| Graphene, the building block of all graphitic materials, is a single layer of sp2carbon atoms, in a closely packed honeycomb two-dimensional lattice. Since its isolation by Geim and Novoselov in2004, its unique physical and chemical properties, such as the electrical conductivity, high mechanical strength, large theoretical specific surface areas and so on, have attracted much attention from different research fields. Also, graphene-based materials demonstrated potential applications in different fields, for example, field effect transistors, supercapacitors, sensors, etc. In this thesis, we focused on the large-scale preparation of graphene, the functionalization of graphene, its optical limiting properties and also its applications in biosensors. The main content is described as follows:In chapter one, we introduced different methods for the preparation of graphene, the modification of graphene, its applications, and also some urgent problems to be solved. Basing on these, the designed strategies and research topics were put forward.In chapter two, using graphene oxide (GO) as the precursor, polyacrylic acid (PAA) modified graphene sheets could be prepared by the in-situ polymerization of acrylic acid in the presence of GO. The resultant material RGO-AA could be well dispersed in water, and this method could be used for the large-scale production of graphene. The composite of graphene and Fe3O4nanoparticle was prepared by a physical mixing process, the resultant material RGO-AA-Fe3O4showed good absorbing ability towards organic dyes in water. With the aid of a lodestone, RGO-AA-Fe3O4could be easily collected and removed from the solution.In chapter three, the main content could be divided into three parts. In the first part, we synthesized polyacetylene containing the azido groups as the pendants. By utilizing the nitrene chemistry, a serial of polyacetylene-functionalized graphene derivates Pac-G-n-S (n=10,5,3), which could be solved in common organic solvents, were prepared. We measured the luminescent behaviors of Pac-G-n-S, the quantum yields of the composite materials were14.04,13.87and14.3%, respectively, higher than that of Pac (8.71%) itself. In the second part, we synthesized a tetraphenylethylene compound ?-1. Also by using the nitrene chemistry, it was covalently grafted onto graphene sheets, and the resultant material was soluble in common organic solvents. For comparison, we have also synthesized another two compounds ?-2and ?-3, which have the similar conjugation, but different configurations. Both of them showed lower ability to enhance the solubility or dispersion stability of graphene. We supposed that as an isolation spacer, compound ?-1bearing the twisted conformation, showed more advantages than the others, and thus the solubility of functionalized-graphene could be improved greatly. In the third part, we synthesized compound ?-4, covalently modified graphene derivative was obtained through the reaction between the azido groups in ?-4and "C=C" bond in graphene. Using TGA analysis, the content of ?-4in the composite material of Cbz-TPE-G was calculated to be about53.9%. Cbz-TPE-G showed good dispersion stability in organic solvents, taking1,2-dichlorobenzene (o-DCB) for example, the dispersion was stable without any aggregation at the bottom of the bottle for one year. Using the Z-scan methods, we found that, even though the covalent modification disturbed the conjugation of graphene to some extent, Cbz-TPE-G still showed good optical limiting properties, which could be attributed to the nonlinear absorption and nonlinear scattering of graphene.In chapter four, we synthesized polymer P1containing terminal alkyne groups. Via "'Click" chemistry, P1was covalently grafted onto graphene sheets. The resultant material rGO-P1was characterized by IR, Raman, UV-vis, fluorescent, XRD, SEM and TEM. The dispersion stability of graphene was improved by the existence of P1. By using TGA analysis, the content of P1in rGO-P1was calculated to be48.7%.In chapter five, we developed a new method for the covalent functionalization of graphene sheets, by using nitrogen-based nucleophiles. We synthesized polymer poly(9,9'-diheylfluorene carbazole)(PCF), which contains active NH groups. PCF modified graphene derivatives was prepared via the reaction between nitrogen anions and the carbonyl and epoxide groups in GO. The resultant products, RGO-PCF-s and RGO-PCF-i, with different sizes and solubilities, were separated by centrifugation. RGO-PCF-s has a dimension of?200nm. The dispersion of RGO-PCF-s was stable in water. However, the optical limiting response of RGO-PCF-s was reduced or even disappeared. The dispersion stability of RGO-PCF-i was worse than that of RGO-PCF-s, but it demonstrated strong optical limiting responses.In chapter six, we synthesized a water-soluble disubstituted polyphenylacetylene P2, with the ammonium groups as the pendant. Water-soluble graphene sheets was prepared via the chemical reduction of GO in the presence of P2. The non-covalent modification was based on the ?-? and electrostatic interactions between P2and graphene. After reduction, the sp2-conjugated structure of graphene was formed, and the resultant material G-P2showed a prominent optical limiting response. This property enables graphene as a good optical limiter, to protect human eyes and optical sensors from the damage induced by intense laser irradiation.In chapter seven, by intelligently utilizing the displacement method, with the aid of GO, the selectivity of aggregation-induced emission (AIE) biosensors, could be improved. In this chapter, the main content could be divided into three parts. In the first part, we prepared GO-A2HPS·HCI, and investigated its sensing behavior towards DNA. With the addition of DNA-CT (calf thymus), the fluorescent intensity of the solution was light-up immediately, at the concentration of70?g/mL, the intensity increased by57-fold, which was strong enough to be observed by the naked eyes. The detection limit for DNA-CT, DNA-ST (salmon testes) and DNA-HS (herring sperm) was2.3,3and3.3?g/mL, respectively. In summary, GO-A2HPS·HCI showed high sensitivity and selectivity towards DNA. In the second part, by changing the structure of AIE molecules, GO could also be used to improve the selectivity of other AIE-based biosensors. We prepared GO-SDBS-TPE-N2C4, and investigated its sensing behavior towards different biomacromolecules. Instead of DNA, GO-SDBS-TPE-N2C4showed good selectivity towards bovine serum albumin (BSA). With the addition of BSA, the fluorescent intensity of the solution increased gradually, and the detection limit was0.7?M. Comparing the different results of these two parts, the structures of A2HPS·HCl and TPE-N2C4were similar, they are quaternary ammonium salts bearing different aromatic blocks, but their sensing behavior were totally different. We supposed that the sensing behavior should be mainly determined by their aromatic blocks, besides the electrostatic interactions, the interaction between the aromatic rings of the AIE dyes and DNA also played an important role. In the third part, we synthesized water-soluble compound TPE-SO3Na, with the aid of GO, GO-TPE-SO3Na could be used for the detection of BSA with high sensitivity and selectivity, the detection limit was0.4... |
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