Gas-humidity Sensing Characteristic Research Of Polyaniline And Its Nanocomposite Thin Film

The environmental pollution is a great challenge for human, which has a big impact to our social sustainable development in the future. With the science and technology progress, the earth is further transformed and damaged during human activities. All kinds of toxic and harmful substance widely exist for environmental pollution. In order to solve the problem of environmental pollution, monitoring the pollutant is a critical work. Therefore, the sensor researched for sensing the toxic substance is applied to industry, agriculture, animal husbandry, transportation,meteorology, aviation and military, which has important social significance and economic benefit.The gas/humidity sensors based on inorganic semiconductor have some disadvantage, such as low sensitivity, slow response, high power consumption,complex preparation process, etc. A lot of researches on the gas/humidity sensors based on polyaniline (PANI) thin film are widely reported, which is simple, reliable, inexpensive, high sensitivity, fast response, able to operate at room temperature etc. Therefore, fabricating the high performance gas/humidity sensor based on PANI and inorganic/PANI nanocomposite is a significant work.The inorganic nanomaterial owns some unique catalytic effects, such as high specific surface area, more active sites on surface, high surface reactivity, high catalytic efficiency and absorbability. Therefore, synthesizing the inorganic/PANI nanocomposites is combining advantages of the two materials, which has small-size effect and surface effect. Moreover, some new character would appear owning to the synergistic effect and/or complementary effect from the two materials. Then, it may improve the performance of PANI gas/humidity sensor. In this thesis, the PANI and inorganic/PANI nanocomposites with different morphologies are synthesized by in-situ chemical oxidative polymerization, which is used to fabricate the gas/humidity sensors for test and study, and the mechanism of the sensor for gas or humidity sensing is discussed.The detailed work and main points can be summarized as follows.1. It's investigated the influence on humidity sensitive characteristics of micro/nano-PANI thin films with different doping degree of(1S)-(+)-10-camphorsulfonic acid (D-CSA) using in-situ chemical polymerization.The PANI is characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), separately. And the PANI is fabricated on interdigital electrodes (IDE) via self-assembly method. Besides, the humidity sensitivity of the PANI films enhances with increasing the molar ratios of[D-CSA]/[Ani] and decreasing the layer number of PANI films, separately. The performance of PANI sensor humidity sensing can be enhanced by optimized PANI parameters of D-CSA doping degree and/or thin film thickness.2. The nanodiamond (ND) has high specific surface, chemical stability,mechanical modulus and abundant functional group. The ND/PANI nanocomposite is obtained using in-situ chemical polymerization for NH3 detection. The sensing mechanism of the sensor for NH3 gas is discussed. The electrical property of ND/PANI is depending on the ND component into nanocomposite for NH3 gas sensing. Compared with pure PANI, the ND/PANI nanocomposite thin film has high detecting sensitivity and fast response on NH3.3. As famous carbon nanofiller, graphene is a single-atom thick with unique structure and property, such as cost effective, excellent electronic property and high quality material. Two types of grapheme/PANI nanocomposites are obtained using in-situ chemical polymerization and physical blending method, respectively.Moreover, the structure and morphology of the synthesized products are characterized by FTIR, BET, UV-vis,PL, XPS and SEM, respectively. The grapheme/PANI nanocomposite is fabricated on IDE for NH3 and CH4 gas detection, which are researched on electrical character. Graphene added into PANI may enhance the sensitivity of graphene/PANI NH3 sensor, and lower NH3 detection limit than that of PANI. And the sensitivity of graphene/PANI CH4 sensor is higher than that of PANI. Also, the detection range of the CH4 sensor is enlarged by increasing the mass ratio of graphene to PANI. The sensitivity of graphene/PANI by an in si-tu chemical method is higher than the sensitivity of those produced by a physical mixing method. Meanwhile, the NH3 and CH4 gas sensing mechanism of the sensor is adequately discussed, which is explained by the effect of the ?-?* conjugation system within the graphene/PANI thin film.