The Fabrication Of Hydrogen Sulfide Sensors

Hydrogen sulfide is colorless, inflammable, corrosive and malodorous gas, which smells like rotten eggs. When its concentration is higher than a certain value, H2 S can be very dangerous to human health and even cause death. Because of its high danger, the detection of hydrogen sulfide has great significance to both human daily life and industries. So far, much work on H2 S gas sensors has been done at home and abroad. In this work, hydrogen sulfide gas sensors based on different sensitive materials were prepared and the response properties of sensors to H2 S at room temperature were tested. The main work was summarized as below:1. In this work, the resistive gas sensor based on the structure of interdigitated electrodes(IDEs) was selected. Two kinds of materials were adopted as sensing materials: one material was multiple-walled carbon nanotubes(MWNTs) and MWNTs doped with HAuCl4(MWNTs-HAuCl4). And another material was polymers doped with MWNTs. Here, polyaniline and DPPD were used as sensing polymers. Finally, gas sensors based on pure MWNTs, MWNTs-HAuCl4, PANI/MWNTs and DPPD/MWNTs were fabricated using air spraying method. The sensing properties of these four sensors to H2 S were tested.2. The sensing properties of MWNTs and MWNTs-HAuCl4 to H2 S at room temperature were tested in this work. The results showed that the sensor based on MWNTs-HAuCl4 presented the higher response than sensors based on pure MWNTs when it was exposed to H2 S. Good repeatability is a very important property for a stable gas sensor. The sensors based on MWNTs and MWNTs-HAuCl4 presented fast response-recovering properties, good repeatability and stability. But sensors based on MWNTs were better. Besides, the linearity is another important factor to characterize the static performances of a gas sensor. It was shown that sensors based on MWNTs presented good linearity and poor selectivity. The scanning electron microscope(SEM) has been taken at the surface of these two kinds of films. It can be seen that more holes were found in MWNTs/HAuCl4 film, which makes a contribution to the response to H2 S. Finally, the sensing mechanism of MWNTs was explained based on the experimental results.3. The sensing properties of PANI/MWNTs and DPPD/MWNTs films to H2 S at room temperature were tested in this work. The results showed that the sensor based on PANI/MWNTs presented a higher response than sensors based on DPPD/MWNTs when it was exposed to H2 S. The sensors based on DPPD/MWNTs exhibited better repeatability, stability and linearity. And the response and recovering time of sensors based on DPPD/MWNTs were faster than those based on PANI/MWNTs. The selectivity was highly improved using organics/MWNTs compound materials. But the selectivity of DPPD/MWNTs to sulfide needs to be further improved. The scanning electron microscope(SEM) has been taken at the surface of both PANI/MWNTs and DPPD/MWNTs films. It can be seen that MWNTs were dispersed evenly in organics/MWNTs films. The differences of SEM between films can be used to explain the diversity of sensing properties.