The Study On The Fabrication And Properties Of Conducting Polymer Nanocomposites And Rare Earth-polymer Materials

Conducting polymers (CPs) have been studied extensively due to their intriguing electronic and redox properties and numerous potential applications in many fields since their discovery in1970s. To improve and extend their functions, the fabrication of multi-functionalized CP nanocomposites has attracted a great deal of attention because of the emergence of nanotechnology. Combined with the intrinsic properties and synergistic or complementary effect of each component, CP nanocomposites will play an important role in a variety of areas such as chemistry, materials, information and so on.The study of optical properties of CP nanocomposites is important to gain a better understanding of their fundamental properties as well as exploit their potential new capability and function for application, thus attracting increasing attention.In such a background, we are facing the following challenges:1) How to investigate the unique optical properties of CP nanocomposites in both theoretical and experimental aspects?2) How to obtain the information on the interfacial effect and the orientation of the polymer molecule from the spectra of the CP nanocomposites?3) How to exploit the potential applications of the CP nanocomposites in the fields such as optoelectronic devices and biosensors and so on?These studies will help us to further understand CP nanocomposites and enrich the scientific meaning of the materials, and have been proven to be an indispensable step in the development and application of CP nanocomposites.On the other hand, over the past decade, there has been a growing interest in the rare earth complexes of organic ligands due to their excellent luminescence characteristics. Because of the electronic transitions between the4f energy levels, such complexes show high luminous intensity, long luminous lifetime and extremely sharp emission bands. However, the rare earth complexes with low molecular weight have serious limitations in practical applications because of their poor mechanical properties and lower physicochemical stability. Similarly the inorganic rare earth complexes suffer from brittleness, poor crack resistance and harsh processability. Incorporation of the rare earth irons into various polymer matrixes combines the luminescence characteristics of lanthanide ions with the light weight, good processability and highimpact resistance of polymers, excellent optical, electrical and lasing properties of the obtained lanthanide complexes make them promising candidates for potential applications in nonlinear optics, organic electroluminescent devices, functional membranes and luminescent materials.In this paper, we try to fully and systematically investigate the unique optical properties of the CP nanocompostites, and develop new approaches to achieve rational design as well as controlled construction of CP nanocompostites.Moreover, we have made great efforts to study fabrication and functionalization of the rare earth/polymer materials. Some novel results have been obtained in this thesis:(1) Unique optical properties of the CP nanocompostitesSurface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are powerful probes for characterization of the electronic processes that occur in the polymer in the undoped or doped states, as well as during doping. However, to our best knowledge, little work has concerned the SERS and SEIRA for the system regarding to the metal/CP nanoparticles. In this work, we study SERS and SEIRA spectra of Ag@PPy nanoparticles. The interactions at Ag core-PPy shell interface of the nanoparticle are investigated. Furthermore, the cause of SERS and SEIRA phenomenon and the relationship of interfacial effect and charge transfer for the Ag@PPy nanoparticles were discussed in detail.In our experiment, the enhancement of peak corresponding to C-H bending vibration with b2mode in IR and Raman spectra of Ag@PPy nanoparticles was observed, which could be ascribed to the charge transfer as a result of the Herzberg-Teller coupling. Surface enhanced Raman scattering (SERS) spectra of Ag@PPy nanoparticles with both488nm and1064nm excitation were investigated. Experimental results as well as theoretical analysis demonstrated that electromagnetic enhancement (EM) and charge transfer (CT) both redounded to the SERS effect of Ag@PPy nanoparticles. The increased doping level of PPy, leading to optimal energy matching between the Fermi levels of the Ag nanoparticles and the energy levels in PPy molecules, amplifying the contribution from the charge transfer, could enhance the SERS and SEIRA signal.These results demonstrated that Ag@PPy nanoparticles were promising to be used as photonics and electronics devices by adjusting the interfacial interaction of core/shell structure and the doping level of CPs. Furthermore, the application of SERS and SEIRA could be extended to investigate the charge transfer process in metal/CP composite nanoparticles.On basis of the obtained results, we further investigate the pH-responsive luminescent properties of Ag@PPy nanoparticles from the aspects of both fundamental mechanism and potential application. By comparison of the emission, excitation spectra and quantum yields for Ag@PPy nanoparticles with different volume ratios of Ag core to PPy shell, we find that the460nm peak originates from the S1â†'S0transition of the PPy, and the520nm peak results from both Ag plasmon emission and charge transfer between Ag and PPy. The two peaks blue-shift with the increasing doping level of the PPy shell, in accordance with what we evaluated from the energy diagram of Ag and PPy. In addition, we record the emission spectra of Ag@PPy nanoparticles in aqueous solutions with different pH values, as well as during the gradual alkalization and reverse acidification of the aqueous solutions. The peak position shows a reversible and fast response to the changed pH value of the medium, suggesting the potential applications of Ag@PPy nanoparticles as a reversible pH-sensor. The significance of our work is not only in providing a route to adjust the emission properties of metal-conducing nanocomposites by the doping effects, but also in paving the path for the metal/conducing nanocomposites to be exploited as pH-sensors.(2) Design, construction and applications of the CP/semiconductor particles.CdTe/PEDOT-PSS hybrid microspheres have been attained via the direct polymerization of EDOT-PSS on mercapopropionic acid capped CdTe quantum dot aggregates. The obtained hybrid microspheres provide multiple-color absorption and emission properties as a function of the pH value of the medium, which indicate the presence of both physical and electronic contact between the PEDOT and CdTe. The pH-dependent absorption and emission properties of the CdTe/PEDOT-PSS hybrid microspheres were relative to the doping-dedoping behavior of conducting PEDOT-PSS and insensitive to the morphology or distribution of the hybrid microspheres. This study gives a route for facile fabrication of semiconductor nanoparticle/conducting polymer microspheres applicable in optoelectronic and photovoltaic devices.On the other hand, we synthesized PPy/PB core/shell nanoparticles via one-step miniemulsion (periphery) polymerization (periphery) polymerization using a metallosurfactant of EPE-Fe (EPE-Fe:poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) terminated with pentacyano (4-(dimethylamino)pyridine)ferrate). The defined nanostructures allow the photoluminescent properties of PB nanoshells and PPy/PB core/shell nanoparticles to be investigated. The hollow structure endows the PB nanoshells with a fluorescent emission band at612nm. On incorporating PPy inside PB shells, a blue shift and an enhancement in the fluorescent intensity were observed as a result of charge transfer from PPy cores to PB shells. The occurrence of the charge transfer was confirmed by IR, UV and Raman spectra. The PPy/PB core/shell nanoparticles can penetrate into Bel-7402cells as evidenced by confocal laser scanning microscopy, indicating potential biomedical applications of the particles. (3) Fabrication and functionalization of the rare earth-polymer materials.We have introduced the Pr3+ions to the polycarbonate (PC) films in a novel route which allows the formation of low-molecular weight organic ligand free rare earth coordination complex, integrating the mechanical and dielectric characteristics of PC, with the optical functions of rare earth ions. The study for the effect of Pr3+ion content on the properties of PC-Prs could help us to design the optimally functional films to match the practical applications in common or specialized fields. It is expected that the extension of PC-Pr to other rare earth ions and polymer systems should permit us to combine multiple characteristics of the compositions to achieve materials desired for diverse and wide applications.