surface. Increasing the sulfur content to 0.24 wt % enriches the shell with ZnS and sulfur-rich domains, altering the ZnO/ZnS and ZnS/Ta 2 O 5 band alignments and generating electron-rich surface states. At 0.36 wt %, nonanal induces a negative CPD shift (−700 mV), indicating reversed charge-transfer behavior. In contrast, 1-hexanol consistently produces positive CPD responses (+445–450 mV) across all compositions, reflecting its weaker electron-withdrawing interaction. N -Decane exhibits weak CPD signals, with small positive shifts in CSs-1 and CSs-2 and a negative shift in CSs-3, consistent with weak van der Waals adsorption and sensitivity to surface polarity. These results demonstrate that sulfur-tuned surface chemistry governs VOC-specific sensing polarity under ambient conditions.