Synthesis And Performance Of Hollow Polyaniline With Gold Nanoparticles Embedded Towards The Inner Shell

To combine two or more kinds of nanomaterials with different functions can solve the problems from the single component upon application. The nanocompoistes not only present the properties of each counterpart but also create some new performance, and their applications are widened thereby. The noble metal nanoparticles behave unique optical and electrical properties, excellent catalytic performances, while polyaniline ?PANI?, as one kind of typical conductive polymers, presents unique doping mechanism, excellent conductivity and biological compatibility. Therefore, people have synthesized different noble metals/ PANI composite materials by various methods in order to optimize their property, and endow them with wide applications in electrical storage devices, biomedicine and catalysis. In this thesis, we mainly described the synthesis of hollow PANI with gold nanoparticles embedded in the inner wallby using SiO₂ as a sacrificed template. The main influence factors on morphology, structure, electrochemical activity and catalytic properties of composites have been investigated in detail. The main contents are as follows:1) SiO₂ nanospheres via Stober method were synthesized firstly. After that, the surface of the SiO₂ particles was modified with AuNPs by electrostatic interaction. Then, an in situ surface polymerization of aniline was carried out with ammonium persulfate ?APS? as oxidant to envision the coating of PANI outside of the AuNPs. Finally, the SiO₂ was removed by etching process leaving the hollow structured Au@PANI. The results reveal that PANI keeps conductive but loses solubility after HF etching. On the contrary, the solubility is good but the conductivity is decreased after NaOH etching, from its conductive to nonconductive state. Cyclic voltammetry test demonstrates the PANI with gold embedded in the inner wall can obviously improve the electrochemical activity of PANI. The increase of the doping acid concentration can effectively improve the oxidation degree and the metal-nitrogen coordination effect, which change the location and dispersion of gold nanoparticles in the polymer, and improve the electrochemical activity of the composite material.2) The as-prepared Fe₃O₄ particles were encapsulated by a layer of SiO₂ via Stober method followed by the above process to achieve Fe₃O₄@SiO₂@Au-PANI. Then the SiO₂ layer was removed by NaOH etching leaving the yolk-shell structured Fe₃O₄@Au-PANI. The thickness of the PANI on the surface could be tuned by changing the concentration of the sodium dodecylsulfate or aniline. Compared with the sample without the protection of PANI shell, the Fe₃O₄@Au-PANI presented a much higher catalytic stability by using the reduction of 4-nitrophenol by NaBH4 as a model reaction, meanwhile the recycling of catalyst is convenient owing to the presence of Fe₃O₄ cores.