Fabrication Of Poly (3,4-ethylenedioxythiohene) And Its Composites Micro-Nanostructured And Their Electrocataltic Properties

Since 1977 when the conjugated polymers were discovered and could be made to not only possess the optical and electrical properties of metals and inorganic semiconductors metal, but also have the flexibale mechanical properties and processability of organic polymer, a considerable number of researches have focused on the field of conducting polymers. Recently, poly(3,4-ethylenedioxythiophene) (PEDOT) becomes more and more important in the family of conducting polymers, due to its high electric conductivity, moderate band gap, good environmental stability, and high optical transparency. It will be applied in various fields, such as polymer light-emitting diodes, sensors, and transparent antistatic coatings. Along with the development of nanoscience and nanotechnology, many attentions have been paid on the synthesis of nanostructured conducting polymers for their potential applications in electrical nanodevices. PEDOT micro/nano-structures were expected to be different from other conductive polymers with superior performance and promisingly play a role in practical applications. But up to now, there is only a few methods which have been developed for preparing the nanostructures of PEDOT and the researches related to their performance are more limited.Therefore, the studies on the micro/nano-structures of PEDOT will be of great significance, and it will be widely used in many fields, such as chemistry, physics, electronics, optics, materials science and biological medicine.In this thesis, we use hydrothermal synthesis, reverse interfacial polymerization and surfactant method to prepare the micro/nano-structures of PEDOT or PEDOT/inorganic composite functional materials. These micro/nano-structures were characterized in detail, and we also discussed their formation mechanism and investigated their electrocatalytic properties and applications.In the first section, PEDOT nanofibers have been successfully prepared through hydrothermal synthesis using CuCl2·H2O as an oxidant in aqueous solution in the presence of sodium dodecylsulfate (SDS) at 100℃. From the TEM image, it can be seen that after treatment with 0.5 M HNO3, PEDOT nanofibers are homogeneous and dominant in the obtained products, and the diameter of the PEDOT nanofibers is in the range of 50-80 nm.The chemical structure of the obtained PEDOT nanofibers has been characterized by FTIR UV-vis-near-IR absorption spectra, XPS and element analysis. Their formation mechanism was also discussed. Then, we have investigated the electrocatalytic property of PEDOT nanofibers modified glassy carbon electrode (GCE) towards oxidation of KI. In cyclic voltammetry (CV) measurements, the oxidation current was enhanced along with the increase of the concentration of KI ([KI]) and increased linearly in the range of [KI] from 1 to 10 mM. The nature of oxidation process of KI proceeded diffusion control. Due to the results of the amperometric response and interference study, PEDOT nanofibers modified GCE indicated excellent selectivity and significant sensitivity as well as effective electrocatalysis for detecting iodide.In the second section, unique poly(3,4-ethylenedioxythiophene) (PEDOT) nanorods with a couple of cuspate tips were successfully prepared by a reverse interfacial polymerization in the presence of sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The morphology of these PEDOT nanorods was very regular and well-dispersed with widths and lengths from one tip to another tip mostly in the range of 40-60 nm and 370-460 nm, respectively. The chemical structure of the obtained PEDOT nanorods has been characterized by FTIR UV-vis-near-IR absorption spectra, XPS and XRD. And their formation mechanism of PEDOT nanorods were discussed in detail AOT played an important role during the formation of PEDOT nanorods. It could be combined with Ce4-to form an unique template for the polymerization of EDOT in the cylindrical micelles formed by n-hexane, H2O and AOT. Furthermore, the application of PEDOT nanorods modified GCE as an electrochemical sensor for detecting nitrite was also described. Due to their good dispersibility and large surface area, PEDOT nanorods exhibited good linearity and sensitivity of CV responses as well as amperometric responses for electrocatalytic oxidation of nitrite. It could result that PEDOT nanorods might be acted as a kind of good steady and sensitive electrode materials for detecting nitrite. In the third section, by using FeCl3·6H2O as an oxidant, PEDOT/β-Fe3+O(OH,Cl)) nanospindle was successfully synthesized in aqueous solution in the presence of cetyltrimethylammonium bromide (CTAB) and poly(acrylic acid) (PAA). The lengths and widths of these nanospindles were in the range of 350-370 nm and 80-90 nm, respectively, which had the good monodispersity. PEDOT/β-Fe3+O(OH,Cl) nanospindles were composed of PEDOT and single crystalline beta-akaganeite, which were confirmed by HRTEM, XRD, XPS and TGA. They had the dual properties of both conducting polymer (PEDOT) and inorganic single crystal (beta-akaganeite). The morphology and crystallinity were afforded by the part of inorganic beta-akaganeite, and the electrical and electrochemical properties were attributed to the part of PEDOT, which were investigated by using a four-probe method and CV. The formation of PEDOT/β-Fe3+O(OH,Cl) nanospindles may be due to the concurrence of the polymerization of EDOT and the hydrolyzation of FeCl3 in aqueous solution at 50℃and the interactional result of them. The influence of the reaction conditions to the morphologies of the products and the sizes of PEDOT nanospindles were also investigated. Interestingly, hollow, core--shell and solid oligo(3,4-ethylenedioxythiophene)s microspheres could be obtained in acetone/water mixed solvent only through simply adjusting acet./H2O, (v/v), [EDOT]/[FeCl3·6H2O] or [EDOT], respectively. Then, we have investigated the electrocatalytic property of PEDOT/β-Fe3+O(OH,Cl) nanospindles modified GCE towards oxidation of KI. In CV measurements, the oxidation current was enhanced along with the increase of [KI]. The nature of oxidation process of KI proceeded diffusion control. Due to the results of the amperometric response and interference study, PEDOT/β-Fe3+O(OH,Cl) nanospindles modified GCE indicated excellent selectivity and significant sensitivity as well as effective electrocatalysis for detecting iodide.In the last section, high-crystalline PEDOT/β-Fe3+O(OH,Cl) nanospindles containing Au nanoparticles were successfully synthesized in the presence of CTAB and PAA in aqueous solution through one-step process. The lengths and widths of the Au/PEDOT/β-Fe3+O(OH,Cl) composite nanospindles were in the range of 210-300 nm and 40-60 nm, respectively. The existence of Au nanoparticles in PEDOT/β-Fe3+O(OH,Cl) nanospindles was proved by TEM images and electron diffraction pattern of single Au/PEDOT/β-Fe3+O(OH,Cl) composite nanospindle. XRD patterns and ICP-AES further confirmed that. an average diameter of Au nanoparticles was about 16.6 nm and the weight content was in average of 8.95%. Because of the introduction of Au nanoparticles, the electrical conductivity of Au/PEDOT/β-Fe3+O(OH,Cl) composite nanospindles at room temperature was higher than that of PEDOT/β-Fe3+O(OH,Cl) nanospindles using a four-probe method. Then, we have investigated the electrocatalytic property of Au/PEDOT/β-Fe3+O(OH,Cl) composite nanospindles modified GCE towards oxidation of D-AA. In CV measurements, the oxidation current was enhanced along with the increase of [D-AA]. The nature of oxidation process of D-AA proceeded diffusion control. Due to the results of the amperometric response, Au/PEDOT/β-Fe3+O(OH,Cl) composite nanospindles modified GCE indicated significant sensitivity and effective electrocatalysis for detecting iodide.