Fabrication Of Organic And Inorganic Hybrid Micro-Nanostructure Functional Materials And Their Dielectric And Photoelectric Properties

Over the past decade, organic and inorganic hybrid nanocomposites have gained interest rapidly due to their favorable and often unique combination of properties. Considerable efforts have recently been directed toward the exploitation of new nanostructured hybrid organic-inorganic composites for their scientific interest and their industrial applications. That is because of their utility and potential as catalysts, sensors, optical and electronic applications, gas selective membranes, energy storage and transform, etc. In general, composite materials are formed when at least two different types of materials (organic, inorganic, or metallic) are mixed. The combination of organic and inorganic materials is expected to provide remarkable and complementary properties, which cannot be obtained with a single material. Organic/inorganic nanocomposites, in which two components were mixed at the nanometer level, usually exhibited improved performance properties compared to conventional composites, in which two components were mixed on a macroscopic scale (> micrometers), owing to their unique phase morphology and improved interfacial properties. Composite nanomaterials composed of different materials can combine the properties of these materials and even produce novel unique properties. It is well known that most of inorganic nanoparticles are difficult to process for their poor mechanical performance. However, most of the common polymers are processable but are rare in functionability. Therefore, the combination of polymers and functional nanoparticles can combine their properties. On the other hand, combination of two different materials with correlative properties may produce more excellent properties.In this thesis, we use electrospinning, polarization coating, spin-coating and sol techniques to fabricate organic and inorganic hybrid micro-nanostructure functional materials, and investigate their dielectric and photoelectric properties.In the first section, we have successfully prepared PVP/ferrocene hybrid nanofibers and membranes via electrospinning and polarization coating techniques, and the dielectric properties of the hybrid materials have been studied in detail. We used 100 kHz and 1 MHz two frequencies to investigate the dielectric constants of composite nanofibers and polarization coating membranes. The results showed that the dielectric constants of nanofiber membranes are from 1.41 to 1.54, which are less than the coating membranes after polarization.The dielectric constants of coating membranes are from 11.51 to 22.60. The dielectric constants under 1 MHz frequency are lower than those under the 100 kHz frequency. Based on this method, we have successfully prepared PMMA/ferrocene composite fibers via electrospinning. The PMMA/ferrocene fibers are smooth and continuous, which are ranged in diameter from 800 nm to 3μm. The properties of PMMA and ferrocene are combined perfectly. We demonstrate that our method is effective in producing ultra-low dielectric constant composite materials. The dielectric constants of PMMA/ferrocene composite fiber membranes are decreasing with the increasing of ferrocene content. And enforcing the fiber prepared voltage can make the dielectric constant increased. The dielectric constants of the prepared PMMA/ferrocene composite fiber membranes are from 1.12 to 1.32.In the second section, PVP/Fe3O4 composite nanofibers have been successfully prepared using electrospinning technique. The composite nanofibers have been characterized by means of TEM, XRD and TGA. Transmission electron microscope images of the PVP/Fe3O4 nanofibers showed that the Fe3O4 nanoparticles with diameter about 10.5 nm were dispersed in PVP fiber matrices. And the TGA of PVP/ Fe3O4 nanofibers show that the content of Fe3O4 nanoparticles in the composite was about 36.8% (mass fraction). The PVP/Fe3O4 nanofibers were found to be superparamagnetic. The hysteresis loop at room temperature showed high saturated magnetization (Ms =15.1 emug-1) and a low coercive force (μc=0). We investigated their dielectric constants from 100 Hz to 1 MHz frequency; the dielectric contant is 1.8 under 1 MHz frequency. Based on this method, we successfully prepared ultra-low dielectric constant PMMA/Fe3O4 composite fiber membrances. The morphology of the fibers is smooth and uniform. We obtained PMMA/ Fe3O4 composite fibers with different Fe3O4 content. When Fe3O4 content is 30%, the dielectric constant of composite fibers is 1.22 under 1 MHz frequency after drying treatment.In the third section, we successfully fabricated PVP/CdS composite micro-nano structure materials, studied their causes and dielectric properties, The CdS nanorods were dispersed into PVP solution to prepare the electrospun PVP/CdS fibers. It has been shown that the morphologies of the PVP/CdS fibers were strongly affected by the CdS amount and the PVP concentrations. At a lower CdS: PVP weight ratio of 1:1000, HHS was formed because of a kind of nano-effect. With the increase of CdS: PVP weight ratio, the CdS nanorods aggregated and the nano-effect disappeared so that fibers and ribbons were obtained. Holding the CdS: PVP constant, the morphology's change from HHS to bead-free fibers with the increase of the PVP concentrations is attributed to the effect of the viscosity and the surface tension of the solution. The dielectric constants of the prepared PVP/CdS composite structure are from 1.51 to 1.55 under the frequency from 100 Hz to 1 MHz. And then, we prepared PMMA/CNT composite fiber membrances with ultra-low dielectric constant, and PMMA/CNT coating membrances with higher dielectric constant.In the last section, hybrid solar cells based on blends of a conjugated polymer regioregular poly (3-hexylthiophene) (P3HT) as electron donor and crystalline SnO2 nanoparticles as electron acceptor have been studied. Composite SnO2:P3HT films were cast from a common solvent mixture. The photoluminescence property has been studied as a function of the SnO2 content. When the SnO2 content is 20%, the device exhibits an open-circuit voltage Voc of 0.37 V, max power Pmax =0.2μWcm-2, and a fill factor of 0.27. Then we prepared P3HT and porous TiO2 hybrid solar cell. Annealing the blend films is found to greatly improve the polymer–metal oxide interaction at the P3HT/TiO2 interface, resulting in increase of the charge separation yield and improving photovoltaic device performance under 1 sun AM 1.5 illumination. After annealing the device exhibits a photocurrent Jsc of 9.72μAcm-2, open-circuit voltage Voc=0.42 V. The hybrid solar cells based on nanocrystalline ZnO nanorods and P3HT are processed from solution and characterized as a function of ZnO concentration. When ZnO concentration is 16 mg/mL, the device exhibits a photocurrent Jsc of 1.9 mAcm-2 and open-circuit voltage Voc of 0.38 V, resulting in a power conversion efficiency of only 0.2%.