Electrochemical Study of a WO₃ NPs/MoO₃ Heterojunction-Based Dual-Enzyme Amperometric Acetylcholine Sensor

This study proposes an acetylcholine (ACh) sensor based on a molybdenum trioxide (MoO3) film modified with tungsten trioxide (WO3) nanoparticles (NPs). The MoO3 film was first prepared by radio frequency (RF) sputtering, followed by drop-casting of hydrothermally synthesized WO3 NPs for hydrogen ion detection. X-ray diffraction (XRD), together with transmission electron microscopy (TEM) and selected-area electron diffraction, confirmed the crystal phase of WO3 NPs, while energy-dispersive X-ray spectroscopy (EDX) verified the homogeneous elemental distribution. In addition, ultraviolet photoelectron spectroscopy (UPS), low-energy inverse photoelectron spectroscopy (LEIPS), and ultraviolet-visible spectroscopy were used to confirm the band structure, and X-ray photoelectron spectroscopy (XPS) further verified successful material synthesis. Electrochemical impedance spectroscopy (EIS) further revealed that the WO3 NPs/MoO3 configuration enhances charge transport across the liquid interface. This sensor exhibits a high sensitivity ( $31.85~\mu ~\text {A}\cdot \text { decade}~^{-{1}}\cdot \text { cm}^{-{2}}$ ), a limit of detection (LOD) ( $1.37\times 10^{-{10}}$ M), and acceptable interference tolerance, offering a novel approach for detecting low concentrations of ACh.