Structural and sensing properties of HfxZr1-xO2 films prepared through a spin-coating sol-gel method for pH and procalcitonin detection

In this study, Hf_xZr_1-xO₂ (HZO) sensing films were deposited on highly doped n⁺-type Si substrates using the spin-coating sol-gel method. These films were designed for use in extended-gate field-effect transistor (EGFET) pH sensors and procalcitonin (PCT) detection, a key biomarker for sepsis diagnosis. To investigate the effects of thermal processing on the structural and functional properties of the films, rapid thermal annealing (RTA) was performed at temperatures ranging from 600 to 800 °C. Comprehensive material characterization through X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy revealed a strong correlation between the film's structural properties and its sensing performance. The film annealed at 700 °C demonstrated excellent performance, achieving the highest pH sensitivity (63.69 mV/pH), the lowest drift rate (0.24 mV/h), and minimal hysteresis (0.3 mV). Moreover, for PCT detection, N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide-acivated PCT antibodies were immobilized on a 3-aminopropyltriethoxysilane-functionalized HZO film, enabling specific antigen binding. The resulting HZO-based EGFET biosensor showed high sensitivity (13.6 mV/pC_PCT) across a broad dynamic range (10 fg/mL to 1 μg/mL). These findings highlight the potential of HZO sensing films for high-performance pH sensing and their integration into biomedical diagnostics, particularly for PCT detection in sepsis diagnosis.