Study On Preparation, Property And Application Of Polyaniline/Au Nanocomposites

We mainly reported one-step synthesis of polyaniline/Au nanocomposites in this thesis. Polyaniline andpolyaniline/Au nanocomposites with different morphologies were successfully prepared via oxidativepolymerization of aniline using HAuCl4as oxidant in ethanol solvent and changing different volume ratiosof ethanol/water mixed solvent and different pH values of ethanol/water mixed solvent. Through theanalysis of experimental phenomena and experiment results obtained under above reaction conditions, weexplored the important factors of self-assembly of polyaniline/Au composites. At the same time, wespeculated the structure and possible formation mechanism of as-prepared products. In addition, as-preparedAu@polyaniline nanoshperes as catalyst toward the reduction of4-nitrophenol in the presence of NaBH4was investigated and the catalytic mechanism of this reaction was also discussed. The main results weresummarized as follows:1. Uniform morphology of Au@polyaniline nanoshperes was successful synthesized in ethanol solutionvia rapid mixing reaction of Aniline and HAuCl4without any disturbance. Gold nanoparticles (AuNPs) withsize of about2-4nm were evenly embedded in the polyaniline matrix which acted as the dispersing agent andstabilizer of AuNPs. The possible self-assembly mechanism of as-prepared Au@polyaniline nanosphereswas discussed and ethanol solvent was considered to be a crucial factor for the formation of as-preparedAu@polyaniline nanospheres. Moreover, the catalytic performance and the possible catalytic mechanism ofas-prepared Au@polyaniline nanospheres as catalyst toward the reduction of4-nitrophenol were studied indetail. Finally, as-prepared Au@polyaniline nanospheres were proved to be a kind of stable andhigh-efficiency catalyst.2. Gold particles, polyanilane and polyaniline/Au nanocomposites with different morphologies wereprepared via one-step synthesis of oxidative polymerization of aniline using HAuCl4as oxidant in differentvolume ratios of ethanol/water mixed solution with the aid of HCl or H2SO4doping. The possible formationmechanism of as-prepared various materials was discussed. The solvent of reaction system and the rate ofpolymerization reaction were proved to be important factors affecting the morphologies of products and thecomposite capability of composite materials. Additionally, we speculated that90%ethanol of ethanol/water mixed solution with HCl doping was the optimal condition for formation of composite materials in thisreaction system.3. Based on the results of the previous chapter, polyaniline/Au nanocomposites with differentmorphologies were successfully prepared via one-step oxidative polymerization of aniline using HAuCl4asoxidant and sodium sulfosalicylate as dopant in different initial pH values of90%ethanol of ethanol/watermixed solution. Experimental results showed that the initial pH of solvent played a crucial role for themorphology of polyaniline/Au nanocomposites and the molecular weight of polyaniline. At the same time,we also proposed different oxidative polymerization mechanisms of aniline in different pH values. Themechanism of oxidative polymerization of aniline was chain polymerization in strongly acidic conditions(pH≤1), while the mechanism of oxidative polymerization of aniline was stepwise polymerization when theacidity of reaction system was weak (pH≥2). There was a big difference on the polymerization method ofaniline and the self-assembly of polyaniline/Au nanocomposites in different polymerization mechanisms,and eventually leading to the formation of different molecular weights and morphologies of polyaniline/Aunanocomposites.