Synthesis of Core/Shell WO₃/WS₂ Heterostructure Nanowires with Negative Photo-Responsiveness

WO₃/WS₂ core/shell nanowires were synthesized using a scalable fabrication method by combining wet chemical etching and chemical vapor deposition (CVD). Initially, WO₃ nanowires were formed through wet chemical etching using a potassium hydroxide (KOH) solution, followed by oxidation at 650 °C. These WO₃ nanowires were then sulfurized at 900 °C to form a WS₂ shell, resulting in WO₃/WS₂ core/shell nanowires with diameters ranging from 90 to 370 nm. The synthesized nanowires were characterized using scanning electron microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The shell is composed of 2D WS₂ layers with uniformly spaced 2D layers as well as the atomically sharp core/shell interface of WO₃/WS₂. Notably, the WO₃/WS₂ heterostructure nanowires exhibited a unique negative photoresponse under visible light (405 nm) illumination. This negative photoresponse highlights the importance of interface engineering in these heterostructures and demonstrates the potential of WO₃/WS₂ core/shell nanowires for applications in photodetectors and other optoelectronic devices.