Design, Preparation And Properties Of Nonlinear Optical Functional Materials With Multiple Limiting Mechanisms

The design and preparation of nonlinear optical (NLO) functional materials has been becoming the most highlight and challenged research topic in both basic and applied sciences. Porphyrin, graphene and multiwalled carbon nanotubes have been investigated as the promising NLO (including optical limiting) materials. On the basis of reviewing the current developments of the NLO materials including porphyrin, graphene and carbon nanotubes, it is proposed that simplifying the synthetic methods and recombinating the NLO materials with multi-mechanisms to the benefit of the preparation for the laser protection materials. For this purpose, some novel porphyrin or two-photon-absorption chromophore-containing structural motifs with enhanced NLO properties have been prepared and studied.Chapter2describes the preparation of one novel V-shaped D-π-A-π-D porphyrin (4,5-bis[5,10,15,20-tetraphenylporphinatozinc(Ⅱ)]phthalonitrile). The NLO absorption properties are studied using Z-scan technique at532nm with4ns and21ps laser pulses. Results display that this system exhibit enhanced NLO absorption in comparison to that of ZnTPP. This enhanced response may be ascribed to the introduction of phthalonitrile core. By introducing phthalonitrile core, highly efficient donor-acceptor pairs are formed, in which cyano group as acceptor and porphyrin as donor, which provides an effective guideline for the rational molecular design towards novel organometallic NLO chromophores.In chapter3, a porphyrin derivative bearing strong two-photon-absorption chromophore in the periphery is prepared through a simple method. A strong fluorescence resonance energy-transfer (FRET) from the D-π-A-π-D pyridine to the porphyrin core is observed by research on the fluorescence emission spectrum. The enhanced NLO properties can be ascribed to a combination of reverse saturable absorption with FRET. The improved NLO responses of porphyrin can be realized by altering the structure of porphyrin.Composite materials combining porphyrin with graphene for preparing organic-inorganic hybrid limiting materials are the development tendency of NLO materials. For this reason, two novel graphene nanohybrids covalently functionalized by axially-coordinated porphyrins have been prepared and studied for their photophysical properties including optical limiting responses (Chapter4). Attachment of porphyrins to the surface of graphene oxide significantly improves the solubility and dispersion stability of the graphene-based materials in most common organic solvents. Results display that functionalized GO with porphyrin can enhance the NLO performance in nanosecond and picosecond regime, implying a remarkable accumulation effect of nonlinear scattering and/or two-photon-absorption with reverse saturable absorption, and photo-induced electron or energy transfer from the electron donor porphyrin to the acceptor graphene. The results suggest that porphyrin and graphene oxide combined system (GO-TPP) can efficiently improve the optical nonlinearity.An organic solution-processable functionalized GO nanohybrid material with the V-shaped D-π-A-π-D pyridine molecules is prepared and characterized by FTIR and Raman patterns in Chapter5. The V-shaped D-π-A-π-D molecules are directly reacted with surface-bonded acryl chloride moieties of graphene to afford GO-Pyridine. The pyridine molecules covalently linked on the surface of graphene oxide is supported by different kinds of physical and spectroscopic technologies. This material exhibits strong nonlinear scattering at higher intensities, which evidently comes from graphene counterpart. The GO-Pyridine show enhanced nonlinear absorption, which may be ascribed to a combination of excited-state absorption with the nonlinear scattering, and photo-induced electron or energy transfer from the D-π-A-π-D pyridine chromophore to the GO moiety.In Chapter6, MWNTs-TPP hybrid material has been prepared through1,3-dipolar cycloaddition reaction. The attachment of TPP in this nanohybrid system is supported by FTIR, UV/Vis, fluorescence and Raman spectroscopies. The open-aperture Z-scan measurements suggest that MWNTs-TPP exhibit enhanced NLO properties in comparison to that of the free porphyrin. For nanosecond laser pulses, this nanohybrid system exhibits excellent optical limiting responses. These results indicate that organic-inorganic hybrid materials exhibit special advantages in the development of optical nonlinearity.