Study On The Design, Preparation And Sensitive Properties Of Polyaniline And Its Nanocomposite Sensitive Materials

Sensors have significant applications in modern society, and great attention has been paid to the development of high performance sensors. In view of the great progress achieved in nanoscience, preparing novel nanocomposite sensitive materials with improved sensing properties has become one of the focuses of the researches on sensors. In this thesis, nanostructured polyaniline (PANI) and its composites were prepared and employed to fabricate three types of sensors, including (1) electrospun nanofiber humidity sensor, (2) layer-by-layer self-assembled ultrathin film ammonia sensor and (3) electropolymerized nanocomposite glucose sensor. The composition, structure and morphology of the sensing materials were characterized by FT-IR, UV-vis, QCM, XPS, XRD, SEM, TEM, AFM, BET, etc. Room temperature sensory properties of the sensors were investigated, and optimized by manipulating the composition and morphology of the sensing materials. Moreover, the sensing mechanisms were explored.Impedance-type and surface acoustic wave (SAW)-type nanofiber humidity sensors were prepared via electro spinning. Formation of beads in the nanofibers was found to greatly promote their adhesion to the substrates, and the heat-induced cross-linking could effectively improve the water resistance of nanofibers and thus enhance the stability of the humidity sensors. Impedance-type humidity sensors were featured with good sensing linearity, fast response, small hysteresis and good repeatability. In addition, they displayed a sensitivity of two orders of magnitude higher than corresponding thin film sensors. An electrical equivalent circuit was established via electrochemical impedance spectroscopy analysis to model the impedance response to humidity variation of the nanofiber sensor. SAW-type nanofiber humidity sensors exhibited very high sensitivity (-75 kHz/%RH), ultrafast response (1-2 s) and good sensing linearity (R2>0.999). Specifically, it could detect very low humidity (-0.5%RH).Nanocomposite gas sensors were fabricated by depositing electrostatically self-assembled PANI/TiO2 ultrathin film on interdigital gold electrodes. The ultrathin film gas sensors displayed high sensitivity, fast response, good reversibility and stability to ammonia of low concentrations (ppm) at room temperature. Nanocomposite glucose sensors were constructed by electrochemical deposition of nanostructured PANI, glucose oxidase (GOx) and polydopamine (PDA) onto the platinum needle. The mechanical strength and stability of the PANI based biosensor was enhanced significantly due to the cross-linking between PANI, GOx and PDA. Furthermore, the prepared sensor shows improved sensitivity with a detectability of 3 uM.