Tungsten Oxide Organic Activation

For stable and efficient detection of nitrogen dioxide gas at room temperature. The use of organic substances to activate tungsten oxide is a better choice, for example, polypyrrole and tungsten oxide are combined. Polypyrrole-tungsten oxide composites, depending on the amount of polypyrrole incorporated, can exhibit characteristics from semiconductors to metallic conductors.

Polypyrrole-tungsten oxide composite gas sensitive materials were prepared by solid-state mechanical mixing. Due to the addition of tungsten oxide, a porous structure is formed on the surface of the polypyrrole, which is beneficial to the improvement of gas sensing properties. They found that the polypyrrole-tungsten oxide with a doping concentration of 50% had a sensitivity of 61% to nitrogen dioxide, a stability of 78%, and a good selectivity to gases such as ammonia, alcohol, and hydrogen sulfide.

The polypyrrole-tungsten oxide was added with dodecylbenzene sulfonic acid (DBSA). When the mass fraction was 20%, the sensitivity was the highest, and the sensitivity to nitrogen dioxide was 72. Adding DBSA to polypyrrole-tungsten oxide gas-sensitive material can significantly improve the stability of the sensor. When adding 20% mass fraction of DBSA, the stability was increased by 12% compared to the gas sensitive material without DBSA. Using polypyrrole/tungsten oxide structure in addition to nitrogen dioxide gas can also detect hydrogen sulfide gas.

Hydrogen sulfide can be detected by photopolymerization of polypyrrole nanoparticles and tungsten oxide nanoparticles on an alumina substrate. At room temperature, its sensitivity to hydrogen sulfide is 81%. And the sensor's sensitivity and concentration show a good linear relationship. The sensor also shows good repeatability and stability. It mainly affects the performance of the sensor by affecting the width of the depletion layer of tungsten oxide and polypyrrole on the surface of the sensor, but the response recovery time is longer.

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