Abstract
Engineered defect chemistry in ultrathin (≈5 nm) hafnia through substitutional cobalt (HCO) is investigated for selective glucose sensing. Thin films of HCO, grown using chemical solution deposition (CSD)-traditionally used to grow thick films-on silicon, show significant glucose sensing activity and undergo monoclinic to orthorhombic phase transformation. The presence of multivalent cobalt in hafnia, with oxygen vacancies in proximity, selectively oxidizes glucose with minimal interference from ascorbic acid, dopamine, and uric acid. Theoretical investigations reveal that these oxygen vacancies create a shallow donor level that significantly enhances electrocatalytic activity by promoting charge transfer to the conduction band. This results in considerable selectivity, repeatability, and reproducibility in sensing characteristics. These findings highlight the technological importance of using CSD for thin films, paving the way for ultrathin CSD-processed HCOs as potential candidates for selective glucose sensing applications.