Study On Gas-Sensing Properties Of Tungsten Oxide/Vanadium Oxide Core-Shell Nanowires Array Sensor

Nitrogen dioxide?NO2?is a highly harmful atmospheric pollutant.It contributes to PM 2.5 and it is also the main source of photochemical smog and acid rain.With the development of society,environmental problems become a major problem that aroused individual's great concern,and everyone has to face it.Therefore,the fast and reliable detection of toxic NO2 gas is therefore important for both environmental protection and human health.In particular,tungsten oxide,a typical n-type semiconductor,has exhibited remarkable sensing performance to NO2 gas.This study aims to discuss W₁₈O₄₉/V₂O₅ core-shell nanowires,which have highly gas sensing characteristics.It was synthesized by a two-step growth method through DC magnetron sputtering and horizontal tube furnace in our lab.First,the W₁₈O₄₉ nanowires with diameter of about 20 nm were grown via insitu thermal oxidation of sputtered W film in low press,low oxygen partial press and high temperature.Then,A crystalline V2O5 shell layer was pseudo-epitaxially coated on W₁₈O₄₉ nanowires via sputtering deposition and annealing.The W₁₈O₄₉/V₂O₅ core-shell nanorod structure is confirmed by X-ray diffraction?XRD?,scanning electron mic rocopy?SEM?,transmission electron microscopy?TEM?,energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy?XPS?.Interestingly,the formed W₁₈O₄₉/V₂O₅ core-shell nanorods array exhibits an improvement in alignment when rising the vanadium deposition time.The core structure of tungsten oxide nanowires is single crystal,while the shell structure is polycrystal.We carefully study the W₁₈O₄₉/V₂O₅ nanowires gas-sensitive property conducted by the static gas sensor test system.According to the experimental conclusion,we find that the W₁₈O₄₉/V₂O₅ core-shell nanowires sensor can work at a low temperature?25°C?,2min-sputtering of vanadium synthesis the 8nm thickness shell layer's gas response to 1⁵ppm NO2?working at 25°C?reached 5⁷ times enhancement compared to that of the W₁₈O₄₉ nanowires?working at 100°C?.It illustrates that W₁₈O₄₉/V₂O₅ core-shell nanowires have a better gas characteristics,and with the increase in thickness of V2O5 shell layer,it will fall off,however,the nanowires become more vertical orientation.The enhanced gas response to NO2 is discussed in relation to the thin V2O5 shell layer and core-shell configuration of the nanowires.