Tungsten Oxide Sensor Gas Sensitivity

A lead-containing tungsten oxide sensor is prepared by hydrothermal synthesis and the operating temperature is lowered to room temperature. The hydrothermally synthesized tungsten oxide gas-sensitive material has better gas-sensitivity than the tungsten oxide gas-sensitive material prepared by the mechanical mixing method and the pure tungsten oxide gas-sensitive material. The addition of lead effectively changed the response characteristics of the sensor. The sensitivity to hydrogen at room temperature was 34 and the response time was 24 s. And it has very good selectivity and repeatability.

The use of iron can reduce the characteristics of the band gap width of tungsten oxide, and a novel spray pyrolysis method is used to prepare an iron-tungsten oxide alcohol gas sensor. Tungsten oxide is a single crystal that preferentially grows in the (200) direction, and iron activation reduces the band gap width of tungsten oxide from 2.9 eV to 2.59 eV. When the mass fraction of 5% iron was added, the sensor had the best response and the sensitivity to alcohol gas could reach 78.

The metal activated tungsten oxide gas sensing layer also responds to oxidizing gases such as nitrogen dioxide in addition to the reducing gas. Titanium oxide nanowires with added titanium and oxygen defects were prepared by a hydrothermal synthesis method. Titanium was added by physical impregnation and chemical synthesis, respectively, and chemical synthesis was found to inhibit the dispersion of tungsten oxide nanowires. Physical impregnation can form well-distributed spot-like particles on the surface of tungsten oxide, thereby improving its sensing performance. The addition of titanium metal can not only reduce the operating temperature from 150°C to room temperature, but also increase the sensitivity and response characteristics of the sensor.

In addition to titanium doping, non-stoichiometric tungsten oxide nanowires may be doped with metallic vanadium for the detection of nitrogen dioxide gas. The solvothermal method was used throughout the synthesis and the resulting sensor exhibited good response to nitrogen dioxide. The doping of vanadium not only inhibits the axial growth of the tungsten oxide nanowires, but also leads to the secondary growth of the nanowire bundles.

The doping of vanadium not only lowers the operating temperature to room temperature, but also lowers the detection limit. In addition, vanadium-doped tungsten oxide nanowires exhibit anomalous p-type semiconductor properties at room temperature. And p-n transition occurred at 110 °C.

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